ET: Engine (Twin) Half Time Pinion (Punch Dot Marks not present)

[Phil Arundel]

Hi all,
I am rebuilding my 1952 Rapide and am ready to fit the Half Time Pinion.
I find that the pinion does not have the punch dot marks to line up with the idler and the crankshaft keyway.
Does anyone know how I can determine the punch dot positions in relation to the half time pinion gear teeth?
Thanks,
Phil

 

[Rob H]

Hi not as much experience as some of the guys here so if I make an error hopefully they will correct me.
I just replaced the cams and sorted the timing on my twin. You will need a timing disc for the big end quil and also a dial gauge on the valve. A piston stop is also helpful to determine top dead centre for the timing disc. Set the cam gears and the idler up with the dots as per Richardsons book then find the position for lift of the inlet valve on the rear (number 1 ) cylinder. Turn the crank to the appropriate degrees before TDC on the rear cylinder and then you can fit the halftime pinion to mesh. You will have to try a few positions before the teeth will line up with the idler gear. I did this by eye and then put the halftime pinion on part way the check figures before putting on fully. When correct you can then mark the pinion if you wish for future reference

 

[davidd]

Phil,

This is from the Instruction Sheets:

David

 

[Phil Arundel]

Hi not as much experience as some of the guys here so if I make an error hopefully they will correct me.
I just replaced the cams and sorted the timing on my twin. You will need a timing disc for the big end quil and also a dial gauge on the valve. A piston stop is also helpful to determine top dead centre for the timing disc. Set the cam gears and the idler up with the dots as per Richardsons book then find the position for lift of the inlet valve on the rear (number 1 ) cylinder. Turn the crank to the appropriate degrees before TDC on the rear cylinder and then you can fit the halftime pinion to mesh. You will have to try a few positions before the teeth will line up with the idler gear. I did this by eye and then put the halftime pinion on part way the check figures before putting on fully. When correct you can then mark the pinion if you wish for future reference

Thanks very much Rob. I will give this a try.

 

[Phil Arundel]

Phil,

This is from the Instruction Sheets:

View attachment 20476

David

Thanks very much David.
Regards
Phil

 

[Robert Watson]

I just did a set of Robinson Mk1 new cams. Set the valves at equal lift on No1, set the crank at 4 deg BTDC found the keyway that lined up and tapped it in. Rolled it through and checked it and No1 =lift at 5 deg BTDC and No2 at 3deg. Close enough for pretty much any street bike. Then rolled through and checked all at .005 lift and all either within or almost within numbers in Richardson.

 

[Phil Arundel]

Thank you Robert -very useful.
Cheers
Phil

 

[BigEd]

Dear Phil,
Lots of good advice above. I prefer to use the method outlined in Robert's post #6. I don't rely on marks on the cam wheels as if the camshafts have been pressed off the gears at any time there is no guarantee that they have been pressed back on in the correct place. If you are lucky the marks will all line up correctly so that next time you just have to do as David has posted in post #3.

 

[vibrac]

Singles are a doddle twins as in many aspects are a compromise around 3 to 6 degrees is the best I found generally

 

[Phil Arundel]

Dear Phil,
Lots of good advice above. I prefer to use the method outlined in Robert's post #6. I don't rely on marks on the cam wheels as if the camshafts have been pressed off the gears at any time there is no guarantee that they have been pressed back on in the correct place. If you are lucky the marks will all line up correctly so that next time you just have to do as David has posted in post #3.

Thank you BigEd - very sound advice. I will take note - if I can get my fingers to work in the freezing garage!