I have fitted an expansion tank from a light aircraft (it was cheap)

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The problem is, it was fitted with a 1.8bar rad cap, this seems to be a bit high for a bike engine?
I can buy a 0.9bar cap from here, but £50?
Anyone know a cheaper place, or would 26psi be ok for a bike engine cooling system?
Dimensions here:

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Description
The hard to see dimensions are 25mm.

Try looking at bike caps, they are much smaller than car ones, you might strike lucky.

I'll measure my R1 cap when I get home to start you off....

Plus My L200 has a small cap, where abouts in Chesterfield are you? I'm presently next to Brampton Manor.

[Edited on 8/6/12 by r1_pete]

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Originally posted by r1_pete
Try looking at bike caps, they are much smaller than car ones, you might strike lucky.

I'll measure my R1 cap when I get home to start you off....Plus My L200 has a small cap, where abouts in Chesterfield are you? I'm presently next to Brampton Manor.

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you want the correct release pressure, what does haynes say it is for the donor bike? if you can get this info, post the cap to me or visit me in macclesfield and we'll match it up at the shop.

Hi.

I think a lot of USA and Jap cars use a small rad cap.
Pic shows a 0.9 bar MX5 one but the height is only 17mm. (about £4 from MX5 bitz)


small rad cap. 0.9 bar


The pressure that a cap blows off at depends on the amount the spring is compressed.
When I made my header tank I found that with a drift and a tap with my trusty hammer
I could make a 15psi cap blow at 11psi, which is what my Lotus should run at.

In another instance, a mate with an original Lotus 7 that was always boiling over, had a cap
that didn't match his rad, and a deeper cap solved the problem.

HTH
Paul G

My R1 5jj cap is 40mm dia and 15mm rim to rubber seal, and the L200 (2010 model) is nothing like a conventional cap on the seal side.

Sorry not to be more help but its two possibilities dismissed.