Help - new carb on OHH50, will not idle

[wb4rt]

I am re-building a wrecked go-kart for my grandson.

It has a OHH50 Tecumseh engine and while the engine was only run for about 5 minutes before the previous owner wrecked it, it has sat for 3 years. I changed the oil and could not get it to run except for spraying carb cleaner in the carburetor so I replaced the carburetor 640017 with a new one from OldMiniBikes. This is a direct replacement with the primer bulb.

Now the frame is all rebuilt and everything back together, so tried cranking it this morning. It fires up and runs if I move the throttle, but I cannot get it to idle. It does accelerate with the throttle so it is not just a runaway. There seems to only be one screw that can be adjusted. I have tried moving it in and out with no apparent effect.

I have not spent a lot of time on it yet, but wanted to get some guidance and opinions on next steps as I am not much of a mechanic.

Any help is appreciated!! :smile:

 

[OND]

Can you post a pic of the carb ?

 

[wb4rt]

Can you post a pic of the carb ?

Stock picture.



I can try to take actual picture tonight.

 

[OND]

Stock picture.

View attachment 66868

I can try to take actual picture tonight.

The screw on top is the Idle screw...screw it in and it opens the butterfly, I would turn it in until It does start Idling and maybe listen and fill around the gasket area fot a vacuum leak ( Warm the engine up for a couple of minutes)

 

[wb4rt]

I put new gaskets both front and back, but I put them on dry. Remember I'm no mechanic. Should I use something on them to make sure they seal?

So screw it IN, not OUT? Is there any rule of thumb on this - in all the way, then back out 1 1/2 turns or something?

 

[UnorthodoxCreat]

I would buy a carb with adjustable idle screw and manual choke. I have that engine and it never started or idled well from new. I bought a compatible carb off Amazon for about $30 and now the engine runs and starts amazing.

 

[cdoublejj]

I put new gaskets both front and back, but I put them on dry. Remember I'm no mechanic. Should I use something on them to make sure they seal?

So screw it IN, not OUT? Is there any rule of thumb on this - in all the way, then back out 1 1/2 turns or something?

spray paint, give em good nice coating of black spray paint let it sit and START to cure once it's tacky, bolt it on.

 

[wb4rt]

I would buy a carb with adjustable idle screw and manual choke. I have that engine and it never started or idled well from new. I bought a compatible carb off Amazon for about $30 and now the engine runs and starts amazing.

That may be necessary. Can you tell me the part number of that carburetor that is compatible?

 

[wb4rt]

UPDATE: This morning I was able to get the engine to run continuously (well, close) and almost idle. It will rev up and down ok.

The idle is still too high rpm's. Any further adjustment down and it dies. So that would be ok, but the clutch is engaging. So unless the brake is on, the kart is moving at the idle. I switched out the old clutch thinking it was probably rusty and stuck. I put on an almost new Hilliard Extreme clutch and it is not engaging as much. I can live with it the way it is, but it is not really right.

So options?
1. Buy another new carburetor with adjustments.
2. Is there any way to adjust the clutch so it will not engage at those rpm's? Springs?
3. Buy a clone engine and be done with it.
4. ???

 

[buckeye]

Turn the screw out until you get good idle. Like 1/8th at a time.
Then get ya a adjustable carb.

 

[UnorthodoxCreat]

This is what I bought and it solved all my problems. Before the bike would run well if you were giving it gas but as soon as you let off the gas it wanted to die, it wouldn't idle and was a pain to start. I had to bend the choke lever because of my custom exhaust but otherwise it was a direct fit. With a stock exhaust it should bolt right on.

Amazon.com: Carburetor Tecumseh 640340: Automotive

 

[buckeye]

There ya have it.

 

[tecumseh power]

X2 on that carb above. The fixed jet carbs suck and the primer ball carbs really suck! Tecumsehs are not real tolerant to trash in the fuel, old gas, etc., so I'd add a fuel filter when you change the carb.

 

[wb4rt]

New carb ordered! I'll let you know how that works.

 

[wb4rt]

New carb in and installed. I can adjust it much better and it seems to be about right now.

It has been too cold and muddy to ride it. I'll report back after a few laps when it warms up outside.

 

[joshua. c.]

no one mentioned it but you coold have fixed the idle of the stock carb . there is an ajustment screw hidden under that grey plastic cap on the side of the carb. you just need to pick that off and turn it just a little. less than a quarter of a turn to let it line up better and richen the mixture. iv done it on mine. My carb is was the older flip choke fixed jet type but the jets are set up the same way. also the screw dosn't have a spring on it to keep it from moving like the fully ajustable carbs so it gets loose once you turn it. You may have to do somthing to keep the screw from moving afterwards. i lerned that the hard way. my screw fell out on the trail and now i need to replace it. luckily my local mower shop can order replacement screws and even the plastick cap.