Yamaha TRX850 Enthusiasts Forum

Well, struggling a bit with the jetting as i´m going up on the dyno on friday...(it sucks really great now with the 878cc)
Think i´ve got most things right exept...when at ~4500-5k rpm and wack it in high gear it hesitates really bad (1st 2nd 3rd are OK)

When going WOT thru the gears it´s awesome...so it´s the transition between needle and mains right??
I followed some advice a while back to set needle at 3rd from top....but thinking of it...carbs jetted for airbox is 4th clip position. Shouldn´t it be more the other way then with no airbox?!

I also think that it would be better if the pump where completely stiff and not spring loaded....think it´s to late as is. Anyone done it??

And i guess to have a chance getting it correct i should disengage the acc pump??

What´s your thoughts??

mine is in third from top and running no airbox and is still a bit rich you might need to try 2nd from top give it a go if its worse then deff needs to be the fourth could poss be running more efficiant with the higher comp and so need to be leaned of at half throttle openings, correct me if I am wrong someone what mains you running with the twin pipe set up out of curiosity

cheesie wrote:mine is in third from top and running no airbox and is still a bit rich you might need to try 2nd from top give it a go if its worse then deff needs to be the fourth could poss be running more efficiant with the higher comp and so need to be leaned of at half throttle openings, correct me if I am wrong someone what mains you running with the twin pipe set up out of curiosity

After the 878 i´m down to 160 mains (used to be 170...167 when temp is up)....but that´s just by feel. Dyno on friday as said!
I´m going to disconnect the pump tomorrow....it only fekks things up, sad it´s going to rain as goddam here tomorrow!!

Killerwhale wrote:

cheesie wrote:mine is in third from top and running no airbox and is still a bit rich you might need to try 2nd from top give it a go if its worse then deff needs to be the fourth could poss be running more efficiant with the higher comp and so need to be leaned of at half throttle openings, correct me if I am wrong someone what mains you running with the twin pipe set up out of curiosity

After the 878 i´m down to 160 mains (used to be 170...167 when temp is up)....but that´s just by feel. Dyno on friday as said!
I´m going to disconnect the pump tomorrow....it only fekks things up, sad it´s going to rain as goddam here tomorrow!!

A revision...
After temp went down in Sweden bike was worse and worse so i took a chance and went up again to 170 mains and that was spot on. I´ve also did what you said and put the needle 2nd from top and added half a turn on the slow air screw.
Graph and video under my bike....

I done mine by feel then went up one jet size to be safe, took it to the dyno and was spot on with my first judgement, could prob be a little better still aroun, part to half throttle if anything its a little rich there but at £35 a go on the dyno it,ll do me