Hi, first time Ive had my commando apart, and a very long time since Ive built a four stroke engine so Im a bit green.
The engine seems generally in good condition but the cam followers surface seem pitted but the cam looks pretty good to my unexperienced eye.
Any comments appreciated
The cam / follower interface has been a commando weak spot almost since it was introduced. Once they start to spall, it can only get worse and the debris will cause other damage.
Personally, I wouldn't put an engine back together with either the cam or followers in this case, although if the followers are of the later spigotted type then they are worth grinding but any guarantee on a new cam is likely to be dependent upon fitting new followers too.
Thanks Richard I feared as much, I was hoping to just get away with not splitting the bottom end and just fitting new or reground followers, but as you say this might be false economy........has anyone got a good source for the parts required
Followers: David Newman Cams reground a set for me when buying one of their new cams back in 2002. I agree that none of the components should be reused as they are now.
Before splitting cases, I would measure crank end float, then you will know what shims to add or subtract when reassembling: aim for 5 thou. inches.
If removing inner main bearing races from crank, IF necessary!, look up tips on how to do that well.
I would grind the followers flat and reuse the cam, but also use an oil with a proven ability to protect flat followers which rules out all the low zinc modern oils.
Instead pick an oil with good results from this list
Thanks John, any idea who could re grind the followers? The cam to me looks in relatively good condition but I'm no expert.
Actually I had bought some Mobil 1 v twin oil to use with the bike, this looks like a good option?
That pitting looks like either a very poor quality follower or damage by debris from an earlier problem possibly ring fragments..I would want to check the pump too.
Yes that might make sense, there was a broken top ring in the top groove of the right piston but no scoring of the barrel and we were pretty sure we collected it all out of the groove.
Anybody any suggestions for someone to regrind the followers, failing that a supplier of the parts, thanks
I can reface your followers, Cost would be £40 plus p&p
I have never had any cam or follower issues with dommies,and after hearing of all the issues that Commando's can have I don't think I want one. If by chance I was to own one and had it appart I would build the motor to a very soft tune with a cam to Daytona profile . a welded cam tunnel to reinstall the oil bath and some softer valve springs.
Mobil 1 V twin 20/50 does reasonably well in the tests, I would use it. Ask whoever grinds the followers to give you how much they had to grind off. Test your rocker geometry as you may need to add that amount back on to the pushrods.
On closer inspection today I can see this on one of the lobes can this be taken as damage and require a cam change?
Its junk now. Looks like its been tidied up enough to run for a sale. That's why private sales need to be a good bit cheaper than from a dealer with a warranty. Been there a few times myself. The only honest bike I ever bought came in rusty polythene bags. A wreck.
New cam required then......whats the best profile to use.....thats probably opening a can of worms!!!...........actually Ive run that bike 15 years since I bought it but not very heavy mileage but decided to strip it as Ive now got time.
Looks like the cam has been repaired by welding the lobes in the past, I would replace with the std cam.
Recently replaced the cam and followers on my 850 and used the PW3 cam which I'm very happy with so far, it did necessitate removing a smidge off the push rods though to get the rocker geometry correct. I'm sure the standard cam is a good option too.
Any competent machine shop but looks like you have a good offer there.
Great job, thanks Peter......looks like I need a new standard 850 cam but the standard cam from Andover and RGM seems unavailable at the moment, has anyone used one from Norvil? I havnt tried them yet.
You won't get anything from the two sources that you mention, as for the moment they have no stock and I'm not permitted to say why.
If you get in touch with Newman cams they will more than likely be able to supply your cam and they do a nice job of resurfacing the followers at a reasonable price.
I believe also that the cam you had intended to buy from Andover would have been supplied by Newman cams.
I have recently restored an 850 mk1 and replaced cam followers with oversized +020 which I sourced from Andover and although the camshaft looked very good decided to replace it with a Newman standard camshaft chilled cast iron. I dont live that far away from them and visited the factory which was great as they were very helpful and gave us a tour of the factory and the machinery they use. So I can definitely recommend them.
Point to remember with the chill cast cams is the torque for the nut is a lot lower than for the steel cams. Use the factory torque for steel can and the end of the chilled cam can snap off.
What it the part number of the cam you are looking for?
I will check my local sources here in California for you.