Small Vacuum Diaphram?

[redbug2]

Hello,

I've been thinking about the small external vacuum diapham? that I had to remove when I was removing the mouse nest from my carburetor. The diapharm unit was external to the carb and attached to it by a small vacuum line. What was it, what does it do, and where can I get a replacement?

Thanks,

redbug2

[steve w]

hi the diaphram is to open the secondary throttle valve.rotary recycle should have one.

[redbug2]

OK, I found it in the parts PDF. Its on page 33, Ref. No 1, Part Number 33240-37030. Switch Assy, vacuum.

[pmcburney]

You can get away without using it at all if you wish.


Find yourself a small, short screw, nut and washers.

Fit the screw into the linkage just behind where the actuating arm for the secondary butterfly fits into it.

This 'locks' the secondary butterfly to open at precisely when that linkage starts to move, which is (I think) when the primary butterfly gets to about a 75% wide-open position (which is when it is free to move ordinarily with the vacuum diaphragm in place).

This may be a better arrangement as there is no lag between when the secondary is free to move and when it actually moves and its rate of movement is directly controlled by your hand (the throttle cable) rather than by a vacuum switch...

I'll take a pic of mine and post it up to better explain if you like.


Good luck
Paul McB

[pmcburney]

Here's a view down on to the primary and secondary linkages on my carb.



Where I've placed a red circle is where I've installed a small screw to lock the secondary linkage in place - it now moves as soon as the primary linkage allowed it to move originally (which is about 75% or so) and is not controlled by a vacuum switch at all anymore, only by throttle movement.

This could be a helpful mod for those with a missing or failed vacuum switch.


Cheers
Paul McB

[redbug2]

The linkage solution is interesting and may be an option.

Are we talking about the same vacuum switch? The part number 33240-37030 was up in the frame and did not seem to have any linkage connected to it. Was there an electronic switch within it? Was it just a vacuum storage unit?

[pmcburney]

It seems we're talking about different parts.

The vacuum 'switch' that resides on the carb and opens the secondary butterfly is a 13510-37011 (marked as '20') and looks like this:



This is the one I was referring to and it can be eliminated by the method described above.

The other vacuum diaphragm/switch does indeed live up on the frame and looks like this:



I'm not too sure what it does... it may be part of the secondary points arrangement - in which case it may be unnecessary depending whether or not your bike still has this feature fitted.

BTW, you can't get either of them new anymore - best chat to Jess if you want/need to replace them.


Hope this helps
Cheers
Paul McB

[redbug2]

Yes, I have communicated with Jess and they have some good used ones. I only have one set of points on my RE5 so I don't want to buy this if I don't need it... I am going to buy some other parts from them today.