cam timing placement and shims....

jimathy · Borekit Bruiser Joined: 22 Apr 2009 Karma :

I am in the process of putting back together my engine. Only issues now are
a/ do I want the thicker shims on exhaust or inlet sides?

and b/

Where should I place the cams in relation to TDC? Both are identicle, but have several differing number/letters etc on them. Going clockwise from E) E1 16E (1/4 turn) I, (1/4 turn) 3 (2 teeth) 1, (1/4 turn) 2, back to E. How do i want to place them on IN and EX in order for them to do the right thing?

any help appreciated

EDIT, IN on the right of pic

jimathy · Borekit Bruiser Joined: 22 Apr 2009 Karma :

can anyone one help with the timing especially. I can't see any marks on the block to line up the E or the I, but i assume they will want to go at TDC, but will they want to be horizontal, or level with the top of the head (given that the engine is on an angle), or do they want to be 3 o'clock on the IN and 9 on the out, or what?!?!?!?

Please help!

Billing · World Chat Champion Joined: 12 Mar 2009 Karma :

On my NC23 you're supposed to line the crank up with the marks under the cover, then fit the cams so that the appropriate marks are touching (IN mark @ 3 o'clock, EX mark @ 9 o'clock.)

It would probably be best for you to get a workshop manual for your bike, or tell us what bike it is so we know Laughing

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steven_191 · Nearly there... Joined: 31 May 2009 Karma :

cam timing 'usually' starts with piston 1 at TDC. but ive only got that experience from car engines.

jimathy · Borekit Bruiser Joined: 22 Apr 2009 Karma :

Pete. · Super Spammer Joined: 22 Aug 2006 Karma :

As a rough guide, the cam lobes will be pointing at 10 o'clock and 2 o'clock on TDC when they are set right. If you have marks that make them do this and none others nearby then use those marks.

Make sure that once you fit the cams up you turn the engine over two whole turns carefully by hand in case you got it wrong.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good Very Happy

jimathy · Borekit Bruiser Joined: 22 Apr 2009 Karma :

and any idea on the shims if they are different thicknesses?

thicker to IN or EX?

Pete. · Super Spammer Joined: 22 Aug 2006 Karma :

You cannot guess where to put the shims, you have to use the proper size on according to your valve clearances.

Read my thread on shim-based valve adjustment here:

https://www.bikechatforums.com/viewtopic.php?t=150267
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good Very Happy

jimathy · Borekit Bruiser Joined: 22 Apr 2009 Karma :

Pete. · Super Spammer Joined: 22 Aug 2006 Karma :

Well then you fit all four shims and measure your clearances. If you get any with no clearance at all you have put in a thick shim where a thin one should be.

Don't get this wrong it will burn out the valves if you have too little clearance.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good Very Happy

jimathy · Borekit Bruiser Joined: 22 Apr 2009 Karma :

Pete. · Super Spammer Joined: 22 Aug 2006 Karma :

Where the shims reside makes no difference. First measure your shims and make a note of where you put them in the head. Next, assemble the whole camtrain and make sure you line up the marks so the valves open the right time, to stop the valves from hitting the piston at around TDC. Now you must follow the method in my post listed above, for setting valve shims.

If your clearances were within spec before you started you should only have to swap shims around to achieve correct clearances. If not, you're gonna have to buy a shim or three.

I think you should really find some knowledgable help, seems like you're struggling a bit here.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good Very Happy

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

Presume you mean they go under a bucket, with the cam operating the bucket. They take up the excess clearance so the clearance between the bucket and the cam is correct (ie, they just lift the bucket up a bit).

They are made very precisely and there will be numerous different sizes available. A small amount of wear in the valve seats or small differences in manufacturing tolerances (ie, tiny difference in valve length, cam size, etc). Hence you need to measure the clearances and choose and appropriate size shim to get the clearance within specs.

All the best

Keith
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jimathy · Borekit Bruiser Joined: 22 Apr 2009 Karma :

Pete. · Super Spammer Joined: 22 Aug 2006 Karma :

Many bike manufacturers use similar diameter shims, such as 9.5mm, you need to measure yours and buy the correct diameter ones.

I have a bike shop locally that has boxes of them and does them on exchange for £2 each. Places like wemoto sell them new.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good Very Happy

jimathy · Borekit Bruiser Joined: 22 Apr 2009 Karma :

Pete. · Super Spammer Joined: 22 Aug 2006 Karma :

Here's a pretty good reference for what models use the more popular shims, 7.5 and 9.5mm:

https://www.sudco.com/75valveshims.html

https://www.sudco.com/95valveshims.html
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good Very Happy