1979 Enticer 340 backfires

Weez1

New member
Joined
Feb 10, 2009
Messages
11
Age
46
Location
Quebec
Hello everyone! looking for some advice...

My son was riding his 1979 ET340 yeterday when it suddenly quit on him. He left it until I arrived a few minutes later. When I started it, it would barely idle and as soon as a little throttle was given it backfired (seemed to be through the exhaust) and it died.

Here's what we've checked so far:

- Compression is 100 PSI each cylinder. We checked the compression a few weeks ago out of curiosity and noticed it was at 100 PSI. Figured we'd wait and do a piston/ring job in the off season. Maybe this was a bad idea and we should have done it right away. I figured 100 PSI would be enough to continue on the rest of this winter. Unil yesterday the machine ran great and no starting issues.
- Spark plugs appear dark brown, maybe even blackish (not grey).
- Was thinking maybe crank seals, so started again in the garage and while running we sprayed WD40 on the clutch side crank seal (oil pump is removed we're running pre-mix), no apparent change in RPM at idle.
- We noticed the outlet of his muffler (out the bottom) was dented pretty good and was almost closed right up. Was likely from a stump or something he must have hit. We swapped mufflers with another ET340 I own, no change.

Any advice for next steps or possible issues would be greatly appreciated?

Thanks!!
 

Kinda funny but I just found the problem and thought I'd share in case anyone else ever has similar symptoms on their machine.

Ignition coil ground wire was heavily rusted and only attached by a few strands. I guess under load or vibration the wire giggled around and gave a weak spark or none at all. Cleaned wire, and all mating faces, new connection and good as new!!
 
good that you found it. last time i had one backfire like that (30 years ago) it blew the piston on the stand when i did the monthly run on it.
 


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