3 Seater Go Cart

WingingIt74 wrote:Once started, it's just like a needle valve on a Cox.

Just remember though, it's an idle mixture screw, NOT a full throttle mixture screw.

microflitedude wrote:So I just move it around until it runs smoothest?

MFD:

As to what I wrote, yes. Start at the center of the adjustment range.

Thanks guys. So I'm looking for the smoothest idle.

microflitedude wrote:Thanks guys. So I'm looking for the smoothest idle.

Yes, except the best indication of correct mixture is plug color. You are looking for nice cocoa/tan deposits on the spark plug.

Ron:



But WAIT a minute! People here are fixated on scrubbing off deposits off pistons.

Now this? Tan deposits are OK on spark plugs? This is getting funnier by the post!

A couple of tests you might apply to the idle mixture are:

Try to accelerate quickly out of idle. If it dies relatively quickly it is probably too lean. If it bogs down and slowly accelerates it is probably too rich. If it accelerates smoothly it is probably pretty good.

Also, while it is idling, pich off the fuel line quickly and completely. A good idle mixtutre should give you a small noticable rise in RPM just before the engine dies cleanly.

I have used spark plug deposit color more as an indicator of mixture at operating speeds.

Just to let you know I am not a small engine mechanic by trade, though.

Good luck,

Bob

Ugh... Did not go well. I've got a blood blister from all the pulling.

It pours out smoke (which I think is raw fuel) when it runs OK. But when you try to lean it it out, it shuts off. It wasn't like this week ago - no smoke, super low steady idle, and a smooth throttle curve.

I'm stumped. I'm ready to borrow the Subaru off the other cart.

MFD:

Going back to where this all began, what made you think that the carburetor needed to be rebuilt in the first place? What were the symptoms?

You may have misdiagnosed the problem.

SuperDave wrote:MFD:

Going back to where this all began, what made you think that the carburetor needed to be rebuilt in the first place? What were the symptoms?

You may have misdiagnosed the problem.

When we bought it, it would not draw fuel. If you sprayed carb cleaner in the intake, it would run until it burned it off. I pulled the diaphragm cover off, and saw that the diaphragm and reeds were deformed and rotten. I replaced all the gaskets, diaphragm, and thoroughly cleaned all orficces in the carb. I also replaced the gas tank which was rusted on the inside.

It cranked right up after that and ran fine. I don't know what I did wrong or where, but I can't pull the cord anymore.

Also, it will not idle. Even if you turn the idle screw all the way in.

microflitedude wrote:
It pours out smoke (which I think is raw fuel) when it runs OK.

What colour is the smoke? Black is unburnt petrol (too rich), whilst blueish white is burning oil. Is the engine 2 or 4 stroke? I expect it would be a 2 stroke, so start with some fresh petrol and be careful about mixing the correct amount of oil in it. Nice crispy, fluffy white smoke is burning metal (aluminium or magnesium), which I very much doubt is the problem here. However, it is important to differentiate between too much fuel and too much oil.

It's a four stroke. The smoke is whitish blue, so I guess I have a bad piston ring.

microflitedude wrote:It's a four stroke. The smoke is whitish blue, so I guess I have a bad piston ring.

Could be piston, rings, valve stems, valve guides and/or valve guide seals. It could also just be grossly overfilled with oil. The last one could be it given that you describe that smoke "billows" out of the exhaust. What ever it is it sounds pretty dire, so if it was fine before you stripped the engine down then you'd ought retrace the steps you've taken so far. It would be difficult to do that much damage and not know it.

dinsdale wrote:

microflitedude wrote:It's a four stroke. The smoke is whitish blue, so I guess I have a bad piston ring.

Could be piston, rings, valve stems, valve guides and/or valve guide seals. It could also just be grossly overfilled with oil. The last one could be it given that you describe that smoke "billows" out of the exhaust. What ever it is it sounds pretty dire, so if it was fine before you stripped the engine down then you'd ought retrace the steps you've taken so far. It would be difficult to do that much damage and not know it.

This started a while after I rebuilt the carb.

You might have something with the oil being overfilled, as it started once I replaced the old oil with new stuff. (30W) It said to fill the crankcase up to where it was almost coming out of the filler hole. (which I did) I wonder if it was too much, and oil is getting forced into the combustion chamber...

Drain a little and try it. I think most have the oil up to where the threads start.

WingingIt74 wrote:Drain a little and try it. I think most have the oil up to where the threads start.

I will do that. I've got it up to where they end - maybe I misunderstood the instructions.

If the engine was a non-runner from the start someone prior to you might have "tinkered" with it without knowing what they were doing. Therefore there are a lot possibilities when it comes to the problem to be corrected.

Apprently the engine has spark which narrows the serch to carburetion. How certain are you that the carb linkages are in the correct positions? Where the orifices blown out with compressed air? (Particles of the rotten parts may be blocking them) New parts won't remove such blockages.

Carburetor cleaner, such as "Gum-Out" works well for cleaning but ether (starting fluid) is a better indicator of any engine's possibility of starting. (Ether is high explosive so use it only in light applications).

If all else fails, obtain a repair manual for your specific engine and go through the diagnostic procedures described. Genaric manuals are generally are not adequate in my experience.

I drained some oil - we'll see how it goes.

dinsdale wrote:

microflitedude wrote:
It pours out smoke (which I think is raw fuel) when it runs OK.

is burning metal (aluminium or magnesium), which I very much doubt is the problem here. However, it is important to differentiate between too much fuel and too much oil.

about the "Nice crispy, fluffy white smoke'' what are the possible fixes for this? my lawn mower does this on occasion like maybe 1-2 times a season

mitchg95 wrote:
about the "Nice crispy, fluffy white smoke'' what are the possible fixes for this? my lawn mower does this on occasion like maybe 1-2 times a season

I doubt it. You're probably looking at oil burning. The quote above was a little bit of a joke in this context. Actually setting fire to the metal is real problem in aircraft fires, particularly in crashes, but it's entirely unlikely with your lawn mower. Once you get the metal burning you can't put it out with water. That's what makes aircraft fires so ferocious.The magnesium gets going relatively easily, and that gets the aluminium burning. Aluminium is the next most reactive metal after magnesium. Once your lawn mower does this there's no recovery at all.

For possible reasons for excessive oil burning refer back to my list above. There are ways of narrowing that down but it is quite technical and beyond the scope of this thread.

Best o' luck.

THANK YOU Travis, draining the oil did the trick. Most of the smoke is gone, maybe draining some more oil would help. I left it level with the end of the threads. (a new piston ring/gasket would help the problem a lot, I think) It is also much easier to pull the cord on the downstroke. (lower crankcase pressure)

When I went outside to start it, first pull and it idled perfectly. Talk about inconsistency! It still does some buggy things, but it should be fine for Joe Nall. I wired a kill switch into the steering wheel.

I noticed something odd, though. When the motor is running, the slighted touch on the pedal and the engine will slowly start accelerating until it reaches peak. When it is not running, it doesn't do it. I'm guessing it's the governor. I disconnected what I thought was the governor pushrod, but it did the same thing.

Thanks to Dinsdale as well, he brought up the oil problem too.

My friend is picking up the two carts, and then we will rendezvous at Triple Tree tomorrow afternoon. He is bringing an extra one, so three carts and five people should be fun.

Did a few extra things like putting thread locker on the spindle bolts, and replacing the brake band.