Brains Rocker Arm mod.


BRA mod. (Brains Rocker Arm) mod.

 Here is one of the easiest mods that we can do to improve power with out tearing the motor all apart. I have a fair amount of experience with Small Block Chevy engines. One of the best ways to increase power without having to buy a new cam is to change the rocker arms to a different ratio. This effectively increases the valve lift without affecting the duration or cam lobe center-line or "overlap". this will make the engine run much stronger and is an easy swap for the most part. I thought about our bikes and the lack of cams shafts available. I thought about getting cams reground but that requires extensive engine tear down and to get cams made up is difficult and expensive at best. Then it hit me. I am in the process of rebuilding my 350 SBC engine and i just bought some 1.6:1 ratio roller rockers. Stock ratio is 1.5:1. the change in ratio makes my .525 lift cam in to a .560 lift cam. This is a very large increase and I didn’t have to buy another expensive cam to reap the benefits the increase in ratio provides.

Picture of Yamaha 113 CID rocker arm

So, being I'm in the machining industry I thought I could change this ratio to help our bikes roar along just a little bit better. Or maybe a lot better. But first, I needed to do a little measuring and calculating. I did that this morning and have the info here to share. Very soon we will be able to jam some new rocker shafts in to the heads and along we go.






Delete SectionMove Section UpMove Section DownEdit SectionAdd New Section Below

Measurement Data and material info



Well here is the measurement data I got from the rocker arms off my eBay heads. I even did the valve curtain math (the amount of area that is open at max lift) and compared it to a small block Chevy. This was the closest fit to our bikes. I thought a BBC would be closer because of the cubic inches (113 x 4 = 452 CID) so a 454 Chevy would be dead nuts, but it wasn't. The small block with 2.02 valve was almost exactly the same and since this is a very common engine, it's the easiest to compare to, that most people can relate to. I think I have most of the info covered here. I even show the difference in valve lift from stock. The amount the lift changes is really quite small because of the 4 valve configuration. Look at how much the SBC chages compared to the 4 valve heads it is almost double. I think the 2 mm pivot point change will be the best option. It shouldn't add a huge amount of stress to the cam, lifter, push rods. The 3 mm move starts to worry me a little plus it starts to move off the "cup" cast on to the rocker arms. Not sure what kind of load increase this will give the cam lifters and push rods. Also a SBC with a .540 lift is pretty stout. Nothing to snivel at that’s for sure. This isn't a fair comparison as my Malibu has 254 deg Dur @ .050 but I made 435 Hp for a 355 CID engine. That’s 1.225 Hp per cubic inch. That would make the 113 CID have 138 hp, I'm sure my large duration has a HUGE impact on the Hp. Even getting close to 1 Hp per cube would be great and I'm sure the torque would increase as well. Very common these days to see stock Chevy LS engines with over .500 lift and a short duration 218 @ .050 and large lobe separation angle 112 - 114 to help with the idle characteristics. They seem to have great torque and horsepower and they don’t have to rev to the moon to get this. I would think we would be similar to those engines but everything is different so comparing is all hoopla until a guy actually sticks a set of these in and cracks the throttle open. 


Now for the trouble area. I knew the rocker arms were forged so they would be pretty tough to machine. A quick machinist test to check hardness is to run a file against the material in question. I did exactly that this morning. The rocker arms are HARD. At least 58 Rc hardness or harder. I couldn’t hardly make a shiny spot with the file. Bummer. Going to be very hard to machine. This would also mean the cup should be hard as well. This means heat treating or possibly hard welding. I need to check in to this. What this means is, It's going to cost more money as I will need to send the rocker arm shafts out for welding and heat treating. One caveat to this cost it that there are minimum charges and if I can get the quantity up that means it's cheaper per rocker arm. The welding would have a min charge and a per piece price. Heat treating might just be a min charge no matter what but I won't know until I get a quote. So this won't be for free but should still be less than cams and far easier to install. I have options for doing this service.

    1. I can buy the rocker arms new ($375.00 for all 4) and calc the cost of alterations, welding, heat treat, machining, shipping and any other costs plus a little for the "Save the Brain foundation" which shouldn't be to much as I'm not greedy. A lot depends on the quantity I can produce and I can't afford much at $375.00 just for 1 set of rockers.


