Mikuni CV carb diaphragms

[koko64]

The bloody diaphragms shrinking gives me the shits.
I try a few things to get them back big enough to fit and not leak but I have had to redo them more than once when the slides stop lifting.

What are your tricks?

[MonsterMadMarty]

Don't buy parts via any Ducati parts dealers. Look up Yamaha parts then Mikuni parts from there they will be a fraction of the cost.  After all they are a Japanese built carburettor   

Or you could call your trusted parts supplier in Perth, WA..... Can't remember his name off the top of my head !

[Speeddog]

I keep them in place, captured between the carb body and cap, as much as possible.

I've tried a bit of heat and gently stretching them, but it didn't seem to help.

This stuff may help, haven't tried it:
http://www.permatex.com/products-2/product-categories/gasketing/gasket-sealants/permatex--high-tack--gasket-sealant-detail

[koko64]

Thanks fellas.

I've tried the heat and stretch method and the WD40 soaking method. I have thought about tacking the diaphragm lip in place at points around the carb top so I'll check out the Permatex range.
It's true that storing them well clamped in the carb is the best way. I swapped in a set from a closed carb and they seated immediately.
I have a set I need to rehabilitate.

[Speeddog]

Mmm, rehabilitation then.

Perhaps stretch them over a piece of tubing/can/screw-top lid/bottle and let them sit for a few days?

They may not be very cooperative about staying on, so may need some safety wire or the like to keep them in place.

[koko64]

Good idea. Maybe stretched over some tube with strong rubber bands holding them in place. Cable ties might cut in ay?

[ducpainter]

Buy new ones ya cheap SOB. 

[koko64]

make the beast with two backs that at $100 USD per diaphragm/slide unit.

[ducpainter]

make the beast with two backs that at $100 USD per diaphragm/slide unit.

Have you priced them from a Suzuki?

Over here they're less than half of that, and you don't buy the entire slide. Just the bare diaphragm.

http://www.ducatimonsterforum.org/index.php?topic=698.msg860841#msg860841

[koko64]

Just the diaphragm is good. Mind you the slides wear too, so depends what you need.. Great link.

I read that someone soaked them in WD40, but didn't work for me.

The $100 USD was from Partsnmore.com in Canada. There would have to be somewhere much cheaper in the U.S. for the whole part?

[ducpainter]

Just the diaphragm is good. Mind you the slides wear too, so depends what you need.. Great link.

I read that someone soaked them in WD40, but didn't work for me.

Most likely the slide is available separately also, and for far less then the OEM Duc combination.

Most 'rubber' parts exposed to fuel either swell, shrink, or in this case distort when removed and need to be replaced.

It almost isn't worth the time and eventual failure to keep messing with them.

[koko64]

Yeah, you get it working right, then later at an undisclosed time the slides don't rise or one doesn't move with the other. Pita for sure.

[koko64]

As the actual plastic slides wear and develop some slop, you will get uneven rising of the slides as they stick and they also start returning at an uneven rate. I wish Ducati had run simple Mikuni VM 38-40mm roundslide carbs in downdraught form with leaned off jetting. Good basic carbs and I would still run them.