Being able to hit full power would rule out fuel pressure as a possible as well as plugs, coils and so on. Those faults would show up under high load and high rpms. Not the case here. It does sound like it's lean. Have you done any mods prior to the ill running? Any chance you have a leak at one of the throttle body sockets. At idle the IAC could counter this leak and at full throttle the leak has little effect. Just off idle to 3/4 throttle the leak would have the most effect on running. Do you have any combustion error codes currently?
Ron

 

Hey Ron,

Thanks for the reply. No mods on the bike other than rear brake light. No codes last time I checked but I’ll check again. Only other thing I could think of was an air leak somewhere. What you describe with the throttle body sockets sounds exactly like what it’s doing.
Cory

 

If I remember correctly early V's had issues with IAC pintle moving. I know I had to replace mine on my 06R. It would start and idle but sounded like it was laboring until RPM's got above 3000, then it ran great. IAC is supposedly adding air up until approx 3K rpm.

 

Thanks for the reply. I did replace the IAC and it didn’t change the problem. At this point I think I’ve changed everything that can be changed. I will look into that in case I did something wrong.

 

Have you tested the map sensor? Usually throws a code but it's duty is both timing and fuel. Only other one left is the IAT but doubt it would cause a problem. My best guess is still an intake leak. This can be from either tb socket or a missing rubber vacuum plug on the rear tb.
Ron

 

if you do suspect a leak, can you spray some starter fluid toward the suspected location and see if it increases revs? And if not starter fluid, how about wd40 or anything combustible but not corrosive?

I wouldn’t rule out fuel delivery. I understand it runs well at full throttle after it gets up there. How about electric like boots or harness to the coils?

 

It’s going in the shop today to check for leaks. I really appreciate all the responses.

 

If possible, data log the map sensor. Should be about 97-99 depending on day baro and location, key on and engine not running. Should be about 25-28 give or take a couple at idle. An intake leak on the front tb will effect map reading when running.
Ron

 

Also remember these bikes are lean from the factory and always need more fuel in the low mid to upper mid range area - any restriction in the fuel injectors from old fuel results in an even more lean condition - mix in some Sea Foam into the fuel, and consider a fuel manager to adjust fuel mixture - luckily my bike came with one and all I had to do was adjust it but it absolutely ran like shit - like I was dropping a spark plug above 6000 Rpm until I leaned it out - after that the flat spot in the mid range was tuned out with enrichment - there may be nothing wrong with the hardware on your engine, it could be all old fuel and improper mixture related - just a suggestion based on my experience - best of luck with it !

 

Hi, replace the IAT, speed sensor, MAP sensor,water temp sensor, as they are really cheap and you never know, had similar issues and the speed sensor change eliminated it, although the bike RPM was crap even when stationary.