    2. I can just charge to perform the alterations to you rocker arms. This would put the bulk of the rocker arm cost on the customer and i would only need to foot the bill for the welding and heat treat plus tooling that won't last very long machining this hardened steel. This would allow the buyer the choice of where the rocker arms come from. Right after I bought my eBay heads for $188.00 there was another set that popped up for $110.00 - could have saved $70.00. My point being you the buyer could find the rocker arms and save some money if you can find them cheap. The one draw back to this is if the tooling fails and I screw up your rocker arms somehow. This won't be easy to machine due to the hardness so the possibility of scrapping something out is always there. If they aren't ruined I could have them re-welded and start again. Sometime the carbide becomes imbedded in the base material and you can't get it out and you can't machine carbide that’s imbedded or you just ruin your new cutter at $25.00 a pop. This is something I will have to work out with you guys.


Number 2. is my choice so far.


Delete SectionMove Section UpMove Section DownEdit SectionAdd New Section Below

Valve Spring coil bind

Well, I checked the valve springs for total travel and came up with approximately .415" of spring total movement. Without using a calcuator i knew this seemed pretty close to the minimum safe distance required as they recommend max valve lift +.06 as the safe clearance amount. If we have .3554 and you add .06 thats .415 - thats exactly the minimum safe clearance and didn't sound right as this was right at the nats ass and didn't allow for any modification at all without machining. then I read this

"Coil Bind

In any spring installation, coil bind is to be avoided at all costs. If the coils stack solid or bind at or before full lift, at a minimum, the now-infinite load on the valvetrain will cause its weakest link to fail. If you're lucky, the result is merely a bent pushrod. If you're not, you're looking at a broken spring, a dropped valve, or worse.

When installed at the correct height to develop the right seat and open pressures for the application, the spring needs to have a safety margin before coil bind occurs. The simple formula used to determine whether a spring has sufficient coil bind clearance is: [valve-spring installed height on the seat - (cam lobe lift × rocker arm ratio) + valve lash - safety margin] gives you the remaining open spring length, which should be equal to or greater than the spring manufacturer's published coil bind height.

Thinking has evolved on how much safety margin is needed. About 0.060 inch used to be the textbook minimum, with more OK and even desirable. That's still an acceptable standard for everyday performance use, but Massingill says that in some cases "0.060 has become the maximum rather than the minimum." Godbold notes that "from high-speed video and testing, it is clear that adjacent coils contact as you approach the valvetrain limiting speed. Hence, modern springs are designed to run near coil bind and use the coil-to-coil interaction for improved damping at or near max lift. This interaction is one of the most effective means of dampening spring surge, but the valvespring must be properly designed in terms of solid stress to safely use this interaction." Depending on the intended use, the spring and cam-lobe design, and the engine builder's preferences, you will now see coil bind safety margins vary from as low as 0.015 inch to as high as 0.120 inch, with tighter numbers predominating on very stiff valvetrains. In a serious valvetrain, anything more than 0.150 inch can cause spring surge, which can greatly reduce the available spring load needed to close the valve.

Read more:

So now i don't know what to think. Here are some pictures of the heads. The valve spring looks to have a progressive wind to it. One that gets stronger as it is compressed more and nears coil bind. 

Picture of Yamaha 113 CID engine, valve spring.

So, once again i'm not sure. Part of me says to go for it the other thinks no. I would use just under half the safe clearance amount with the 2mm pivot move. The 1mm pivot move would not scare me as the .013 would be nothing. The .0285 lift that the 2mm move creates uses up half of that .060 safe distance. I could use a little valve spring guidance right now. Am i safe with the .0285 move?


Delete SectionMove Section UpMove Section DownEdit SectionAdd New Section Below

Welding update

Spoke to my buddy Dave. He ownes a company called Micro-Weld. He is the one that does mold repair and much more welding. He laser welds medical instruments for the company I work for. He told me all i needed to do was let him know how hard the weld needs to be and he will get it welded to the same hardness. Going back to the rocker arm ratio in my calculations. I think I will move the pivot point 1.5mm which is the equivelent of a .525 lift on 2 valve heads. Thats still a .021 increase on our 4 valve heads. This is what it would look like.


