Briggs and stratton 18.5 hp wont turn over at proper speed

[agatto2]

Hey ... first post is a questions...

I have a briggs and stratton model 42a707 twin 2 that is giving me a fit.

Here is whats going on. Its real slow cranking and almost stops on compression stroke. The starter cranks fine when the plugs are out

I pulled the starter and cleaned it up real good, re-installed and its working a bit better but wont turn the motor over fast enough to start.

I am going right from my motor in my cherokee 660 amps to the post on the starter. The voltage drop on the battery is 12.57 to 11.5 which seems reasonable even though i cannot figure out exactly what the amp draw and voltage drop are supposed to be.

I am starting to think that its the valves, so i pulled the heads and they are carboned up a bit, not terriable. The valves seem to be seating properly and at the proper time.

I have never had to set valves like in this motor before . Does any one have suggestions or point me in the right direction for getting the valves into spec so i can rule that out.

tks in advance

 

[Fish]

Common problem on that engine. Totally de-carbon the heads and piston/valve area, that carbon kicks up your compression ratio
exponentially... But keep in mind, by now, that you may have starter damage as well, and those twin starters are bad for a lot of wear on the top shaft of the starter...

But do the de-carbon first!!! That will probably take care of it!!!!!

 

[Fish]

Take a wire brush and scraper, and get to work. If the gaskets are still in 1 piece, reuse them!!!! Try it now and get back to us here!!!

 

[agatto2]

Take a wire brush and scraper, and get to work. If the gaskets are still in 1 piece, reuse them!!!! Try it now and get back to us here!!!

already on it... one side cleaned and ready. Will get the other in the morning, cold ones were calling

I did notice that the wiring inside the starter looked a little burnt... prob did not help that the starter was dirty as could be inside.

Will let you know how it works out. My plan is to get the carbon off the flat heads and valves, that should help her out quite a bit....

However when i turn it over by hand it does not feel like its a high compression thing, meaning i just adjusted my valves on my honda 390 because when you pulled the start cord it practically ripped your arm off with compression back lash...

 

[agatto2]

Update.....

I cleaned both heads , pistons and valves.

Note: one of the intake valves had soot on it like a exhaust valve would (like its not seating properly on the exhaust stroke). Will have to keep an i on that if it runs poorly when i get it started.

Also have a cleaned up starter.

The motor is cranking over better now. Enough for it to fire and start up. However the starter is getting hot. I am guessing that its shorting out and was giving the previous owner the business... no wonder i picked it up so cheap.

Another interesting find --- there were two new spark plugs in the engine when i bought it. One was a bit loose in the socket. I deduced that there might b a spark problem so i tested. No spark. New spark plugs that have never been used.

I took a good known spark plug and put it in and it sparked. I have to think that the original owner bought two brand new spark plugs because he was not having spark and they did not work either....

Whats the odds????

will update after i buy two new "good spark plugs" .

As i sit now i am thinking a new starter and battery will be in order. However i want to get it running first.

T