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I had a question so..........

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jlaird

jlaird

Great Pumpkin
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I took Miss Agatha out, and for the very first time drove it like I stole it. Wheeeee.......darn that was fun. I mean like I was 30 again. Good thing I don't have a 1275, a fella could get in big trouble.

Anyway......

Reguarding clutch.

All is well from start and into second at 5K even. Then I get from 2ed to 3rd and 3rd to 4th at 5K a clutch release but it grabs on release of the pedal at about 1 inch or so from the bottom. The release when shifting is not as clean as I would like either, however, if I then pump it one time all is fine.

This is a 948 with smooth box and it has a White Post rebuilt MC, a Quinton-Hazel clutch set, and a new Lockheed slave cylinder. Hard line has been blown both ways with carb cleaner at over 70 lbs pressure.

It is not getting any worse and may even be getting a bit better??????
 
Jack - I know nothing about this stuff but I wonder if your clutch springs are binding? I'm trying to imagine the movement and can imagine two possible scenarios.

1. There is sideways pressure (from the rotation of the engine) that is hanging up a spring slighty - hence the "grab" when it releases. or

2. There is forward/ reverse pressure doing the same thing.

Could this be caused by something as stupid as a burr on one of the springs or one slightly out of alignment? Or could it be that the springs and mechanisms just need to wear a little and work into place?

just thoughts.

BTW we need a head scratching icon
 
/bcforum/images/%%GRAEMLIN_URL%%/devilgrin.gif It must be something stupid. In any case seems like it might be getting a bit better, we will see.
 
I been thinking. 948 and 1150 slave cylinder is 5/8 inch and 1275 is 1 inch. Wonder which I have.

Guess I need to get under and measure the diameter.

Wonder if that would make a difference even?

If I had a 7/8 MC feeding a 1 inch slave seems it would not move far enough, etc. etc. I wonder, I just wonder. Know I ordered the right one. Wonder which I got. They both look the same.
 
Jack, we finally got you to quit saying 1297 :smile:, now we got to work on the 1098 thing /bcforum/images/%%GRAEMLIN_URL%%/smile.gif
 
You raise a good point about bore sizes Jack. As I have noted before on this problem, I definitly think the problem lies in the hydraulics, not the clutch itself, especially since a pump on the pedal seems to improve it!!
 
That "double pump" thing with an improvement would tend to indicate air in the system ~someplace~, tho I know you've bled it repeatedly.

Have you measured slave travel by having the pedal pushed ONCE to the board, measure travel, then have the pedal released and depressed fully a few times and held down... there should be NO increase in travel between the two operations. If there IS an increase in travel after being pumped several times and held, there's AIR in there somehow.
 
Ok Hap, I know, 948, 1098, and 1247. It's just that my fingers have not learned it yet.
 
jlaird said:
Ok Hap, I know, 948, 1098, and 1247. It's just that my fingers have not learned it yet.
Click to expand...

1247??? /bcforum/images/%%GRAEMLIN_URL%%/smile.gif /bcforum/images/%%GRAEMLIN_URL%%/smile.gif /bcforum/images/%%GRAEMLIN_URL%%/smile.gif
 
I am going to throw out a crazy idea that is probably way off, but I figure it can't hurt to throw it out there.

It sounds like what you are describing is double clutching, which would be consistent with worn synchros. Now, I know your gear box is a rebuild, but it is an old rebuild, right? What if... and remember I said this is probably stupid... the problem is your gear box oil. When that smooth case box was designed (and rebuilt) oil was very-very "low tech." What if the modern multi-viscosity oil you have in there is "too slick" for the synchros to grab at high revs. I wonder if putting the single weight oil that the gear box was designed for will correct your problem.
 
jlaird said:
I been thinking. 948 and 1150 slave cylinder is 5/8 inch and 1275 is 1 inch. Wonder which I have.

Guess I need to get under and measure the diameter.

Wonder if that would make a difference even?

If I had a 7/8 MC feeding a 1 inch slave seems it would not move far enough, etc. etc. I wonder, I just wonder. Know I ordered the right one. Wonder which I got. They both look the same.
Click to expand...
Jack, they are different in the line connection. The pre-1275 take a hard line and a 3/8-24 single flare.

The 1275 takes a flexible line, and a 7/16-20 straight pipe and uses a copper gasket at the hose to cylinder connection. You can't get that wrong. No need to measure.

btw, I like the synchro idea being the problem.

Peter C.
 
Thank you Peter, should have remembered that, but what would worn synchros have to do with clutch travel part of the time?

Rember just from second to third and forth does the pedal go way way down then grab just as you start to release it.

I saw the synchros in fact, they were not worn, in fact looked new and unused.

When shifting at lower RPM third and forth is smooth as butter.
 
OK... thinkin' out loud, here (scary)
What if....
The pressure plate's throw-out bearing collar were loose enough so that at high RPM it would lift away and push the release bearing back. Similar to run-out on brake rotors which can push the pads back in a caliper, and cause you to have more pedal travel, and need to pump the brakes. First clutch pump moves the bearing close enough that the second pump will do the work.
I remember you posted a pic of your QH pressure plate. Can you show that again? Maybe the little collar retaining springs are allowing the collar to lift off at high RPMs. I know you said it only happens from second to third, and third to fourth, but I'm thinking with a Sprite gearbox, you don't spend a lot of time in first at 4000 rpm.... may twenty feet.

Eh? I like it.

Peter C.
 
Great post, we've got the 1297 and shifting out of first at 5k.

I like both Peter's and Hap's suggestions.

Still partial to the MC adjustment (since I am naive).

Pat
 
I never too a pic of that but did notice that the throwout bearing was thinner than the other newish one I had, like a quarter of an inch thiner. Wonder why that was, maybe I should not have used it. sigh

And I compaired sets very carefuly for size thickness etc etc.
 
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]I saw the synchros in fact, they were not worn, in fact looked new and unused.[/QUOTE]

To be clear, I was not suggesting that the syncros are worn out. I am just suggesting that they are not compatible with modern super slick oil. Perhaps they need SAE 30 to function properly. Again, I am very willing to accept that this is an unlikely explanation.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]When shifting at lower RPM third and forth is smooth as butter.[/QUOTE]

That is exactly how your transmission would preform with slightly worn or poorly gripping synchros. It would shift fine at low revs and roughly at high revs.

I must confess, I don't really understand your description of how the clutch behaves. Do you mean that when at high rpms, the clutch pedal has no "back pressure" until you pump it?

Or do you mean to say that it does not accept the next gear until you pump the pedal. If this is the case, this, again, would be a symptom of poorly gripping synchros....

I think.
 
Well let me try again.

From second to third and third to forth.

Up near 5K.

Pedal will go to almost floor before releasing clutch. Then when letting clutch out it bites when released about one inch or so.
 
Oooooooooh!

Now I get it.

I am slow mostly.

Please disregard all my previous comments.
 
Hay, no one else seems to ever have had this prob, like most of mine, nor do they know how to fix it. Course I don't either, treading new ground here.

Good thing is little engine is very happy all the way to 5K.
 
Much as I hate to say this (because as you well know it means another engine-pull), Jack, but perhaps you should just get rid of that questionable T/O bearing and get one that is "correct". A 1/4" difference between pieces seems quite significant to me!! At least once the motor is out and separated from the tranny the part switch is a simple 2 minute job!!
 
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