Yamaha TRX850 Enthusiasts Forum

Hi folks,
Hoping you can help me with a couple of issues.

Firstly one which I assume is carburation - bike accelerates normally all the way through to 100mph then STOPS - just for a couple of seconds - almost like it's clearing its throat - then continues accelerating. Any ideas what might cause this? It's not that I routinely ride at those kinds of speeds but I do like to give her a squirt from time to time.

Secondly, there's already been quite a bit of chat about cooling on this forum so i'm sorry if I missed the one that might have put my mind at rest but here goes.
Bike stationary - temperature creeps up to above 100C - fan cuts in as it should - temperature comes back down to 90C ish. All fine.
Bike on the move - riding back from Birmingham yesterday - ambient temp was around 10C. Temperature needle never left the stop.
Now in anybody's language this is a clear symptom of a thermostat jammed open, but everything I've read on this forum suggests this is quite normal. This only makes sense to me if the temperature sensor is located close to the exit from the radiator, but I think I read one post that said the sensor was located near the thermostat itself which I assume is at the radiator inlet. If that is true I find it hard to believe that coolant was coming off the engine at a constant 50C throughout a 120 mile high speed run. Help!!!!

Re the temp, it is normal.
The TRX runs very cool unless sitting still.
Just get used to it.

Pretty sure its just the gauge on these.
I ended up chucking a different model thermo in for a marginal improvement and a 5c cooler fan switch. Yes it got it where i wanted it so temps are more stable, higher lows and lower highs but a bit of investigating with the I/R gun and temos were actually within Yamaha spec any way.

Many thanks guys. At the end of the day the bike runs fine - apart from the (assumed) carburation issue that is - so I shall do my best to get used to the quirky cooling arrangements.

Meanwhile - any TRX's on the Isle of Man this year?

Re the cooling "issue" . I've only had mine since last November so the runs i had on it before its winter refresh were in cooler temperatures but i wondered at the time if they all ran cool on the move.Just before Christmas on the charity toy run to Addenbrookes hospital we had to stop briefly in town for 3 or 4 minutes in the middle of hundreds of bikes and the temp shot up to 100 , not being familiar with it i was half expecting a hose to go and i'd dissapear in a cloud of steam! but the fan came on and all was well.......i've since put a small switch on it to put the fan on manually in the same sort of situation.

Thanks for letting me join , I have recently rebuilt a TRX , it was running very rich , I bought a keystar carb kit and replaced all the internals jets needles cut of valve ect , I took the bike for a run and it would not carbuarate cleanly , it was bogging down on initial throttle opening , I put back in the standard needles and it was fine , but they are worn, the identification no on the original was 5E185 and the keystar ones were Y365 but not identical in width, have any of you guys fitted the same ? I did not change the clip position on the needle either, I know I could have got to a bit better by dropping the clip on the needle , also when Itook apart the carb top ares I noticed a lot of black residue like a material that the slides are made from , ( plastic composition ) I am begging to think the slides are worn and the other plastic internal housing section that the emulsion tubes runs through and secured it in place , I would appreciate any info please , cheers