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Up Topic C1 Information / Repairs - Faults & Fixes / Shims & Reluctor
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- - By Spud Im Irish Date 19.09.15 16:10
I've measured the valve clearence- None for IV's (but valve cap can rotate so believe that meanes no real pressure on it).- One EV at .15 other at.29
The manual says IV should be .05 to .14 and EV @ .2 to .29
I could swap 3 of them around and they would just be in tolerance- but obviously don't want to have to do this again in a hurry- so what end of the spectrim should I go for or mid point of them?

The valve caps have their sizes printed on the inside- how can or can they be increased / decreased- As I understand it a Shim is a thin piece of metal- like a feeler gauge so presumemable can only add? or is there something in the valve cap that can be removed and swaped with something thinner?-

Other question is in replacing the chain- manual says to remove oil pump hence remove reluctor- the main bolt in the middle- releaseing that won't do the job?- does the special bolt press on something to release unit?- so bolt needs to be same thread but just longer?
Thanks again- would be lost without the help

Parent - By HelmetHair Date 19.09.15 18:04
My two penneth is that the shins are bought in various sizes and that is how the gap is adjusted
be careful to recheck the gaps after you've torqued the cam carrier, because the tightness alters the gap.
Parent - - By jeb Date 19.09.15 19:07
Hi Spud.     the reluctor bell is fitted on the shaft via a taper and woodruff key,   to remove it you need a bolt which is  an M16 by 1.5 mm pitch thread.   screw this into the reluctor which can be very tight on the taper to release   you can hold the boss of the reluctor with spanner or grips to enable more purchase   Sometimes a sharp tap on the bolt when under load does the trick. anyway, persevere and I am sure you will achieve.
Parent - - By alunt Date 19.09.15 19:44
The large oil drain plug fits the thread to get the reluctor off. The shims are all available from BMW and not that expensive, so I would advise getting them from them.
Parent - - By Spud Im Irish Date 19.09.15 21:36
Never having seen a shim- before - can the dept of the valve caps be reduced- is there something in it that can be remove?
Where on the scale e.g IV .05 - .15 should I strive for?
Parent - - By HelmetHair Date 19.09.15 22:28
Anything is possible, but you shouldn't alter the shims you have.
The gaps are altered by
Parent - - By Spud Im Irish Date 20.09.15 19:40
The reluctant is reluctant!
Removed it once- then put back on to make sure I could- then when removing again sump plug sheared their threads- not sure if sump plug or threads in reluctor gone- only way to remove to send to engineering company to re-bore?
Or any other way?
Parent - - By leonm Date 20.09.15 20:31
Hi spud
1.  Valve clearances decrease with use, so choose clearances on the high end.
2.  Valve stems increase in length at temperature, so gap decreases from cold measurement. No measurable gap at cold will result in burnt valves over time.
3.  The m16x1.5 bolt must be 8.8 tensile strength or higher (marked on bolt head). The reluctor material is very tough and would not have stripped it’s threads. The reluctor wheel is held fast by the tdc special bolt when tightening. Remember Loctite on reluctor taper when installing. Advisable to closely follow the repair manual procedure.
Parent - - By Spud Im Irish Date 20.09.15 20:41
Leon thanks for reply- i used the sump plug to try to remove reluctor and now the bolt is just spinning- is there any cunning way of getting it out?
Parent - - By jeb Date 20.09.15 22:36
bad luck Spud.   you can try getting a screwdriver under the edge of the bolt head and levering it  whilst turning the bolt anticlockwise    As Leonm said it is doubtfull that you have stripped the thread in the reluctor boss cos it is made of a decent quality steel,  unlike the sump bolt.    last resort maybe drilling the sump bolt out as it is fairly soft metal.
Parent - - By Spud Im Irish Date 28.09.15 13:18
Well that's part of my life I won't get back-
Managed to eventually drill and manipulate the large sump plug ftom the reluctor.
Had to re-tap the threads of relict or but hopefully with the correct tool will be able to remove to get to lower part of engine.
Will have a job to remove the filings!!
Talked to my local BMW guy- he said that as plug is only a soft alloy you should never use it to remove reluctor- I won't!!