Push rod pivot moved 1.5mm ( .059”)

rocker arm shaft I.D. 0.708 18.0
valve tip centerline 1.458 37.0
push rod cup centerline 1.003 25.5
rocker arm ratio 1.45

cam lift int 0.2591 diff from stock
Valve lift int 0.3766 0.0213
valve dia int 1.41735
valve curtain area 1.6770691778
valve curtain area x 2 3.3541


This way I only use 1/3 of the safety clearance instead of half the safe distance. I would gamble that yamahe valve springs are pretty high tech. Look at all the experience they have with crotch rockets and ATV's the measly little 5000 rpm this bike turns compared to the 15,000 rpm the crotch rockets spin the valve springs are probably over kill. I've never come close to hearing the bike have valve float. I'm going with 1.5mm. I just need to drop the rockers off at Micro-Weld and get them welded up.


Delete SectionMove Section UpMove Section DownEdit SectionAdd New Section Below

Valve and head pic's

Here are some pictures of the heads, valves, rockers and some other mics stuff. The intake valves are back cut to allow for more flow. You don't typically see this on cars coming from the factory, at least not the old schoool stuff. The hot rod guys are all doing this for increased flow. It isn't much but after you add all the small horsepower increases together they start to add up.

Yamaha 113 CID Intake valve with back cut angle for improved flow on the right, Exhaust valve on the left.

 The next picture is of the intake and exhaust ports. The ports look really good for a stock valve job. Very little bowl blending would be needed. For the most part the intake port is in pretty good shape and will allow for good flow as it is from the factory. The exhaust port was a little different. It seemed rather small and tight. they again were in nice shape in the bowl area but cramped up right after the valve guide. Of course if I were to take the heads off to do the exhaust port I would surely massage the intake ports as well. The purpose of this mod is to take as little of the motor apart as possible so all of this is for informational purposes only.


Yamaha stock 113 CID intake port.

Notice how close the machining is to the cast bowl surface. It is very close and if it were just .010 over the machining would have been perfectly centered to the cast port. Very little work to make this match up, very open and non restrictive.





Delete SectionMove Section UpMove Section DownEdit SectionAdd New Section Below

Valve Spring data

I have been a little slow to update. I was able to get some more measurements so I could get a bit more solid valve spring details. I also asked a "Pro" and he kept giving me the run around. All he would say about the coil spacing was .008 to .012 clearance between the coils with .012 being the safer amount. This didn't really tell me what I needed to know about progressive wound valve springs or maybe it did. I will go out and compress a valve spring to the desired height and check between the coils for spacing.


Valve spring data

Valve spring free length 1.85
Valve spring solid length 0.845
Valve Spring Installed height 1.28
Retainer installed height 1.28
Retainer to Valve guide seal contact 0.7
Total Retainer movement 0.58
Total Retainer movement to coil bind 0.435
Stock valve lift 0.3554
Safe travel distance 0.0796
1mm alt 0.3691
Safe travel distance 0.0659
1.5mm 0.3766
Safe travel distance 0.0584


Delete SectionMove Section UpMove Section DownEdit SectionAdd New Section Below

Final Rocker Arm pivot dimensions and status.

I'll target the 2mm move amount. this only adds .0285 extra valve lift and the valve springs are designed to handle this type of performance. With the final lift at .3839 and the toal travel of .435 this still provides .050 safe distance. Again look at a feeler guage with .0285 and it isn't much. But the extra flow from these 4 valve heads will really help the breathing.

The rocker arms are being welded up now or very soon. Dave at Micro-weld is a great guy and is whipping these up to my hardness level which I determined with Daves help. I still need to machine these and they are going to be pretty hard. We went with 410 stainless steel. The stock rocker arm shafts check between 56 - 58 Rc hardness which is pretty darn hard. the 410 SST will be in the 48 - 52 Rc range which will be easier to machine and should still be hard enough hold up. Being as these are the prototypes I will just have to see how they hold up. Now I have a different delema. The stock exhaust is already limiting my power output. The stock head pipes are already stealing 6 - 8 hp, increasing the lift will require more free flowing exhaust to handle the extra air I will need to pump through the engine. I have been looking into some 2:1 pipes but not sure what are the best pipes to get. So the final valve lift is going to equal a SBC with 2.02 valves having a .538 valve lift. that is a very substantial increase in flow as the stock 113 valve lift was equal to a .498 lift SBC cam. thats a .040 increase (SBC equivilent).

