M18 issues

[wjamesm]

Hello all . i have a 1812 with the mag 18 and has about 550 hours on it . i didn't use it this winter , so it sat and the carb leaked gas through it and into the oil . i bought a new replacement carb for it and got it installed and after changing the oil and filter tried to start it to tune the carb . the carb didn't respond to any adjustments and the engine was running rough . I did have the valve cover off to check the valves on the cover that has the vent hose going to the air cleaner . I replaced the gaskets and the rubber button because i broke it when cleaning it . put that back together and tried to run the engine , The engine was revving pretty high . i had the governor arm off when trying to get the linkages back on the carb and after reading found i had left the tension off the governor spring so i loosened the governor arm bolt and opened the throttle fully and used a pair of pliers to rotate the governor shaft clockwise till it stopped and tightened the bolt . That helped but the engine is still running rough . i replaced and gapped the plugs in case on was fouled from all the gas . still no improvement . When i had the motor running it wasn't smoking but i pulled the oil fill cap off and it almost shot out of my hand , so there was alot of crankcase pressure . So through reading i though maybe a head gasket was blown . I ordered 2 new ones and started to take the right side head off . I was surprised there was a metal head gasket when i pulled the head off and it didn't look like it was blown out any where . I am going to get sand paper tomorrow to true the head before putting the new gasket on but i am not sure the head gaskets are the problem . Could the gas have washed the cylinder walls of lubrication and wiped out the rings causing the blowby ?

[ol'George]

Whoh there!
You are making a lot of of assumptions.
first off the original carb prolly only needed a needle valve/seat for $10-12.
and a bowl gasket.
As far as pulling the fill cap off and experiencing a shower,pretty normal and typical for a novice.
About like pulling the lever on a garden hose nozzle to see it it is turned on while pointing @ your face Ha,LOL
you will not do that again.
It is possible you got some crud under the needle in the new carb, or it is the wrong carb or it is defective.
If it were me I'd take the bowl off the old carb and inspect things, as you knew the old was was good till it got crud under the needle or it was time for a cleaning.
FWIW:a leaking fuel pump diaphragm can piddle gas into the crankcase also.
now clean up the head and put on a new gasket.
After you fully warm the engine a time or two ( operating temp) then retorque the head because if you don't, you will replace the gasket again because it will blow as sure as rain. If you haven't downloaded the FREE
jinn u wine service manual from our technical section get er done.
That will keep you busy for a while and don't fear to ask "stupid questions"
( stupid questions are those not asked)

[wjamesm]

This is the carb i got off of ebay http://www.ebay.com/itm/311742901569...%3AMEBIDX%3AIT I did have to change the choke shaft from the old cab to the new one . The original carb was a adjustable needle type . What about the metal head gaskets ? Are they the original oem parts ?

[ol'George]

Normally, the fellows seem to have good luck with that carb you bought.
Metal head gaskets that have the "fire ring" have been proven to not give problems Ebay # 271824562906 is an example.
they are stens and are good.
Some have used the non metal type but I have not personally.
On your new carb, are you not seeing a change when you adjust the main jet?
Are you getting black smoke indicating rich mixture or is it starving ( lean)
Get it back together and we will help you get it right.
Do keep an eye on the dipstick as you could have a bad fuel pump.
but one step @ a time.

[wjamesm]

When i adjusted the main jet it would stumble and about stall when i turned it in . I set it at 2 1/2 turns out from lightly seated before i started the tractor . but no black smoke to indicate a rich condition . I'll see what it does after i get the head gaskets back on and torqued tomorrow . If it still dosen't run right i think i will put the old carb back on and order a new needle and seat and bowl gasket .

[ol'George]

Originally Posted by wjamesm

When i adjusted the main jet it would stumble and about stall when i turned it in . I set it at 2 1/2 turns out from lightly seated before i started the tractor . but no black smoke to indicate a rich condition . I'll see what it does after i get the head gaskets back on and torqued tomorrow . If it still dosen't run right i think i will put the old carb back on and order a new needle and seat and bowl gasket .

I'm cheap prolly need a bowl gasket but you might have something simple like a hair or other chit in/under the seat of the old one.
see what it needs first, might get by inexpensivly, they are simple inside.
Sometimes a piece of the fuel hose gets into the carb nipple and causes a problem in one or both so look, and blow it out.
also it is possible that you have a plug fouling because of the flooding.
It wouldn't hurt to put in a different set, don't have to be new as long as you know they are good ones from something else that is running, as a test.
Also make sure your choke is opening properly/fully when warm as you did some work there.