10 replies to this topic

[MiniLuke]

Hi, I have an issue with a heavy clutch pedal on my completely rebuilt engine.

So, a 998 a series. Non verto clutch
New master, new pipe and hose (not twisted), new slave.
New arm, spring, plunger, and bearing. Plunger is free to move in wok.
Properly bled, and pedal to master cylinder rod pin properly in place.
Adjusted in line with Haynes book

All gears select fine. Car drives.

Pedal is very heavy though. Compared to my other mini too, I am sure something is amiss.

I’m trying to think back to when I built up the flywheel assembly. I know the flywheel was one I had from another engine, however I replaced the backplate with nos one I bought with a 1300 flywheel. It had the same part number so I went for it. In my mind I considered if this needed to be balanced with the flywheel, and as both flywheel and backplate have balancing holes drilled, and it’s just on a little 998 engine I thought it would be ok. I used a standard new Borg and beck clutch plate kit, as far as I remember. I think I used new bolts too, but not the straps.

Now, I’ve done about 50 miles, and there’s definitely a slight judder at higher revs through the car, and a little when engaging going down the gears. I sense the flywheel isn’t in balance, or something else is amiss.

I’ve also thought whether i lubricated the splines. I can’t honestly remember. Could this cause some of the symptoms?

What’s the thoughts on pairing a new backplate with an old flywheel?

I’m resigned to pulling it apart, just wanted to get some advice if possible please. If I wanted a good balanced flywheel and backplate balanced off the shelf, where would I get one? They all seem to be lightened ones. Or maybe I take what I have to be balanced somewhere? This doesn’t solve the heavy clutch pedal though. I sense there’s a few things going on here, so any pointer/advice welcome! Cheers

[Hpal]

Hi, i probably don't have your answer here, but when I built my clutch for my 1100 supercharged engine I set it up as per instructions on, I think, minimania, where it said to machine a bit off the backplate posts to bring the spring to near flat so as to have the most clamping force. I did this and installed it in the engine. It had a shudder in it even after balancing, and a very heavy pedal, so much so that when pushed in it stalled the motor or at least dropped the revs significantly. It wasn't set up right and was pushing so hard on the crank it slowed the engine. I pulled the clutch out and put a washer under each post to undo what I'd taken off the posts. Now its pretty good.  I'd be looking at something like this or getting your one set up better and balanced as a unit. – MED Engineering Ltd MED ST1 ULTRA LIGHT ASSEMBLY - Med Engineering (med-engineering.co.uk)

[mad4classics]

Not sure how heavy you're experiencing, but bear in mind that an "original" 998 installation would have been fitted with a green spring diaphragm; these are no longer available.

If you've fitted a new standard "one size fits all" Borg & Beck kit, this comes with a blue spring diaphragm, which does make the clutch noticeably heavier by comparison.

Borg & Beck now seem to have stopped marking their new standard spring with a colour identifier.

Edited by mad4classics, 28 August 2022 - 07:39 AM.

[gazza82]

Borg & Beck now seem to have stopped marking their new standard spring with a colour identifier.

Could be down to the new owners, First Line, who probably just get them made by the cheapest supplier possible (some of their product quality is a bit dubious judging from reviews and feedback on forums!)

[ACDodd]

Fit this ;

https://minispares.c...|Back to search

It’s colour coded blue but actually is a 998 item.

Ac

[MiniLuke]

Hi, i probably don't have your answer here, but when I built my clutch for my 1100 supercharged engine I set it up as per instructions on, I think, minimania, where it said to machine a bit off the backplate posts to bring the spring to near flat so as to have the most clamping force. I did this and installed it in the engine. It had a shudder in it even after balancing, and a very heavy pedal, so much so that when pushed in it stalled the motor or at least dropped the revs significantly. It wasn't set up right and was pushing so hard on the crank it slowed the engine. I pulled the clutch out and put a washer under each post to undo what I'd taken off the posts. Now its pretty good. I'd be looking at something like this or getting your one set up better and balanced as a unit. – MED Engineering Ltd MED ST1 ULTRA LIGHT ASSEMBLY - Med Engineering (med-engineering.co.uk)

Thanks, interesting. I’m thinking that setup at MED might be a bit much for a standard 998. I see there’s a lighted one available from others which suggests the weight is a third less at 5kg. Is that going to be helpful in a standard 998? I’m thinking maybe just get the standard one checked and balanced with a new diaphragm as advised above, if I can find somewhere that can do it…

[MiniLuke]

Fit this ;

https://minispares.c...|Back to search

It’s colour coded blue but actually is a 998 item.

Ac

Hi, I’ve just removed it. It has a blue dot on it.

I reckon the whole thing needs setting up, like you show here… https://youtu.be/myx0mnLYv4g

Thanks

[ACDodd]

Yes setting the horn height correctly does reduce the side loading on the crank thrust washers and reduces the pedal pressure. To be sure what diaphragm you actually have measure the thickness with a vernier calliper and post back.

Ac

[MiniLuke]

Yes setting the horn height correctly does reduce the side loading on the crank thrust washers and reduces the pedal pressure. To be sure what diaphragm you actually have measure the thickness with a vernier calliper and post back.

Ac

Hi, measures a smidge over 2mm.

I looked at the straps and their not straight, they’re all needing thicker spacers I think.

Also, when looking at the marks on the diaphragm it’s deffo not been sitting square on, on the flywheel. Marks on one side, nothing on the other.

[ACDodd]

Yes 998 ones are nominally 2.05mm thick, 1275 ones are 2.2mm thick.

Ac

[red81]

When I had my clutch horns machined I took an equal amount off the clutch face, I read this was required somewhere.  You don't seem to have done that so may be a factor, I'm not sure.