Clutch problem

[s800racer]

After installing motor after a rebuild, clutch won't disengage. I bled the clutch and believe all the air is out of the line. pushrod from slave cylinder appears to have good movement when the pedal is depressed.

I will try adjusting the free play but I'm not confident that will do the trick.

Question - what happens if the clutch bobbin is installed backwards? This is one of the few things that I can think of that might be different from before the motor rebuild.

Gearbox is a Hewland mk series and the clutch is a Tilton. slave cylinder is external style.

[s800racer]

I adjusted the free play and took up some slack there but clutch still does not disengage.

looks like I will have to pull the motor and get the gearbox off to see what's going on.

[Lotus7]

maybe clutch disc is in backwards ?

[teamwisconsin]

Yes, if the bobbin is in backwards, the smaller end might just be moving inside the fingers of the clutch and not causing it to release. You want the small end against the t/o bearing, the big end against the clutch fingers. However, if this is not the case and all your parts are functioning as they should, investigate one of these two choices.

Option 1: Check to make sure your clutch stop isn't misadjusted allowing the release bearing to over stroke the clutch. If it pushes past the point of release, it can start to re-engage by the fingers of the clutch cover touching up against the disc.

If you put the car in gear and either with it on the ground or with a helper pushing on both the rear wheels at the same time, slowly depress the clutch. If as you depress the pedal it breaks free but then starts to drag again and lock up the clutch, you just need to adjust your stop out.

Option 2: your input shaft is bottoming in the back of your crank. If you have any of a new crank, new block, new input shaft, new adapter plate/bellhousing, new gearbox case, or any combination of the above, you must check crankshaft end float when the engine and gearbox are mated. If the crank cannot move back and forth by .003-007" then you will burn out the thrust bearings. It will also, (in cases of extreme lack of end float) lock up the input shaft from the pressure on the end of it and not allow the drive to be broken by the clutch. The solution is simple, you must grind the end of your input shaft until it has the required end float your engine builder specifies.

Good luck!!!

[Charlie Schmidt]

Also possible that the TO bearing has come off the two arms that push it forward, or one of the arms has failed --

How's the pedal effort? "normal"?

Some bellhousings are cut away on the bottom more than others, maybe you can get a light/mirror up in there

[s800racer]

engine out. clutch bobbin was correctly installed.

engine rebuild includes new crankshaft so I'll try to check crankshaft end float.

[s800racer]

Fixed! Problem tuned out to be the pressure plate. Engine builder flipped it so the side that had been facing the clutch disc was facing the flywheel. I don't honestly see exactly how that made such a difference but after flipping back and re-installing, the clutch worked properly.

[Bernard Bradpiece]

Well Done. Now no excuse not to get to Dominion this week, and with a hot new motor no excuses at all!
Best
BB

[s800racer]

I've got lots of excuses left! I'm still without a working ignition but parts should be delivered on Tues. to fix that so it should not be an issue.

Other excuses:

Rust - I have not driven the car since May at the Jefferson

Gearing - Even if I wanted to gear properly for this track, I don't have the time to fool with such endeavors so anyone that changed gears will nullify my "hot" motor.

alignment - Very unlikely that the alignment is right. Last time I set the car up, it had (unbeknownst to me) a broken frame. with all the work to put the rebuilt motor in - out - in, I probably will not have time to check and adjust the alignment.

See, with all those disadvantages, I should be easy meat for anyone with even modest preparation and driving skills.

But I will be there if nothing else goes terribly wrong. knock on wood.

[DK540]

Considering the caveats about taking it easier at Dominion this weekend due to the dust and lack of some curbing, width, runoff, etc., just bring what you've got and have fun and get to know the track. That's my plan anyway.

DK

[Bernard Bradpiece]

David,
Take no notice of him, with that litany of mega problems - worn out old engine, broken chassis etc he still won the sprint race at the Jeff beating Scott, Joe and Bob Bruce doing 1-21.6 (probably on worn out tires too!).
Look forward to the weekend,
BB

[scott fairchild]

Doug is one of the best armchair racers out there he's also one of the best on track racers too.

Doug, did you install the new rear attenuator for bump drafting yet?

[s800racer]

no rear attenuator - i'll be lucky if I have time to clean the Summit Point bugs off the bodywork.

[DaveW]

Fixed! Problem tuned out to be the pressure plate. Engine builder flipped it so the side that had been facing the clutch disc was facing the flywheel. I don't honestly see exactly how that made such a difference but after flipping back and re-installing, the clutch worked properly.

I don't understand what you said - the side that faces the clutch disk IS the side that faces the flywheel...

Anyway I think I understand what you did - flipped steel part of the PP over. So I am guessing that this is a 2-piece PP, the aluminum triangular cross-section fulcrum piece, and a flat ~3/16" thick steel PP.

So I think the reason flipping it worked is that the "flat" PP was warped (maybe 1/16" in to out) from heat into a shape similar to a Bellville spring.

I've had that warpage issue myself.

[nomis]

I've once experienced a similar problem. a 7 1/4 Tilton clutch with a FT box assembly, I put the car together as I have on numerous occasion's and found the clutch to be engaged after assembly. What it turned out to be was the leading edge of the splines on input shaft where burred (I assume this is from when the engine and gearbox was split where dirt etc entered the splines) then when sliding the gearbox on the clutch the burrs pushed the clutch plate out of the flat plane making a slight warp as mentioned in another post where heat had caused this issue. so being in this huge rush we started the engine in 1st gear hit the brakes and bang it made a noise like a plate being hit with a spoon. all good after that it ran perfect at the race meeting and on disassembly we saw the burrs which have been fixed with no problems since, even using the same clutch disc.
Race cars ! so many things to go wrong that only race car people experience !!

[s800racer]

I don't understand what you said - the side that faces the clutch disk IS the side that faces the flywheel...

Anyway I think I understand what you did - flipped steel part of the PP over. So I am guessing that this is a 2-piece PP, the aluminum triangular cross-section fulcrum piece, and a flat ~3/16" thick steel PP.

So I think the reason flipping it worked is that the "flat" PP was warped (maybe 1/16" in to out) from heat into a shape similar to a Bellville spring.

I've had that warpage issue myself.

I didn't describe it very well, but I did what you described - flipped the steel part of the PP.