Yamaha TRX850 Enthusiasts Forum

HI NEED SOME HELP JUST PURCHASED A TRX WITH ABOUT 60000KS BUT HAS NOT BEEN STARTED FOR 6TO 7 YEARS HAVE DRAINED PETROL TANK CLEANED FUEL BOWLS AND JETS BUT WONT IDLE WITHOUT CHOKE ON AND HAS TROUBLE REVING FREELY ANYONE THAT CAN HELP THANKS

It might help to know where in the world you are located.
Has the bike been sitting outside or was it covered up?
Things perish over time, like the rubbers on the inlet manifold. If these crack you'll have no end of trouble getting the bike to run smoothly.
Another carby part that can deteriorate over time and crack is the white plastic cover over the air-cut valve. This is visible on the side of the carb on the RHS of the bike.
Also check the vacuum lines to the fuel tap and fuel pump for any leaks.
New spark plugs wouldn't hurt either.

THANKS FOR YOUR HELP DICKY WILL TRY, SORRY I LIVE IN ADELAIDE

if it wont idle without the choke you will need to adjust the tickover until it will idle at 1250rpm or thereabouts without choke

if that doesnt work to get it to idle you will need to investigate further

It's not a very complicated bike.
That you can actually start it is encouraging, can't be too hard to get it sorted.
I'd check the diaphragms in the top and all other seals and o-rings, I have found perished rings under the main jets before.
Check the jet sizes and that the needles are in the right position.
Have a look in the Members Download section for assistance
Who knows, some one may even offer up a known good set of carbs to check with.

THANKS ALL WILL INVESTIGATE FOR JUST JOINING SEEMS TO BE A FRIENDLY SITE UPGRADED FROM A CX 650 TO THE TRX FINALLY

Hi,

Welcome to the forum.

Is it the bike that was on Gumtree at Coromandel Valley? If so:
From memory it had a black engine in a silver frame. That would imply that the original engine has probably been replaced with one from a '95 or '96 import. Those early engines are prone to the valve clearances closing up due to an issue with the valves wearing where they seat and recessing into the head.
It may be worth having the clearances checked anyway, especially if there are no recent service receipts from a reliable mechanic indicating that they've been checked.

When running, the engine should be making 'tickety' noises from the top end. If it's too quiet, that would indicate that the clearances are too tight and the valves may even be being held open. This could be a cause of the symptoms you've described.

Cheers

THANKS FOR HELP YES THATS THE BIKE RUNS BUT WONT IDLE WITHOUT CHOKE HAD A LOT OF CRAP IN FUEL BOWLS DID ALL THAT BUT STILL SAME PROBLEM AND MISFIRES BACK THROUGH CARBYS OCCASIONALLY AND SOUNDS VERY QUIET IN TOPEND NO TAPPET NOISE THANKS FOR HELP.

Check the valve clearances..
Do you know what what year the Trx was manufactured???
Early models 95-96 had intake valve issues. The part number now has been revised to the later 97-99 model intake valve.
Issues started sround the 60,000 mark

cobbadiggabuddyblooo wrote:Check the valve clearances..
Do you know what what year the Trx was manufactured???
Early models 95-96 had intake valve issues. The part number now has been revised to the later 97-99 model intake valve.
Issues started sround the 60,000 mark

Haa, my issues started at 9000 miles! 4 intakes at minus zero clearance.

Might be worth getting a Litetek carb seal kit from Thailand. Search for Litetek. They are ethanol proof and well worth the effort.

KYMFITZ wrote:THANKS FOR HELP YES THATS THE BIKE RUNS BUT WONT IDLE WITHOUT CHOKE HAD A LOT OF CRAP IN FUEL BOWLS DID ALL THAT BUT STILL SAME PROBLEM AND MISFIRES BACK THROUGH CARBYS OCCASIONALLY AND SOUNDS VERY QUIET IN TOPEND NO TAPPET NOISE THANKS FOR HELP.

That's not great
The backfiring through the carbys could be due to the timing being out but it's most likely due to the inlet valves not sealing. It's probably been like that for awhile and if the exhaust gases have been blowing past the valves they've probably been burnt and damaged. It's possible that the valve seats are damaged too, although they are made of quite hard material.
I suggest that as a first step the valve cover needs to be removed to check the timing and to measure the valve clearances.
It's likely that the head will have to come off and the valves replaced. The valve seats may need to be re-ground as well and the new valves lapped-in.

Sorry to be the bearer of bad news.

Should have kept the CX.

they will backfire through the carbs without the airbox on though, even with the clearances good and in a good state of tune. If it doesnt do it when it is warm and the airbox is on then thats ok

THANKS AGAIN DOES ANYONE KNOW HOW EASY OR HARD TO ADJUST VALVE CLEARANCE HAVE DONE CARS BEFORE BUT NO BIKES

KYMFITZ wrote:THANKS AGAIN DOES ANYONE KNOW HOW EASY OR HARD TO ADJUST VALVE CLEARANCE HAVE DONE CARS BEFORE BUT NO BIKES

pretty easy on the trx, the workshop manual in the downloads section covers it very well