Author Topic: Elusive springs!  (Read 329 times)

Offline Athame57

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Elusive springs!
« on: February 01, 2024, 12:11:32 AM »
I'm gathering up the gaskets, seals and cam system parts I want ahead of a planned rebuild in a couple of months, but something I just can't find anywhere, not even on CMSL is the two springs for the cam bar ( bits 53 & 54 in the image. After 46 years I feel they ought to be changed, but is that likely to be necessary? Strange that they are two sizes, does one fit over the other? Anyone know where or how to get them if they really are needed?
Should new piston rings be fitted as a matter of default while the engine is this open? Leaking gaskets is the main reason for this rebuild.
« Last Edit: February 01, 2024, 12:13:30 AM by Athame57 »
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Offline Oddjob

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Re: Elusive springs!
« Reply #1 on: February 01, 2024, 06:49:56 AM »
Oil leak or compression leak?

I’d do a compression test and see what that reads, if ok then reuse the existing rings, if not consider replacing them after checking the bores/pistons/rings first before buying anything.

Test the existing springs to see how they perform, they’ll most likely be ok. One sits inside the other iirc
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Offline Bryanj

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Re: Elusive springs!
« Reply #2 on: February 01, 2024, 09:33:25 AM »
Those springs have not been available for a long time, maybe 250/360G5 or T would do if you can find those

Offline K2-K6

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Re: Elusive springs!
« Reply #3 on: February 01, 2024, 10:29:04 AM »
As noted already, if compression is in spec there'd be no reason to change rings. New rings...and you'd conventionally need to hone the bores at least to get them to run in properly.

The springs...are highly resistant to change and should be OK to keep if the length checks out in specification.  Spring steel is heated toward 1000 C then quenched to first harden it and give spring characteristic...then tempered at around 350 ish to stress relieve the grain structure and bring long lasting resilience to the component. Theres really not that much can change a well made spring when used in this situation.

Valve springs have a much harsher life and survive fine over the same period.

Offline Oddjob

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Re: Elusive springs!
« Reply #4 on: February 01, 2024, 10:38:30 AM »
Oddly I can find both springs, not exactly cheap, around £20 for both springs. Quite a few outers but only 1 inner up to now.
Kids in a the back seat cause accidents.
Accidents in the back seat cause kids.

Offline Athame57

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Re: Elusive springs!
« Reply #5 on: February 01, 2024, 10:42:10 AM »
Oddly I can find both springs, not exactly cheap, around £20 for both springs. Quite a few outers but only 1 inner up to now.
You are better on google than me then!  ;D
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Offline Laverda Dave

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Re: Elusive springs!
« Reply #6 on: February 01, 2024, 10:45:48 AM »
If you do need new springs and are unable to find any nos you may be able to have some made. There are companies that make one-offs although likely to be on the expensive side.
Here's a typical company:
https://www.ashfield-springs.com/
1976 Honda 400/4
1977 Rickman Honda CR750
1999 Honda VFR 800FX
1955 750 Dresda Triton
1978 Moto Morini 350 Sport
1978 Honda CB400/4 'Rat' bike
1982 Laverda 120 Jota

Offline Laverda Dave

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Re: Elusive springs!
« Reply #7 on: February 01, 2024, 10:46:48 AM »
Oddly I can find both springs, not exactly cheap, around £20 for both springs. Quite a few outers but only 1 inner up to now.

Wow that was quick work Ken!
1976 Honda 400/4
1977 Rickman Honda CR750
1999 Honda VFR 800FX
1955 750 Dresda Triton
1978 Moto Morini 350 Sport
1978 Honda CB400/4 'Rat' bike
1982 Laverda 120 Jota

Offline Oddjob

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Re: Elusive springs!
« Reply #8 on: February 01, 2024, 02:26:18 PM »
Well the inner spring has been sold already. Someone must have wanted that badly.
Kids in a the back seat cause accidents.
Accidents in the back seat cause kids.

 

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