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Posted by wcoates1 on 07/18/12 - 9:42 AM

My 1976 Johnson 75 HP will immediately stall when putting in to gear. I have replaced the coils, cleaned the carbs, cleaned the fuel line screen, replaced the plugs, got new gas, and can't find anything that tells me where to look next. What troubleshooting items should I go for next?

Posted by wcoates1 on 07/24/12 - 4:17 AM

OK - for the guy that doesn't know this - explain link 'n sync for me. I have guys that can help me with this but I need to know what to tell them.

Posted by dbcollen on 07/24/12 - 7:53 AM

link-n-sync is setting all the carbs so thier throttle plates are the same, it should be in the manual. You shouldn't work on a high performance 2 stroke engine without the manual, there is too many ways to burn them up if the mixture or timing is off.

Posted by brooks89 on 07/24/12 - 8:51 AM

Have you done a compression/vacuum check on each the cylinders?

A Two Stroke Engine must have compression above and below the piston rings. We all know about taking engine compression readings from the spark plug hole but a lot of people seem to forget that a two stroke engine must have a sealed bottom end that will hold both compression and vacuum.

When the piston in a two-stroke comes down it compresses the air/fuel charge in the crankcase and pushes it, through the ports in the sides of the cylinder, into the combustion chamber. As the piston rises a vacuum is created under the piston. That vacuum sucks the air/fuel mixture through the carburetor and into the crankcase.

Does the motor sound "normal" as compared to when you were happy with its' performance? If you are missing on one cylinder the motor will idle but stall out under load.

Edited by brooks89 on 07/24/12 - 8:54 AM

Posted by wcoates1 on 07/24/12 - 12:17 PM

Thanks guys - this will get me "back under the cowling". The only way I know to check for firing is to remove a plug and, with it still connected to the coil wire and using insulated pliers, hold the tip near the block while turning the ignition to see if there is a spark. If here is a better way, let me know.

New Q: If the power pack is bad in any way, will the engine still run? In other words, can a dead cylinder be the result of a bad power pack?

Posted by brooks89 on 07/24/12 - 12:51 PM

I suspect it's not a power pack problem. Again..have you done a compression check? A vacuum check? Does the motor sound in any way different now at idle than it did previously? Before worrying too much about ignition I would make sure this 36 year old motor is holding tight.