/5 Carb piston spring missing?

[greyhead]

greetings

I am working on a friends /5 and took the carbs apart for cleaning. I noticed there is no spring associated with the carb piston holding the needle. Checked the parts dealers and they show a spring present in the microfiche but don't show part number or price. I checked the previous posts and did find some interesting threads discussing improved response by changing to newer springs. Does /5 come with these springs normally? current symptoms are the engine bogs badly when throttle is opened but idles okay ( like the engine is getting way too much gas and spark plugs are dark). I am checking the fuel enriches ( choke) to make sure it is not stuck partly open.

thanks for feedback!

[greyhead]

Some important details I forgot to post - engine is 75/5 and carbs are CV

[Deleted User 72]

My experience has been that the 64/32/09 & 10 Bings on the /5 do not use springs over the diaphrams' pistons.

I have also been very publicly wrong here before.

[Garnet]

The springs did not come along till 76 or 77.

[SteveD]

The springs did not come along till 76 or 77.

Can they, should they be retro fitted for improved performance?

[Garnet]

Yes they can.

The springs slow the rise of the pistons and cause temporary a rise in air velosity in the venturi which in turn results in a temporary rich condition or accelerator pump affect. They where used to allow leaner mid-range settings without losing performance. In the mid 80's the springs where stiffened.

[hal]

So if I'm to retro fit springs to my /6, should i use the older or newer type?

[Duane Ausherman]

I am trying to remember just when they added the spring. It is important to tell us the carb numbers and your symptoms that you wish to correct.

[chasbmw]

My R90/6 from 75, did not have springs fitted when I got the bike, I will be fitting springs in the next couple of weeks and am fiting the later 32mm springs . I can't remember the part nos, there are on snow bums site and the springs are available in the UK from motorworks.

One of the reasons for fitting the springs is that they will help the carb piston to close properly, which should help starting.

Charles