Thoroughly stumped at the moment SPARKLESS

[luvzvintage]

thanx for the reply 400
yes, it is definately the 340/5. Prior to my issue with no spark this sled fired up by 5th pull every time and idled very well. It was only after scores of pulls to try to start the machine before i realized i had no spark that seemed to screw things up. This thing would continuously run fine on a stand but once under load it would bog at about 15 mph and just stay like that. At one point i got really ticked and just held WOT during the bog. After about 10 seconds of WOT, things seemed to clear up and the sled took off and then ran fine even at the previous bog area, however, that excitement only lasted till i got to an intersection and let off the throttle back to idle. Then upon acceleration, the same bog as previous was back. I've gone thru the carb numerous times, i run 50:1 premium fuel, like new Comet 102C with the correct weights and spring, original reconditioned secondary, correct belt, track is adjusted correctly and turns easily, tried numerous clean plugs, spark is healthy, exhaust is clear...etc, etc.

I don't know the history of the sled, however, i'm thinking that the owner previous to my brother transplanted the engine from the 22 to the 5 and then just bolted on the stock 22's Mikuni, had problems with the mid-range, and then just sold the sled???

I think what i'll do is try ur suggestion for main jets and see how that performs. I'm hoping my starting issue will be resolved once i've got this engine buttoned back up with all new seals and gaskets.

regardz

Lloyd N.

[400brian]

Could you post some photos of this set-up? Did they have the Cyclone exhaust bolted up to it?

I'm thinking the 340/5 I had the Mikuni on, had a 250 main in it. It ran great cold, but once warmed up, it would spit back through the carb, and would just load up and die. The 340 RS/2 engine is even more prone to this, with a seemingly much smaller temperature window of proper operation.

Watch your plug colors, especially if it's running really good.

[luvzvintage]

yes it has the original 340/22 exhaust on it and the original cyclone Mikuni

thx!!!