Yamaha TRX850 Enthusiasts Forum

Was faffing around with carb setup to try and eliminate annoying hestitation just off idle. Tried testing TPS adjustment and process failed. Nothing happens. Went through lots of head scratching and meter testing. Eventually switched back to the standard ignition box o a hunch and the process worked showing TPS at 1000 rpm so adjusted to correct 4000rpm. Put the ignitek unit back in and not working again. So I guess my question is is it just my ignitek unit that doesn't work for setting TPS or is it all of them? If all best hang on to your original

Aha. Brain flash. Probably not an issue as the Ignitek software can calibrate the TPS in whatever position it is. Still I like to have the adjustment correct according to the workshop manual just in case they chose that position for any specific reason. All good. Brain exercised twice in one day. Must be beer o'clock.

My bike has an annoying hesitation just off idle as well, I'm guessing its more a result of the CV Carbs delay between demand and supply? I'm hoping a service of my carbs with new jets will alleviate the problem even if it won't fully go away?

Symptoms:

Slow [<15mph] sharp corner or roundabout, letting momentum roll the bike in with the throttle closed, guide it round the corner and open the throttle... nothing happens for a second or two then it picks up.

When i first experienced it I nearly fell off as i was expecting the bike to throttle out of the corner and it nearly tipped over. The carbeuration is pretty solid through the whole rest of the range, its just at very slow engine speed/low throttle.

Rubes, did you manage to make any progress on chasing out the hesitation?

If you can't get rid of it via your fuel mixture screws accessed from under the carby look at the air cut out valve cover.
If you can't nail it there, try taking a little of the advance off from the 2 to 10% throttle to see if you find improvements.

Cheers Cobba, I bought some thumb screw fuel mixture screws so it 'should' be easier to get the settings spot on.

Was surprised how little adjustment to the f/a mixture is needed to make a difference. I'd been making 1/4 turn adjustments and still swinging wildly between rich and lean. Real close now on less than 1/8. Just ever so slightly rich but I'll do a tanks worth to get the best overall feel. Also just received new carb rubbet boots as the old ones were, well, old so will do my next adjustment after fitting them. Such a pain having to remove tank, airbox and carbs to adjust mixture. Sure makes the process time consuming. Not sure what I'll do once I finally get the setup perfect

Mixture screw aren't linear in the sense that if you screw the mixture all the way in then turn it out 1/2 turn will do very little compared to screwing it further for another 1/2 turn as the needle/screw rises off from the seat. Screwing it out further again you'll need even less increments as the volume of flow increases.
There are some flex jets you can get for the carbies which makes life easier or the other option is a mixture screw driver with a 90* head and screw adjustment on the end of the shaft.

Oh those flexjets look the dogs bollocks! Only for you lucky buggers with FCRs though? Couldn't see any for the poverty pack originals.

Overlord Neil wrote:Cheers Cobba, I bought some thumb screw fuel mixture screws so it 'should' be easier to get the settings spot on.

Where do you get thumb screw jets for the CV carbs Neil?

http://www.factorypro.com/Prod_Pages/prody85.html

My kit of parts arrived yesterday, so thats just shy of 2 weeks delivery, but there was no additional duty to pay.

Overlord Neil wrote:http://www.factorypro.com/Prod_Pages/prody85.html

My kit of parts arrived yesterday, so thats just shy of 2 weeks delivery, but there was no additional duty to pay.

Thanks. I think I'd be embarrassed to ask for a "Long boy screw kit"

Ha, could have been a whole lot worse if Litetek supplied it... being Thailand based. Besides, it came in 'discreet' packaging

Lol

Rod has flex jets set up on his std CV carbies so the options there..