belt drive tension

On going problem...I usually have to rattle first gear into position. Last winter I rebuilt the entire gb just to address this annoying problem. I got the gb to shift up and down easily (after MUCH fiddling with the hairpin spring) but only halfway solved the first gear problem. The belt tension is not what is usually called for...instead of the 90 degree twist it is about half that....where I would adjust the primary chain. I would like to put in a bit more free play but it is a real bear to adjust the trans and get the belt running true. 5 or 6 hours including test riding. It runs well except for the shift into first gear. The layshaft first has a new bushing. Is it possible that the belt tension is the culprit?

Not sure if true on Nortons but on Triumphs, especially Tridents, that problem and difficulty finding neutral are usually the clutch not fully releasing. I would re-check that before anything else. If it is fully releasing, then I would check the clutch bearing and I would get the belt tension right. If I remember right, you also changed the sleeve gear bushing - was it completely smooth and free on the mainshaft?

If belt tension were the culprit, you would notice a difference in shifting from cold start to hot engine/primary/tranny, since belt tension increases as primary components expand. Do you notice a difference in your described 1st gear shifting issue from cold start-up to fully hot (20-30 mi of operation) riding?

No difference between hot or cold.
This has an old Tony Hayward clutch...a Triumph clutch center with an adaptor to fit a Norton mainshaft. Perhaps 20 years old. The clutch center has been replaced once. Both sets of plates were replaced about two years ago. The mainshaft checks out in the lathe. The clutch basket does not wobble.
Here is a clue: At a stop sign I push off with one foot, it will rattle into first. If there is a slight slope and the pushing off speed is tripled then first gear engages just like it should. So what is happening?
As I remember the sleeve gear bushings went in and turned easily on the mainshaft.
I'm afraid it will be another long winter project trying this and that with no real idea what to change.

I went through the clutch about two weeks ago, cleaned up the plates and checked for free movement in and out the basket.

seattle##gs said:

No difference between hot or cold.
This has an old Tony Hayward clutch...a Triumph clutch center with an adaptor to fit a Norton mainshaft. Perhaps 20 years old. The clutch center has been replaced once. Both sets of plates were replaced about two years ago. The mainshaft checks out in the lathe. The clutch basket does not wobble.
Here is a clue: At a stop sign I push off with one foot, it will rattle into first. If there is a slight slope and the pushing off speed is tripled then first gear engages just like it should. So what is happening?
As I remember the sleeve gear bushings went in and turned easily on the mainshaft.
I'm afraid it will be another long winter project trying this and that with no real idea what to change.

Click to expand...

Not familiar with that clutch - does it use three springs like a standard Triumph clutch? It so, watch the pressure plate as you actuate it - does it lift evenly?

It is a three spring. I have spent oodles of time making sure the solid aluminum MAP pressure plate lifts evenly.

seattle##gs said:

It is a three spring. I have spent oodles of time making sure the solid aluminum MAP pressure plate lifts evenly.

Click to expand...

OK, sounds like you've eliminated the clutch. So some to check:

Camplate has a problem (worn, rough, catching on something, etc.) Remember the problem you had changing the bushings for the camplate and gearchange quadrant.

Damaged selector fork or gear

You're still fighting the shifter (selector pawl floppy or sticking on the shaft, hairspring)

I recently had one that the slot for the gearchange quadrant was not quite deep enough - the quadrant touched it just as 1st was being fully selected. There should be a small gap when fully in first.

If you mean the gears crunch as you engage first gear then that does point to the clutch not fully disengaging (dragging). If you pull the clutch in with engine off and operate the kickstart it should feel like there is nothing attached to the kickstart other than a spring. Does it?

I don't know about the Tony Hayward belts, but that belt would be too tight for a Norvil or RGM Gates type belt. The TH one runs in oil doesn't it? If the above test is ok it's definitely worth trying to adjust the belt.

Good luck with gear selection, but i can tell you the correct tension for belt drive is- should be able to slide the belt off and on by hand. Loose is GOOD. Any tighter and it will never track.Cheers.

Is that sliding on and off hot or cold? There is a big difference. I have three BNR belt drives. On the Norton, if set loose, as in turn the belt 90 degrees twist motion, it will rub badly on the alternator studs even after the studs were seriously relieved. In time it peeled the back right off the belt. I tightened it and the rubbing almost ended. Shifting was unaffected. I believe the rubbing must have happened when cold and when hot expansion tightened it .
So my experience is it doesn't need to be loose as a goose. But after fully hot, do as suggested and
push the kicker down whilst pulling the clutch in to feel where it engages and make sure you get full disengagement.

ringydodds said:

Good luck with gear selection, but i can tell you the correct tension for belt drive is- should be able to slide the belt off and on by hand. Loose is GOOD. Any tighter and it will never track.Cheers.

Click to expand...

I'm no belt drive expert. That said when torquing the rotor nut and the belt jumps teeth I'm pretty sure it's too loose! The belt quit jumping teeth when it would turn about 60 degrees cold. At 90 degrees the belt could only handle 45 ft lb. I do not know the age of the belt or whose belt drive it is (it's not cNw) but it looks new and it fits the pully very well.

I’ve only used synchronous belts in an industrial setting - big motors driving big extract fans with shaft centres circa 1.5 metres apart.

They were a fickle beast indeed, too slack and they would track off just out of spite, too tight and after a few days would strip the teeth from the belt. Fans were computer controlled and would need lots of heavy load adjustment / compensation so a bit like a gearbox.

Used to use tension tool when fitting a new belt which would give a deflection value relative to applied load, deflection was determined by inputting data into a formula that took into account application.

I’ve no experience of a belt on a motorcycle having only used a chain but just a thought, do the belt conversion sellers provide tension data / deflection values for their kit ?
Further, does the website for the belt manufacturer give tension values or an equation to calculate this out ?

Most likely is clutch drag.

My Norman White belt drive is run with a TTi gearbox, so Triumph clutch actuator. The 40mm belt is fixed and not adjustable, the slack is less than 90 degree twist, but close. And it is what Norman set when he made the belt drive for the bike.

Clutch lift is critical, and it takes a lot of work to get smooth first gear selection. I end up with less free play than recommended, but that is what works.

And I have an expensive Domino GP 33mm fulcrum lever, which helps somewhat. After market levers that have with between 27mm and 29mm fulcrums don't work with my set-up. (a crappy old chrome steel one I have does because the concave shape of the lever wraps on the grip, giving a little more movement!)

Check everything in the clutch operating system to ensure you are happy with the lift you are getting.

Going into 1st gear comment: Clutch drag is the only thing that ever made any clutch I've used crunchy to get into 1st with the AMC gearbox. The little spring clutches I've used on the Norton are real sensitive to gear oil contamination.

Different belt clutch: My belt clutch goes into 1st so easily and silently I often don't think it is in gear when making the shift from neutral to 1st at a stop light. I modified my inner cover a little to let the quadrant go down about 1/16" further in the slot. (Right hand shift old Norton shift pattern.) Seemed to help in my AMC gearbox. Also have a diaphragm spring clutch that to date has been an improvement in every way possible over the small spring clutches.

Excessive layshaft end float might make a difference getting into 1st. Not sure though. That's one of my guess don't test thoughts.