carb return springs.

redfox

redfox

Hero member
Hi all,
I was wondering what is the standard installment of return springs on say an RGS or SFC1000?
I tried to look in the Laverda Service Manual and do a search on here, but didn't really find an answer.
I am looking at Stein Dinse's spring scheme, and they list 4 values for the PHF carburettors:

0,7 Kg; 1,1 Kg; 1,4 Kg and 1,77 Kg.

So, which is standard on these bikes, and is it possible to install a 1 step Down lighter spring (-set) withour risking gas slides staying open?

Kind regards,
Jacques
 
Back in the old days when we was young and stupid Duck & Goose owners complained about heavy throttles... Cutting loops outta the carb springs wasnae unusual. Plenty died but not generally from weak carb springs.
 
All right, but I'd like to keep the original springs in a box and install a slightly slopier set.
Someone who knows the value of the standard factory springs?

Kind regards,
Jacques
 
Hello,

I worked with this issue a couple of years ago:

Dell'Orto number 8550 is 0,7kg spring
Dell'Orto number 8532 is 1,1kg spring
Dell'Orto number 9389 is 1,4kg spring
Dell'Orto number 14870 is 1,77kg spring

If I remember correct the 8550's (the lightest ones) were similar to originals. You can check the dimensions from here:
https://www.dellorto.co.uk/shop/dellorto-motorcycle-carburettors-parts/carburettor-parts/phm-parts/internal-slide-spring-weak/
https://www.dellorto.co.uk/shop/dellorto-motorcycle-carburettors-parts/carburettor-parts/phm-parts/internal-slide-spring-medium/
https://www.dellorto.co.uk/shop/dellorto-motorcycle-carburettors-parts/carburettor-parts/phm-parts/9389-dellorto-internal-slide-spring-strong/

Personally I ordered new 8550 springs and cut three turns off from lower ends. Then I bended the spring ends that way it will take the load perpendicularly to the slide and the end of the wire does not hit anywhere. I have had no problems at all to return the slides.

At the moment my local distributor has spring number 9425 on their catalog as "0,51kg spring to PHF" but I do not promise that it fits and has suitable strength. This distributor is known of its unreliable information. This spring is mostly sold to PHBH carbs.
Seems to be available also in here: https://www.stein-dinse.biz/Complete-partlist/Husqvarna/Carburetor/Springs-accessory/Carb-slide-spring-PHBH-1-2-kg::3457.html
I don't know is it compressed that much more on PHBH (smaller carb) to reach this 1,2kg.
Price doesn't seem to be too high to order all three of them with 8550's just to try how it fits.
If someone tries this 9425 I'm interested to hear.

And yes, lighter springs increase the possibility not to return slides down.
 
I haven't had a close look at the work involved, but it may be possible to convert the Dellorto throttle cable crank to a two cable push pull system (or pull open - pull shut to be more precise, and make Davo happy).

That would reduce the risk of throttle hang-up with lighter springs. All the springs would need to do is assist gravity to return the slide to the bottom. They won't need to overcome the friction of cables and shaft bearings.
 
You must log in or register to reply here.
Back
Top