The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Gearbox, Clutch, Primary => Topic started by: adunham1 on 14.11. 2020 03:18
-
Hi all,
Putting a Newby clutch in my 61' SR and have a couple of questions. I've got the crank pulley and clutch basket installed, but the belt seems rather loose. I've searched all around and only found on person (on here actually) that mentioned the belt should be able to rotate 90 degrees. But I haven't found any other information.
Also... as a matter of course before I proceed... is there anything other than the sliding plate and felt washer behind the clutch basket? Normally the clutch center would come from behind the inner timing cover (I think) but don't need that now.
Thanks for any help!
-
Hi all,
Putting a Newby clutch in my 61' SR and have a couple of questions. I've got the crank pulley and clutch basket installed, but the belt seems rather loose. I've searched all around and only found on person (on here actually) that mentioned the belt should be able to rotate 90 degrees. But I haven't found any other information.
Also... as a matter of course before I proceed... is there anything other than the sliding plate and felt washer behind the clutch basket? Normally the clutch center would come from behind the inner timing cover (I think) but don't need that now.
Thanks for any help!
I fitted the newby drive and left the sliding plate in place. As the clutch centre is a close fit in the sliding plate and is not used with the new clutch a gap will remain between the gearbox shaft and plate. Obviously oil leaks past the plate are not an issue as the belt runs dry.
I used the adjust belt such as still be able to “twist belt 90 degrees” method of adjustment, to me that leaves the belt a bit slack, and certainly not pulling on the front pulley, or leaving significant tension in the belt. The advice I have read is to err on the side of loose not tight.
Edit: I forgot to mention that you use the std method of getting the belt adjustment correct, by moving the gearbox just the same as adjusting the std chain.
-
From my time setting car timing belts, failure was due more commonly from insufficient tension than overtightening. Usual failure presented was missing teeth. The broken belts were from foreign matter eg a stone trapped....run with no cover, or high milers, driven hard by leadfoots, belt never changed.
The drive is transmitted by the force of the belt against the pulleys, not the teeth, which serve solely for location. Insufficient tension puts more lateral drive force on the teeth, which shear off. Much too tight meant whining noises, and alternator and water pump bearing failures over time.
My take is the belt tension needs to be more on the tight side, and while the 90 degree rule is a good start I'd make it a tightish 90, rather than a loose one. Difficult to describe as experience tells what's right. No guidance from the maker? There is always good old YouTube as a looky how others do it.
Try rotating the rear wheel (in gear) to tension the lower run, then remove as much slack as shows in the top run as an initial setting. You may find the tension varies with a hot motor, so a bit of suck it and see may be in order. It has to be a compromise. Too tight loads gearbox sleeve gear bearings. Too loose risks losing teeth. A good tension is when the belt runs smoothly between the pulleys, with no sign of whip as the throttle is blipped.
The sliding plate can remain as a way of keeping road grit etc out of the primary case.
Swarfy.
-
Thanks guys. My Dad and I were able to get the clutch on, belt adjusted to a "tight 90" and things look and feel great. Even put on a new drive chain and feeling good about progress. The engine has been apart for a year and a half, so any progress is good at this point.
I have noticed, however, that my old pushrod seems too long. Maybe 1/2" or so too long. Can anyone confirm if the Newby kits need a shorter pushrod? I've got an e-mail out to them, but I assume I won't get a response until next week sometime.
Shouldn't be an issue to find one, or I could cut this one and re-harden. That might be the best option.
-
Thanks guys. My Dad and I were able to get the clutch on, belt adjusted to a "tight 90" and things look and feel great. Even put on a new drive chain and feeling good about progress. The engine has been apart for a year and a half, so any progress is good at this point.
I have noticed, however, that my old pushrod seems too long. Maybe 1/2" or so too long. Can anyone confirm if the Newby kits need a shorter pushrod? I've got an e-mail out to them, but I assume I won't get a response until next week sometime.
Shouldn't be an issue to find one, or I could cut this one and re-harden. That might be the best option.
I did get instructions with mine and yes it says you may have to shorten the push rod, just 1/4 of an inch in my case, my push rod is in two halves with a ball bearing in between them to help reduce wear on the rod and clutch drag. I cut a bit off and heated the cut rod end to dull red and quenched it in water to make sure it was “glass hard”.
Do you know about making the end of the rod into a “bull nose” shape to suit the pressure plate? And putting a bit of grease on the rod end?
Edit: I did not tighten the spring adjusters as much as the BNR instructions said, this being just a 30 odd horse power A10 and this clutch is used for much more powerful bikes, on my B31 I used just 3 turns, and on the A10 4 turns from memory. Makes for a lighter clutch.
-
Unfortunately mine did not come with instructions. I bought it from a separate distributor and not Newby direct. I wish I had now. Would you mind uploading a picture of the instructions if you are able?
I'm fine with cutting the pushrod to length and re-hardening. Can you tell a difference with the half rods and a ball in the middle? I figured the clutch itself would be enough of an improvement in feel and effort required at the lever. I did not know anything about grinding the end to a shape. Is this so it fits better in the pocket of the Newby allen head bolt?
Is that 4 turns in from lightly seated?
-
Unfortunately mine did not come with instructions. I bought it from a separate distributor and not Newby direct. I wish I had now. Would you mind uploading a picture of the instructions if you are able?
I'm fine with cutting the pushrod to length and re-hardening. Can you tell a difference with the half rods and a ball in the middle? I figured the clutch itself would be enough of an improvement in feel and effort required at the lever. I did not know anything about grinding the end to a shape. Is this so it fits better in the pocket of the Newby allen head bolt?
Is that 4 turns in from lightly seated?
Here u go, yep 4 turns from lightly seated.
The split push rod is a common mod for std clutches, so I just used the old rod rather than get a new one, I don’t know what difference it makes to the newby clutch but the 6 spring I had before was just as light as the newby and drag free, but I was due for some new plates and chain after just 9000 miles odd from replacing them so I sprung for the belt instead.
The newby is a bit harsh at low revs compared to the std chain, but I suspect thats mainly because my bike misses and hesitates a bit at low revs so things are bit rough anyway, but its made a little worse by the more directness of the belt drive.
The clutch is improving as it beds in, finding neutral is easier than before, albeit it was fairly easy to find neutral anyway.
-
that clutch assy looks really good Kiwi, but I'm intrigued , how you can get away without the engine "damper" spring, I thought that was a key element of these engines to get some level of vibration control, without it, what happens??
-
that clutch assy looks really good Kiwi, but I'm intrigued , how you can get away without the engine "damper" spring, I thought that was a key element of these engines to get some level of vibration control, without it, what happens??
As above the transmission is slightly harsher at low revs on the A10, oddly on my B31 fitting the belt drive made the transmission much smoother, and that has the same spring cush drive as the A10.
I guess the effect of “cush drive delete” will depend on how good the std primary drive was before the belt was fitted, a primary chain with tight spots (as they most have) would probably make the belt drive feel smoother in comparison.
Any additional harshness is not a reason to not fit a belt drive in my opinion, its not that significant, particularly if you consider all the other advantages of a belt. I’d bet money no one with an A10 could ride my bike and immediately know its got belt drive, unless they noticed the lack of screws in the primary cover *smile*
SRM do a belt drive with cush drive, but its expensive *eek*
To me one of the surprising things was how slow the belt goes around, seen with cover off, the clutch runs at half engine speed so spins pretty slowly at normal round town engine rpm.