scifi Posted November 7, 2017 Report Share Posted November 7, 2017 Bought a TL 125 with a 150 cylinder, and when I rode it towards a log and blipped the throttle, it would backfire and make the engine kick backwards. I got a 125 cylinder and the same problem occurs... sounds like... bup bup bup bup bang, with the instant stop. Twiddled everything on the carb, it must be some sort of pre-ignition. Quote Link to comment Share on other sites More sharing options...
keychange Posted November 7, 2017 Report Share Posted November 7, 2017 (edited) Could be ignition timing - if you move the timing plate you have to reset the points gap. Check valve timing and valve clearance and don't ignore possibility that timing chain has jumped a tooth. Edited November 7, 2017 by keychange Quote Link to comment Share on other sites More sharing options...
scifi Posted November 8, 2017 Author Report Share Posted November 8, 2017 Thanks for the reply, I set the ignition when I changed the cylinder, so have had a gauge down onto the piston to check for TDC. I did note that the screws on the points plate were very worn, as if the previous owner had been adjusting the timing many times. I tried it again tonight, and got some of the petrol on my fingers, it wreaked of turpentine, so maybe its gone stale, will empty the tank, and try fresh fuel tomorrow... fingers crossed. Quote Link to comment Share on other sites More sharing options...
copemech Posted November 8, 2017 Report Share Posted November 8, 2017 Yu do realize these 4T things DO spit back at you when whacking the throttle open too quickly, do you not? Quote Link to comment Share on other sites More sharing options...
scifi Posted November 8, 2017 Author Report Share Posted November 8, 2017 A bit of spitting I can accept, but this little monster is refusing to jump, and throwing me over the handlebars ! Quote Link to comment Share on other sites More sharing options...
copemech Posted November 9, 2017 Report Share Posted November 9, 2017 17 hours ago, scifi said: A bit of spitting I can accept, but this little monster is refusing to jump, and throwing me over the handlebars ! I would not expect one to jump. You gotas to roll the throttle on. Quote Link to comment Share on other sites More sharing options...
croatan Posted December 8, 2017 Report Share Posted December 8, 2017 I remember a big bore 150 honda single that backfired thru the carb being extremely lean. a 105 jet in the Kehin and new springs for the advance mechanism fixed it. What is the static timing are all the marks lining up? If they are right then set the dynamic checking advance mechanism with a timing light at 3/4 throttle to see if it advancing too far. The advance springs could be weak. Disclaimer: Your bike maybe different than those of my experience. Quote Link to comment Share on other sites More sharing options...
scifi Posted December 22, 2017 Author Report Share Posted December 22, 2017 I think it must have been the petrol, which was the stuff that was in it when I bought the bike. I tried some new fuel and so far I can't get it to repeat the problem. I know the seller was riding a different bike in trials, so maybe the fuel could have been a few years old. Thanks to all that replied. . 2 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.