Belt drive alignment

Had an MOT booked for 12 noon today but had to cancel it as last night my new RGM surflex that "may need some edges taking off with a knife" clearly required more than that. Must have spent 4 hours today filing/cutting all four surflex plates to fit the new cutch centre. Then the thicker steel pressure plate was the same. Very frustrating and clearly no idea of tolerancing unless these were out of spec. Anyway once back together I fired it up with new Mikuni carb and barrel hone, new rings and complete head job. Runs very sweet and ticks over low. Nice Spent hours on the bike today but so nice to hear it running again. No smoke and doesn't stink of oil now.

Last jobs are to align the belt drive which was very tight and change the rear tyre tomorrow for mot now, Tuesday.

Gearbox has both LH and RH adjusters. LH one is difficult to adjust and requires slackening the nut that fixes it to the cradle to adjust but it is do-able.
I got the belt tension about 1/2inch free play and/or 80 degrees of twist and then locked up the left side adjusters. I then pushed the RH gbox adjuster forward expecting that the belt would go tighter on the outside (as recommended though nigh on impossible to judge on a 32mm belt..) but the whole belt went tight again. Any tips here to try to get the gbox shaft away from the crankshaft? The main top and bottom gbox bolts are so big that I suspect they overide the adjusters? Should I pull it back by the LH final drive chain instead?

1. you have belt damaging tight if can only twist 80' when cold, likely hot can't twist it much at all but for shafts at either end. Optimal tension is gotten by a chart for each pulley teeth count plus total belt teeth count which gives ideal center/center distance or but those who run belts for dragster drive and pumps etc, get longest run able to twist full 89 to 91' cold. Belts well transmit shock load not absorb it.
2. take off alternator and front crank pulley side plate.
3. first get belt tension so you can work-slide-push belt on by hand and blunt probes, which just so happens to land ya in zone #1 above, so 3 ways to get it right.
4. then turn and turn and turn engine, socket on crank nut easiest, until belt begins to walk off clutch basket one way or the other. Then play with each adjuster to see what their effect is, going back and forth between them till belt stays on clutch and crank pulley w/o any side plate help and still ~90' twist.
5. Knife edge mark gearbox to cradle both sides position and weld it up fixed in that place forever more, [if you had to] as that adjustment should never need changed, just returned to if tranny removed, but don't thrust em till ya turn and turn engine again to make sure. Belts don't stretch to detect over time. Their edges are the delicate side.

The key to getting the primary belt set correctly is to first realize the tremendous backwards pull that the rear chain has, and that it is critical to adjust following this sequence. Bike on centerstand, motor in neutral.

First, slack off both upper and lower gearbox fixing bolts, then slack both right and left side threaded adjusters quite a bit by releasing their securing nuts and threading them out almost a quarter of an inch so you have lots of room.

Second, push the gearbox all the way forward so there is maximum slack in the belt.

Third, going back and forth between the right and left side move the gearbox backwards a little at a time until the desired belt slack is achieved. You may also push down on the rear chain to help move the gearbox back a little.

Then when you have belt tension so there you can grab the upper rung and twist it about 75 degrees turn in your adjuster nuts so they nip up.

Then remove the spark plugs and use the kickstarter to rotate the motor so the belt moves around and around and around. This is where you watch the belt run to see if you got it as centered and not touching as you can.

If needed at that point, move the appropriate adjuster just a litle until the belt runs true.

Nip up all the adjuster nuts and then have an assistant push down on the rear chain while you fully tighten the upper and lower gearbox big nuts.

Lastly, reset the rear chain tension by having someone sit on the saddle with full weight while you set the tension to about 1/2-3/4 inch slack.

As reminded on the drive chain tug, belt drives can not be made to stay on by themselves if there is much wear in sleeve bushes and main shaft bearing and clutch center bearing which shows up as clutch basket pulley wobble and belt running off or rubbing itself to death on the front pulley side plates.

Belts don't require much tension to grip their teeth, they tighten up in primary as much as a chain so if going by 75' at top run - hope you've plinged it when fully heated. Too tight wears the wobble items above faster than might be expected. It is safe to error on the too loose side but damaging when too tight. Beware.

Thanks. Just tried all this and can't get belt to centre on front pulley despite all adjustments to adjusters. Going to tighten up with good amount of free play and see what happens. Belt is quite old so suspect will need another soon anyway.

Touch wood I've never had this problem.
Try setting the belt as slack as mentioned then with the primary outer cover off start motor up. If the belt runs towards the motor the crank and gearbox shafts are splaying out purely misalignment. If it runs away from the motor the shaft ends are converging. Converging can be the caused by misalignment or as hobot says wear in the sleeve gear bushes or the big ball race, and of course if it stays steady it's OK. However, wear in the sleeve gear bearings sometimes only manifest under load.

Cash

Hi Fred,
When I installed my primary belt I found it helpful to temporarily remove the inner primary drive case. With the inner case off it was very easy to eyeball the set-up and use various straight edges for accurate alignment.

