HELP! Old K&B40 Broken Ring / Startup
 

I’ve had a broken ring on my old K&B40(model 4011 / produced until about 10 years ago). I’ve sent it out for replacement and cleaning and now when I started to run it won’t work at all as I was expecting. It won’t idle at low speed and it seems that it reaches full rpm at half throttle. If I open the carb fully it slows down and eventually dies. I’ve tried setting the needle valve differently but I get the same result.
What am I doing wrong(I even took the entire carb assembly out - thinking that it leaks air somewhere – and tighten it back in)? Should I replace the O rings on the carb and where can I get them from? (see my old post HELP ! Old K&B .40 on 1/4/2004)

RE: HELP! Old K&B40 Broken Ring / Startup
 

There's a air leak somewhere? What about the back plate? I got my O rings at the local hardware store the last time but I have gotten them from the bearing store.

Enjoy,

Jim

RE: HELP! Old K&B40 Broken Ring / Startup
 

I don't know. It doesn't seem like. How can I tell?

RE: HELP! Old K&B40 Broken Ring / Startup
 

Your particular engine is a little newer than 10 years ago unless someone changed the carb on it.

While looking at your parts pieces in the picture, there are both a front piece and a back plate to your engine. But most important is the presence of only one gasket. Where's the other gasket?

Enjoy,

Jim

RE: HELP! Old K&B40 Broken Ring / Startup
 

There're two gaskets front and back (see attached picture/you might not see the front one as is attached to the crankshaft). They're not cracked and seem to be all right when I attached them to the engine. Also, while holding carb lever the carb barrel is not moving (up & down) but I thought if the O-rings are old maybe the air still can pass through.

RE: HELP! Old K&B40 Broken Ring / Startup
 

How much break in time have you given the new ring? Is the engine too tight again to turn up to higher RPM or idle properly? When you install a new ring the engine needs to be broken in again to seat the new ring. Even Dykes rings need some break in.

RE: HELP! Old K&B40 Broken Ring / Startup
 

Yes you're right. I've done it and it runs good now. Thanks for your help. I've also changed the plug (it was too worn out and a little cold it seem).