Cam timing ES2

Previously wrote:

I am restoring a 1938 ES2 and am at the engine rebuild stage, although on dismantlingI marked the cam wheels and pinion, during the cleanup stage these marks dissaperared! Does anyone have an idiots guide or an easy way to do the valve timing from scratch?

The old handbook I have gives the values ie 30 dgrees BTDC inlet opening etc,it alsostates 'time the inlet first and on the exhaust stroke', but as the inlet runs off the exhaust cam I cannot see how you can time this first, it also states 'adjust pushrods first', but once assembled it is not possible to alter the cams without first dismanlting again!

Q. Presumably the valve opening value is at the very first movement?

Q. Is it absolutely neccessary to use a dial gauge on the valve to determine the first movement?

Q Can I time it with just the pushrods sitting in the followers and mark the pushrods to better see the first movement?

Q. The crank pinion has three keyways, this, in my unfamiliarity with these old engines I failed to mark, where do I start with this one?

So, if anyone has experience of timing these old singles I would welcome some advice!

Regards to all.

Nigel -Mike Pemberton should be able to help- I seem to recall an article in Roadholder on valve timing that he penned no ttoo long ag Richard

Hi Nigel,

as i read you post i find myself in exactly the same position you were in. How did you get on? Do you have any nuggets you can pass on.

Regards Johnny

Timing is symmetrical on the ES2. So inlet opens 30 deg before TDC, and exhaust closes 30 deg after TDC. So if valve clearances are not correct, these values will both change by the same amount e.g. to 31 and 31, or 29 and 29 or whatever.

I've got my '51 ES2 in bits at the moment and I have put a dial guage on the cam followers to check the timing. With the dots lined up the timing is a mile out! To get it right I have to move the cam gears 2 teeth away from where the marks are (that equates to 36 degrees on the crankshaft!)

Is this common? Mike Pemberton suggested I check it before re-assembling the engine but I was expecting acouple of degrees, not a couple of teeth!

Anyone else found this?

Andy

I also have a 1938 ES2 and made the same mistake when restoring.

It is important that the valve clearance is set correctly (zero). The timing should be set when the push rods start to move. As David mentions, equal overlap of 30 degrees for inlet and exhaust.This gives a total overlap of 60 degrees. On the 38 engine this is done by the relative positions of the cams to each other.

The timing to the crank is correct when TDC occurs mid point of the sixty degrees and can be adjusted via the three keyways.

Hope this is of some use

Colin

Thanks Colin

On the '51 there are marks on the gears for the timing, but they appear to be a mile out. I'm confident I'm doing the timing properly I was just wondering if anyone else had had this?

Hi Andy

I had meant to reply to the original post in this thread but pressed the wrong button. Sorry if I caused confusion. As a matter of interest do you need to advance or retard the cams to make the timing correct?

Colin

I'm retarding the inlet and advancing the exhaust. So reducing the overlap, but keeping it equal.

I have only recently gone through this cam timing exercise after I initiallyre-assembled my '51 ES2, following the gear wheel timing marks. It bacame evident that all was not well when the engine would not pull as well as my mates up in the hills, though it would rev out easily. Fuel consumption was also very poor and it would stall when least expected. After considerable investigation, It became evident that a sidevalve inlet cam had been fitted in the pastto give the engine better performance by longer valve duration and higher lift.(apparently a common hot up once used) I found a Norton valve timing article on how to time independently of timing marks in theJ.B.Nicholson book on Modern Motorcycle Mechanics.

Quote;... locate piston 5/16" past TDC, installEX cam meshing with timing pinion so valve would have just closed. Turn crank back so piston is 5/16" BTDC and fit inlet cam so inlet valve is just commencing to open when cam is rotated clockwise. Rotate motor and re check, inlet valve just starts to open 5/16" BTDC and EX valve is just completely closed when piston is in same position past TDC.....Un quote.

I found in my case, the exhaust camwas 'spot on' to the above,but the inlet was openingapprox 1-1/4" BTDC. (too far advanced). I then retarded it one tooth which had the inlet valve starting to open at approximatelly 3/8" BTDC. Retarding by 2 teeth on the cam wheel brought the camtiming way too retarded.(ATDC)

At the time of my cam timinglearning episode, a fellow NOC member advised me to also check via degree wheel on the crankthat the inlet and exhaust should be at 128 deg. BTDC & ATDC for eachwhenat maximum lift on the cam lobes.

Back on the road,the bike pulled top gear way better and the fuel consumption is a lot less. The idle is more consistently steady as well.

I note that the valve timing in early 1930's was 1/4" B &ATDC , and was changed to 5/16in the late '30's for theOHV and some side valves.

Hope this helps.

Paul

Thanks Paul.

I've had a bit more of a play this morning and by using a different woodruff key slot in the half time pinion I can get the timing spot on on both inlet and exhaust. Mike Pemberton suggested I should be aiming for 25-30oBTDC and ATDC for the inlet and exhaust opening and closing so this is what I have gone for, measuring it in the bore it is pretty close to the 5/16 mentioned in the book and by you.

However, with this timing corectly set my maximum lift occurs at 145orather than at the 128oyou suggest. Different cams? I've always understood its the exhaust closing and the inlet opening times that are most important so I will probably leave it as it is and see how it runs.

Thanks for the advice

Andy