21 replies to this topic

[Aridgerunner]

I have been doing short drives (less than a mile) recently, mostly just to have a little fun until I get the car into the upholstery shop for the headliner. So driving it without windows is maybe a little on the illegal side? But we live out in the sticks.

The car has always started easily and idles smoothly at 900 RPM. The engine is bored .060" with shallow dish pistons and evo 002 cam and 1.5 roller rockers. Cylinder pressure is 200.

Yesterday it was time to load it on the trailer to go to the upholstery shop. I warmed the engine up before the trailer arrived then shut it off for a few minutes while waiting. Then, in my excitement I tried to start it with the clutch pedal depressed. It acted like the battery was nearly dead. When I realized what I was doing I let up on the pedal and fired right up.

Do I have a problem?

[coopertaz]

do the revs drop at all if clutch is pressed when engine idling?

[Aridgerunner]

Yes. But it doesn't stall. Just slows down.

[Aridgerunner]

I forgot to mention that the flywheel is a Mini Spares light weight. And so is the pressure plate. The clutch disc is new and so is the diaphragm and the plunger and the bearing and the clutch arm.

[68+86auto]

Sounds like worn crankshaft thrust washers to me. Quite common due to people pressing the clutch when starting.

 

I've seen videos where the play can often be seen at the crank pulley.

[Aridgerunner]

I guess we'll have to remember not to depress the clutch pedal when starting the car. Thanks for the help.

[68+86auto]

I guess we'll have to remember not to depress the clutch pedal when starting the car. Thanks for the help.

 

It really means an engine rebuild is required.

[gav]

Check primary gear end float, had a customer with the same problem a few weeks back. Ideally use 2 feeler gauges so the gear doesn't rock and throw off the reading.

[Ethel]

Are your throw out stop nuts correctly adjusted? The lightweight goodies will be lacking a bit of inertia & depressing the clutch will remove a bit more.

 

Is it Verto or PreVerto (diaphragm)? How the latter is set up can make a big difference.

[Aridgerunner]

It's PreVerto. What would be difference in set up with the lightweight goodies? I followed the instructions in the manual for the adjustments.

When assembling the engine I verified that that crankshaft end play was correct. The engine now has about a total of one hour run time. Most of that has been in the garage setting it up.

The car will be coming back from the upholstery shop later today. I will check the adjustments then.

[Ethel]

It will carry less inertia to compress the next cylinder to fire. The exhaust valve of the cylinder doing the pushing will already be open as the  next approaches TDC & maximum compression. That will also have an effect on the ignition  timing because the engine fires before top dead centre and relies on inertia to carry it past TDC so the power stroke starts pushing the piston with the engine rotation instead of against it. You could try disconnecting the vacuum advance (assuming you have it) to see if it improves the idle. Block the pipe to the carb for thoroughness, but it shouldn't make much difference. You'll still want to run with vac advance, but it will be useful info if it does idle better.

 

As for the clutch,

 

As the diaphragm flattens more of the spring tension is held inside it. If you got it perfectly flat all the tension would be internal, like a ball balanced on top of a dome, but the slightest nudge would make it fall. You can set the clutch up so it's just short of the "top of the dome" when it releases its grip on the friction plate*. To do so you'd either have to add shims between backplate & pressure plate, or (as may be likely with lightweight clutch supplied for tuning) machine down the backplate horns to get it just so.

 

* which will also give you the maximum clamping force when the clutch is released.

[pete l]

https://www.theminif...ustment-issues/

[Spider]

 

I guess we'll have to remember not to depress the clutch pedal when starting the car. Thanks for the help.

 

It really means an engine rebuild is required.

 

 

I'm inclined to think there maybe an issue, as 68+86 has pointed out.

You should never start these engines with the clutch depressed. Doing this loads up the Crank Thrusts Bearings, which with the engine not running, have no lubrication on them. This is the same for any car, not just Minis. I am aware that modern cars require that the clutch be depressed to be able to start them, but they have teflon thrust bearings to cope with this situation, Minis, do not. I only recently had to replace a crank, primary gear and clutch plate in a Moke from the owner starting his Moke in this way.

 

Given your engine is new, it may also be that the Crank Thrusts has been fitted back to front, with the steel side to the crank, offering no bearing surface what so ever to the crank, they tend to bite rather than slide when like this.

You can check the Crank End Float with the engine installed, it may give you a guide as to an issue here, but, at this early stage, it may not. If it has increased at all over what it was when the build was done, then you can be sure, there is an issue here.

[Aridgerunner]

I feel stupid. The problem was a weak battery. After letting it on a charger/maintainer over night there is no problem. And as for the drop in RPM at idle with the clutch depressed that is a drop of 100 from an idle 1000. I don't think that indicates a problem. If I'm wrong please let me know.

Once again, thanks!

[bpirie1000]

I would also check the earth strap is good connection