GB

Commandos are a maturing influence on me - no freaking shorts cuts allowed by their construction and geometer, so to run a belt drive one must first make sure the drive train is stable as can be. Before I bit the bullet and rebuilt gearbox I got to make a one time close acquaintance who drove me and Peel 60+ miles back home after dark because he took pity on me seeing the belt all chewed up and piled up around the crank shaft because the belt tended to need and rub the front pulley plate to stay on the clutch basket, after about 120 miles of fine flings that memorable day. It was a brand spanking new belt ok, so what do you think your chances are of meeting accommodating strangers far from home or pestering family or friends to retrieve ya on old belt that don't stay put on its own?
I had time to practice meditating and a bit of praying laying back on side of road and heat and bugs wondering how this stranding would end, for maybe 3 hours watching sun set on me.

Once you do have a stable drive train and reliable belt run, who'd go back to oiled triplex chain except to play caveman hunting with spears and bow and arrows instead of a rifle. There is extra level of smoothness that a belt provides over the chain gang, if you are man enough to make it so. ugh.

Hobot

Your right re no shortcuts. I have been here before 15 years ago after fitting an RGM belt drive and fell foul of the fact that it doesn't have the clutch bearing retaining circlip fitted but advises to 'just fit it'....I was in the IOM for the TT but Roger did ship some new parts out and I fixed it, belt shredded etc. Not the only one to caught out by that reading the threads..

Anyway it just got worse. Thought I'd fit the new rear tyre (TT100 x 19) then all ready to go and check belt alignment when running. Guess what. The back wheel is an 18 inch!!!! :shock: Thought the wheel rim dropped in easy! Who fits TT100's to an 18 inch wheel when there is better rubber available. Front is a 19 inch TT100. That's why the bike looks nice though as I just realised (high front squat rear - bit like the wife )

My fault. Fortunately my gym membership finally paid dividends today to lift the bike back into the agrage without a rear wheel.

Should have this running by December Mid week hopefully after taking tyre back.

Note agrage = garage although I have invented 'garage rage' this weekend :roll:

Gosh fastfred, them is healing words to hear from someone else straining jaws into neck on what I now call...
"The Blank British Iron Stare" at stupidity, over sight or some not understood mystery trouble. When this teeth grit neck setting events strike me, it cuts on, [ugh] off, some blood flow to what little brain I've got let [ugh] left and scrambles my spelling and grammar just like yours for strangers to solve. I look up to your seasoned experience on avoiding belt drive issues now.

Funny Hobot. Still kicking myself for not checking that damn tyre size. Didn't know they made 18" TT100's, do now

Ugh, quit it already as likely I'll do similar again and I enjoy my ignorant bliss intervals between reality checks on jaw slacked realizations. hobot

Latest update in this nail biting saga of general Norton feetling and incompetence...

Ordered correct size tyre yesterday from Vintage Tyres, Beaulieu near Southampton. Top guys. Collected old one today and delivered new one by 9:30am. Took tyre levers to work and fitted tyre on office floor at lunchtime.

Put wheel put on when got home tonight. Fiited new alternator stator spacers ( some doughbrain fiited some beauties that both fouled the outer belt pulley keeper plate and put the stator on the p*ss). Now have 8 thou gap.

Positioned front tyre against brick wall, started engine, selected first gear. Bike stalls.

More late night filing of steel pressure plate required

Sounds like a clutch adjustment, not filing.

I believe that any Commando would kill the motor if the front tire was against a wall and put into first gear with the clutch engaged.



As swoosh says, that is not a "test" from which to conclude anything from, the motor is killing as it should be.

No Swoosh

The new RGM pressure plate is very tight in the clutch drum

Will be on milling machine tomorrow at work for some light dressing

FastFred said:

No Swoosh

The new RGM pressure plate is very tight in the clutch drum

Will be on milling machine tomorrow at work for some light dressing

Click to expand...

I believe I took .040 off of mine. Fits well in the hub but clutch seems too light on the pull. May take off another .010 or.020 to bring the diaphram more engaged.

Hi Pviss

This is the thick steel RGM pressure plate. Is yours? I think you mean you faced off 40 thou to increase the pressure on the plates?

My first problem is that it is very tight on all faces of the outer tangs; very disappointing that I am having to prat around with this..

I am going tpo skim the outside diameter and takes a gnats nadger of the angled faces

then will face off if any slip etc

Please help if you can advise

pvisseriii said:

FastFred said:

No Swoosh

The new RGM pressure plate is very tight in the clutch drum

Will be on milling machine tomorrow at work for some light dressing

Click to expand...

I believe I took .040 off of mine. Fits well in the hub but clutch seems too light on the pull. May take off another .010 or.020 to bring the diaphram more engaged.

Click to expand...

I may need to do the same. My clutch is very light and works well, unless you are in 3rd or 4th and really hit it, then it slips. Either the clutch stack needs adjusting or the old fiber plates are leaching oil when it gets warm.