I asked a question about shims that I didn't really get an answer- so if someone can confirm that would be great.
Guido in C1 Teile said you cant change the shim alone- must change whole valve cap? Is this correct as people have mentioned changing shims (which I know you can on some bikes) but never requiring completely new cap??
Parent - - By Gerard Date 28.09.15 13:48

To clarify, there are no shims as such. There is an inverted metal bucket that sits on top of the valves. The cam lobe pushes on the outside base of the bucket which in turn pushes down on the valve. The valve clearance is set by using buckets with a different thickness of the base. Each bucket has a number to denote the thickness of the base. You measure the current gap and if it needs adjusting, you note the number on the bucket for that valve and then obtain a new bucket with the appropriate base thickness number to give the required gap. The buckets are the same for inlet and exhaust, so sometimes you may be lucky enough  to shuffle your current buckets around to get the required clearance. Having said that, I have never been that lucky. There is a post somewhere on the forum which lists each bucket number and the resultant thickness.

You may be able to machine a bucket to alter its base thickness and thus the valve clearance, personally I wouldn't want the hassle, I would invest in a correct bucket.
Parent - - By Spud Im Irish Date 28.09.15 14:33
Ok thanks for that- not sure why people were using terms like-"changing shims" when in fact they are changing buckets / caps
Thanks for confirming
Parent - - By alunt Date 28.09.15 14:48
We're not fully trained BMW technicians you know, just keen amateurs trying to help :-) If you want the correct name it's a "bucket tappet", which contains a small disc in the base which I would describe as a "shim". It's fixed in there so you are changing the shim and the bucket tappet in one piece.

Have you got a workshop manual? It's all in there.
Parent - - By leonm Date 29.09.15 07:20
hi andrew
on a point of detail, bmw call the bucket a cam follower, which i suppose is correct if you think about it,  and there is no shim. the inside of the bucket has a raised portion which bears on the valve head. years ago i ran a lotus elan with a cosworth head where the exact system you describe was used.
Parent - - By alunt Date 29.09.15 07:43 Edited 29.09.15 07:49
On page 11.20 and 11.21 of the workshop manual BMW seem to refer to them as bucket tappets. I can't see cam followers mentioned but I'm sure it means the same thing. I'm just trying the keep the terminology consistent with BMW speak in the manual for anyone who is using it.
The shim isn't mentioned either because it's the variable thickness disc which forms part of the bucket tappet, so it's never a separate piece of metal. However, on the forum we usually see the bucket tappets referred to as shims.
Parent - By leonm Date 29.09.15 16:36
you are correct. it appears bmw refers to the part as a cam follower only  in the parts catalogue
yes, i place great score on the bmw repair manual, excellent piece of work but i must say that the bmw repair manuals which i use for the restoration of my 1957 and 1972 bmw 500cc r50 models are much more detailed.
   but even these are put in the shade by some of the info readily available from an unbelievable dutch site at:
  especially strong on old british bikes
Parent - By HelmetHair Date 28.09.15 21:23
Well, I myself personally used the word shims as you used it in the heading to this topic that you posted.

Do you have the manual?
Parent - - By alunt Date 28.09.15 14:09
I'm amazed you managed to strip the threads before the Alan key hexagonal hole rounded off! Based on advice from others on this forum I've used a sump plug, as they have, to do that job several times without a problem by tightening it then tapping the reluctor with a rubber hammer, then tighten a bit more, tap it again and off it comes. Maybe I'll look for a proper bolt to do it in future after your experience.
Parent - - By Spud Im Irish Date 28.09.15 14:36
Most "damage" to the threads were done in extracting! Didn't require full re bore or anything like that but needed to get re-tapping cutter to fix up. But yes- the right tool is defo an advantage- lesson learnt!!
Parent - - By leonm Date 28.09.15 14:50
2,50MM  11 32 1461906
2,50MM  11 32 1461906
2,55MM  11 32 7666043
2,60MM  11 32 7666044
2,65MM  11 32 7666045
2,70MM  11 32 7666046
2,75MM  11 32 7666047
2,80MM  11 32 7666048
2,85MM  11 32 7666049
2,90MM  11 32 7666050
2,95MM  11 32 7666051
3,00MM  11 32 7666052
3,05MM  11 32 7666053
3,10MM  11 32 7666054
3,15MM  11 32 7666055
3,20MM  11 32 7666056
Parent - - By patc50 Date 28.09.15 21:44
Just for info, above, Leonm has kindly posted the bucket tappet size (thickness) with appropriate part number.  It's a job I too need to do!


