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Discussion Starter #1
Ok some back ground

Dad has overhauled the engine by a local shop.
in the process he switched the alum, boxy carb (MS??) for the cast iron Zeinth.

Just prior to the OH we installed the Pertronix electric ignition, works well BTW. http://www.pertronix.com/prod/ig/ignitor/default.aspx


Startes great...but
Now it smokes like a diesel idling and misses with fast to moderate throttle application, it can smooth out after it "catches up" its like it loads up.

My question is what size jet should be in the carb....or is there replaceable jets in idle circuit within the carb?? Seems like it is over fueling on idle with some improvement at full throttle.

thanks,M
 

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For idle mixture you should be able ot adjust the mixture screw at the top part of carburetor near the throat. If you can turn the mixture screw all the way in with out any improvement, you probably have a float problem. Either float could be adjusted too high or float valve may be leaking, or float may have a hole in it. Jet size should not be too crucial unless it is too small and making it too lean since you have adjusting screws.
 

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Discussion Starter #3
For idle mixture you should be able ot adjust the mixture screw at the top part of carburetor near the throat. If you can turn the mixture screw all the way in with out any improvement, you probably have a float problem. Either float could be adjusted too high or float valve may be leaking, or float may have a hole in it. Jet size should not be too crucial unless it is too small and making it too lean since you have adjusting screws.
Idle screw doesn't seem to have much of any affect when adjusting it untill almost shutting it off.

I found another site that has a great pictorial exploded view http://www.robertscarbrepair.com/ then look under the carburetor parts tab .

something for sure isn't right...right now the plugs are fouled..so that is 1st thing to fix.

but yeah, the float might be miss adjusted...it is a brand new carb....wouldn't imagine that the float is bad....maybe:dunno:

not trusting the shop right now that sold and installed it ...he said there is no jets in there....and clearly in the exploded view...there is.
 

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Discussion Starter #4
well I finally got some time to tinker with it.
replaced the cap and rotor and plug wires, all of which were fairly new eer atleast low hours...but
on closer inspection of the cap...2 of the wire towers on the cap were very corroded which didn't help matters, and those wire weather caps were kinda loose to around the wire itself...must of allowed moisture to migrate in. new wires got some dielectric compound treatment. got a bit dark so new plugs had to wait.

initial results were much improved throttle response...no more missing and popping around until it gets warmed up. I also destroyed the old cap so dear ole dad can't "save it for just in case".

bit disappointed with the shop that OH the engine for not putting on new wires and cap
 

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Discussion Starter #5
well I finally got some time to tinker with it.
replaced the cap and rotor and plug wires, all of which were fairly new eer atleast low hours...but
on closer inspection of the cap...2 of the wire towers on the cap were very corroded which didn't help matters, and those wire weather caps were kinda loose to around the wire itself...must of allowed moisture to migrate in. new wires got some dielectric compound treatment. got a bit dark so new plugs had to wait.

initial results were much improved throttle response...no more missing and popping around until it gets warmed up. I also destroyed the old cap so dear ole dad can't "save it for just in case".

bit disappointed with the shop that OH the engine for not putting on new wires and cap
got the new plugs went in today.....but instead of the recommended plug gap of .025, I went to .033-.035. To help create a bit of a hotter spark. Mostly because it generally don't get run long enough to fully get warmed up, unless field work is involved.

I thought about about 3E plugs but they do not make a plug for this application, I have tried them in lawn mowers with improved starting. This time I went with Autolite plugs because the Champion's tend to fowl easy. the old plugs were pretty well carboned up again.

now if the old carb needs tweaking, everything else is up to snuff
 

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got the new plugs went in today.....but instead of the recommended plug gap of .025, I went to .033-.035. To help create a bit of a hotter spark. Mostly because it generally don't get run long enough to fully get warmed up, unless field work is involved.

I thought about about 3E plugs but they do not make a plug for this application, I have tried them in lawn mowers with improved starting. This time I went with Autolite plugs because the Champion's tend to fowl easy. the old plugs were pretty well carboned up again.

now if the old carb needs tweaking, everything else is up to snuff
Glad its better. I saw you replaced the MS with a Zenith. I am wanting to replace my MS with a Zenith on my 4010 and have asked in this forum and others if anyone knows if the Zenith will mount up without changing linkages etc. How was your swap?

tks
Tom
 

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Discussion Starter #7
Glad its better. I saw you replaced the MS with a Zenith. I am wanting to replace my MS with a Zenith on my 4010 and have asked in this forum and others if anyone knows if the Zenith will mount up without changing linkages etc. How was your swap?

tks
Tom
I didn't do the swap personally...it was done when Dad had it Over hauled.
It appears that no linkages needed to be changed, might need some minor adjustments, but everything looks original.

Might want to call this place http://www.robertscarbrepair.com/default.asp
I'm sure you can find a cheaper carb but this outfit claims to have a lot of over fueling issues resolved
 
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