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Anyone ever had their Flywheel Machined


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Hi Everyone,

Has anyone ever had their flywheel re machined? If so what are your experiences of the process?

Has anyone got a flywheel for an S4s or S4 lying about I think my flywheel has been machine too far and is now unusable!!!

Cheers Mike :censored:

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  • Gold FFM

I had mine Blanchard ground, both surfaces (friction surface and the pressure plate mounting surface) to maintain the proper step height.

Step height is 0.5 - 0.6 mm (0.0197 - 0.0236 inch) for Esprits with a Renault transaxle

Travis

Vulcan Grey 89SE

My Lotus Photo and Projects Album

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Mike,

I've replaced several clutches on various SE, S4 and S4s Esprits in the last few years and have had similar problems as you with not being able to get proper disengagement on a few of them.

Before you pull the gearbox again you might want to consider a couple of things.

I don't think your problem is the flywheel being turned below spec, unless it was way below the 12mm minimum. It's possible but I would not assume that.

I don't think it's a problem with the step either. Too small or no step would generally cause a slipping problem. Too large of a step could cause a disengagement problem but it would have to be way over spec. Note that I'm not saying that neither of these conditions exist with your flywheel as it could very well be out of spec.

First, is the adjustment bolt on the clutch fork set to spec, 9-12 mm from the forward face of the nut to the end of the bolt?

Have you tried screwing it in further than the 9-12mm spec? Does it make any difference on disengagement?

In two instances I have actually had to make a longer fork pushrod in order to get the clutch to work properly and basically disregard the factory specs.

You might want to try making a new pushrod using a bolt with similar diameter about 3/8" or so longer than the current one. Start with the adjustment bolt setting at about 5mm and do the test that you mentioned in one of your earlier posts with the car sitting on an incline and not running and pushing in the clutch pedal so see if it disengages. Keep threading the adjustment bolt further in until you can get the clutch to release. Don't go any further than is necessary.

You want to be sure that you don't put too much preload on the clutch with the longer pushrod or it could cause the clutch to slip. You should be able to spin the rod with your fingers.

You also want to be sure that you don't push the clutch pressure plate in too far causing overtravel on the clutch as this will damage the pressure plate and also cause disengagement problems. NOTE: It is possible if you or someone else has been playing with the settings and pushed the pressure plate fingers too far (overtravel), that the clutch is damaged already and will never work properly.

When setting the fork pushrod adjustment, there is a "sweet spot" when it is in just the right place that gets just enough movement to disengage the clutch without overtravel or too much preload on the clutch, and that's what you are trying to find.

This is all assuming the rest of your specs are correct with the pedal, properly functioning master cylinder and slave cylinder and the system is completely free of air.

I don't know why this situation occurs but I have personally seen it enough to know that it is an issue. IMHO, I think it has something to do with some slight changes in clutch manufacturing specs or suppliers over the last few years but that's just a wild guess.

Good luck!

Jim

Edited by lotus4s

1995 S4s

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I have used the adjuster on the clutch fork to try and compensate for the machining of the flywheel, however this has made no difference. From reading up on the system this adjuster is there purely to allow the maximum use of the clutch friction material while making sure the clutch cannot wear beyond the friction material thus causing metal to metal contact and potentially damaging the flywheel etc.

I dont understand how a longer push rod would work?

Surely the master cylinder after the first pedal push would simply compensate for extra length?

This is the second clutch fitted to the same flywheel since it has been machined. Both clutches failed to be able to disengage in exactly the same way. There can be no damage to the clutch as there has been no extra pressure placed on the clutches other than that exerted by the hydraulic system fitted to the car, which if anything is not exerting enough pressure.

As for the flywheel, the flywheel had to be machined twice. This was due to the first machining causing the friction surface not to be flat it ran off at approx 5 thou at its worst in the centre. The step in both instances was re machined correctly back into the flywheel.

Has anyone bent a clutch fork? If yes what effect did this have?

All your comments are greatly appreciated keep them coming.

Cheers Mike

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A long shot, but check the tube over the input shaft. I've seen where it was too long and fouling full travel of the throw-out bearing.

It was only a few millimetres but enough to stop proper clutch disengagement.

DanR

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It's possible to bend the fork but usually it cracks when it bends

The adjuster nut does serve to preserve the flywheel from damage but it does more than that. It also determines how much preload is on the fork and clutch.

The reason a longer pushrod works is that when you push the pedal in, the piston in the slave (which is pushing against the pushrod) bottoms out on the c-clip in the cylinder. A longer pushrod at that point, will push the clutch fork that much further.

Dan,

Why would the sleeve interfere with the release bearing? Are you saying it was long enough to be pushing on the friction disc?

Edited by lotus4s

1995 S4s

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Hi Dan,

That is a good point about the cylinder bottoming out I will have to check that. Although I must say I think (I could be wrong) that the slave on my car does not get anywhere near the circlip. I wonder if a larger capacity master cylinder might give me more travel at the slave cylinder?

Has anyone tried this? My current master cylinder is the larger of the 2 sizes Lotus used being a .7.

Cheers Mike

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I meant the free play for the clutch plate not the slave. The clutch plate should be working properly, not fouling on the tube andI doubt you have a problem there. Being a single plate there's nothing really for it to bind to but still worth checking.

Do check the slave draw too like you said. The piston should be fully retracted or at least more than is necessary to shift the rod and fork.

DanR

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  • 2 weeks later...

Latest.

Having used a professional pressure bleeder and approx 5 litres of brake fluid I swapped to bleeding the system the manual way and managed to get a lot of air out with only a few cycles of bleeding. The car now has a clutch!!!! It starts to bite at approx 3 quarters of the travel of the pedal quite near the floor but it is progressive (does that sound about right for an new clutch). Hopefully I will get to road test it this weekend.

Cheers Mike :thumbsup:

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