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Post by trashman36 on Apr 23, 2020 17:52:31 GMT
Hello,
Hope everyone is doing well. I'm trying to figure out what's going on with this 340 in my Oly. This thing sat out back behind my garage for several years. Over that time the mice had used the carburetor for a urinal. Needless to say they ruined it. So found a different carb rebuilt it and put it on now when I start it up it revs up to I'm guessing 5000+ rpm and it won't idle down. I'm at a loss any suggestions would be greatly appreciated.
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Post by olyman on Apr 24, 2020 17:07:31 GMT
Is the throttle free and able to close up enough to rest on the idle screw? If it is then what about the Jets - what are they set to? If they are close to spec (3/4 turn on the low speed, high is fixed) then start thinking about it getting excessive air from leaky seals. Best way to check that is spraying wd40 on the when it's running. If it sucks it in there it will snuff it out. If you sprayed Ether into it I'd expect it would race even more so don't use it.
Place to start anyhow
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Post by ericr on Apr 25, 2020 2:44:25 GMT
I have a 71 399 I bought cheap, seventy five American bucks complete with carb and clutch, supposedly 125 psi in both sides- fired it up on the bench and it does like you describe your 340- noted it dribbles BAD out the carb throat. I wonder if you have a needle/seat leaking past? My 73 340 had leaky crank seals and for that matter the whole case half gasket on the clutch side (pressure tested the long block) but it did not act like the mill you have. It ran good cold but once warmed up would bog and die if you did not hold it over half throttle.
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Post by trashman36 on May 1, 2020 20:28:49 GMT
Eric
I discovered what i think is the problem. I pulled the pulse line off and pulled the plugs out puleed it over and gas ran out of the pulse fitting. Im thinking the carb that was on it the wrong carb btw was dumping gas and filled up the case.
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Post by olyman on May 2, 2020 13:02:46 GMT
What carb are you running on it? The crankcase is where any carb sends the fuel on these things, and then it comes around up through the transfer ports to the piston dome area. So if you see some come out of the pulse port its suggesting that the carb is putting lots in, but if the engine is racing then its getting air too. If it wasn't getting air the it would still have lots of gas but couldn't burn it and would flood out. Maybe it's the throttle shutter plate not installed properly and can't close the gap when closed?
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