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1983 MHR 900 electric start.

Posted: Sun May 21, 2017 12:50 pm
by Feusi
I have a seemingly weird problem. My 1983 MHR 900 electric start engine runs somewhat ok with the choke out. Once I close the choke, the front (horizontal) cylinder dies. I know you're thinking vacuum leak. I did too and triple checked and overhauled the carburetor and it's mounts. I pulled the plugs and checked the sparks. The front visually seems to have a weaker spark. After checking and swapping the coils, I determined they are ok. Do I have to dig into the pick-ups, or could it be the Bosch ignition module? Can it be something trivial as the spark plug caps? I'm running NGK 5 Ohm with Champion L86C plugs. The ignition system is all stock. The bike sat for 10 years, well taken care-of and prepared for long storage. I'm stumped.
I'm thankful for all you suggestions.

Re: 1983 MHR 900 electric start.

Posted: Mon May 22, 2017 7:45 am
by wdietz186
What were at one time considered eternal, the ignition amplifiers do seem to be starting to fail after only about 25 years. I've seen them work OK when cold and then go wonky as the engine warms. Some will not advance or retard causing irregular running and hard starts. Try switching the plug leads and the amplifier plugs to see if the problem changes cylinders.