Parent - - By Spud Im Irish Date 01.10.15 15:39
Tool arrived today- two turns- job done- reluctor removed.
I have the new chain and guides in- having trouble getting chain around both cam sprokets.
Took nut out of upper guide to try to give a bit of slack- but no joy- anyone got a tip on getting chain on.
On positive note- presume new chain is tighter!

Thanks again


may not sound it but enjoying trying to get through this!
Parent - By jeb Date 01.10.15 16:03 Edited 01.10.15 16:09
have you removed the chain tensioner?  what you also can do is to remove the camshaft retaining cover and tip the camshaft slightly .    when assembling the timing  make sure the crankshaft is locked with locking bolt and that the timing marks are correct  then turn engine over and rechech a few times.  the timing marks do not seem to line up exactly but should be as near as possible   do not undo the camshaft sprocket (cogs)bolts.
Parent - - By leonm Date 01.10.15 16:08
hi david
max slack is achieved with tensioner and bottom slide-in guide removed. if still too tight, remove eight bolts holding what bmw calls the camshaft support bracket, lift slightly and tilt one of the cam wheels, slip chain over sprocket teeth. fiddly job because cam teeth must line up with tensioner inserted.
Parent - By jeb Date 01.10.15 16:12
Parent - - By HelmetHair Date 01.10.15 18:16
What they said!
Do not undo the cam sprockets under any circumstances!
Parent - - By Spud Im Irish Date 01.10.15 19:14
ehhh- what's implication of undoing nut holding cam sprockets?
Won't say if I did or didn't (but had already!)
Chain back on- manually rotated a couple of times - TDC marks seem fine.
Good advice about loosening cam to get final bit of slack.
Now the bad news- re measured from the tensioner- got about 10mm!
Not even close to the 4 I was expecting!
Any idea how long the tensioner is from the bottom to the lip of the outer that I measure from - but don't see how this could wear?
Parent - - By HelmetHair Date 01.10.15 21:05
The cam sprockets move, and your engine is destroyed.
Parent - - By Spud Im Irish Date 01.10.15 21:09
Once I use locktight and torque to correct number- Is there a further risk?
Parent - - By HelmetHair Date 01.10.15 21:49
From what I've read on here-yes.
You could weld them in to place?
Parent - - By Spud Im Irish Date 02.10.15 04:51
Got it! Will get it welded as suggested.
Any idea on length of tensioner? My one isn't rounded anywhere- so don't see how there could be wear.
Chain probably needed changing anyway (25000 miles) but don't understand measurement I'm getting?
Thks D
Parent - By leonm Date 02.10.15 06:21
......and measure from engine casting ie with washer removed
Parent - - By leonm Date 02.10.15 06:08
hi david
how did you manage to undo the cam sprockets? they are torqued to 30nm and difficult to grip, hope you did not place new cam chain under tension in the process?
  when you do the check measurement, the tdc locating bolt and both chain guides must  be in position. measure to outer piston rim  while pushing inner piston of tensioner downwards. are you using new chain guides? are you using a depth gauge for measuring?
  the tensioner length is not affected by wear
Parent - - By Spud Im Irish Date 02.10.15 07:27
Yes new chain, new guides. All in place.
Chain to really tight but measuring with digital calliper getting about 10mm from lip of casing to ridge on wider piece of tensioner. There weren't any changes in design of tensioners where there? Do you know what length of lower wider bit should be?
I haven't fully tightened cam nuts back up- loosened cam when old chain was on. But good point about tightening. No point changing it then stretching it to put nuts on!
Parent - - By leonm Date 02.10.15 12:29
hi david
  length of outer piston is 36.5mm
cam nuts must be sufficiently tight to prevent tilting of cams when chain is tightened
long shot, but i seem to remember that chain has 115 links. perhaps variobob can comment on whether he has ever come across a chain which is too long.
  your measurement points to a  chain path which is  too long  and this can be the result of a short  non-spec (too short) tensioner,   too long chain or incorrect  chain guides.
  this problem is hotting up and probably has a sherlock holmes solution
Parent - - By Spud Im Irish Date 02.10.15 18:21
I guess I can use them as worry beads and get counting.
Got them from guido in C1 teile in Germany so would be confident they are right!
So will just go over my fitting again- but seemed fine- upper guide screwed in etc
Will let you know-
Guys thanks for help!
Parent - - By variobob Date 02.10.15 22:43
A) I do not get the reason why everybody is so keen on changing the guides. If they don't show any signs of wear you can simply re-fit them;
B) I never came across a new chain that turned out to be too long;
C) If one does not put in the lower long chain guide (the one you can extract easely once the black valve/cam cover is taken off) the chain will have too much play as well;
D) If the chain somehow slipped of the crankshaft teeth it might 'gain' length as well;
E) Please always make sure to refit the C-shaped guideing part neer the teeth on the crankshaft. It is easely forgotten...

