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
(http://i43.photobucket.com/albums/e375/cbartlett419/DynojetSheet.jpg)
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?
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!!!
Does that say 19 bhp ???
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?
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?
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.
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.
it'll do 80 [thumbsup] 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
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.
Quote from: Artful on October 06, 2011, 01:02:38 PM
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.
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.
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
^ that. you would KNOW if a750cc twin was making 20hp. it wouldnt go ANYWHERE, not in a hurry atleast.
20 HP might be correct if one spark plug was unhooked.
Quote from: Speeddog on October 06, 2011, 03:18:10 PM
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?
this is what's so boggling about the whole thing, The bike runs fine, it falls off higher in the rpms but doesn't hit a wall as if something catastrophic has occurred. Look at the power curve, nice and linear it rides like that. What bothers me is him saying he added enormous amount of fuel and the air/fuel curve still climbing out of range. Has anyone here operated a dynojet machine?
I'd say operator error or dyno malfunction.
I've ridden a Ninja 250, and IIRC my comment upon return was 'painfully slow'.
Those are ~25HP.
Well, for starters, you did some serious dinking with the exhaust, which is usually the source of gains but you could also go backward too if the flow isn't done correctly. Pods, when not properly set up don't get instant gains either. Last, while I'm not an expert on smaller Monsters' heads, you put 620s on a 750?? Is that working backwards, or is that reasonable to do? I'm just asking.
I agree the numbers read low. But your curves are also erratic. The F/A should at least progressive, and yours is jumping around a lot. That engine needs to be baselined, run on a consistent dyno with any changes you make. A single peak number will not a great engine make.
620 heads flow better than 750 heads.
Hard to read the date and time stamps on the two dyno runs but it looks like they were on different days? Is it possible he got some other bike's dyno runs confused with yours? Not likely, but something sure isn't right.
My main concern is that the lean condition that damaged your original heads may still be there. If the dyno run printout is correct, it sure is still there. I don't think you mentioned what the exact problem was with the original heads?
Bob
Something doesn't look right, what type of method did the tech use to read the A/F? was it a "Sniffer probe" or a screw in type sensor? My money is on what others have said- the dyno may be out of Cal. I'd find another shop and have it re-done just to be sure.
A Honda rebel makes 18 HP and weighs 320 lbs top speed claimed 80 but it's really between 65-71 at least for me.
The monster easily weighs 100 more so if it was making 19 HP top speed would be 50-59 ish.
Was there any wheel slip? I would have them do back to back runs between the monster and one of their bikes.
Quote from: cbartlett419 on October 06, 2011, 05:32:32 PM
The bike runs fine, it falls off higher in the rpms but doesn't hit a wall as if something catastrophic has occurred.
BTW, exactly this is what I experienced with a 2 into 1 with my 900 track pregnant dog...so I changed out to a regular high mount exhaust once I realized I was shortchanging myself in that regard...hence why I said what I said in my 1st post on this thread...but yeah, either the machine operator is not able to do his job properly, or their machine is way out wack in terms of calibrationwhich is why I said to contact Dynojet for other authorized places...
Good enough. Dynojet's website steers me to a shop an hour away, I'll drag it over there whenever I put the fires out in my world
BTW the valve guides went bad in the stock heads, lost power from the top down until it got to the point that at 4K rpm it was chugging out. I was making a 6 hour ride every other weekend for a couple months, it didn't take long.
Thanks for everyone's input, I'll let you know what the next guy says. [thumbsup]
there is no calibration for a dynojet in acceleration mode, it is what it is. i don't see what being a harley shop has to do with it either. dynojets are pretty fool proof. don't understand the 19hp tho. it would have to be very sick to make 19hp. if it had that little comp i don't think it'd start. it's not some sort of partial load run maybe to get a number like that? never played with a dynojet 250i with a brake enough to know if you can do that.
i don't see why the mods you've made would destroy both heads either. has it got fuel pressure, had the filter replaced recently, got dirty injectors, etc? a good 750 should do pretty close to 200km/h (120mph) i'd think.
*noted you sound smarter than the average bear concerning the dynojet machine, would the air/fuel curve trouble you?? I can't remember when the fuel filter was changed, I'll put that on the list of things to do.