Motorcycle Repair: suzuki gn 125, motorcycle safety course, suzuki gn 125

Question
hi there i have a 1993 suzuki gn 125 which ran great for first three weeks of me buying it then it conked out on me and when i tried to re start it it backfired really loud anyway brought it home on trailer tested all electrics and im getting a spark so i then stripped carb and cleaned all jets tried to start it and another massive backfire so i took left hand engine casing off and noticed neuteral/gear position switch was broken but also the cam chain was slack so i think th cam chain has jumped putting the timming out. anyway my question is could the neuteral/gear position switch cause my bike to cut out or is my cam chain theory soun right and what kind of damage could i be looking at? many thanks

Answer
I've never had a GN 125 apart (although I rode one extensively during my tenure as a Motorcycle Safety Course instructor), but a slack timing chain on one is not a good thing. It is possible that the tensioner come loose, which would cause the chain to jump a tooth or two and throw off the timing. Remove the valve cover and spark plug, then put the bike on the centerstand and in gear. Have someone turn the rear wheel while you shine a flashlight in the spark plug hole and watch for the piston to come up to top dead center - both valves should be closed when this happens if it is on the compression stroke. Cycle the piston through all four strokes and watch the rocker arms for movement at the proper times... if a valve is moving when it shouldn't, you will need to re-time the chain.


The neutral switch won't have any bearing on the problem, as it is only used to light up the indicator on the instrument cluster. If I remember right, the GN 125 has a sidestand cutout switch; if the stand is down the motor will not crank over.