August 19, 2013 at 12:54 pm #15140
Lost compression on it a few months ago in the middle of nowhere and have not had the room until I sold the XS400 to open it up. Went out today and had a fiddle. The bike is so easy to work on, from complete to topend strip down took less than an hour
Think it has a .5mm oversize bore and iirc means I may still have a rebore left in it after the one it needs now. Just need to price it up, work out if it was the wrong plug, wrong 2T mix, or just giving it too many beans.
Any tips on how to diagnose the cause?August 19, 2013 at 4:17 pm #66672Swindon AndyParticipant
My guess is running hot. Causes could be weak mixture caused by under jetting, or induction leak, or with bikes with the oil in the fuel – too much oil. I don’t know if the latter applies to yours?
Or something got in the chamber and glowed/rattled up and down?
Any more?August 19, 2013 at 4:43 pm #66673ses310Moderator
Yup a big hole in the piston will certainly cause a loss of compression!
That’s a cracker!August 19, 2013 at 6:25 pm #66674imperialdataKeymaster
Heh, one more conversation piece for the coffee table
I’d go with Andy on the running hot thing, certainly wouldn’t hurt to do a mixture check and plug chop when it’s back together again.August 19, 2013 at 6:49 pm #66675
a friend has their own bike dyno and has offered to give me a hand sorting the jetting. Think the plug was the wrong temp too so when it is back together will get a jet kit and a few plugs. It is running pre-mix…. would too much 2 stroke oil make it burn too hot then?August 19, 2013 at 6:57 pm #66676
I’d definately say it is running hot. Hard to say if it needs a cooler plug or if it is a fueling issue.August 19, 2013 at 6:58 pm #66677
PM lucky rookie, he has a good knowledge of two-strokesAugust 19, 2013 at 8:19 pm #66678Swindon AndyParticipant
It is running pre-mix…. would too much 2 stroke oil make it burn too hot then?
Apparently, yes it does.August 19, 2013 at 9:23 pm #66679
cheers for the tipsAugust 19, 2013 at 10:54 pm #66680
cheers for the tips
Keep us posted on your progress
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