Delete SectionMove Section UpMove Section DownEdit SectionAdd New Section Below

Rocker arms are back from welding

Finally the rocker arms are back in my possesion. Took a while for Dave to get to them but I can't complain as he did it for free and did a great job of welding these up. Since I didn't have a way to check any locating surfaces after welding I asked Dave if he could leave some of the original "land" around the push rod cup area so I could use this to indicate the surface flat and level. This will allow me to mill the pocket to the correct depth so I hopefully wont need adjustable pushrods.

Dave did a great job of leaving me that small ring around the outer edge.Nice welds too, no pits or voids that I can see so far. I am now working on a fixture to hold these while I am machining them. Once the fixture is in place I will be able to machine these with ease, depending on how hard the welds are. Some of the heat treat has come out of the rocker arms. They are softer after welding which I pretty much expected would happen. I don't think it will be an issue. The hard surfaces need to be the contact points that touch the valve tips and not so much the push rod cups. This is a prototype venture for sure and this is what you go thru when doing these kinds of experiments. Will they hold up? We shall see. I also now have new exhaust on the bike. V&H 2 into 1 Pro Pipe Chrome with the standard baffle. They sound very different from the stock head pipes with the Roadhouse slip-on muffler. I wanted to get everything in place before I added the rocker arms to the mix. I am still using the stock ECU at this point. It has been slow to learn the pipes requirements but it seems to be getting better. I should disconnect the battery and let it start to learn from scratch. So far the spark plugs look O.K. but I cal tell I have lost torque in the 2500 - 3500 RPM range and it is annoying me to the max. It was very strong at this RPM range before the exhaust change. I had huge grunt and now it is flat. I will try to put the power commander on again and see if I can richen up the rear cylinder which was dead lean before and the reason I took it off. I really want everything tweaked in before the BRA mod is added to the mix. That way I will be able to tell what the difference is.


Delete SectionMove Section UpMove Section DownEdit SectionAdd New Section Below

The fixture

Well things are progressing nicely. I have the fixture for holding the rocker arms nearly completed. The fixture will hold both rocker arms and will give great repeatability for machining the push rod cup. I still need to make the stop that locates the rocker arm valve tip that will set the cup so it is level, this will be adjustable so everything can be dialed in to perfection.

Rocker arm fixture

Rocker arm in fixture

The fixture locates off the rocker arm shaft so centerline can be controlled. the valve tip stop will go over the rocker valve tips and have adjustment so the cup side can be rotated until level. I just need to make the stop and the clamps to hold it all down.

Getting very close to finishing this up.



Delete SectionMove Section UpMove Section DownEdit SectionAdd New Section Below

Fixture complete and machining has begun

Finally an update. Winter is upon me and it is hard to keep up. My days are not easy. Work at my real job 5:00 am - 3:30 pm, come home and cut wood and split wood for the days heating needs for my home. Then go out to the cold unheated shop and crank on manual mill handles that are 40 deg - cold steel with my bare hands. Gets to be the makings for a long day. Enough of my whining. I spent a lot of time making this fixture (in the cold) but It is going to work really well.

Picture of fixture for machining rocker arms.

I finished the fixture up on 11/19 so not to long ago. I started to machine one of the rocker arms as you can see the shiny surface on the cup arm. It was going really well. The material was not to hard to machine, My carbide end mill made quick work of milling the weld flat and establishing the main surface that the cup will be measured from. All i had to do was put the 9mm carbide ball nose end mill in the collet chuck and plunge mill the cup .220 deep.

Picture of the evil 9mm ball nose end mill and 1/2" dia carbide square ended end mill.

