Question about Yamaha Motorcycles
Can't get spark to the plug on my 1971 Yamaha 250 dirtbike
Posted by Anonymous on
That bike is simple and not much can be wrong, check the coil, the wire where the plug goes, check the points, service manual
Posted on Apr 21, 2015
The most likely thing to cause that is a faulty primary ignition coil it's very very common on older model motocross and trail bikes.
Posted on May 02, 2015
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Posted on Jan 02, 2017
Really...strange what you need to do is see if the bike is running too fat. So...warm her up witha fresh set of NGK! spark plugs. After the bike is warm take it down the street and back. When your on the way back get on the throttle and accelerate then shut er down and coast it into the garage. This will give an acuurate read on the spark plugs at operating temperature and under a load. Pull all the plugs. If they are brown like coffee with cream that means carbs are adjusted correctly. If they are black and wet too rich and if they are white or very light brown too lean. Other problems may be oil soaked plugs from loose top end parts. Maybe valves or guides.
Posted on Mar 05, 2009
ill do a list of things that can help or be the problem.
1) Pull the coil off and wire brush down all the bare metal. then do the same to the frame where it bolted on. Make sure there is a grounded wire that bolts back onto the coil if there was one, Replace the wire end for the ground peice.
2) Pull off the spark end cap and cut the wire down a few mm until you see new wire then screw it back on. (if its NGK)
3) follow the wire from the kill switch and make sure it isnt grounding out.
4) Hotwire - find the kill switch and unplug it. if this doesnt help unplug the ignition key wiring. on older bikes it will work for ignition but not lights for the key part. if this helps you need a new Ignition barrel / Kill switch.
5) check your wiring harness make sure it isnt grounding anywhere exept where its ment to.
6) make your your engine to CDI is plugged in and has no oxide in it
7) try and find somone with a running bike the same as yours and borrow there CDI, if this helps you need to buy a new CDI or check yours for wiring shorts.
hope this helps if not buzz me (skuly@Hotmail.com)
Posted on Feb 17, 2010
The above site has full diagrams for the whole bike (1971 DT1E), diagr. below from site shows elec. components, hope it assists you.
Posted on Apr 27, 2010
spark plug brand i am using is an NGK IRIDIUM IX (BR8EIX) number 3669 fires up first time everytime i have a yz 250 1995 model aswell
Posted on Oct 19, 2012
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