Author Topic: Mirage 1200TS valve shims  (Read 328 times)

Offline lawrence

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Mirage 1200TS valve shims
« on: April 16, 2019, 19:30 »
I've decided - after some years riding with Axtell cams - I will swap them out for the OEM cams that were standard with the low-compression North American model.  I've long since lost the data sheet for the original cams, so I have no idea of the shim sizes that were used.  My question is, how can I approach this swap with a minimum of work?  Should I just install the smallest shims possible, such that I can measure the valve lash? With a mere 40K kilometers on the clock, there should be minimal wear on the valves and seats.  Is there a shim size that would be expected to be the "norm" on an engine in excellent condition? TIA
Idaho, USA

Offline psg

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Re: Mirage 1200TS valve shims
« Reply #1 on: April 16, 2019, 22:48 »
If the base circle of each lobe on the Axtells is the same as the original cams, then use the shims that are installed now, otherwise you should be able to use thicker or thinner shims as determined by the difference in base circle for each lobe between cams. That should at least give you a good starting point when you install the cams. You shouldn't be too far off whatever clearance your looking for. I'm assuming the Axtell clearances are the same as the stock cams (A11).

Stu
Laverda 1200 (Mirage spec), Triumph T100R, BMW HP2S, BMW K1300S, John Deere X739

Offline Vince

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Re: Mirage 1200TS valve shims
« Reply #2 on: April 16, 2019, 22:50 »
Why, the blokes who have those cams here are really impressed with the torque improvements they produce. Of course, it's your bike to do what you want too.

Offline lawrence

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Re: Mirage 1200TS valve shims
« Reply #3 on: April 17, 2019, 00:40 »
Don't read this request as an oblique criticism of the Axtell cams.  He was a tuning genius.  It's true the low end torque is fatter with the Axtell cams, but you do see the top end of the rev range curtailed.
I had the Axtell cams reground from A11s I bought used.  The regrind required a lot of meat from the journals (?); the shims are much larger on the Axtells. 
I'll measure the two sets when I pull them off and go from there. That sounds like a good place to start. Thanks.
Idaho, USA

Offline IAG

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Re: Mirage 1200TS valve shims
« Reply #4 on: April 17, 2019, 03:37 »
PM sent-
1976 3CL#5148 
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Offline motoddrob

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Re: Mirage 1200TS valve shims
« Reply #5 on: April 17, 2019, 05:13 »
When I fitted an Axtel cam in my 1200 I found the base circumference was less than the A11 which meant that the shim sizes went up about .5mm.
They were reground from an old set of 4C cams.
I really like the Axtel profile and the extra torque from lower revs at te expense of top end. Not really interested in top end anymore as it can cause all sorts of trouble like having the bike impounded and imploding wallet.
Motodd 1200, SFC750

Offline wdietz186

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Re: Mirage 1200TS valve shims
« Reply #6 on: April 17, 2019, 16:45 »
Generally when cams are reground for higher lift/duration the base circle is reduced to effectively raise the tip of the cam lobe. The nose and flanks are sometimes welded and reground to change the rate of lift and closing too.