Lack Of Power, Poor Throttle Response...

Havent been on in awhile, but an issue has gradually been getting a bit worse, and now that Ive figured out that it's not actually my imagination, i wanted to check in....

'02 non abs, 54k miles. Gradually over the last year and especially the past few months, I thought I had been intermittently noticing the throttle response dropping off a bit, and generally just having a bit of a lack of power. The engine is still running smooth....it isnt a misfire or rough running kind of thing. But, i compare it more to as if you were riding into a strong wind constantly, or riding up a steep long grade. I have noticed at times too that the characteristic 4500rpm flat spot seems worse or more noticable than it ever has, on certain days.

The way it runs before it warms up seems a bit off too. The bike has never run all that great upon first cold startup, but last night I noticed the obvious constant hesitation all the way up until it was at normal operating temp. And even then, it seemed like it was a bit down on power. In general, warm and especially cold, it just seems to require more throttle when riding. It is noticable.

Some other info. New OEM plugs as of this year, as well as new OEM air filter put in about 3k miles ago. Starter valves were adjusted last season. No "FI" light that I have seen, although i have not checked for codes yet. Valves have NOT been checked or adjusted yet at all....but I dont feel that would necessarily cause this type of issue. As well, fuel filter was replaced about 10k miles ago, when I replaced the fuel tank due to an accident. Battery replaced last season, and charging system is at 14.0 volts while riding. As well, everything is all stock....no power commander, bike is still running stock exhaust, etc. 87 octane fuel is what I typically use.

So...any thoughts or general ideas would be appreciated, as I think the issue is slowly getting worse.

TIA

If you have an intake valve that is staying open, it might cause some of those issues...right? I would check the valves...not the easiest thing but you are well overdue. Of course a leakdown test should determine if you have a valve staying somewhat open, but might not be any easier than testing the valves.

[image: View Post]Adam30, on Sep 2 2009, 06:21 PM, said:

Valves have NOT been checked or adjusted yet at all....but I dont feel that would necessarily cause this type of issue.

The valves actually could cause this. I normally wouldn't think they would, but I have no idea what else it could be. Perhaps you could test the compression first, it'd be easier than pulling all the heads. ???

I guess it would be a good idea. I havent started looking at it at all yet....but doing a compression test would be a good idea. I would think though, if I had a valve or more hanging open a bit, that id maybe be getting more of a rough type of running issue...or an intermittent misfire. But either way, ill be checking compression soon, just so i know where its at...

No great input for you other than; "Think Simple, First". Before you start thinking major engine problems there are a host of minor systems that could be in play. You might want to start with a visit to a good mechanic. Also, are you really sure power is down? Get a dyno done to be sure before you start rip'n into things.

Good luck

Thanks for the replies so far. Yes, Im about 90% sure things arent quite right. It maybe wouldnt be totally obvious to someone who doesnt know the bike as well, but its been a gradual thing that Ive been noticing for most of this season. But, I think checking compression may be the first thing (it wouldnt be a bad idea to check it anyways), and then move on from there.

I would suggest checking Fuel pump pressure.

The slow degradation of power would indicate something like a clogging fuel filter or low/decreasing pump pressure increasingly robbing engine power IMO.
I doubt compression would be an issue on these engines. :blush:

Check this thread - it might help somewhat.