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Discussion Starter #1
Hi,
I have a Ariens 926 OHV engine i'm working on that occasionally spits back out of the carburetor. At Idle, the engine hunts a bit and will spit back out of the carburetor every 8 or 10 seconds. I completely and cleaned out the fuel system including removal of the tank, fuel line, removed the carb, took off bowl, cleaned main jet, cleaned out the body of the carb, blew out the carb w compressed air, reassembled and it runs no better. It almosted seemed like the plug was occasionally not firing but i put a new plug in and also put a plug tester in line with the high voltage lead to see if the ignition was dropping out here and there. It seems fine. When I run the engine at full rpm, it runs pretty well but not perfect. It's hunts a tiny little bit here and there. I'm thinking the carb is bad (idle circuit) from sitting all summer. This is the 2nd machine of this exact same model I have seen that runs like this. The last one was fixed by really cleaning the carb out well. I'm not sure why it spits back while it's running. A sticky valve? Too tight a clearance ont he intake valve? I check the valve lash and it had a little bit of play (seemed about right). The compression release is on the exhaust valve and while i had the valve cover off, it looked like the cam was bumping up the exhaust valve a bit as expected and then closed it at the 50% mark on the compression stroke. Has anyone seen this? Is this kind of backfire common on the overhead valve engines? You can see the engine run here michaelandmadison dot comm . Any ideas would be appreciated. Thanks!
 

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You really need to check the valve clearances with a feeler gauge, It's pretty hard to eyeball. You may also want to take a look at the flywheel key to be sure it's not slightly sheared.
 

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Discussion Starter #4 (Edited)
When I took the caburetor off the engine and took the bowl off, I noticed lots of crap/water in the bowl. So I cleaned the bowl and blew everything out..... except I didnt remove the low speed fixed jet.
Because the engine ran pretty well at high speed, I assumed the low speed circuit may be at fault. If you watch the video, you can see when the engine idles, it spits back once every 10 -12 seconds when the govenor opens the throttle wide. I figured the low speed circuit must be blocked because idle was poor and high speed was pretty good but no perfect.
I forgot to pull the fixed low speed jet when i cleaned out the rest of the carb. I found the small center hole on the idle jet to be completely clogged. I soaked it and ran a solid wire through it to open it up. I was hard as a rock. I reassembled everything and it starts and runs perfectly.
Shame on me for not removing and cleaning the low speed circuit. Most problems tend to have more than one contributing factor. This one had crap in the bowl, tank, and fuel line and had a completely clogged idle jet.
I appreciate your help on this 30Year.
 
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