Someone mentioned in another blog that a plastic manifold causes problems w/warpage. My manifold looks like cast iron, but there is a black square between the manifold and the carb, but when I tap it it feels like steel not plastic. Like I mentioned, engine now sputters at full throttle, so I dont think it is an idle jet.

below is a link to photobucket with some pics of my carburetor.

Here is a link that might be useful: photobucket pics

Heres a link to partstree.com for my engine.42A707-2238-E1 You can zoom in or go back to complete parts list on their page

Here is a link that might be useful: partstree

Now that I see it does have a fuel pump on partstree, and that is part of a "carb rebuild kit", I'm really suspecting the fuel pump. Any comments anyone?

"Any comments anyone?"

Yes, assuming your model number is correct, why did you put that it was an OHV engine?

I would remove the hex head plug at the lower right side of the carb when looking at the Intake Manifold. Be aware that gas will run out and maybe water/crap. Blow compressed air in there and or probe with a tag wire. See if that helped.

Check for leak in the fuel pump vacuum line running from the crankcase to the bottom of the fuel pump. Is the line from the fuel pump to the gas tank clear?

Walt Conner

Walt - the engine owners manual states it is a "twin cylinder overhead valve (OHV) air cooled engine." It does not show any discrepancies between the 2 models covered in this manual (420000 and 4600000 series) for that statement. There is a discrepancy with the mower sales sheet however, that sheet simply calls it an "Industrial plus opposed twin engine", whereas some other models specify "OHV". Hard to believe the engine manual is wrong, but I guess it could be.

the vacuum line is black and looks good. I'm gonna try a pump diaphram rebuild kit first. I'm guessing that rubber diaphram has been weakened over time. I imagine it gets worse at low speed because of slower pump cycling / weak diaphram.

I checked my owner's manual and indeed - it states this is an OHV low emission engine. I assure you it is not ohv.

the engine performance improved when you partially closed the choke. This is an indication of a lean fuel air mixture. The fuel pumps are usually very reliable, but there could be a leaking diaphram. My suggestion is to renew the entire carburetor and fuel pump. The pump pulse hose should be clamped. Hoses develop cracks and become hard - especially around the ends. Air leaks are common. I know you replaced a section of hose. The fuel hoses around the engine frequently become hard, then cracks form. The fuel pump draws in air. Also the ends of the fuel hose also allow air leaks.

The current ethanol fuel sometimes leaves residue on valve stems. The valves may not be closing fully due to sticky valve stems. There could be excessive carbon on the valve seats and in the combustion chamber.

The opposed twin was a great engine and is well worth maintaining provided the equipment is in reasonable condition.

Well, it ended up being something in the carb, not sure what. Like an idiot, first I bought a fuel pump rebuild kit, not knowing that you can't buy a full carb rebuild kit that doesn't already come with the pump kit. So when the fuel pump kit didn't help, I had to buy the full carb kit, which worked for who knows why (new needle,main jet, pilot jet, gaskets. My carb looked really clean inside. Now I have an extra fuel pump kit.