Bonneville America Forums Forums Technical Forums Performance Mods dynoed my bike

well i got it dynoed today and to say the least i am VERY disappointed. i gained 10 hp all the way through the rpm range then it fell on its face in the high end. i only gained 4 peak hp. dont get me wrong the bike feels great and pulls good but i can feel it lay down at 6500-7k. only thing i can think of is i need freer flowing pipes. or i just have to deal with it haha. i would post the sheet but its in adobe and i cant figure out how to change it. but i thought i would post the results

Frank

Hey Frank,
What were the numbers????

I was wondering what the numbers were as well. On the bright side you gained 10HP where you probably use it most.

peak of 64 and 53Ibs. i got huge gains in the mid then it falls off. i know the dyno i used it a bit on the conservative side but i was still looking for bigger numbers

Frank

Man I am suprised at those numbers.

your telling me. but i must say it runs very strong. i thought i would have MINIMUM 75 at the wheels.

Frank

The fact that you've got 10 hp gains all the way up has to be a good thing considering that's where the needle spends most of its time anyway. That in itself is all good. I'd assume, as you do, that there's more life at the top and probably has to do with fuel and or air flow - either in or out. I'm sure you'll sort it out. Keep at it.

You could try replacing the exhaust cam with an intake cam.
Fastdude, one of our Swedish members, has done it on his bike, he said 76hp.

But that was on a 360 with a ported head and new carbs, iirc.

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You could try replacing the exhaust cam with an intake cam.
Fastdude, one of our Swedish members, has done it on his bike, he said 76hp.

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Frank, you gotta budget for those Supertraps now and let that sucka breathe! What was the A/F ratio above 5K?

all i needed to do was lean the needle one notch, above 5k it settled to a tic over 13. i dont know if i want those supertrapps because they are so short i dont know if they will look good. i was thinking of scepters as they seem to be very free flowing and stainless. i would be lieing if i said i was not disappointed but the bike does run pretty hard.

Frank

I wouldn't want to spend all that money on exhaust and then not like what my bike looks like either.Really too bad I feel for ya I would be disappointed too with all the work you have done.

sorry to hear that Frank. I was recently doing the numbers, figuring out what performance mods I wanted to do to my bike, how much would it cost, what would I get out of it, would it be worth it, stuff like that. After going through everything I decided that the amount of money I wanted to spend on performance mods would be much better spent on a hefty down payment on a speed triple or something. Then I'd have my speedy for when my girlfriend and I want to take a leisurely ride through some twisty back roads and for commuting and stuff, and a 130hp monster of a bike for when I want to hit the track or just give the authorities the ol' GFY and haul out on the slab...

Frank, when mine is done I will post numbers and see if the Scepters will be worth it for you (even with my stock carbs), should be soon now!

would i do it all over again? you bet. it really is a whole new bike. i do know every dyno is different and a real test would be a side by side run with another 904 bike. i am not going to lose any sleep over it as it really does run good and strong. just wanted to see some bigger numbers to give more justification to the time/money and have some bragging rights. but no biggie

Frank

Hello,
One thought regarding the sort of lower than expected HP figures on the high end - could it be that the clutch starts to slip? Revs goes up - power goes down?
regards
Hasse

I don't know Frank, I think a better test would be a side by side run against a fairly stock bike. That way you'd get a better assessment of how ALL the work you did improved your bike.

My bike is a Bonneville 904 cc with slightly ported head, exhaust cam swapped for an intake cam and Weber 45/Dellorto 45 carb (I still haven't decided which one is the best).
The ignition has also been tweaked by Jojje with different curve according to my specification and RPM limit raised to 9000.
After having the bike broken in (the 76 RWHP run was done directly after the BB kit had been installed) and also with the dual Dellorto fitted again instead of the Weber I think I should be close to 80 RWHP.
I will try to have it dynoed again later this year.
I don't think the cam swap gave much of a difference to the stock exhaust cam though.

My dyno runs are here if anyone is interested.

790 with Dellorto and tweaked ignition.
http://www.algonet.se/~uran/images/790_dellorto_dynorun_res.jpg

904 with Weber tweaked ignition and ported head.
http://www.algonet.se/~uran/images/904_weber_dynorun_res.jpg

Did they track the mixture? And, while most dyno shops don't do it, it would be a good thing to track the vacuum as well. If the vacuum starts dropping off earlier than 600 - 800 RPM before the power peaks, a bit of polishing and porting, more open exhaust or bigger valves may be needed.
If the mixture starts leaning out near the topend, more fuel flow is needed.

def no clutch slippage, already have larger valves and port/polish. i have no idea

Frank

Haven't folks had a hard time dialing in those carbs before? I would start there, seems simplest. If Pat would chime in, I bet he would vote keep the Tbike pipes, but who knows... Maybe you can swap pipes with someone and run just to compare?

carbs are actually very easy to dial in, and since the work i get zero bogging at wot and it runs like a top. i may try out a pair of scepters a generous member on here may loan them out to me. we'll see what happens

Frank

Exhaust may be an issue I think. I'd try anoher dyno run with some cheap aftermarket silencers with free flow. You won't get optimal performance but they'll point you in the direction telling you if exhaust "blockage" is the problem.

i may bring it to another dyno as i know operator can make a big difference. plus i am not sure how accurate his sniffer is because tony has his bike done there, he said it was lean in the mid, we richened it up and it actually ran better leaner. we will see

Frank

An engine will run better a little lean but it isn't good for it.

If we were to extrapolate the results to automotive engines,
many have paid much, much more for a 10 HP gain

That's roughly a 16% increase.

In the sense of scale, on a 300 HP engine, that would equate to around 48 extra HP

Not bad at all for a one or two phase (polish & port?) engine campaign

If you want extreme, I believe cams and a turbo would be indicated
( see also - what I'd do when I win Powerball - the sleeper Trumpet!)