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Tecumseh OVRM120 Surges


edge10's Avatar
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NJ

08-31-08, 07:08 PM   #1  
Tecumseh OVRM120 Surges

I have a 7 year old Tecumseh OVRM120 that surges mostly on the low speed setting. It is worst during cold start probably due to the lean condition, but on the high setting the surging is almost gone. I think I have traced it down to a bad throttle shaft - the rpm smooths out when I spray the throttle shaft with carb cleaner. I have a few questions. Can I replace throttle shaft on this carb? Does the carb body normally wear on this carb instead of the throttle shaft? Does anyone know the carb number for OVRM120? Where I can get an on-line manual/diagram? Thanks

 
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08-31-08, 07:50 PM   #2  
The spec number off your engine is also needed to locate the correct part number for the throttle shaft used on your engine.

Yes, sometimes the body of the carburetor also wears in addition to the throttle shaft.

It's also possible that you may have some ristriction in the metering circuits of your carburetor causing this problem.

 
edge10's Avatar
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08-31-08, 08:53 PM   #3  
OK, here are the numbers:
Spec number is 22043E
Eng Family 195AA
Date of Mfr 0335J

Can I mic the throttle shaft or check something else to determine if it is bad? The shaft does not feel like it has play in it. Can these carbs be rebuild with a cleaning or a dip and a kit, or is it better to replace?

 
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08-31-08, 10:56 PM   #4  
You may be able to straighten it out by cleaning it with a good spray cleaner and replacing the orings in the carb. If you don't feel play in the throttle shaft, it's not bad enough to be the cause of the problem.


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09-14-08, 06:59 PM   #5  
I took a closer look and there is definitely about 0.020 " play in the throttle shaft. Looks like I'll replace it and hope the carb body is not worn. Anyone have the diameter spec of the carb body or throttle shaft?

 
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11-19-08, 09:55 PM   #6  
Posted By: edge10 I have a 7 year old Tecumseh OVRM120 that surges mostly on the low speed setting. It is worst during cold start probably due to the lean condition, but on the high setting the surging is almost gone. I think I have traced it down to a bad throttle shaft - the rpm smooths out when I spray the throttle shaft with carb cleaner. I have a few questions. Can I replace throttle shaft on this carb? Does the carb body normally wear on this carb instead of the throttle shaft? Does anyone know the carb number for OVRM120? Where I can get an on-line manual/diagram? Thanks
Most likely the 2 small o-rings in the center of the carb have hardened and deteriorated. I had the same problem with my snow blower when it got to 10 years old. The carb is not difficult to clean or repair. Getting it off the engine might be the hardest part. Once it is off, remove the large brass nut on the bottom of the float bowl and remove the bowl. Be sure to note the direction of the bowl before removal - the deep part of the bowl should be oposite side from the fuel inlet. Remove the float hinge pin and float & needle valve. Be careful not to loose the small wire clip or needle - they should be ok to reuse. Spray the carb out with carb cleaner and compresed air if available. Clean the main bowl nut which is also the main jet. It has 2 holes near the head of the nut, and a very small one further up near the threaded part. That small hole can be opened with a small copper wire - I don't recommend steel wire as that can damage the hole. Now - the important piece is the "emulsion tube". It is a plastic tube that runs up the center of the carb and has 2 orings on it. To remove the tube, simply use a small flat screwdriver to reach in through the choke opening and push down on the tube - slight force should be all that is necessary. The tube should either fall out the bottom, or you can use a needle nose pliers to carefully pull it out. Be sure both orings come out - sometimes the upper oring stays in the carb - if so, pull it out with a piece of wire of paper clip with a very short "hook" on the end. Clean that section of the carb again and blow out with air. The orings (Tecumseh part # 632547) can be purchased separately from most small-engine repair shops, or they come in a carb rebuild kit. If you are careful, you may only need the orings and can reuse the other parts & gaskets. Reassemble the carb using a small bit of lubricant on the orings when you install them on the plastic tube, and insert into the carb. Use the brass bowl nut or a small allen wrench to carefully push the tube into place. Reassemble the carb including the float & needle valve, bowl & bowl nut/jet (float adjustment should be checked before installing the bowl. The float should rest completely flat when you hold the carb upsidedown). Replace the carb on the engine, being careful to put the throttle linkage wire back into the same hole it was in when you removed the carb. Make sure your fuel line from the tank to the carb is not damaged or kinked. If fuel does not flow normally, the carb bowl will not stay filled, and the engine will surge due to a lean mixture operation. Hope this helps! Lee

 
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