And another Camshaft identification question.

Sorry to start my very first post with a common question, but I'd appreciate some advice from you guys with all the experience. I bought a Commando 850 more than a decade ago, Mk11, kinda cafe racer style and a real bitsa. After a long rebuild I'm nearly back to the std Roadster I always wanted. When I bought it the guy told me it didn't have a standard cam, in fact nothing on the bike was standard, but that was another story. Whilst the head was off the bike I took a few cam lift measurements with a dial gauge thinking I'd manage to ID the cam easily, however.....doesn't seem so easy now.

The figures I saved were
(measured at .040" lift at followers)
Inlet Valve @btdc = 31deg
Inlet Valve @abdc = 61deg
Ex Valve @bbdc = 59deg
Ex Valve @atdc = 32deg

Max Cam lift (inlet) =.383"
Max Cam lift (exhaust) = .335"

Lift at TDC was
Inlet = .146"
Exhaust = .142"

Give or take some error in my measurement accuracy, and Looking at the table in the UK NOC, some of the figures match the megacycle 560-SS cam, but others are way out. Is it possible my Cam is just worn out giving erroneous figures? was my method maybe wrong?
Wish I had pulled the barrels and had a look whilst the engine was last out :cry:

Any detectives out there!

Pete

Sure seem to be a 2s or equivlant to me. Is the head shaved or is this running with stock compression?

Let me be the first of many to say, Where's the pictures?

pvisseriii said:

Sure seem to be a 2s or equivlant to me. Is the head shaved or is this running with stock compression?

Let me be the first of many to say, Where's the pictures?

Click to expand...

Thanks for the input pvisseriii. I thought it didn't match much of the 2S spec in the NOC table, but hey, I'm no expert. Regards the head, it is skimmed .040" (it's actually an RH10 head). I was saying other stuff turned out to be non standard, that was one of em! The head had also been reworked, presumably a Hemmings job, the valves are bigger, and reangled. The bikes only been run for fun whilst I've had it, and I've had no issues with the cam/head, and it's run nice. But I've always had that desire to know what cams fitted.

Pictures? Do you mean of the old bike? The rebuild is not that far advanced, lots of bits still lying in the spare room(sorry wife) waiting for spring.

Old Bloke said:

Pictures? Do you mean of the old bike? The rebuild is not that far advanced, lots of bits still lying in the spare room(sorry wife) waiting for spring.

Click to expand...

We just like pictures and we do find builds in process interesting.

The motor sounds interesting so far. What kind of exhaust is being used?

ok no problem. I'll have a read on posting pics, no photobucket or similar account thought.

The exhaust system is the RGM part number 050018, basically the big bore downpipes with straight through reverse cone silencers. I've had these fitted already, and (again) they are sitting all polished up in the spare room!

The 2S (SS) and the 560 are clearly stamped.

grandpaul said:

The 2S (SS) and the 560 are clearly stamped.

Click to expand...

It's still in the bike and was checked with a dial indicator from the out side. I do not know if the markings are visible while installed.

I might think that actual data would supersede markings and would confirm any markings/stampings.

Indeed, checked with the Barrels still fitted. As the bores looked ok, and as I had no oil leaks from the base, I adhered to the "if it's not broke don't touch it" philosophy, and never removed the Barrels. I also had the thought that if the barrels came off, and the cam looked iffy, then I'd be looking at a replacement, and a substantial bottom end rebuild which I've not the money for, and would probably scupper any plans I had for getting it back on the road this spring.

pvisseriii said rebuilds might be of interest on the forum. hopefully my one is not going to cost a lot! The main reason for the rebuild is to get a more standard bike than the cafe racer it was, so the alloy tank, seat unit, mudguards, rear sets are all removed(and probably going on Ebay!) and Roadster stuff is going on. The Frame/cycle parts are all powder coated and in various states of assy, and I'll be rewiring from scratch, negative Earth, and using a Boyer powerbox and ignition(which was fitted previously) and single dual o/p coil. The head gasket needed replaced, leaking oil like a good un.

A problem I will soon get to is the replacement tank I have had since I bought the bike. It's a fibreglass Roadster tank, probably not OEM, but it's new and never been used and was treated with Tankseal about four years ago, then got put back on the shelf. Unfortunately, Tankseal is not proof against Ethanol, and there seems to be no way of removing it, to allow a fibreglass friendly sealant to be applied. Replacing that tank may hurt!

If you already have the bike apart, and the power unit out on a bench, I'd say it's "false economy" NOT to open the bottom end and ensure you aren't building a tear-jerker (also called grenades, money holes and other interesting names).

I can't argue with that logic, however it's just requirement creep as the motor is running fine. I'd never planned a total engine stripdown, in fact the only reason the motor was out the bike was to get the Frame+ powder coated before It gets "De-Cafe'd", and the only reason the head was off the motor was to fix the oil leak at the head joint!
My Commando will never be a concours example, as I don't have the time and money to do it, but it's always(at least since I've had it) been maintained well, sounds and feels mechanically ok, and has no apparent "bits" in the oil during changes therefore I'm reluctant to be tearing it down for no good reason. I've learnt that lesson in the past

Old Bloke said:

I can't argue with that logic, however it's just requirement creep as the motor is running fine. I'd never planned a total engine stripdown, in fact the only reason the motor was out the bike was to get the Frame+ powder coated before It gets "De-Cafe'd", and the only reason the head was off the motor was to fix the oil leak at the head joint!
My Commando will never be a concours example, as I don't have the time and money to do it, but it's always(at least since I've had it) been maintained well, sounds and feels mechanically ok, and has no apparent "bits" in the oil during changes therefore I'm reluctant to be tearing it down for no good reason. I've learnt that lesson in the past

Click to expand...

