Dyno run finds fatigued engine??

[cbartlett419]

So I need some thoughts. I have an 2002 M750 that I've put pod filters and a custom 2into1 exhaust (baffled and packed with muffler packing). I also installed a PC3 after doing all of that. I never had it properly mapped and subsequently destroyed the stock cylinder heads. I parked it for 12 months with 21000 miles. I bought a set of 2004 620 cylinder heads with 8000 miles logged and put those on the bike, I checked the cylinders and they are in tolerance, I set the rockers to tolerance. I've put 300 miles on the engine since the heads went on. I took the bike to a local Harley shop to have them map the PC3 as they are the only shop with a dyno in my area.

Here is what they came up with



The mechanic seemed to think there was enormous intake leak and that the bottom half of the motor is loose (cylinders, rod bearings). It's also idling up to 2K rpm sporadically which wasn't an issue before the dyno run. What do you guys think?

[zooom]

I think the 2 into 1 exhaust robs you of top end power, though is good for down low honkin torque...

that and maybe you need to tear into the motor and go whole hog!!!

[stopintime]

Does that say 19 bhp 

[cbartlett419]

sure does. and this is my concern, is this dude correct? is my motor sloppy and therefore super weak?  He said it's acting like it has intake leaks (ugh) I'm a decent wrench but this is boggling me. Aside from the high idle it's running great

Look at the curve on the air/fuel mixture, it climbs and climbs until it's out of range. He said he added 100 parts fuel in some spots and it's still lean at the top. Does anyone have FHE with a Dynojet?

[stopintime]

You should be able to tell if it's really only developing 19 bhp.

I wouldn't trust, or like, those numbers.

Maybe he's right about the issues though - can you get a second opinion from a Ducati shop?

[battlecry]

At 19hp, your bike should have similar HP/Weight as my Vespa.   If you can ride past 80mph, I'd think the dyno was not calibrated right and they owe you another run. 

[cbartlett419]

Nearest one is 6 hours away, I'm hoping someone can confirm or discredit here. I'd like to avoid making that trip only to have the next guy confirm this guy's prognosis, that would be bad for moral.

[cbartlett419]

it'll do 80  it's never done much past that as I've got 15/46 gearing. Like I said it's running great aside from the occasional super high idle, then again I can't really recall what it was running like in 2008 before I hacked up the exhaust and airbox

[Artful]

You took a Ducati to a Harley shop. Put out your knuckles, they need a good rapping.

That dyno is wrong. I couldn't imagine a 750 making 19whp that didn't include oil spraying out of every crevice and hacking like a pup seal with kennel cough.

[cbartlett419]

You took a Ducati to a Harley shop. Put out your knuckles, they need a good rapping.

I know man, It's what was most convenient.

[zooom]

I would contact Dynojet and ask them to locate the nearest authorized service place for them, and go from there to wherever they send you.

[Langanobob]

Something just does not compute here.   You say it's running great but the dyno says 18 or 19HP?  What does your butt dyno tell you about the acceleration?  My Yamaha XT225 trail bike makes about that same HP and can barely top 65mph.   If the dyno was correct and you're only making 19 HP, you would know.

But hard to imagine the dyno being that far off, even if it's at a Harley shop.

But something caused your original failed head.  What happened to it, burned valves or something indicating a too lean mixture?

Have you double checked for intake leaks?  

That's all I can come up with.  Hard to imagine an intake leak big enough to cause a 40 HP or so loss in power while still leaving the bike, as you say, running great.

Bob

[He Man]

^ that. you would KNOW if a750cc twin was making 20hp. it wouldnt go ANYWHERE, not in a hurry atleast.

[Speeddog]

20 HP might be correct if one spark plug was unhooked.

[He Man]

20 HP might be correct if one spark plug was unhooked.

last time i rode around with a whole cylinder not firing, it was vibrating like hell. not to mention, i think the cylinder would flood with unburnt fuel no?