Piece of cake. Then I realized this was a 9mm solid carbide end mill and the shank was 9mm as well. I don't have a stupid metric collet to hold the end mill. So once again the project hits the skids. So far i have about 15 hours in to the fixture, $85.00 in to the tooling and now another $21.00 for a collet. It will be here around Thanksgiving or a little after. Now I think you can see why this is going so slow. One cool thing though. I realized that I can make the ratio whatever you would like it to be. the fixture locates the rocker arms really well and i can move anywhere you would want the cup to be positioned. If you supply the rocker arms i think i can do this for very little money. Probably 2 hour of machining at $50.00 per hour is $100.00, tooling will work it's way into the picture. They don't just give solid carbide end mills away. I would like to propose that I charge $100.00 for the first 10 sets of rocker arms. This will help me get a benchmark on tooling so I can make a more accurate estimate on machining charges. I can make these to your specs. Since I am only performing the machining function I am not responsible for what happens to your engine. In other words, pretty much the same thing as buying aftermarket hot rod parts for my small block Chevy. I can buy what i want but the warranties don't cover much more than a new replacement part. Since you get to pick the A/R ratio I am off the hook. I would suggest 2mm or less. I have the software so you can pick your ratio based on the valve curtain area. My excel file also lets me change the engine of comparison so you can picture the increase against what you know. Ford, Chevy, Mopar, Volvo, Lambo, I think you get the idea. So, First i need to get my set finished. Blow up my Stratoliner and then buy a new Deluxe. Make a tamer set of Rockers and then enjoy the benefits. LOL, I'm not going to blow up my Strat.She means to much to me. So as soon as the collet arrives i can finish this up. Slowly install in to my bike over the winter, after i cut and chop wood, after i get home from work, out in the cold.

One thing. I need a PCIII USB map for a Stratoliner with BAM + K&N & V&H Pro-pipe. I'm using a Barons BAK and V&H Pro-pipe now. It is close but not quite right. I couldn't beat my brother and i usually walk away from everyone going thru the gears. If you have a map please use the contact link on this website. If you really want to mess with other bike riders minds do this. Challenge them to get in 5th gear, slow to 2000 rpm, then race right from there. I did this to my brother. It was ugly. I was 2 blocks ahead and i could;d see the despair in this eyes as i pulled away.

Delete SectionMove Section UpMove Section DownEdit SectionAdd New Section Below

Revised valve lift calculations

Well, I finaly got one of the rocker arms out of my Stratoliner so i could measure it in detail. I had welded up the rocker arms that are going to be modified before i got everything measured. Now that I have the dimensions checked and verified to within .001" I re-did the excel sheet i had made to do the calculations. The results are that the cam lift is far tamer than the previous data sheet. The comparison to a V8 with 2.02" dia valves has the stock 113 cid at around .453 lift, not .498 as I previously rough measured with my dial caliper. Now I have mearsured this on our optical measing machine at work. our OGP Smartscope came up with this data and it gives me more hope for a better power increase. Right now the valve lift isn't even a factor as far as making contact or mashing the valves. there is a boat load of room. I am very tempted to go 2.5mm on the push rod cup.



Delete SectionMove Section UpMove Section DownEdit SectionAdd New Section Below

The "BRA" mod is completed.

Well, it is finally done. I finished machining and installed the BRA mod today. Here is a picture of the completely finish machined rocker arms

Picture of completed rocker arm cup for Yamaha 113 CID engine.

They turned out fantastic. I even went as far as to buy the same size balls as what is on the end of the push rods. I could then measure exaclty where the push rod should sit in the stock cup. I then set the remachined cup to the same dimension and the preload on the lifter is exactly the same. No need for adjustable push rods. I saved even more money. The installation is a little techinical as you need to be able to envision where the piston is in the valve cycle. I had to rotate the motor so the piston would be down and all the lift off the rocker being pulled. Not that hard for me but an inexperienced guy would struggle I think. The tricky part was trying to get the rocker arms rotated so I could get the push rod out of the cup to relieve all the valve spring pressure. I had to use a little brain power and came up with a simple method. I wrapped heaver wire around the push rod cup arm and pried it open with a screw driver. It actually worked like a charm and we were able to pop the push rods right out. Then it was just a matter of pushing the rocker shafts out, switch the rocker arm, and install the shaft again. I filled the rocker arm cups with moly break-in grease and filled the rocker arms with oil from my squirt can. 

 in my frame. One I just had to drill this hole. This allowed the rocker arm shaft clamp bolt to be raised high enough so the rocker shaft would slide out. Both the intake rocker arm bolts hit the frame. The exhaust rocker bolts came out without a problem.

