21 replies to this topic

[bluedragon]

I'm installing a Mini Spares belt drive kit to replace my OEM timing gears. But, when trying to fit the replacement belt gears (Mini Spares' term) they are a very tight fit.

 

The Mini Spares instructions indicate these should be no more than a "light slide fit." But these are anything but. I would need to use a driver tool to pound these on, if they can be fitted at all, and I don't want to take that chance unless I get experienced opinion that's an appropriate action. The original sprockets were not hard to remove (no puller needed) though I did have to use a punch to knock the Woodruff key out of place - it was tough to remove for me.

 

It doesn't seem right, but what are my alternatives? I could try to grind out the belt gears for more clearance, but I'm worried about doing it precisely enough to maintain concentricity. Lubrication is no answer with this much resistance (I've tried.) Perhaps heat the gears? But I doubt the heat expansion, if it worked, would last long enough to slide the gears all the way in (and what do I do if I need to pull it out again?)

 

Has anyone experienced this with standard chain sprocket sets (simplex/duplex/OEM/aftermarket, etc.?) If so, what was the solution?

 

 

Dave

[panky]

Make sure the woodruff keys are level and free from burrs, the sprockets should be a nice slide fit with maybe a gentle tap to get them on.

[Northernpower]

Do the gears slide on without the woodruff key fitted? If they don't, I'd ring Minispares before doing anything else.

Edited by Northernpower, 13 January 2017 - 10:54 AM.

[GraemeC]

Try them with no keys in the slots first - just to see if they theoretically fit.

 

Then a light de-burring of the edge of their bores, and the end of the shafts, with a fine needle file.  

If they are still a mile off, contact the supplier.

[gazza82]

Well before you damage or modify them talk to Minispares. The clean up the faces of the cam and crank with wet&dry/emery paper and maybe a gentle clean in the gear bores?

 

When I fitted my vernier gears I had a real issue with the new woodruff key which was far to wide and needed a gentle rub down on a diamond plate to get it to fit

[AeroNotix]

I don't have any advice but to satisfy my curiosity, why would one want to make this modification?

[Northernpower]

I don't have any advice but to satisfy my curiosity, why would one want to make this modification?

That was the question I meant to ask as well.

[Dusky]

Heat expansion would work.
Getting them back off would be done with a 3 legged puller. Similar way of fitting/removing a lot of sprockets/pulleys on other cars ( atleast on the american v8's I work on).

Belt drive has a few pro's and cons :
Easier adjustment, takes up some harmonics and a bit quiter.
Cons are the fact thats its a belt that ages, costs quite a bit and can snap.
 

[tiger99]

For these reasons the belt drive conversion has lately gone out of fashion on the Mini. Indeed, people sometimes would like to convert belt drives on other cars to roller chain, if they could. Some manufacturers have gone back that way, or at least half way. For instance, many Ford diesels use a Gemini chain drive to the injection pump, for best timing precision, and a belt from there to the camshafts, which are less critical. Various other very modern engines are all chain. I think it is generally recognised that the belt drive was a big mistake, resulting in many thousands of smashed engines and/or seemingly high maintenance costs if not DIY,  so some people will never drive whatever brand of car it was again. A gear drive would make most sense, but in the A series would present some challenges. Not impossible, but helical gears would be needed, so end thrust would appear. Not as much as the drop gears, fortunately!

 

If I had the money when the belt conversion first appeared I might have been tempted, because everyone thought that belts were great. Not now, with the evident disadvantages and the apparent lack of quality control by the supplier.

 

The only good thing is that as far as I am aware (unless someone has gone almost impossibly wild with the camshaft and/or roller rockers), the Mini is not an "interference" engine and will not smash itself when (I say "when" rather than "if" because it is a typical amateurish design) the belt breaks. When that happens you will be refitting the chain. Where is the belt tension roller? Without one, how can the belt ever to be set at its correct tension so it will neither break nor jump teeth?

 

By the way, timing belts are great in many situations, it just happens that a car engine is not one of them.

[Tupers]

A gear drive would make most sense, but in the A series would present some challenges. Not impossible, but helical gears would be needed, so end thrust would appear. Not as much as the drop gears, fortunately!
 

MED do a gear drive conversion as well as belt and conventional chain systems. http://www.med-engin...haft-gear-drive

I don't think Vizard was too fond of the gear system though. I seem to remember him mentioning transferring harmonics from the crank into valve train unlike a belt of chain system in a lecture that's on YouTube.

[Ethel]

Don't know what sort you have, but I fit mine up by fitting the cam pulley to its hub with the belt on.

 

Lack of chain rattle and more accurate timing are the main advantages*. The latter is negated by modern ignition timing run off a crank sensor, doubtless it has something to do with engine manufacturers going back to chains.

 

*It'll also absorb a fraction less power and makes cam timing on the fly a bit easier as you can run the engine with the, dry, belt pulleys exposed.

[limby2000]

I have a triger kit on mine, probably 30 years old, good quality belts cost 25 quid and are good for 30000 miles.

[bluedragon]

Thanks for the tips. Since I won't be taking another crack at installation for a while, I'm open to any other great suggestions. :)

 

I bought the kit 6 or 7 years ago, maybe longer (memory's not so good anymore...) Back then, the IWIS timing chains didn't exist (or were not as widely known as they are today) so I decided on the belt kit as the better alternative to a duplex chain. Today, I would go with a simplex IWIS chain, less trouble to fit, little to no "stretch" and long-lasting.

 

But I've got the kit so I want to use it. It still does have some advantages though marginal compared to the IWIS solution. Plus I have, and can get more of, the Kevlar belts fairly readily (though the price on these doubled since the late 2000's.) The other couple belts I have as stock seem to be known brands like Gates. Being an MPI engined Mini it's not as much trouble to get to the timing assembly as a side-rad model.

 

I did try installing without the Woodruff key (I wanted to trial fit things first) and it's tight even before getting to the key. I suppose I should contact Mini Spares, though so much time has elapsed that I don't know what they will do for me outside of (hopefully) an installation tip.

 

If it takes heat to do the install, I will. But it would be removal of same would seem to be an engine out job (don't see how I can get any kind of puller in there to remove them while the engine is in place. No room to pull.   ) And of course Mini Spares doesn't seem to think it's needed, though I agree this is common for many automotive applications.

 

On the technological side of the discussion, I believe manufacturers are trending towards chains again because they need to make the engines narrower. Belts take up more space (wider) generally for a given load. Belt technology has advanced, too, and a state of the art belt is more durable than those before. But chains still can be designed to take up less space, and worth the extra noise to get the packaging benefit.

Edited by bluedragon, 13 January 2017 - 10:07 PM.

[icklemini]

Common problem on most of the aftermarket gears... both duplex or belt drive.

Usually a bit of fettling is needed to achieve a proper fit... dont heat it or use hammers... lordy!!

If you have the original gear and that slides on the cam nose ok.. then check the new gear... probably needs a once over with some abrasive paper... the same result would be achieved by using the paper on the cam nose...(though personally i prefer to 'adjust' the cheaper/easier to replace part)

Once the gear slides on nice... fit the key and check the fit again.. if its gone tight then the key or alot may need a tickle with a needle file...

All perfectly normal practice with engine building...

Need to check the crank sprocket fitment too... and the sprocket alignment... and cam end float...

Hth
Dave

Edited by icklemini, 13 January 2017 - 11:20 PM.

[gazza82]

OK after 6 years you probably aren't going to get a refund or exchange so emery cloth. Work it bot by bit and it should take enough off. Chamfer the leading edge too.