rebuilt engine; only idles

I rebuilt my Sachs 505 1/A with a new kit, carb, ignition, and so on. Upon sorting out my timing, it now starts and idles, but no matter what you do to the throttle it will not rev. I played around with jetting, going from a size 60 to 68 (dell SHA) but no higher or lower because thats all I have for jets for now. I though if i was running super rich/lean i would get some change with the different jetting.

So, if anybody knows what these symptoms are indicative of, i would like to know. air leaks went through my mind, but i would they cause these symptoms? Ive been playing with this thing for 2 days now.

Re: rebuilt engine; only idles

Are you running with the stock air filter?

Re: rebuilt engine; only idles


sounds pretty lean still, and those jetting changes are fairly minor. maybe try choking it some by hand and see if you can get some more go. Timing could still be an issue, but probably not; also if you clipped or caught the rings and chipped it at all when installing it, you'll drop the compression and have that sort of problem too.

airleaks can cause such a problem because it'll lean out your mix further, but sachs seem pretty resilient against airleaks. I think too-low jetting is most likely. I run mid 70s on a 50cc.

also depending on the kit, you may need a long reach plug. The athena 80 and I believe the 70 as well take B7ES instead of HS plugs

Re: rebuilt engine; only idles

Plug is long thread. I'm going to buy some carb cleaner and check for leaks, and probably check the rings. I tried choking it by hand but that usually does nothing except kill it if I over choke.

Re: rebuilt engine; only idles

Probably Fred /

What size sha ?

Re: rebuilt engine; only idles


Carb cleaner indicates no leaks. So it can still be timing or kit issues. Now, I did notice something; there is a 'chhh' sound as it idles that seems to come out of the carb. I don't think it did that before. Is that blowby I'm hearing slipping past the ring?

« Go to Topics — end of thread

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account