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Calculating shim size after re-seating valves

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1975-S1C
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Calculating shim size after re-seating valves

#1 PostAuthor: 1975-S1C » Thu Aug 17, 2017 5:57 pm

Hello chaps,
Progresss on rebuilding the head on my Z900 has been a bit slow of late, what with one thing and another, but I'm back on it.
The valve guides and seats were in a pretty shocking state to I fitted new guides myself and had the seats recut and valves resurfaced and lapped in. So far so good.
Assembled the head on the bench with the existing shims and just as I worried, I now have no clearance to the cam. All but one of my shims are 2.65, but I do have a 2.30 which I tried but still no gap :roll:

I guess I should try to get the smallest shim (2.00 ?) and see if I have a gap then and if so I can then do my calculations.
I guess I could have the valve stems ground a little, but without any reference point I don't know how much would need to come off.

Is the first step to get a 2.00 and try that ? 9if so, anyone like to sell me one ?) Or is there some other way to figure out the best way forwards ?

Cheers in advance
Paul

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Re: Calculating shim size after re-seating valves

#2 PostAuthor: zed1015 » Thu Aug 17, 2017 7:40 pm

Yes! you need to start with a 2.00 shim and go from there.
if you still have no clearance you can initially tip the valves by .30mm with the stock valve collets
If that does not do the trick there are a few other options before resorting to new seats.

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Re: Calculating shim size after re-seating valves

#3 PostAuthor: 1975-S1C » Thu Aug 17, 2017 8:49 pm

Thanks for the advice. I'll see if I can get one from eBay land then.
Cheers

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Re: Calculating shim size after re-seating valves

#4 PostAuthor: 1975-S1C » Thu Aug 17, 2017 9:03 pm

Ouch, best part of 20 squids for a 2.00 shim on eBay.
Didn't I read somewhere on here that there is a shim swap arrangement somewhere ?

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Re: Calculating shim size after re-seating valves

#5 PostAuthor: z1bman » Thu Aug 17, 2017 9:27 pm

the club has a shim swap service but the 2mm is not a common shim

if you cannot find any used ones cradley have them in stock part no 12037-001 £9.56 or you can use BMW k100 series shims same diameter & probably cheaper than kawasaki prices

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Re: Calculating shim size after re-seating valves

#6 PostAuthor: z1bman » Thu Aug 17, 2017 9:46 pm


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Re: Calculating shim size after re-seating valves

#7 PostAuthor: 1975-S1C » Thu Aug 17, 2017 9:48 pm

Thanks mate, much appreciated

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Re: Calculating shim size after re-seating valves

#8 PostAuthor: 1975-S1C » Fri Aug 18, 2017 1:23 pm

A new 2.00 shim is winging its way from Crawley Heath to Bristol, hopefully I'll have some sort of clearance with that !

Thinking about the valves though, the Service manual says you have to leave 4.1 mm of stem above the groove. Mine are all about 4.75 mm. Any reason why I shouldn't whip 0.6mm off anyways in order to hopefully claw back some shim adjustment later on ? Or is there a good reason why one should only take off 0.3mm ?

Sorry for yet more questions, but I'm learning as I go.
Cheers
Paul

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Re: Calculating shim size after re-seating valves

#9 PostAuthor: Big Fluff » Fri Aug 18, 2017 3:32 pm

If you grind any more than the stated maximum off the top of the valves then you'll remove all the case hardening and the valves will wear at a rapid rate!
It sounds like someone has recut the valve seats, and without being predantic, the majority of people in possession of a valve seat cutter know fuck all and they should be taken off them!
I've seen countless heads with valve seats recut, and all by dickheads!
The ONLY time you should EVER recut a valve seat is after fitting new guides or actual valve seats, and then only by the absolute tiniest amount.
I can't put enough into words that these idiots who own valve seat cutters just cause misery and massive expense to the customer/end user.
If you hadn't guessed it, they really make my blood boil! :twisted:
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Re: Calculating shim size after re-seating valves

#10 PostAuthor: 1975-S1C » Fri Aug 18, 2017 5:54 pm

Don't sit on the fence there amigo, say what you really think ! :lol:

I understand what you're saying, but the guides were shot so I changed them and the seats and valve surfaces were quite badly pitted and needed recutting. The place that did the seats is a localish machine shop that were well aware of the need to take off the absolute minimum. Don't think I'd blame them really.

Anyways, as they say, we are where we are. So I need to fix it up one way or another. The 2.00 shim should be here soon and hopefully that combined with taking a small amount off the valve stems will put me back on track. If not, i'll be back for more advice !

Cheers for explaining about the 0.3mm max off the valve stems.

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Re: Calculating shim size after re-seating valves

#11 PostAuthor: z1bman » Fri Aug 18, 2017 8:10 pm

the reason for not grinding of more than the specified amount is if you you do there is a good possibility the cam bucket will flick out the collets & cause catastrophic engine damage

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Re: Calculating shim size after re-seating valves

#12 PostAuthor: 1975-S1C » Fri Aug 18, 2017 8:25 pm

Ah, yes, I see. That makes sense.
I'll try the 2 mm shim, perhaps 0.3 off the stems if needed and hopefully we're back in business.

If not, I'll get back on here for possible plan B's !
Thanks

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Re: Calculating shim size after re-seating valves

#13 PostAuthor: 1975-S1C » Sat Aug 19, 2017 12:28 pm

Well this morning brings better news on the shimming front.

The 2.00 shim arrived from Crawley Heath Kawasaki and with it fitted as a reference I measured the gaps on all 8 valves and all are providing well over the 0.15 mm gap, so no need to go valve stem grinding after all ! Happy days.

So I guess I just need to do some shim swaps now, who's the person I need to contact please folks ?

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Re: Calculating shim size after re-seating valves

#14 PostAuthor: Big Fluff » Sat Aug 19, 2017 2:10 pm

An acceptable result for you there, but just bear in mind that valve clearences close up as the engine gains mileage.
Providing that your shims when fitted are around 2.10mm, then you should be okay for around 10k miles before having to do surgery on it.
To give the valves and seats an easier time you may want to look at adding a lead substitute in your fuel :roll:
Regards Will
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Re: Calculating shim size after re-seating valves

#15 PostAuthor: 1975-S1C » Sat Aug 19, 2017 3:20 pm

Thanks Will.

I calculate I would need one at 2.1 mm and that gives me the max 0.15 clearance.
One at 2.15mm and another at 2.20.
All the others are all at 2.25 or above.

You've set me thinking again now, is it worth grinding some off the valve stems now to gain some extra adjustment for the future I wonder ? Even if it's just them 3 lower ones ?


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