blats Posted October 3, 2015 Report Share Posted October 3, 2015 I have a '73 620, manual trans. DCH340-12 carb. I've been working on a power problem and finally took the carb apart, found a missing part that doesn't come in the kit. Overall the carb seems in OK shape but I can't get this part anywhere. Its the check valve in the accelerator pump output - the weight and spring on top of the ball bearing check valve is totally missing. Someone thought it would be a good idea to just toss a second ball bearing in there. Let me know if you have a junk carb or a serviceable one would work too. Quote Link to comment
datzenmike Posted October 4, 2015 Report Share Posted October 4, 2015 There is only a very 'soft' spring and a BB. It allows gas to be sucked past it but prevents gas being pushed out on the down stroke. Any L or carbed Z series will work Quote Link to comment
stormsinger54 Posted October 4, 2015 Report Share Posted October 4, 2015 i have a l20b hitachi just taking up space in my garage...not complete but has all internals i just took off the accelerator linkeage...the rest is there....would that work??ill send it to you for cost of shipping 1 Quote Link to comment
blats Posted October 4, 2015 Author Report Share Posted October 4, 2015 Yes, the spring is missing. I'm having problems with the bowl either emptying completely or overfilling, can't seem to get float set right. I'm thinking the suction from the accelerator pump output tube in the air flow may be pulling gas from the bowl. Popping and flooding, very strange symptoms. Quote Link to comment
datzenmike Posted October 4, 2015 Report Share Posted October 4, 2015 I don't think the reverse flush from the pump would do this. Do you have the stock mechanical fuel pump? Was it replaced by an electric one that may provide too much pressure? Remove the inlet needle valve and check for dirt or any obstruction that would prevent it closing. The float setting is very delicate, a small adjustment can swing between flooding and running dry. The proper setting for the float is that in the full up position it is horizontal with the needle valve closed. Another way is to turn the carb upside down so the float hangs down (in the fully up closed position if right side up) The top of the float should be horizontal to the top of the float chamber top... roughly 0.28" between them. 1 Quote Link to comment
blats Posted October 5, 2015 Author Report Share Posted October 5, 2015 I set the float per the manual and got no gas. I did check the needle etc as well. I checked the fuel pump, 5psi pressure which is higher than spec as far as I can tell. A new fuel pump has the same pressure, so I'm confident its not the pump. Tested the line from the tank and fuel flowed freely. I'm digging now looking for what could be causing, and this is the only thing I've found out of order. There was some gunk in the bottom of the slow jet bore but not much. When I reassemble I will set the float to spec, but I need this spring first. Thanks! -david Quote Link to comment
Boxcar Posted October 9, 2015 Report Share Posted October 9, 2015 I've got 2 siting on the shelf. 1 rebuilt the other is a rebuilder. You can have the rebuilder if you want it. Its all there and clean. Do you ever get to Astoria???? Quote Link to comment
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