splittie65 Posted October 26, 2011 Posted October 26, 2011 Is there another way of checking the timing besides buying a special tol and measuring when the piston is 1.8mm before top dead centre? And is there a way to adjust it apart from adjusting the point gap size?
nayruf Posted October 26, 2011 Posted October 26, 2011 Hi To check the timing on my DT175 Twin Shock, I broke out the ceramic parts of a spark plug, cut the earth electrode tang off and cleaned up the remaining metal part, I then got a long bolt that would fit the resulting hole in the spark plug with a bolt head that wouldn't let the bolt fall through the plug. I then fitted the contraption and rotated the piston slowly to TDC making sure that the bolt wouldn't jam against the piston, I then marked the bolt shank took the bolt and marked a line on the shank 1.8 mm lower, at this point I adjusted the contact points so that they were on the verge of opening (just like it states in the Haynes manual) this can be proven with a volt meter or a small light bulb. The manual also states:' that as a final check connect a DC voltmeter to the moving contact lead on the points and to a reliable earth, as the points open the meter should show a reading and at the same time the piston should for my bike be at 1.8mm BTDC, a light bulb can be substituted for a meter, This works ok for me as the plug hole is centrally mounted over the piston. I know of no way to adjust the timing, other than the points and the advance weight in the fly/magneto wheel so I figure that if the timing is out I must have worn components such as a worn points cam,
splittie65 Posted October 27, 2011 Author Posted October 27, 2011 Thanks for that...although doesn't sound easy. I'll give it a go, but measuring 1.8mm sounds a bit difficult. How critical is it?
Moderator mervin Posted October 27, 2011 Moderator Posted October 27, 2011 TBH the answer to your question is NO get a dial gauge and do it properly if ya want your engine too last Merv
nayruf Posted October 28, 2011 Posted October 28, 2011 Thanks for that...although doesn't sound easy. I'll give it a go, but measuring 1.8mm sounds a bit difficult. How critical is it? I used engineers blue and made a 1.8mm wide line in it which was measured with a vernier caliper, Timing is critical if the timing is wrong the engine will suffer, In my case I am confident that the ignition timing is correct and the bike runs very well, I just make sure that the advance mechanism in the magneto is properly lubricated and has not worn, Mr Mervin is correct a Dial gauge is one of the most reliable ways of measuring the piston height but access with the engine in the frame and the exhaust still fitted was too tight for my dial gauge to fit, so I improvised,
splittie65 Posted June 1, 2012 Author Posted June 1, 2012 I just make sure that the advance mechanism in the magneto is properly lubricated and has not worn Is there an advance mechanism? No mention of it in my manual when timing it?
gemini Posted June 2, 2012 Posted June 2, 2012 easiest way is to take the head off and use a feeler gauge and a straight edge, this is the only way to get an accurate reading as the piston is domed on top and the plug is on one side, the advance should be held open when you set the points, a cotter pin spread apart works well to hold it open
splittie65 Posted June 2, 2012 Author Posted June 2, 2012 But IS THERE an advance and retard??? My manual mentions it for the 125 electric start models with generator but not the standard CT3 with magneto.
gemini Posted June 2, 2012 Posted June 2, 2012 just take the cover off and have a look, the electric start 125 does have one, yours may not
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