C-81 fun.

[Stormin 4,458]

   The C-81 has been playing up for some time now. Would idle really nice. But open it up and it would frap and bang and die, unless you shut it off quickly. Fuel starvation symptoms. Though could be ignition ones. 

  Not really had time to sort it, as the C-121 had precedence. Decided to see what I could find yesterday. I'd already tried another carb some time ago. The original is a fixed main jet, while the other is adjustable, but slightly smaller bore. Also the original has a plastic float while t'other is brass.

 Coil had been swapped and another fuel pump, (Courtesy of The Showman) fitted and tried. No joy. Checked for sticking points. OK there. So carb off again, cleaned out, though float bowl clear. Blown and poked and float level checked. Float bowl gasket made from two 'O' rings and carb replaced.

  No change and the float bowl still leaked.

 The previous process was repeated several times during the afternoon and early evening, with no improvement. Finally decided to call it a day out of consideration for my neighbours. Those next door anyway. I like them. The others are sort of in-laws. The C-81 is not the quietest of things as some will testify.

 This morning decided to fit the other carb. Cleaned it out, checked it over, made a gasket and fitted it. Some tweaking of cable adjustment and fired up.Things still the same, though you could open it up a tad more before things went pop and bang.

 Idle mixture was carefully set and the engine put, putted nicely. Main jet mixture screw twiddled a bit and things marginally improved.   

 SWMBO took the dogs for a walk and next door went out. So fired up and ran the revs up while twiddling the main jet screw. Eventually I got it running reasonably well. Not perfect, but much better.

 I think a silencer that silences may improve things, so one of those is on the to do list. I'll give it a run out tomorrow and see how it performs.

 

 Oh yes! The float bowl leaks.

[S1g 579]

Have you reground the exhaust valve? I'd have suppisions that it may be leaking.

[Stormin 4,458]

Engine's not been touched. Got good compression and doesn't burn oil.

[meadowfield 1,900]

fingers crossed Norm!

[S1g 579]

Engine's not been touched. Got good compression and doesn't burn oil.

If it was mine playing up like that I'd pop the head off and regrind the valves.

[Anglo Traction 1,016]

If it was mine playing up like that I'd pop the head off and regrind the valves.

I didn't want to be first to say that, but I agree........... It probably hasn't ever been off/de-coked in it's life Norm. Go on, give it a Birthday    

[Stormin 4,458]

 I just might do that this winter. Although the piston crown looks pretty clean through the plug hole. The Spitfire goes to a new home this week, so that'll free up a lot of space in the workshop.

[Stormin 4,458]

  Well I think I've finally found the problem. Swapped the condenser over from the C-125. Now running as it should, full revs and no problem. I've done this before with no change in the bad running. The 81's condenser I put on the 125, expecting that to start playing up. It didn't. So I'm assuming the condenser was not earthing properly, even though the securing bolt was fully tight.

  I also tweaked the carbs and both have been given runs up the lane and all is now well.

[meadowfield 1,900]

Good news at last!

[Ian 2,417]

That's good news Norm