HeadSmess
Well-Known Member
- Local time
- 5:32 AM
- Joined
- May 17, 2010
- Messages
- 3,048
yeah, teflon tape works but as long as youre tightening the plug up properly, its pointless. (and run the risk of insulating it from the head which will prevent spark) heat is right, colour looks good, if a touch rich really.
remember to use the killswitch at the throttle position youre testing when checking the plug colour. pointless if you let it idle at all.
the way it idles is the best sign of air leaks...if it just revs out, even with the idle screw backed right out...theres an air leak.
does it start easily or need some persuasion?
im starting to really suspect its an ignition issue. happen to have spare CDI unit to pop on? check position of keyway in magnet, might be a bad one. its not too easy checking for ignition timing without a timing light, and the expense of even a cheap one just isnt really worth it if its a one off thing. jaguar did post a schematic for a simple timing light with an LED, might be worth searching for. then you gotta find TDC, and mark the magneto for it, but that isnt too hard to do, either. google
where is your cdi located? possibly getting too hot?
and exhaust. pop the exhaust off. can you blow through it easy peasy or is it feeling all restricted? there should be some resistance, but not TOO much.
this one IS a doozy!
last thoughts.... the piston is oversized, cylinder is undersized... once it gets warm, they start rubbing and wham... did happen to my last skyhawk, but took a good 5-6000km to start doing it! only way to check that is to pop the head, check the bore with piston at the bottom. any scratches? remove cylinder, trying to keep bottom gasket intact. check piston for same thing, big patches where its obviously been rubbing. there wil always be some rubbing, but if its a whole section, aye...that will do it. might simply be the relief at the top of the piston, around the rings, wasnt machined in deep enough. they do expand when hot!
oh! and the chrome plating! if thats got any patches missing, same deal... it will start fine, run fine, but after a few minutes, it will die or lose power...
remember to use the killswitch at the throttle position youre testing when checking the plug colour. pointless if you let it idle at all.
the way it idles is the best sign of air leaks...if it just revs out, even with the idle screw backed right out...theres an air leak.
does it start easily or need some persuasion?
im starting to really suspect its an ignition issue. happen to have spare CDI unit to pop on? check position of keyway in magnet, might be a bad one. its not too easy checking for ignition timing without a timing light, and the expense of even a cheap one just isnt really worth it if its a one off thing. jaguar did post a schematic for a simple timing light with an LED, might be worth searching for. then you gotta find TDC, and mark the magneto for it, but that isnt too hard to do, either. google
where is your cdi located? possibly getting too hot?
and exhaust. pop the exhaust off. can you blow through it easy peasy or is it feeling all restricted? there should be some resistance, but not TOO much.
this one IS a doozy!
last thoughts.... the piston is oversized, cylinder is undersized... once it gets warm, they start rubbing and wham... did happen to my last skyhawk, but took a good 5-6000km to start doing it! only way to check that is to pop the head, check the bore with piston at the bottom. any scratches? remove cylinder, trying to keep bottom gasket intact. check piston for same thing, big patches where its obviously been rubbing. there wil always be some rubbing, but if its a whole section, aye...that will do it. might simply be the relief at the top of the piston, around the rings, wasnt machined in deep enough. they do expand when hot!
oh! and the chrome plating! if thats got any patches missing, same deal... it will start fine, run fine, but after a few minutes, it will die or lose power...
