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I've got a little 3 hp Tecumseh on a mini bike. When it's running a little puff of white smoke will come out when I hit the gas. Is this normal or the beginning of a piston ring replacement? It does not smoke at idle or when I maintain a higher rpm, just when I hit the throttle.

:welcome:

In general,
White smoke under load = worn rings
White smoke backing off = valve guides

Is it using oil? Bad valve guides will also cause oil consumption.

bertsmobile1 said:

:welcome:

In general,
White smoke under load = worn rings
White smoke backing off = valve guides

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That's kind of what I thought. So it's probably the rings. Does it even have valve seals since it's a horizontal shaft?

reynoldston said:

Is it using oil? Bad valve guides will also cause oil consumption.

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No not really using any oil that I can tell. But its only ran maybe two hours since the last oil change. Actually I filled it just a tiny tyne bit over the fill line. Like maybe a cm.

I wonder if I should add some of that Engine Restore from Autozone and see if it stops smoking. I don't think it will hurt the engine anymore than what it already is. It's only a couple bucks and if it works then that beats the hell out of tearing the engine down and replacing the rings. Any thoughts?

Nothing you can pour into the engine will ever fix anything, just mask the symptoms till the engine goes bang.
As it is a "toy" you will have to make call on it.
If the engine has a C I linner then no great drama but if it is plated running on bad rings will kill the engine.
Again depends how long you want to keep it for.

bertsmobile1 said:

Nothing you can pour into the engine will ever fix anything, just mask the symptoms till the engine goes bang.
As it is a "toy" you will have to make call on it.
If the engine has a C I linner then no great drama but if it is plated running on bad rings will kill the engine.
Again depends how long you want to keep it for.

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Yeah I'll probably just rebuild it. I have been looking online for awhile and I can't seem to find a complete rebuild kit for a 3-1/2 hp Tecumseh. The only thing I found was a set of new rings with a new piston. I figure if I'm gonna do the rebuild I might as well do it right and replace the gaskets and everything else that comes with a complete kit.

Post your engine model number.

0352 said:

Yeah I'll probably just rebuild it. I have been looking online for awhile and I can't seem to find a complete rebuild kit for a 3-1/2 hp Tecumseh. The only thing I found was a set of new rings with a new piston. I figure if I'm gonna do the rebuild I might as well do it right and replace the gaskets and everything else that comes with a complete kit.

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There is much more to it then installing a new gaskets, seals, piston and rings to completely rebuild a engine.

I'm not sure where the model number is on the engine. Ok, so here is something very unusual and weird. The engine started to stumble and backfire and wouldn't idle. So I figured there was some foreign debris in the carburetor, so I took it apart cleaned it and put it back on and that fixed the backfire issue. But now it doesn't smoke at all. Full throttle, idle and in between. Now don't get me wrong I'm thankful it's fixed I just want to know how. It's like someone replaced the rings without me knowing. I didn't add any additive to the crankcase. Any ideas on how it could have repaired itself. I have never seen this in my 25 years as a mechanic.

reynoldston said:

There is much more to it then installing a new gaskets, seals, piston and rings to completely rebuild a engine.

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Yeah I know I just didn't want to have to go into detail about it.

0352 said:

Yeah I know I just didn't want to have to go into detail about it.

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To do a complete rebuild right you could buy a new engine for less money. Machine shops aren't cheap unless you own your own equipment.

reynoldston said:

To do a complete rebuild right you could buy a new engine for less money. Machine shops aren't cheap unless you own your own equipment.

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I have my own equipment. I build all kinds of engines. From stock all the way to an ASCS outlaw engine.

I'm just wondering if maybe the oil rings were stuck somehow and the backfire caused them to break loose and work properly.

0352 said:

I have my own equipment. I build all kinds of engines. From stock all the way to an ASCS outlaw engine.

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Seeing you have a complete machine shop and build engines I think I better keep my opinions to myself.

I still have not seen anything like this. I mostly deal with large V-8's. Does this happen with the small single cylinder engine? I am not very familiar with these. I know most engines use the same concept (intake, compression, combustion and exhaust) just applied with different parts and designs. Just because I have access to a machine shop does not mean that I know everything. I have seen some strange things happen to engines, just not this.

Through the last 120 years or so, other then a few odd balls the basic 4 cycle piston engine hasn't changed. The same principals applies for a small single cylinder gas to a large diesel engine. Don't let the size put you down. I really do think someone should come up with something better and cheaper then the piston engine but it hasn't happen yet. When it dose happen the car manufactures better watch out or they will have on there hands what happen to Kodak.