394xp rpm issue

sean donato

sean donato

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Time to dig into the carb, just because it's new old stock. Doesnt mean the diaphragms didnt get dried out from sitting on the shelf. Typically when you have lack of adjustability of the carb, low max rpm it suggests the carb needs some work. Kits are fairly inexpensive, and easy to Install.
 
MAngelotti1

MAngelotti1

Red Cows, Orange Saws
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I did find a kit in my bin last night. Will do. I haven’t had an rpm issue before. Usually lack of fuel so I’m hoping to learn something new! Last attempt to run I took another compression reading when hot and it dropped considerably. Pulled exhaust again and it looks good no scoring. I am going to pull the cylinder and investigate. Is it possible this compression issue would cause a rpm limit? I wouldn’t think it to but that’s why I’m asking!
 
CausticUC

CausticUC

Need to fix that pull!
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I doubt it, unless it has next to no compression to begin with, and then it would start hard (I would think)
Normally what happens is it is easy to kick over but the piston moves too fast since there is no/low compression and it will not stay running as the combustion blows by.

If you have a cylinder where the rings are starting to get too worn, the engine will start, idle, and run unloaded fine. When loaded it will bog or die when the rings cannot hold the combustion.
 
albert

albert

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Post the compression numbers.
Too much fuel or not enough air from your answers. Should scream to the moon at 1/2 out on the H. Probably should die all the in. Check your choke and entire intake tract for restrction.
 
CausticUC

CausticUC

Need to fix that pull!
Joined
Mar 12, 2019
Messages
586
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Found compression issue. Pulled cylinder and found a broken ring. Don’t ask how but no scoring. Some debris in transfers and 1 small piece in case. Cleaned it all up and now waiting on piston kit. Going to kit carb and start over when I have piston in.
Are the rings directional for that model?
 
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