Carb or Governor Problem

[bob]

White Lt13 lawn tractor with Tecumseh OV490EA engine

With lawn tractor sitting and idling at low speed or at high it surges up and down or runs rough. Under a load such as cutting grass or just driving it is fine. I did raise the governor spring up a couple of holes and it did help but still surges. I can put my finger on the governor and it does seem to smooth out. I still wonder if it is carb. I have cleaned but could have missed something. How can I test for carb or governor problem and then go from there.

Blair

[38racing]

Has the carb been off/on recently. I assume that the carb has no mixture adjustments, not even for low speed? You could try a static governor adjustment. You loosen the nut/bolt holding the governor lever to the the governor shaft piece coming from the engine. Rotate the governor lever so that throttle fully opens. Hold it there. rotate the piece from engine that it's bolted to in the same direction of rotation that you did the lever. Hold it too while tightening the bolt with your third hand. given that it could be surging and running rough might mean it's running lean and needs a carb cleaning. That's got the plastic bowl carb held on by spring clip? I just had issue with crud blocking the main jet.

[Arkie]

How does it act if you give it some choke.
If you cannot apply a manual choke as such remove the air cleaner so as you can hold you hand or fingers over the carb throat for a choke while it's surging and hunting. Try this at idle speed.
If this helps reduce the hunting it's running lean due to most likely the carb jets restricted. Sometimes you can take the carb off, remove the bowl, clean it out, blow low pressure air or carb cleaner from a spray can through the passages and get a go.
If giving it some choke does not reduce the hunting at idle try just holding the governor arm steady. If it still hunts it's running lean.

You are lucky that you can get a replacement carb for that Tecumseh for less than $20.
Hang on to your old carb if you replace. Good chance you might need some parts later.

Most generally on them later model Tecumsehs that have the low emissions non-adjustable Al Gore carb's the idle jet will get little bit restricted and they hunt and some of them will hunt and surge for about first 30 sec's after they are started up cold.

[bobodu]

Nothing hunts like an Injun.....

[Arkie]

Nothing hunts like an Injun.....

Right: Tecumseh Injun.

How do we know that.

[bob]

I tried what you suggested Arkie and it didnt make any differance and did take carb off and clean again and still the same. What I finally found and helped with surging was spring around throttle. I had to tighten spring by seating it in a different spot. That did help. Does that make sense to you ? I would not say it is running completely smooth but it is much better. Still have to do a load test and I like I said before it was fine there.

Also I did adjust governor. With lever off and turning governor shaft it only turned about 1/8"either way. Is that natural ? I thought there would be a hard spot and maybe a nothing spot. Thanks

[Arkie]

I tried what you suggested Arkie and it didnt make any differance and did take carb off and clean again and still the same. What I finally found and helped with surging was spring around throttle. I had to tighten spring by seating it in a different spot. That did help. Does that make sense to you ? I would not say it is running completely smooth but it is much better. Still have to do a load test and I like I said before it was fine there.

Also I did adjust governor. With lever off and turning governor shaft it only turned about 1/8"either way. Is that natural ? I thought there would be a hard spot and maybe a nothing spot. Thanks

I'm not sure on that engine about the 1/8 of turn on the gov shaft maybe someone will chime in to your question. Most generally on other small engines about 1/4 of turn of the shaft at least and a definite hard stop at each end of rotation. Usually you do not have to remove the lever when doing a STATIC governor adjust, but the amount of rotation of the Governor shaft should move the throttle from full throttle to idle as the gov shaft is rotated manually when the STATIC adjust is done correctly. You can review how to STATIC gov adjust on-line search.
Theory of manual adjustment is same for most all small engines.

Since a choke did not do any good and your tightening up the governor spring helped you may have a stretched governor spring that is too weak.

[38racing]

The governor shafts don't turn much and I've always found a hard stop in either direction. Did you adjust governor and spring at the same time or separately? And adding a bit of choke did nothing?
Also can you confirm it's the plastic bowl carb? It might need ultrasonic cleaning for that idle jet. Then gasket between bowl and body has to seal good and I notice on mine that the bowl warps from body.

[bob]

I did the adjustment with the spring on. And just to clarify things the spring that I tighten by putting in another postion was not the governor spring but the actual spring that goes around the throttle shaft that keeps tension on it. That helped level. The part I still do not understand is when I start it up it will probably still hunt but once I start cutting grass it will stop and work fine and then once warmed up it will be good. I can not see this as a carb problem but I have no way to test without another carb. I do not know if ever worked good or not. Bought tractor with a seized B&S 13HP but guy sold me the Tecumseth as a replacement. He never used it as he had problems with mounting. I might have to buy new carb as now I have a crack in the plastic bottom from using screwdriver on heavy spring taking it apart. Tried expoy and worked for awhie and then started leaking. Melting plastic this time and see if that will work. That for the help guys

Blair

[38racing]

You just buy the whole plastic bowl assembly for reasonable price. That's the beauty of that design.
Put your ov490ea into partstree.com and find your spec number. Carb number will be item 380 in second diagram. Then put carb number in as a model number. 25a if the bowl assembly. Likely this one
https://www.partstree.com/parts/tecumseh-640334/
Shop around for prices.
Your description that better under load and when hot indicates a lean condition. I had a push mower engine that I had to pump primer continuously for 2 minutes until it would stay running. I had a blocked jet which would only supply enough mixture for a hot engine.
Given that you are mostly working under load you cdn ignore the surge.