Right now its not starting. popps through carb. seems to be out
Of time.cant seem to be able to time it.plug , points coil all new . have timed it in the past by eye ( no light ) ran fine also having tough time feeling cam chain with adjuster. I still think its a timing issue . 3100 miles great shape please help. thanks. Toots p.s. cleaned up carb new float and gaskets
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Re: right now its not starting. popps through carb. seems...
Its easy to time it, remove the side cover to see the megneto there you will find the timing marks T and F aligne it to T and thn remove the spark pulg to feel the piston if its on TDC (top dead center),
remove also the point plate and the rotor assy you will come to the camshaft sprocket ..there too you will see marks on the camshaft gear which should be to its mark on the head.If they align tht means the timing is ok i.e the valve timming , now u will have to set the igintion timming , by refitting the point plate and adjusting it clockwise or anti clockwise, set theengine to be on the firing stroke and get the plug out thn turn the engine keeping the igntion 'on' you should see sparks at the spark plug as the piston is going downwards.
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The shadows have an issue with the gunk getting built up in the carbs. I would take them off get a carb cleaning product and spray the living heck out of it making sure you get into all the ports and everything. This seems just like a carb issue and nothing else
it probably isnt a firing order problem, or it probably wouldnt run
one coil fires 1 & 4 cylnder, the other coil fires 2 & 3 cylnders, as the pick up gets its signal from the crank, it sends a spark to each cylnder on the exhaust stroke as well as the compression stroke, ignition timing also doesent change as it is electronic and cant drift out like when points wear.
a short in the ingnition or kill switch can occasionally cause a backfire
Backfire can also be caused by
lean mixture, dirty carbs, loose carb clamps
leaking inlet or exhaust flanges and gaskets
tight valve clearances, burnt valves
make sure everthing is clean and tight, good air filter and exhaust, check valve clearances ,and give it a compression test, check the valve timing, incase it has been assembled wrong,(they rarely jump a tooth unless the chain and tensioner are completely stuffed)
you need good compression ( at least 90 psi , kicking it with the throttle open) , good crankshaft seals for sucking the fuel/air into the botton end, proper point gap and timing set for spark ( spark should be big and fat,if not the source coil is weak,, this is a flywheel magnito ignition and it needs no battery to fire the plug) if you clean the carb, make sure you also clean the choke pickup tube or it wont choke. also make sure you have the slide installed in the right direction ( not backwards and the idle is not set too high at first...compression/****-good spark at the right time-proper fuel/air ratio and it will run
With a bike that is 35 years old lots of things could be the problem. I will list what to look for in a "most likely" sequence but with a mind to some of the easy things to check first.
Got gas and is it turned on? Clean air filter?
Have a buddy kick the starter while you look for spark.
Assuming no spark, How good is your battery? Fuses good? Kill switch on or shorted to the bars or elsewhere?
carb, head, intake manifold and carb mounted tight?
Does the carb intake manifold have reeds? What condition are they in?
I don't recall for sure, does the bike have CDI? If so, have the dealer test it and the coil.
If no CDI, when was the last time the points and condenser were replaced or points filed and set? Get the coil checked.
Remove the flywheel cover. Take hold of the flywheel and, without turning the wheel, lift the flywheel up and down then left and right. Any movement or was the flywheel rock solid? If movement then the crank bearings need replaced along with the crank seals.
Speaking of crank seals, how old are your seals? The bike ain't gonna run with bad seals.
This is a pretty good list of things that should keep you busy for a few hours. Wish I were there to help. It's been a long time since I serviced an old Yamaha 250. I was a shop mechanic for ten years.
Let me know what you find out.
Please rate this answer. Thanks Brandon!
I hate to tell you this but, if the bike sat for a year with gas in it after the carb work, it'll likely need another carb cleaning. Crying or Very sad Over time, gas in the carbs turns to varnish and gum which clogs up the passages.
What makes you think the starter is not working right, Kar? Does it sound funny, or what?
About the compression test, you'll need a compression gauge - most automotive parts retailers have them. It's a small gauge with a flexible hose that you screw into the spark plug hole.