None of the above mentioned points of attention is meant negatively, although it might sound like that.


Parent - - By Spud Im Irish Date 03.10.15 22:11
No negative infrenence taken!
I was thinking D was the most lightly- that's what I was going to check first.
What is the black cam cover??
The lower guide can't be removed Easly - might indicate top is too slack so bottom is too tight?
Parent - - By variobob Date 03.10.15 23:28
'The black cam cover...'

The lower guide is unscrewed and should be easely removed. It is this one:

Just pull it into the direction of the front of the C1 if the engine is still built in.


Parent - - By leonm Date 04.10.15 05:55
this illustration may also be useful:
Parent - By leonm Date 04.10.15 15:56
Parent - - By Clunkfish Date 04.10.15 10:16


Originally by Fleetwood Mac (the Peter Green incarnation), not Carlos Santana ;-)
Parent - - By variobob Date 05.10.15 20:17
I stand corrected! Love any version of the song, to be honest!

B :) B
Parent - By Clunkfish Date 06.10.15 11:51
I'll be singing "Got a black plastic cover" next time I hear it :-)
Parent - - By Spud Im Irish Date 05.10.15 16:34
I've taken a few pictures of the engine- The upper chain is very tight- so can't see how it might have sliped a tooth.
The upper guide is flush againt the engine case -(at bottom of hole of tension gauge)- I can't depress this it all- so no play on chain.
The bottom rail is also tight- variobob had indicated that possible should be loose.

Other than a dirty engine- anyone spot anything that could be amiss?


Attachment: IMG_7348_B-867.jpg (115k)
Parent - - By HelmetHair Date 05.10.15 16:50
In the first picture, the chain looks like it isn't straight. It's probably just a difficult to see picture, but is the chain sitting on the cogs properly?
Parent - - By jeb Date 05.10.15 17:50
this is a very interesting thread,    but I find it difficult to see how you could put the chain on incorrectly.   a new chain will be reasonably tight on the sprockets so a mystery it seems.  it will be very interesting to see the final result. of this rebuild.  I am sure all will be revealed in due course
Parent - By jeb Date 05.10.15 18:06 Edited 05.10.15 18:14
just had a real good look at the photo,s    is the chain fitted on the crankshaft cog properly,   very difficult to see even when enlarged.   must surely be worth checking as Helmethair suggests
Parent - - By variobob Date 05.10.15 20:16 Edited 05.10.15 20:27

Here are some questions from overseas:

And this is a point of concern as well:

Please also check this:

The C-shaped guide can be easely forgotten and also mounted incorrectly (Murphy law enters the building).

It would be very helpful if you could add two more detailed photos of both A and B marked zones. A bit more light would be great as well ;-)

The A-marked zone captured in more detail could also reveal if the chain is not correctly mounted on the crankshaft.

I am as curious as you are by the way.


Up Topic C1 Information / Repairs - Faults & Fixes / Shims & Reluctor
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