MBP 7mm Collet Installation - Ducati.ms - The Ultimate Ducati Forum
 
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post #1 of 10 (permalink) Old Jun 10th, 2010, 10:44 pm Thread Starter
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MBP 7mm Collet Installation

This is for the DS1000, but figured i put it up here instead because its a 7mm collet.

Anyway, I purchased these from a member here so they are used, but they are pretty much in great shape.

They werent easy to install simply because its hard to get them seated. I am having problem installing it on the last valve im wokring on, specifically the exhaust valve for the vertical cylinder.

The closing shim was originally 3.13mm, and it is now 2.95mm. A call to EMSDUC revlealed that certain batches of collets can cause variance up to .012" or .30mm. That means i still have .12mm to shave off before i start getting out of the norm.

However, on the other 3 valves, ive only had to remove about 0.10mm, not .20mm or .30mm. The cam will not spin at all since either the collets are not seating (ive done everything i can to get them to seat). or the closing shim is too tight.

There is one odd thing out of all this. If i install one particular shim, it will not cause the cam to bind. If i install the other shim, it will bind.

So the question becomes, is there something wrong with the other shim? or does installing one shim not have any relevance?
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post #2 of 10 (permalink) Old Jun 11th, 2010, 12:21 am
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The shims can vary even if they gauge the same. Depending on the radius pocket diameter/depth the split rings or collets seat in can easily cause a difference in clearance.

Certainly if the collets are not seating in the shim fully you’ll have the same problem. The collets themselves can vary slightly also. Given the right combination (or wrong however you care to look at it) you can run into what you are experiencing.

If you have another shim that is close to what you need, try swapping it out with another - Or try installing the trouble collets in another known acceptable clearance valve you‘ve already adjusted and see if that will help verify if it’s a shim problem or collet.

Also on EMS there is a install guide that might help if you haven’t already seen it.

There could also be a burr around the groove on the valve that won’t allow the collets to seat easily or properly.

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Last edited by yellow blur; Jun 11th, 2010 at 12:45 am.
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post #3 of 10 (permalink) Old Jun 11th, 2010, 5:04 am
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I recently fitted MBP collets to my 916, I took the heads off because I didn't want to deal with tricky access to the exhaust valves, especially the rear cylinder where access is very tight and because I had to replace 6 rockers and the valve stem seals at the same time so for the price of the gaskets I saved myself a lot of struggling and got the valves, pistons & heads cleaned up too.

So with the heads on the bench quite a straightforward install, I only used the existing closer shims as a guide to what size I might need as they all required a different shim due to the collets tightening the clearances and incorrect clearances in the first place and then the opener shims are different anyway.

I had to fine-lap almost every shim to get them to a perfect clearance but I was aiming for spot-on settings, rather than accept a tolerance range, especially as then at the next check I will know exactly how much they have moved (hopefully not at all) .

It's not difficult to lap them if you have the time & patience but each shim maybe slightly different, despite measuring the same due to the seating as mentioned by Yellow Blur, go on the clearance not the shim measurement.

I bought a shim kit, along with the rockers from EMSDUC (thanks Mike!) to save me running backwards and forwards to a dealer, so now I'm hoping for much less valve shimming in the future.

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post #4 of 10 (permalink) Old Jun 11th, 2010, 10:10 am
 
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The latest batch of 7mm MBP Retainers and 7mm closer shims are easier to install than previous batches. The decrease in closer clearance when MBP's are used is much more consistent with different shim/retainer combinations. Also the change in clearance is now around .10 mm (tighter) when MBP retainers are installed. Guy Martin and I have been working together by playing with tolerances to make them easier to install.

The factors involved in the fit are the tolerances of the valve stem, shim, and retainer geometries. There are tapers involved in the geometry and with this design, slight changes in tolerances can change the fit of all the parts dramatically. We are also finding the heat treat process is critical so the parts do not change size significantly.

The result now is a system that should be easier to install without having to go back and forth many times to get the correct clearances.

Mike
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post #5 of 10 (permalink) Old Jun 11th, 2010, 10:27 am Thread Starter
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Originally Posted by yellow blur View Post

If you have another shim that is close to what you need, try swapping it out with another - Or try installing the trouble collets in another known acceptable clearance valve you‘ve already adjusted and see if that will help verify if it’s a shim problem or collet.

Im going to try this. However i almost certainly need a 2nd hand because i have to tap on the shim pretty hard to get the closer shim to drop and reveal the collets. Using forceps wont help because im tapping the closer pretty hard.


Do you guys have any tips on how i should hold the valve up? THe forcep thing doesnt work here because my valve covers are round, theres less space, and the shim doenst just drop. Without extra hands i cant think of anything.

heres a pic of how it looks like when they seat properly.

This one valve will not seat like this, it looks like its sitting just about 1/2 or 1 full millimeter higher.Is there anyway i can hammer it in?

This is the shim thats causing the headache. theres no visible problems with it, but ill try swapping these collets out with a known good one. then see what happens.

Last edited by He Man; Jun 11th, 2010 at 10:38 am.
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post #6 of 10 (permalink) Old Jun 11th, 2010, 10:50 am
 
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Here is what I do to unseat the shim. I make sure the piston is at TDC and I let the valve drop down to touch the top of the piston by depressing on the closing rocker. (you have to have the belts removed to spin the cam to allow closing rocker to depress). I then take a very small jewelers hammer and tap slightly on the edge of the closer shim to unseat the shim from the retainer.

If the retainer is just not fitting, let me know and I can send you another one. As I said previously, the batch of retainers I have now fit easier than some in previous batches.

Mike
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post #7 of 10 (permalink) Old Jun 11th, 2010, 3:55 pm Thread Starter
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I labeled the bad collets and bad shim in 1 group and started swaping with known good shims and good collets.

Here is how my testing went out

Bad Shim + Bad Collet= negative clearance causing binding
Bad Shim+ good collets = Positive clearance @ .001
Good Shim + bad collets = negative clearance causing binding
God shim + good collets = Positive clerance @.001

i purchased these used from a member here, so i dont know how it worked on his bike, but these "bad" collets just arent fitting my bike.
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post #8 of 10 (permalink) Old Jun 11th, 2010, 5:52 pm Thread Starter
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Called up Mike at EMSDUC aka ducatimike aka THE MAN! Going to send me 8 new collets because these might be part of a bad batch. Depending on how they fit i may or maynot need new closing shims. Got a shim kit from a friend and will be using it to check my clearances and ordering shims if needed!

Big props to EMSDUC for doing this!
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post #9 of 10 (permalink) Old Jun 17th, 2010, 3:56 pm Thread Starter
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So an update Mike at EMS sent some new collets over to replace the old collets.

BIG difference in installation. They seat completely differently. The closing shim does not get stuck on the collets, you can slide the collet down with your fingers.

It took less than an hour to install the new collets. I am very pleased with the new collets and it was easy to zero out the closing shims with the new collets.

Now time will tell how long they last. I have a habbit of redlining my DS1000 motor in the city and broke a few closing shims before.

I definitely recommend them as a replacement for stock collets in terms of ease of installation. They are drop in, reshim and ride off.

Props to mike at EMS again!
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post #10 of 10 (permalink) Old Jun 17th, 2010, 4:03 pm
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They should last great for you. I've been thrashing my 748 for a couple seasons at the track, and there has been very minimal clearance change in that time.

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