2 stroke bicycle engine - getting richer with break-in??

Pablo

Master Bike Builder & Forum Sponsor
Dec 28, 2007
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Just as the title says, did your 70cc 2 stroke engine - get richer with break-in??

I'm just about done with my first tank of fuel (as a time measure) and the engine is still somewhat breaking in. The only problem now is that it's getting progressively richer - to the point of me wanting to go messing with the needle. Plug is wet with fuel and when warm if I wick on full throttle it really bogs and sops with unburned fuel.
 

deacon

minor bike philosopher
Jan 15, 2008
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north carolina
Re: 2 stroke engine - getting richer with break-in??

Then move the needle. There doesn't seem to be any rules. If it isn't doing right try it you can always move it back.
 

Can Harm Hen

New Member
Mar 1, 2008
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Davis, California
Re: 2 stroke engine - getting richer with break-in??

Have you tried changing the spark plug and wire? My spark plug wire actually fell apart after the second tank of gas. Thanks to cruiser, who sent me a new one!
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
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I'll say the plug is definitely a real piece....try a new NGK first, then if it's still rich, change the needle.

It is possible that it can "get richer" since, after the engine starts to break in, will make more compression and draw a better charge into the cylinder each stroke.

Also, check your air cleaner element, mine got full of crud and spit back fuel relatively quick.
 

Norman

LORD VADER Moderator
Staff member
Jan 16, 2008
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pampa texas
You do have a fuel filter on it don't you. These engines are I'll say almost the bottom of the barrel in being well make very sloppy tolerances. I'm even wanting to say rejects are being sold to us and we are happy to get them. As you ride your carbs metal parts are also takin a seat or mating/wearing in so you might need to lean out the needle one notch. Or your float needs to be adjusted so the float chamber is not so full of fuel that its leaking out of the float gasket. Sometimes I think these little engines think up ways to pizz us off. I'm wondering about a good American or German spark plug with the proper thread reach and heat range.I will sometime check into it I'd like to know just what the china plugs letter/number mean in thread reach and heat range then I would kind of know that to look for in a champ or bosh plug. All well I'm in no big hurry its warn here and good weather to go ride but I'm tired and still messing with all you guys on this forum.
 

deacon

minor bike philosopher
Jan 15, 2008
8,117
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north carolina
Only filter I have is in the tank If there is one. after all this poor engine has been through with me messin' with it, i figure it will run till it gets tired me then throw up on me. Till then it gets nothing a poor chinese peasant wouldn't give it.
 

Norman

LORD VADER Moderator
Staff member
Jan 16, 2008
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Deacon
Better be wearing a good pair of pedaling shoes running without a fuel filter. The tanks fuel valve filter only gets the big lumps out the main jet is 0.026 in dia. so it will nail you when you don't need to be nailed. You can get a good paper fuel filter at walmart in the mower department for around $4.00 cheaper to me than a melt down pedaling it home.
 

Can Harm Hen

New Member
Mar 1, 2008
38
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Davis, California
Z4 072?! Where'd that come from? I got two Z8C with my bgf 70cc kit.

In any case, the Z indicates a M14x1.25 thread and 11mm reach. So, look for that when shopping for plugs.