Checked timing with a timing light today

I have two cags one is only a month old and at this point is std 49cc. the other has some mods, 44mm 2piece head kit, fat boy pipe , bw triple stage reeds, moded std carby ect. before I start mods on the new one I wanted to now where the ignition timing was to see whether i should install a rocket key. I removed the spark plug, the pull start cover, coil and the clutch housing. First step was to locate true TDC, I meausred the distance between the two head mounting bolts on the coil side , and put a mark in the case in the centre of the two bolts, I used a piece of 60" welding wire down through the spark plug hole and turned the engine over by hand in both directions marking the flywheel both times where it lined up with the mark on the case, in the centre of the two marks on the flywheel will be the new mark for TDC. Then I removed the wire positioned the engine at TDC, went around to the clutch side of the engine and put a white out mark on a clutch shoe and a mark directly in line with that on the case, I put the coil, spark plug and pullstart cover back on leaving the clutch cover off so I could use my timing light to see where the white out marks lined up. This would give me an indication of exactly where the coil fired in relation to the magnets, once you know this you don't have to use a timing light. I started the bike and aimed the timing light at the clutch the timing looked a lot further advanced then i expected, so with the engine running and the timing light on i marked the case in line with the mark I put on the clutch shoe. Stoped the engine removed the pullstart cover and coil again, and lined up the mark on the clutch shoe with the new mark on the case (were ignition actuly happens) the centre of the second magnet was lined up with the centre of the head bolts . I measured from the centre of the second magnet back to my TDC mark on the flywheel and got 25.5mm, the diameter of the flywheel is 267mm, divide this by 360 to find out the measurment for every deg. 1 Deg = 0.742mm so 25.5 mm = 34 deg timing, and this is with out a rocket key, that would advance it another 10 deg, to 44 deg way to much. This might explain why some bikes hit a point where they just wont rev any harder, I am no 2 stroke expert but I build and tune engines for drag racing, speedway ect. and when an engine comes in that the customer has set up and the timing is this far out (i have seen 40-60 deg sometimes) the engines just don't rev and don't make any power. Sorry for the realy long post but I didn't know an easyer way to explain how I tested this.

Now to a Question, who knows exactly how much timing they are running and what have you found to be a good setting, I have read in some Blata tech article that they are set at 19deg. Now not being a 2 stroke tuner I would gess that more timing for more torque and less timing for rpm any one have any thoughts

there are a few maths problems plus technic problems here that will put all on the wrong track when trying to find the select timing.
1] welding wire down the cylinder is a no no.
2] the flywheel is not 267mm diameter its 100mm
3] for correct timing check must use the flywheel diameter not crankshaft diameter with a timing light.
4] running this type of engine without the clutch bell with shoes still attached is not a pretty site for the shoes. when the timing is advanced on a drag car you must know if this advancement increases rpms or decreases rpms, the same is with a 2 stroke engine, you may have to go back to the drawing board and re calculate things. best of luck.

Thanks for replying and picking up some of my typing mistakes there RD racing
1] used welding wire as a posative piston stop to find true TDC, engine is only turned over by hand using the flywheel how is this a problem?
2] sorry i ment circumphrence (need to check the spelling of this) not diameter
3]I used the flywheel not the crank shaft
4] the engine was only run with out the clutch bell at idle so the clutch shoes would be in the same positon as if the engine was turned off, you would have to rev the engine up to 6000-7000rpm to get the shoes to hit the case, not recomended.

ok enough about that any way last night i removed my flywheel and set the timing up at 25 deg on my stock cag, first thing i noticed was it sarted alot easyer and didn't try to rip the starter out of my hand, ( i have already brocken the stock plastic pawl on this bike from it kicking back). when i took it for a ride i noticed a small reduction in down low torque but did it rev, on the test track i use (around the sheds in the industrial area outside our workshop) before i adjusted the timing it would rev to a point half way down the straight and would sound funny ( thought it was reed fluter due to std reeds) after adjusting timing the bike pulled strong all the way down the straight and there was no fluter, need to put the memory recale tach on of the other bike and do a before and after rpm

RD racing do you agree that at 34 deg std and some one was to add a rocket key making the timing 44 deg that this is way to much.

I used the timing light on the clutch insteed of the flywheel because of the cooling fins and the fact that I would have to start the bike and then remove the pull start from the bike, not recomended.

thought something wasn,t right there. anyway the cag engines are all different in regards to ignition timings, some come from the factory with retarded timing and others come with advanced timings. when i check the timing i use a degree wheel as i have found these handy little tools are worth there weight in gold [very accurate] the good part with the cag engine is all the coils are set the same so its only a matter of setting the flywheel correctly with the crankshaft, i will give you some numbers for the spot on ignition timing sets tomorrow when i go back to the workshop.

Thanks RD racing that would be great these are the first two strokes I have worked on. Degree wheels are great I have two different sized ones in the work shop, a small 10" one i use to check cam specks in the car if I suspect the customer has fitted cam wrong and a larger 13" one I use when assembeling a motor on an engine stand. I used the small one and a dial indicator to check the port timing of my 2 piece head kit.
I have read almost all of your posts and must say- u da man- hope to learn alot from you keep up the good work

where do you get a degree wheel and how do you use it?

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47cc cag:-
air filter
BM6A spark plug
ADA fibreglass reed
10 Degree Radial Advanced Timing Key
big bore kit
ported head
quickturn throttle
alloy pullstart
fatboy exhaust
dellorto 14/14 carby
4th bearing clutch kit
soon to be installed:-

hi !

has any1 this mentioned data to share or for sale ? if its not free im willing to buy the info.

if the data or some of it is at some topic, please people point me into the correct topic. i havent found any with Advanced forum search or google search pointed to this forum.

bye
markus

This is a five year old thread mate. None of those people use this forum now.

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