Hi guys/girls

am a newbie been reading through the forum alot looking for any answers for my problem but its a little more complicated as i have a xt 600 engine in a quad bike

so my problem is, i have a hard time starting my xt 600 engine and also when running it runs fine but release the throttle and i get alot of back fire, could this be down to valve clearance and the reason for both problems ?? i have looked through all the valve clearance threads and found 1 post that could be helpfull but am not a mechanic so need more guidance. the manuals i have found and looked at are all owners manuals which say 1 simple thing specialist yamaha tec should do it. the owner manual dosent say how todo it or even give u a clue.

unforunatly i dont have the funds to sit my bike test so i went the quad route using my car licence and i plan on doing a nice long trip and go site seeing like so many of you have done but not before i have every little problem sorted as a brake down and stranded (god knows where) will cause me alot of trouble.

the engine was professionally fitted and wasnt a noobie job, so i just need some guidance and help.

thanks in advance

My 3Aj Tenere sounds like it backfires when I shut the throttle off suddenly. It has an air leak into the exhaust which I haven't got around to fixing. I just have to remember not to suddenly run up behind horses and slam the throttle shut.
Yours may be a completely unrelated problem but with a hybrid exhaust it has a chance.
Best of luck sorting it.

There are also diaphrams in the carbs (if they are YPVS) that shut down the fuel supply when the throttle is closed. If these are worn or punctured the rich mixture on overun will pop in the exhaust. Try NRP in Manchester for carb bits. Good Luck.

hi there what year is the engine , is it a kickstater only / or a kickstarter /electric starter or just electric starter. if it is a kickstarter only there is a bit of a knack to starting them , if it is make sure you have the decompresser cable fitted or you WILL brake the kickstarter . to set the tappets on all the engines is the same , on the casing in front of the gear lever there are 2 screw in plugs 1 in the middle 1 at the top. undo these and with a socket on the nut in the middle (crank nut) turn the engine counterclockwise ( its easyer if you take out the sparkplug ) there are marks on the rotor you are turning seen though the top small screw hole, align the (T) mark with the mark on the casing the T may be on its side. take off the tappet covers both sets of tappets should wiggle up and down , if not turn the engine one full turn and try again . now with the right feeler gauge for your engine check the gap the inlet and ex will be different you are after the feeler gauge sliding in the gap with a slight drag on the gauge if you need to set them undo the nut and turn the sq bit to adjust then tighten the nut its a bit fiddly at first . the popping may be the exhaust if its a quad it probably is not a standard silanser , or it may be the coasting enricher diaphram in the carb is stuck if it is it will pop and bang very LOUDLY like a shotgun going off how bad is the popping?. i would give the engine a full service new plug airfilter or clean re oil etc to see if this helps the starting also drain the carb by the screw at the bottom of the carb to get rid of any crap in there also set the mixture screw as per your model of engine it could be set very weak , basicly you need a service sheet / manual for your year of engine . good luck zigzag

thanks zigzag i will try to find out what year it is but its def an electric starter, when i get back home i will give it ago with what u said hopefully it will sort the popping out and if lucky the starting am just hoping its not going to turn out an expensive problem but a year on the engine would be a good help i think.

thanks guys

another question (sorry so many) is there away to find out the engine year ?? when all i have to go on is the engine and only that ???

i have a feeling i know the answer that being no lol but hopefully theres away


big thanks for your help guys am on 5 forums and only u huys have replyed trying to help so thanks

a rough guide to engine year is the first 3 digits off the engine number

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hi there do,s the engine have a kickstarter or is it just electric . is the engine black or silver , if its still got the origanal paint that is . zigzag