Yamaha TRX850 Enthusiasts Forum

G'day all, just became a member of the site today. I have a 99 blue trx, K&N airfilter, Megacycle mufflers. Had it since almost new. Love it.
The problem I was hoping someone could help with is some rough running. When riding along in 4th or 5th gear just off idle it hunts, or runs really bad. If you give it some it goes away. Also if you back off the throttle, say into a corner, then get back on the throttle it has a moment of no power, like a miss then gets going. It does not do this consistently, sometimes it is good then others it is bad. Hopefully someone can help me.
Cheers
Draff

Welcome Draff.
How many k's?.Could be emulsion tubes, may just be bad fuel.Have you modded the air box? Kinks in the vacuum lines maybe.One of the other more cleverer guys will certainly be able to help.
Terry

It has 25000kays on the clock. The airbox is standard but I will check the others things you say.
Thanks

alecdraffin wrote:When riding along in 4th or 5th gear just off idle it hunts, or runs really bad. Draff

I wouldn't let mine go below 2000rpm in 4th or 5th (well actually 3000rpm), would act like a typical big twin and pig root @ 2000. Hesitation on opening throttle (depending on the rev's) may be fueling. check the carb balance to satrt with. at 25000k's the emulsion tubes should still be ok, but if your getting less than 250k's per tank, check the emulsion tubes.

Sorry, I didn't mean just off idle. I meant when it is just off no throttle. So in 4th at 80kph or in 5th at 100kph. Pretty much at legal cruising speeds.
Cheers
Draff

Oh, OK then. Again if you are using excessive fuel, it could be the emulsion tube wear, if it returns slowly after a quick blip of the throttle, the carbs may need balancing. You shouldn't need to rejet just with a K&N and slip-ons as the TRX normally is slight rich at idle and on the main and slightly lean on the needle, but not that it makes much difference.
Check also that all fittings on either side of the carbs are tight (not leaking).
Just out of left field, how's the chain condition and tension? Poor chain condition and/or tension can cause a "hunting" feeling on light throttle.

They are naturally sensitive at steady state at certain speeds, i found mine particularly so at about 3000 rpm at constant speed any slight opening and closing of the throttle is exagerated. I find it better to run a gear higher and lower the engine speed to about 2500 and its less sesitive.
I thought at first there was something wrong. The above is particularly noticable in our 30mph areas.
Dave