I have completely rebuilt the carbs (w/ new orifces(jets) ) and a new carb kit to include and ultrasonic bath. It starts in the cold while the motor is cold and I am very happy with this; however, it has a miss. The miss was there before the carbs were rebuilt and I thought the carb job would help fix the miss too. In a nut shell, the carb job fixed the starting problem and now onto the next problem, the miss. The miss is so bad sometimes that it will cut the motor off. When I am running at 4200 rpm, the motor runs great, but will have a really small miss occ***ionally, every few minutes or so. At wide open, the motor runs flawlessly. I got home and replaced the spark plugs to see if that would fix the problem (maybe a fouled plug). The miss is still there. Where should I look next? Is this indicative of a larger problem?
Naturally several things can cause the miss. My first guess would be dirty fuel. Running wide open the contaminant might be getting blown through without feeling it but at lower speeds the miss is more noticeable. If you have a fuel filter check it. and if you don’t then I would consider chunking the gas unless it is brand new. I hope Chris V responds. I want to hear his opinion.
Mr Hardware
what kind of motor?
It is a 1982 75 hp Evinrude TLRCNB…sorry I left that out. @ mrhardware, I just replaced all the fuel lines and a new 6 gallon gas tank 3 weeks ago and I use ethanol free gas. The gas is less than a week old. Thanks.
“Highfly” the war horse of Major General James Ewell Brown (JEB) Stuart
Try a compression check. Could have great compression, or low in one cylinder.
Maybe a burnt or bent valve on a 4 stroke or just low compression on a 2 stroke. Either way its time to check that route.
A burnt or slightly bent valve can run pretty well at a high rpm but wont run well at low rpms.
A backfire from that could shut this engine off. A bent valve can be hard to see if it didnt get hit hard. I just wont
seat well enough to seal. I have found older motors with sticky valves that get hit after sitting a while.
Just my experience!! good luck!
Key West 225cc Yamaha 225
Sounds like you still may have a carb problem, can you isolate it to find which cylinder it is? after that, start with a compression test, then check spark on each cylinder with a spark tester. Pull the coils and check the ground strap on each coil. If that doesn’t fix it, use a DVA meter and check the stator and power pack outputs.
its a 2 stroke johnson, sono valve issues
he has goodcompression on all cylinders
im leaning toward a coil failing under load