Here is the other hole. It is much larger. The rocker arm shaft retaining bolt is a flange head and the whole flange had to fit in this one. 

Other than having to drill holes in the frame, the rocker arm change out went really smooth. I did get help from my brother. At times you just need a helping hand or a third arm. I would not have been able to do this alone. I still have not ran the engine but I have turned it over with the new rocker arms in place and everything looks great so far. I want to get this all back together so I can fire it up. I still need to put the rocker boxes and everything else back on.

This is the forward cylinder, The left bolt is the one that hit the frame which is the intake rocker arm. Notice the push rod is out of the rocker arm cup on the right hand rocker arm. This is the modified rocker arm back in place. It just needs the rocker arm shaft rotated so the push rod can be popped back in. No cam timing or anything to worry about. I can hardly wait to fire it up. The valve lift increase should be substantial and so the performance increase should be substantial as well. 



Delete SectionMove Section UpMove Section DownEdit SectionAdd New Section Below

Dyno tune is being scheduled.

I just spoke to Nick from "Those Dyno Guys" in Zimmerman Minnesota. He has dyno time availible and the best part is he is very close to my location. Nick said no problem and that he could fit me in any time. Sounds like a nice guy to work with. I still need to get the bike put back together before that can happen. Looks like I'll need to get out there and put this back together this week. 

Delete SectionMove Section UpMove Section DownEdit SectionAdd New Section Below

The Initial start up with the BRA mod installed.

Everything went really well when i started the bike up with the BRA mod installed. 2 minor glitches fixed on the spot. Spark plug wire was off and the throttle cable were hanging up a little. Other than that the bike ran great and worked as it should. I sounded more snappy to me and like it was "bigger" "meaner" 'more hungry' i think i have myself one bad to the bone Stratoliner on my hands. I called Nick at the "Those Dyno Guys" shop and told him I was running behind because of the weather. Nick said no problem. Any time I am ready just bring it over. It has been snowing a lot and the roads are very dirty with de-icer chemicals. Need to find an enclosed trailer I can use. Sounds like it is going to dip below zero on the temps again as well.



Delete SectionMove Section UpMove Section DownEdit SectionAdd New Section Below

Dyno Magic and Pandoras box

Dyno Magic

Well I got the bike dyno tuned. And it looks like it is running really nice now. This is the dyno set up at "Those Dyno Guys" shop. No trailer dyno here. These guys are set up right. Not only do they have exhaust suction, they have an in-coming fresh air supply so they don't draw a vacuum when the doors are closed.

Picture of my 2007 Stratoliner S on "Those Dyno Guys" Dynamometer 1/24/2014

The map I had installed was way off in certain areas of the map. This made it so they couldn't do a preliminary power run as the A/F ratio was hitting 17:1 and sometimes pegged the dyno software out at 18:1 A/F on the rear cylinder. The front cylinder ran lean at times but not as sever as the rear cylinder. I learned quite a bit about dynamometers's last Friday. I remember reading on one of the forums, a reply about the dyno sheets being posted by people and the comment he made was that all the dyno sheets were basiclly "Dyno Magic" and the numbers don't mean anything. I thought he was off track and that most dyno sheets were probably pretty close. Boy was I wrong. The dyno sheets floating around really are "dyno magic" as there are so many factors that can be tweaked or not tweaked which can result in very different hp/tq numbers. In fact the dyno operator printed me out 2 different dyno sheets right there that were 2 hp 3 tq different and all he had to do was change from SAE to STD for the correction factor. He also said the baffle in my V&H Pro-pipe could cost me between 3 - 12 hp. I totally believe this because I noticed a big drop in power compared to my stock head pipe and the Roadhouse slip-on muffler which is a through hole with no baffle in the way. So there I am poking holes in the brand new baffle at these guy's shop so we can;

1. Get the sniffers for the dyno thru the stupid baffle plate


2. Make it breath better as I am paying for a dyno tune and if I remove the baffle plate later the tune (could possibly) be junk.

