Thread: Jerky Runner
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Old 09-25-2019, 09:58 PM   #31
Fred K-OR
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Join Date: May 2010
Location: Stayton, Oregon
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Default Re: Jerky Runner

Originally Posted by Fred K-OR View Post
Well back in Aug of 2018, I started this post about my jerky 29 coupe. Guess what, here it is Sept 2019 and I have the same problem. Same situation, ran it is 4th of July parade, let it set until now (sept) and the same problem started again. The problem was that when I would start to go, press on the gas it would jerk and backfire in the carb.

So I did some thinking about the situation as to what it was doing--- would "miss" when pressing on the gas starting out from a stop. Well so many people recommended Marvel Mystery Oil so I got carried away. A few days ago I took the plugs out, dumped in a bunch of MMO in each cylinder, and let it set for a few days. Today I got in it, started it up(and it did start) and I had a concern that the neighbors would call the fire department. So I backed outside and let it run for awhile blowing smoke all over the neighborhood. Then I got in it and drove it around the block a few times in 1st and 2nd. At first it still had the problem. Then after a few rounds it all cleared up-smoke and the jerk (not me).

After parking it after a few miles, I turned it off and let it set for while. They I tried to start it. I had spark up, gas lever up and just a touch of the starter, it was up and running! Wow! This start was better that it had done for years. I also pulled one of the spark plugs and looked at it. Before the MMO, when I took them out they were covered with black junk. This time the electro look nice and brown and no black stuff.

Anyway to sum up all these comments- it does look like I had a stuck valve. Putting the MMO in the cylinders and running it after that did clear up the problem of a jerky start where it would jerk and backfire in the carb.

Hope this helps someone.
I also think I need to change the engine oil after this situation because I did put a liberal amount of MMO in the spark holes. I am sure a lot of it got in the engine oil. Maybe that is good for the oil but it is about time to change the engine oil anyway.
Fred Kroon
1929 Std Coupe
1929 Huckster
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