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Hi all,

I'm just refreshing a few parts on the twin HS2 SU's on our '65 Cooper and recently ordered a couple of new 'blue' carb dashpot springs to replace the ones in there which seemed to be a much heavier poundage (possibly red?). In the past I've always found the lighter blue springs to be perfect for the particular set-up I like on a 998. Now, my conundrum is the springs I've received are of completely different lengths, by about an inch, I've spoken to the supplier (Burlen) about this and they said it shouldn't be a problem as long as there are the same number of turns, which having now counted them discovered that again they are different.

I'm reticent to use these unequal length springs as in my mind they may cause an imbalance in performance between the two carbs, what are folks thoughts on this? Am I being too fussy / going into realms?

Cheers, Ed.

I would say you have got 2 different springs if they have not got the same number of coils.

My guess is it wont make a massive difference - but question is how would you know either way?

Which one is right ? maybe both are wrong ?...not really looking good for Burlen

Presumably they have a spec or a drawing some where for the springs, otherwise how do they buy and inspect them when they arrive ?

Could try asking them for a spec , not sure how else you decide ?

If Burlen said that they should be the same number of turns and they aren’t, speak to them again.

You can check the spring "weight" using some scales and a rod. Compress them to the same length (using the rod down the middle to measure them) and check the weight against each other and to the nominated figures from SU. If they are the same at the nominated length then they should be ok

https://sucarb.co.uk/piston-springs.html

Thanks for all the replies folks, really very much appreciated!

I've been back in touch with Burlen following the responses and they've agree for me to return them and are going to make sure they send out a matched pair this time.

I know it's minor details, but I like these things to be right.

As a reference (and maybe I was just lucky), the 2 blue springs which I bought from Burlen last December matched perfectly, with both having 24 coils, 6" free length and 2.5oz load @ 2.625".

Timmy is dead right - again. What counts is the load required to compress the spring over a certain distance. You can easily invent a small gadget to test this in your kitchen - while wife is out of course - using accurate kitchen scales!

For two different unmarked or unknown springs, same loading over the same compressed distance = perfection! I use an old machined down suction chamber of a known weight. The long and short is that I can easily match up the springs and pair them with Timmy's chart