Tecumseh Running Rich.. Help Please!

[Kawabuggy]

Okay guys. I'm back. You may remember me from this thread:
http://www.diygokarts.com/vb/showthread.php?t=14137
After the carb was flooding last time and dripping gas, I went back in and adjusted the float. The carb is no longer leaking gas back through the intake into the air filter.

The cart starts very easy, 1st or second pull when cold, and then starts easily on the 1st pull once warm. However, it is still having issues where it is running excessively rich at WOT, puffing black smoke, and misfiring. I put the back end up on a large crate so that the drive tire was free to run. I slowly accelerated from idle through WOT. What I find is that the cart has great idle, and off-idle performance, then it accelerates briskly up through 1/4 throttle. Once you get to that point, if you try and push it faster, the engine starts mis-firing, hesitating, and blowing black smoke.

I pulled the plug and it is obvious it is running rich. The plug is black with soot. I pulled the valve cover and verified that the valves are still adjusted at .004" intake & exhaust when on power stroke. I rotated the engine CLOCK wise (opposite direction engine runs) to get to TDC as it states to do this in the manual. So, valves are good, engine runs good at idle up through 1/4 throttle, but hesitates and misfires at anything above that. Any ideas what I should be looking at???

I tried running it with the air filter off thinking the air filter may be plugged up. It's new but I thought I should try it without the air filter in place anyway. What I see is that when the engine starts misfiring, and hesitating, that there is reversion present. You can hold your hand in place of the air filter and feel a puff of gas/air against your hand when it misfires as it is blowing it back through the carb. Up to 1/4 throttle when the engine is running well, it does not do this.

Do you guys think this is still a carb issue, or is it possible the valve springs are weak and I'm floating the valves? Hard to imagine that floating the valves could cause it to run so rich, and soot up the spark plug.

Anyway, I'd appreciate any input as to which direction I should go at this point.

 

[Doc Sprocket]

Has your carb got a fixed main jet, or an adjustable needle jet?

 

[Kawabuggy]

Fixed main jet. Non-adjustable carb.

 

[Russ2251]

Floating valves do NOT produce a rich state.
Maladjusted valves will cause a small power loss.

 

[Kawabuggy]

Russ, thanks for the info, any idea what I should be looking at to solve the rich condition?

 

[sexyvicta]

Does it run like this when you actualy drive the kart or just when you have it up on the stand?

Does the carb have idle/low speed jet, adjustment?

 

[Russ2251]

Verify that float level is correct to factory spec.
Verify that metered holes are not damaged (oversized) in emulsion tube and that needle and seat are providing a good seal. Refer to schematics. Make sure everything is in place.

 

[Kawabuggy]

Victa-this carb has no adjustments of any kind. Yes it runs the same when you are actually driving it.. If you give it partial gas, it runs like a scalded dog. If you put the pedal to the floor, it will accelerate rapidly getting up to speed, but once it gets going, if you hold it to the floor, it will start hesitating, misfiring, blowing black smoke, and will lose speed.

Russ how can I verify the float level is correct? Previously, after sorting out the no-idle situation, the float was adjusted incorrectly as it was leaking gas out the air inlet side of the carb when the engine was off. Yesterday I adjusted the float again so that when the carb is held upside down, the floats are exactly parallel with the body of the carb. It is no longer leaking gas when it sits, but still running rich at WOT.

 

[Kawabuggy]

Russ, forgot to mention that when I pulled the bowl on it yesterday to adjust the floats again, there was a bunch of crud in the bottom of the float bowl again. I have an in-line filter on it, but apparently that is just a screen, not a paper type element, and it is not catching all of the "crud" that was still in the tank or lines. I flushed it all out again, and checked the seat that the needle seals against and did not see any contamination there.

Should I maybe try a different carb at this point?

 

[karl]

Lemon juice boil?

 

[Kawabuggy]

Karl, I did do the lemon juice boil previously as I was having "no-idle" issues. I got the cart to idle, but now it won't run WOT..

 

[Doc Sprocket]

I don't know if you have a way of measuring the jet, but I wonder if maybe the cleaning process (or even the previous owner) opened it up too much.

 

[Kawabuggy]

I think I know what may be wrong with it. When I replaced the seat for the needle, I think I may have put it in backwards. There was a smooth side, and a side with "rings". I put it in with the ring side facing the needle. I will have to pull it back off, reverse the seat, and try it again. I say this because even after adjusting the float again to lower the fuel level, I went out today to look at it and it is dripping gas again. When I had it out it did not appear that the float had gas inside of it so I don't think the float is compromised.

I do however think that fuel is leaking past the needle/seat and flooding the carb. I'll have to pull it back off, and check it all again.

 

[Doc Sprocket]

You might be able to test the theory without turning a wrench...

Warm it up to operating temp. With the carb bowl full, shut the fuel valve off, and take a couple of high speed passes. If the leaking seat was forcing the rich condition, it will disappear (till the bowl runs dry). Then, you know it's that seat. Otherwise, look at the jet again.

 

[sexyvicta]

come to think of it my h25 was running the same until i bent the tab on the float a bit. It has an adjustable carb and i spent half a day trying to tune it before i thought to tweak the float haha

you could also check to make sure the throttle butterfly is opening fully/properly and that the choke one is fully open

 

[kendelrk]

do you have the tecumseh tool? theres a tool that not only has a peice for pulling out your seat, but also one to check and make sure your float is to spec, alright now heres a question, i had an h35 that did the same thing, turned out that theres a small metal peice that hooked onto the needle and somewhere else that will tell the float to shut/open, if you dont have it, its open all the time. open all the time and youll flood the carb, which not only makes it drip and pour out, but makes WOT impossible due to an excess amount of fuel in the carb that the engine can not burn

 

[Kawabuggy]

Toy-there is no fuel shut off valve on this cart. In fact, I've never seen a fuel shut off valve, or pet-cock, on any go cart or mini-bike. If I have to keep pulling and installing this carb it sure would be a nice feature to have. Know where I can get one to put in-line??

Victa-this carb is NOT equipped with any type of choke.

Kendlerk-If the needle were not seating I'd think it would be flowing fuel out pretty quickly. As it is now, it is a drop every minute or so. This tells me that the needle is against the seat, but perhaps not sealing fully and allowing fuel to pass through. Then after sitting, the fuel slowly fills up the bowl until it slowly starts to drip out of the air filter side of the carb.

I'll keep messing with it.

 

[Kawabuggy]

toy-I do like your idea and I think I may try it. What I'll do is clap a pair of vice grips across the fuel line to stop the flow of fuel from the tank to the carb. In this manner, if the motor clears out and starts running normally as the fuel level gets lower in the float bowl-I'll know I'm on the right track. If it continues to run raggedy until it finally runs out of gas... Then I think it will be time for a new carb.

I did have one other idea.. It looks to me like that red, plastic, emulsion tube that comes up the center of the carb has some o-rings that seal it off where it rides in the carb. What if those O-rings are bad, and the carb is pulling straight gas up around that tube instead of an emulsified mixture through the center of the tube as designed? My rebuild kit DID NOT come with new O-rings for that tube and when I pulled it out, they looked pretty bad. I'll do some more testing and get back to you guys.

 

[kendelrk]

what about your bowl gasket?

 

[Doc Sprocket]

You might be on to something with those o-rings. check them out and maybe see if you can get some at a hardware store.

Any decent mower shop carries a cheezy (but perfectly effective) plastic inline fuel shutoff valve. Slice your fuel line just below the tank, and install with clamps. Time? 2 minutes.

Kendel- It could have NO bowl gasket, and it would not cause a rich condition.