Makes me wonder why its important to identify the cam then really...it aint broke...don't fix it....

BTW.....'requirements creep'....and living in the North West....don't work for BAE by any chance do you

Good call SteveA, BAE it is :lol: you'll know why I won't want the job to turn into a 6 month rebuild and completely miss Summer then.

In answer to your question. No, it's not important that I identify the cam, I only asked as I'd gone to the trouble of taking some measurements, and thought someone in the forum might recognise the type, or if it looked like wear, or something else. It can wait for another year, another rebuild I guess

pvisseriii said:

Sure seem to be a 2s or equivlant to me. Is the head shaved or is this running with stock compression?

Let me be the first of many to say, Where's the pictures?

Click to expand...

No rebuild pics at the moment, but heres how it used to be:





hope it works ok :shock:

That works just fine.
Wow, what a hotrod. I like it. I am anxious to see what come of it.

Hi all,

I'm interested in the camshaft identification question.
I'm sure I have a combat motor - 1972, black barrels, shaved head, Amal 932 carbs, 'C' stamped under the head steady and it has been previously rebuilt with 2nd oversize bores and new big end shells (has only done 11,000 miles) indicating the old combat standard of expelling its oil via the breather. Trouble is I can't find any markings on the camshaft. Does any one know where I should expect to find the '2S/SS' and is it ground, stamped or etched.

This is how my spare one is marked (stamped):



Russ

Old Bloke said:

Sorry to start my very first post with a common question, but I'd appreciate some advice from you guys with all the experience. I bought a Commando 850 more than a decade ago, Mk11, kinda cafe racer style and a real bitsa. After a long rebuild I'm nearly back to the std Roadster I always wanted. When I bought it the guy told me it didn't have a standard cam, in fact nothing on the bike was standard, but that was another story. Whilst the head was off the bike I took a few cam lift measurements with a dial gauge thinking I'd manage to ID the cam easily, however.....doesn't seem so easy now.

The figures I saved were
(measured at .040" lift at followers)
Inlet Valve @btdc = 31deg
Inlet Valve @abdc = 61deg
Ex Valve @bbdc = 59deg
Ex Valve @atdc = 32deg

Max Cam lift (inlet) =.383"
Max Cam lift (exhaust) = .335"

Lift at TDC was
Inlet = .146"
Exhaust = .142"

Give or take some error in my measurement accuracy, and Looking at the table in the UK NOC, some of the figures match the megacycle 560-SS cam, but others are way out. Is it possible my Cam is just worn out giving erroneous figures? was my method maybe wrong?

Click to expand...

Sorry to bump this thread, but realised I never really got a definitive answer to the original question, it's still relevant as I do not know what the cam is. If I knew, I could also know what to correctly set the valve clearances to. I think someone suggested 2s, but the data in the Atlantic green site didn't look the same?

What happened to the bloke you bought it off / maybe he can tell you .

Hence ; its not a bad idea to measure the clearances on a motor strange to you before you mess with it .

Actually ran a SS at .016 thinking it was a 3S . Was QUITE & went well , But had W&S springs & all clearanced correctly .
040 here and there etc & so on .

Presume theres not the stock spings in there either ? Whats the Jetting its running , while we're there .

I don't think the guy I bought it from knew what the camshaft was either, just "not standard". Not knowing what it is, I did, when I had the head off, measure the valve to piston clearances by using modelling clay. Can't remember what the figures were, but at the time I checked, looked like plenty of clearance, with the tappets set at about 8-10 thou. I wouldn't know if they were stock springs either, how would you know?

Jetting I do know.
Single Amal Mk2 2934
Slide 2928 3 1/2
Needle 2A1 position 3 of 5
needle jet 106
main jet 260
pilot air 1.5 turns out
pilot jet 25

Getting away again from the original question, anyone know what these figures represent, or is there anything else I can check, short of stripping the head barrels off and looking?

sounds like a mild tourquey cam .

Standard springs , if ' Terry Valve Springs ' are horible DRAWN wire , which have draw marks :lol: ALONG the Wire .
They work quite well , but dont last forever . Fancy ' race ' ones may well be ' centerless ground ' which have a SMOOTH
appearance to the wire coils , as the wire is MACHINED / as in ' ceterless ground ' like good fork stauchions . High Grade Finish .

Progressive Rate , the Coils arnt regular , they group together at the head face if not installed backward , the gap between coils is about twice at the open grouping to the closer coils at the other end of the spring . The W&S came with keepers colletts seats & SHIMS , if these are all of high grade finish , and there were SHIMS under the seats , it may be these .

One thing , if youve got the valve clearances to tight , itll spit back , have weak compression Hot , and BURN the Seats if you dont open the clearances .
Id try 12 thou . and if its a bit tackety with a stethopscope / rod at the pushrods , hot , clse em to your 8 & 10 , or 6 & 8 if your daring & listen for spit & hiss in the intakes , with the filter assy removed .

Old degenerates from centuies past likely knew intuitive methods . One is likely checking the pushrods rotate untill near on the flank of the cam . i.e. for about 180 deg. of the Cam. rotation. 360 at the crank , give or take 30 or 40 .

The old bootlace on the shaft trick , as in the white builders line a loop round the top of the rod , to check for free rotation . :?
This is all supposed to be most enyoyable endevous in the exploration of the mechanical functions . So switch brain to ' This is Good '
rather than what a horrible chore , if you try this method . 8)