Forum

[Les H]

Hi John. I find the best tool for static timing is the digital vernier gauge. They are very cheap and perfect for the job, and sold everywhere about 8 quid. How to use: Extend the jaws so the narrrow end-extension bar pokes out of the right hand end. Insert vertical in the plug hole (Tank removed) with the edge of the vernier resting on the edge of the plug hole. Find top centre, by rocking the engine with a spanner on the end of the crank nut. keeping slight pressure on the jaws, monitor the read out for maximum lift to find TDC. Now here is the clever bit....Press the zero button and extend the jaws to add the ignition timing (15.9mm?)to the digital reading....then screw up the lock screw to maintain this measurement. This will have pushed out the end extension probe the precise amount. Turn back the crank and re-insert the extension probe down the plug hole and rest the main part solidly as before. Slowly turn the crankshaft forwards...(anti-clockwise viewed from the LHS)...You will be able to easily feel when the piston just contacts the probe, and repeated rocking will set this absolutely precisely. Then adjust the timing maing sure you fully advance the Advance Retard mechanisim, by turning the cam (Tool available here to lock the cam for this purpose).

[Les H]

Note: REMOVE gauge from plug hole before doing this bit: ........" Press the zero button and extend the jaws to add the ignition timing (15.9mm?)to the digital reading....then screw up the lock screw to maintain this measurement etc. etc.

[ed.lazda]

A kind previous owner stamped some timing marks on the alternator, so I use a strobe light. Lack of an inspection port means it only gets done when it's time to change the primary oil.

[Riggers]

Warming the plug up gets you going in 5 minutes. OOOppps sorry, wrong thread.....

[John J]

Thanks Chevy, I had not spotted that in Mr H catalogue. Howard 612 you are right, the plug angle is important. In Mr H's tech. notes it tells you how to set up the timing. The figure it gives for advanced and retarded takes into account the plug angle of 36 deg. It does not say this. For anyone using true vertical measurement ie with the head off, the numbers need to be modified. They need to be multiplied by Cos36deg.This gives 6.88mm fully advanced and 0.65mm retarded.

[Les H]

I'm afraid John J your simple trigonometry won’t work here. You are forgetting the piston crown is domed. The plug hole is wide enough to get very near vertical, to use the manufacturers stated timing figure so complex maths is not required. Getting the timing right to one thousands of inch or the precise arc minutes is not necessary with the Bullet engine as has been expressed by others here earlier.

[John J]

Hi Les, You are right the dome will come into it, athough it will be very small. Complex maths? I don't think so. A sin function is no more than the distance, above the ground, a mark on a wheel follows as the wheel moves forward. You know this. How do you get 15mm btdc? The stroke is 90mm and the timing is 32 deg.

[Les H]

Hi John...I meant it would be complex if you had to include the dome into the calculations. The 15mm was a guess as over the page it was suggested the timing was 5/8" so I converted that to 15.9mm...I didn't check if the stated figure was correct which is why I added a question mark.....Anyway, you and others might find this useful: http://www.torqsoft.net/piston-position.html....note you can set the piston or crank rotation depending on figures you have.......using Hitchcocks timing it seems the con rod length (centre to centre)is 118mm....with this length the timing figures of 32mm advanced and 8.5mm BTDC work out......However if conrod length is different then the timing figures might be different....have fun!

[John J]

Hi Les, Con rod length is immeterial, it does not affect any timing measurements, angles or linear.

[Les H]

OOOPS...I meant 32 degrees advanced not 32mm.