So my bother and I poked 7 or 8, 3/8" dia holes thru the plate, thanks to the guys at the shop for making a long rod with a point so I could puncture the baffle plate,  and put the muffler portion back on the bike. I plan on cutting the whole plate out with a hole saw later and hope the tune isn't ruined. For this dyno tune I was stuck with the holy baffle plate. So when the tune was over and they were ready to tell me what I got, they asked me what I thought I would get. I told them I was hoping to see 100Hp & 130+ torque. I told them of my previuos dyno pulls and they kind of giggled. They then handed me the dyno sheet and I made 88 Hp & 108 Tq. The dyno sheet made me feel good yet disturbed me though, the one reason being, that it didnt show hero dyno power numbers. Here it is;


So looking at this I was happy to see the nice long torque curve. But the power numbers are way different from my freebie dyno run. These numbers are less than the pull I did this spring. In fact they are much lower. So now I'm sitting there kind of jaded, feeling like "how can I post these numbers on my website. They suck.' 


Then the dyno operator started to speak about the dyno run as he could see I was going to start (crying) asking a lot of questions. He told me about the training he had to go thru when he bought the dynamometer from Dynajet. He is fully trained and this dyno is not a trailer dyno. In fact it is the newest version of their dynamometers. it's mounted in the floor of the shop and the room is set up so the atmospheric pressure remains constant. he mentioned how some shop dynos have suction for the exhaust gasses but no in-coming ventilation and that can lower the air (atmopheric) pressure so the motor will lose power. I told him that the dyno pull from this spring had the correction factor as STD and I was hoping for bigger numbers. He laughed and said ' you want bigger numbers, I can give you bigger numbers at which point he changed the correction factor to STD and like magic it gained 2-3 hp and 3 tq.


He said he could tickle the elevation so that it would really give me big numbers but that wouldn't be the actual numbers now would they. He also mentioned how trailers dynos are probably less than reliable, and that if the dyno is an older model they require calibration and that if the dyno came on a trailer from a higher elevation and they don't do what is needed to correct for it then you get hero dyno sheets that don't mean a thing. Just like the one I got last spring showing 90 hp & 121 tq.

This is one I got at Sturgis, this one was with Roadhouse muffler and thin prototype BAM installed and stock ECU. At least it showed the A/F ratio and the correction factor is SAE. The problem is I don't know if the dyno is calibrated, these guys are close to my location in Minnesota.

The one thing I do like is the torque curve now. Looking at the sheet above my bike is losing torque after 3200 RPM really falling off after 4500 RPM. Now the torque is there from 2500 all the way to 4500, in fact 100 FT/LBS for a full 2000 RPM

Pandora's Box

So now I opened up a whole can of worms with little or no answers other than I have a really good running bike with a baffle that could be costing me 3 - 12 Hp, No actual BRA mod power numbers, no anything. Lucky for me Nick from 'Those Dyno Guys' sent me a text and thanked me for giving them a little plug on my website. Nick then offered to recheck and re-tune my bike if needed after I cut the baffle cap out. He also offered to run the bike with the original stock exhaust on it so I could see if the V&H Propipe is costing me power. Now I don't know about you guys but when someone offers you something like this it really shows you the merit and customer support behind these guys. I HIGHLY RECOMMEND THEM FOR YOUR NEXT DYNO TUNE. They can also dyno snowmobiles and ATV's.

This might not be a chance for me to get BRA mod numbers but it is my chance to get BAM power numbers! To take the BRA mod out and install the stock rockers is just too much work.

So now I will need to wait for warmer weather. I got lucky on the day I took it to 'Those Dyno Guys' and had it tuned. It got up to 34 deg that day and I could start the bike with 20-50 oil in it. Right now the weather sucks, going in to feb they are forecasting single digit highs and below zero every night. In 2 to 5 months winter will be over and I will take Those dyno guys up on their offer.




Delete SectionMove Section UpMove Section DownEdit Section