bobgritz
Petty Officer 2nd Class
- Joined
- Sep 22, 2009
- Messages
- 185
My '98 J20HP doesn't like waking up in the morning. It was a backup motor and doubtfully has 50 hours on it. When first started up it backfires out the exhaust and after two different carbs (both stripped down and cleaned twice using ultrasonic) it still is coughing out the exhaust. When I throttle up and go it smooths out although it does appear to be running on one cylinder for the first 5 or so seconds. The backfiring occurs again when throttling down after running it at full speed.
The motor originally had remote steering which I converted to tiller. It was worth the effort due to its condition. It ran fine before buying it but since I didn't get around to converting it for about 6 months I assumed a dried out and gummed up carb thus the rebuilt carbs. I added a manual primer and removed the original auto-primer. This was one of my first areas of concern so I tested it with the original auto-primer with the same results. A spark test is in order but my question is about timing.
I read that when you get backfiring you should use a timing light to check the timing but in other threads I'll read that these engines are timed at the factory and cannot be timed. I'm familiar with traditional timing techniques but I'm a bit confused with the inability to tweak any advance/retard mechanism. I think I understand the relationship between the cam follower and the two marks on the cam and the opening up of the throttle plate. But I assume the two marks on the cam can be advanced or retarded by adjusting the throttle control rod which I further assume would change the timing of the motor.
Any thoughts would be welcome. Thank you.
The motor originally had remote steering which I converted to tiller. It was worth the effort due to its condition. It ran fine before buying it but since I didn't get around to converting it for about 6 months I assumed a dried out and gummed up carb thus the rebuilt carbs. I added a manual primer and removed the original auto-primer. This was one of my first areas of concern so I tested it with the original auto-primer with the same results. A spark test is in order but my question is about timing.
I read that when you get backfiring you should use a timing light to check the timing but in other threads I'll read that these engines are timed at the factory and cannot be timed. I'm familiar with traditional timing techniques but I'm a bit confused with the inability to tweak any advance/retard mechanism. I think I understand the relationship between the cam follower and the two marks on the cam and the opening up of the throttle plate. But I assume the two marks on the cam can be advanced or retarded by adjusting the throttle control rod which I further assume would change the timing of the motor.
Any thoughts would be welcome. Thank you.
