Performance part..

Don't get excited but I fitted an IWIS supalife chain yesterday and what a difference. All the'transmission noise' has gone (chain fouling the guard) and all the slop in the drive line. I am going to stick with the quick action throttle now. One thing also I noticed was that the slack in the transmission was actually an artefact of the fact that the clutch lifts just with a small touch of the lever. Because I have a number of bikes it then becomes common to fully pull the clutch to change gear. My Velocette Venom for instance needs a good pull because it tends to drag when hot. I need to remember this when riding the Commando because such a long pull then let's the revs drop so there is a speed mismatch when the clutch re-engages feeling like slack.

You are talking primary chain here?

Final drive

Could you supply more info or possibly a link. I need to replace the drive chain on my BSA Thunderbolt. Do these require any machining of the sprockets?

Fred,
Is this chain also known as Megalife? If it is, I hope it lasts longer than the one I fitted to my 930 Triumph triple. I got just over a thousand miles before it started to suffer from seized links. DID x ring chain gets my vote every time.

The mismatch in the revs on downchanges was something I experienced when racing with the standard gearbox. The close box was much better however you need more than four gears. I rarely use the clutch.

I got the info off here last week from an old thread. I don't know what it may have previously been called but it is a slim chain. Just Google Sprockets unlimited at Evesham.

Good point Acotrel, wish I had fitted a close ratio gearset.

How can the revs be mismatched on a Commando - the gearbox is constant mesh ????
It will soon match the revs for you !!

A Commando on the road is about the most relaxed riding possible.
Top gear for about everything except steep hills.
And 1st only if you are stopped.
Just touch the gearlever, and its in the gear you want.
And that great torquey engine (talking 850 here) is ready to haul you anytime, any revs , just twist the go button.

Don't be mislead here, Aco is talking racing again, having admitted to never ridden a Commando on the road.
Perhaps he doesn't know about blipping the throttle on downchanges at higher revs ?
A close ratio box on the road is a PITA, 1st gear is too tall for normal riding. ?

But we diverge, from chains...

Very useful information Rohan but I've had Commandos since 1984. When you lift the clutch the back wheel effectively disconnects from the engine otherwise you would struggle to change gear. As the engine then has no load on it other than mechanical losses the revs will vary generally dropping as the throttle is rolled off. Since there is a finite time required to change gear then any change in speed of either the back wheel or engine will cause a mismatch. This effect will be exacerbated by a slack chain.

FastFred said:

Don't get excited but I fitted an IWIS supalife chain yesterday and what a difference. All the'transmission noise' has gone (chain fouling the guard) and all the slop in the drive line. I am going to stick with the quick action throttle now. One thing also I noticed was that the slack in the transmission was actually an artefact of the fact that the clutch lifts just with a small touch of the lever. Because I have a number of bikes it then becomes common to fully pull the clutch to change gear. My Velocette Venom for instance needs a good pull because it tends to drag when hot. I need to remember this when riding the Commando because such a long pull then let's the revs drop so there is a speed mismatch when the clutch re-engages feeling like slack.

Click to expand...

thats cos you're too slow. but I like the idea of the iris chain. wiil get one as soon as my others have worn out. have used tsubaki rs10b for years. same dimensions and light as well. doesn't rub on the inner primary cover either like the rs30 chain which is recommended by the chain manufacturers. [ wa kers]

You should already be rolling the throttle back on for upshifts, FastFred.
Takes away the 'mismatched revs' syndrome....

I had my first Commando in the late 70s, having previously had an old Dominator, and about then also got a BM 1000cc (airhead) for longer stuff.
As I recall, the BM handbook caused some amusement - it stated that you could test if the gearbox was in top gear by "prodding the gearlever with your foot. If firm, there is at least another gear to go. If in top it will feel mushy." (it didn't quite say that, but thats what it meant.)

This caused some amusement, because if you "prodded the Commando gearlever with your foot", it would change gear. !!
Cleanly, quickly and precisely. A delight to use, with clutch or without clutch. In fact, it changed better without clutch.
Although I have since heard this causes a bit of shock treatment to the gears, and they may eventually wear quicker.
I rode it/lived on some dirt roads back then, and it didn't lock the back wheel to any extent - like the BM did if you did sloppy gearchanges.
You must not be tweaking the throttle quite right ???

BTW, with a lot of practice the BM, heavy flywheel and all, could be encouraged to do clutchless shifts.
You had to be VERY precise with the throttle and back off at just the right instant for the upshifts,
and also blip the throttle for the downshifts.
ANY mismatch in revs would result in it staying in the gear it was already in.
Or chirping the back wheel.
(I practiced this in case the clutch cable broke - was a long way from spares).

Modern superbikes and MotoGP bikes and race car engines mostly cut the ignition for the gearchanges,
they don't even touch the clutch, it is a very finely calculated art these days.

But we diverge from chains, muchly.
P.S. If you have your primary chain too tight though, gear changes are very much more difficult...

FastFred said:

Very useful information Rohan but I've had Commandos since 1984. When you lift the clutch the back wheel effectively disconnects from the engine otherwise you would struggle to change gear. As the engine then has no load on it other than mechanical losses the revs will vary generally dropping as the throttle is rolled off. Since there is a finite time required to change gear then any change in speed of either the back wheel or engine will cause a mismatch. This effect will be exacerbated by a slack chain.

Click to expand...

For info this is the rear chain I am on about but your right I am to slow on the gear change as I said if you read it because the clutch lifts so quick and that combined with a knackered chain makes for slop in the drive and harder downshifts.

It still sounds like it would be worth checking that your primary chain isn't too tight.
(Thats what the removable bung in the clutch case is for)
And that you have enough freeplay in the clutch cable side of things....

FastFred said:

For info this is the rear chain I am on about but your right I am to slow on the gear change as I said if you read it because the clutch lifts so quick and that combined with a knackered chain makes for slop in the drive and harder downshifts.

Click to expand...

I always use my clutch, and always do quick gear changes. I sometimes wonder though if I did use the clutch [ very occasionally ] as it always changes so easily and without any audible sound. The only time I have trouble with a clutch is when I don't ride a bike for months. This allows some rusting of the plates and in the worst case scenario, I had to strip and clean the plates before riding. Until the plates polish up again, the thing clicks going into first from a standstill.
regards, Dereck

I had/have other older bikes, and their clutches mostly almost lock solid if they haven't been used for a while.
It is recommended, even in the manual I think, to pull the clutch lever in and kick until the clutch frees off, before trying to start it.
Otherwise you can find yourself in motion and unable to free the clutch off - if the attempt to get into 1st actually works and doesn't just produce that grinding noise trying it.

Its the quick coordinated clutch / gearlever / throttle action that produces clean fast gearchanges....

I have a belt drive correctly tensioned but how would a tight primary drive make for slack in the transmission I don't understand that?

Anytime the gearbox feels 'not right', a check of the primary chain tension and that the gearbox
is actually bolted down is an automatic part of things to check.

I don't think you have previously mentioned you have a belt drive ?

Something else to check might be that the cush drive rubbers are still intact,
and are still in fact cushioning.....

I've completely dissolved a handful of cush drive pads factory to tire cases to state I never felt a thing w/o them shifting or handling but some extra slack snatch on sharp throttle changes. Start down list already reviewed above til ya solve it or discover a new reason no one encountered before.

Hobot
Please could you turn what you said into English! Do you mean the cush dubbed are not important or that they are. The answer is yes or no. Thanks.