Flywheel removal

[Lewes96]

When removing the flywheel which marks need to line up with what and why?

[72degrees]

When removing the flywheel which marks need to line up with what and why?

The flywheel has a woodruff key, so it doesn't matter that much unless you are also going to take the belt off.

I generally prefer to pull it off when lined up with PMS1 (on compression stroke with valves closed). As the most common reason for taking it off other than just to get at the stator is a belt change it seems sensible to get it in a suitable place for that anyway. If just swapping a stator it's not necessary though.

I'm sure there will be one of Evguru's youtube videos covering it.

[norbert]

I agree, except one point.

For pulling the belt of it is better to turn the motor to the PMS 1 that is not the compression PMS but the "crossing" (?) PMS (there should be no play for the rockers and both valves shoud be under tension). If you pull it of at the compression PMS1 with valve clearance of 0,1mm the springs of the valves of the second cilinder will move the camshaft an you´ll loose your times.

ciao
norbert

[Ming]

Just in case anyone is not aware of the abbreviations, PMS stands for 'Punto Morto Superiore' which equates to Top Dead Centre. 1 and 2 refer to front and rear cylinders.
It took me some time to work it out...

[72degrees]

I agree, except one point.

For pulling the belt of it is better to turn the motor to the PMS 1 that is not the compression PMS but the "crossing" (?) PMS (there should be no play for the rockers and both valves shoud be under tension). If you pull it of at the compression PMS1 with valve clearance of 0,1mm the springs of the valves of the second cilinder will move the camshaft an you´ll loose your times.

ciao
norbert

Well I never. I must have just got lucky over the last 40 years

[norbert]

The manuals say that you should turn the upper pinion of the belt (the one on the camshaft) with the little mark to the top/12h. That is not the compression PMS of the first cilinder, it´s the crossing PMS. I suppose you do it like that as well, or not? Normaly it´s not needed to pull of the small pinion on the crankshaft to change the belt.

norbert

[Greybeard]

Just in case anyone is not aware of the abbreviations, PMS stands for 'Punto Morto Superiore' which equates to Top Dead Centre.

Thanks, Ming. It saved me asking
They reckon it does you good to learn something new every day - that's my quota for Sunday taken care of

Steve

[Lewes96]

Thanks for replies. So, it doesn’t matter too much if only removing flywheel, but small wheel with cam belt has dot at top (12 o’clock), and the flywheel has PMS1 lined up with the other dot on the crankcase at 8 o’clock?

[72degrees]

The manuals say that you should turn the upper pinion of the belt (the one on the camshaft) with the little mark to the top/12h. That is not the compression PMS of the first cilinder, it´s the crossing PMS. I suppose you do it like that as well, or not? Normaly it´s not needed to pull of the small pinion on the crankshaft to change the belt.

norbert

Good point. I'm confusing valve clearance position with belt replacement.

What matters when the belt is replace is that the pinion marks are correct.

Also worth remembering that the PMS reference mark for valves clearance is 8 o'clock on the crankcase on early models but 12 o'clock (camshaft axis) on later ones (also ANT for ignition strobing). The enquirer could do worse than download a PDF of the 'blue book'.

Belt.jpg (91.4 KiB) Viewed 10465 times

[72degrees]

Thanks for replies. So, it doesn’t matter too much if only removing flywheel, but small wheel with cam belt has dot at top (12 o’clock), and the flywheel has PMS1 lined up with the other dot on the crankcase at 8 o’clock?

If just removing the flywheel the position doesn't matter at all. Norbert has the right of it.

[mbmm350s]

While we are discussing pinions. Can anyone definitely state why the Upper belt pinion is marked A B or C. I have heard that it relates to the tolerance of this pinion it being a cast component. Is that it. I have replaced a camshaft with a small woodruff keyway with one with a large key way. I don't have an A pinion with the large keyway I have loads of B pinions. Perhaps I will need a few belts to be sure of a correct fit.
Mark

[72degrees]

While we are discussing pinions. Can anyone definitely state why the Upper belt pinion is marked A B or C. I have heard that it relates to the tolerance of this pinion it being a cast component. Is that it. I have replaced a camshaft with a small woodruff keyway with one with a large key way. I don't have an A pinion with the large keyway I have loads of B pinions. Perhaps I will need a few belts to be sure of a correct fit.
Mark

To quote evguru:
viewtopic.php?f=4&t=4616&p=23548&hilit= ... elt#p23548

[mbmm350s]

thanks
so if I understand correctly then replacing an A pinion with a B pinion makes the belt selection in the middle of the distribution of belt lengths . Across bikes and engines I have 6 B pinions one A pinion and I have only once seen a C pinion.
Anyway it's all about getting the correct tension what ever the pinion is stamped.
Mark

[Lewes96]

Bought a flywheel removal tool from NLM: unfortunately the thread stripped off with no movement in the flywheel, so bought a second with same result. What to do with stuck flywheel?

[MickeyMoto]

Heat... Penetrating fluid... Time...

I had a stuck flywheel on a bike, had to cut it off with an acetylene torch. That knackered the stator. Last resort...