The carb diaphragms; at what point are they shot? Visible holes? "Bare" patches?

[cjard]

My FJ has a somewhat lumpy idle (though this has been caused by blocked air filter, and an air leak in the scottoiler before now) and is quite vibratey/really rattles the fairing at 3 - 4k rpm. I took a look at the diaphragms in the carbs last night and they seemed in reasonable condition but i did note that all of them had one or two marks on the underside, right on creases in the resting state of the rubber, where you could see the fabric/mesh that the rubber's doped onto.. I held them up to the light and there didnt seem to be any holes per se, but you could tell the material was thinner at that point as it was transmitting a little light.

Questions:
Should I be looking to replace them?
Is there a test that i would have been better doing?
Can they be repaired or reinforced with something when they are in this state?

Given that diaphragms seem to be about £70 each, is it possible to buy diaphragms for another bike (Suzuki GS 1200 dia's are £15 each) or actually buy a bank of carbs for some other 1200CC motorcycle (I see 4x whole carbs from 2001+ ZR1200 for less than 4x Yam diaphragms) that are in more common supply and cheap, and fit them?
Going an even more crazy step further, given that the FJR1300 is fuel injected and very similar, has anyone ever converted their FJ1200 to EFI, possibly using FJ13 kit; how hard of a conversion is it?

Thanks guys

[ribbert]

Diaphrams in most cases can be successfully repaired, however, if yours don't have holes in them just refit them. ( I have a bike with repaired diapghrams and it runs like a Swiss watch )

A 3XW with vibration problems is about 99.9999% likely to be seized front engine mounts. You will find the fix somewhere here in the Files.
This job can be difficult depending on how hard the collars are to remove but is well worth persevering. The reward will be turbine smoothness. Once the vibration is removed everything else on the bike stops rattling and buzzing.

Fuel injection conversion - forget it.  It has been tinkered with from time to time but I don't believe anyone's ever succeeded, the cost is enormous, and the problems endless.  Once the carbs are sorted they do a fine job.
Noel

[Alf]

The 3XW FJ doesn´t vibrate at all. It is fantastic in that way!. So it must be the engine front mounts... or those tiny holes in your diaphragms
Take a look to my web. You can reapir them with PlastiDip
Regards
Alf

[cjard]

the plastidip website is trying to sell me primer also 'for non porous surfaces' . did you find the primer was needed for the diaphragms? ive no   idea if the rubber classes as nonporous or not. did you use the spray or the dip can? thanks

[Alf]

I use the dip can. You don´t need the primer. And you´re only to use a tiny quantity of the Plasti-dip: with a little brush, only 1 drop in each hole or transparent point in the diaphragms

Regards

Alf

[cjard]

Thanks for the help on this one guys, after removing the collars and cleaning/regreasing them all the 4K rpm vibes have gone away

I did start out with an impromptu puller like the article suggested but after I stripped the threads on my threaded bar, i took a wr450 engine mount bolt (a long one) and ground the head conical, offered it up to the bush from the inside, put a long socket extension on to make my push rod appear at the other side of the bike and then persuaded it to come out with a heavy hammer while a helper ran a blowtorch on the bush housing.. Worked a charm and in seconds too!

[simi_ed]

If I'm reading this right, you removed stuck motor mounts from the lower bosses in the cases with a hammer & a torch?  Very brave or foolish!  Someone here BROKEN off the mounting boss, resulting in a trashed set of engine cases.  If that is indeed what you've  done, I would not ever repeat that one.

[simi_ed]

Sorry, let me try that again: Someone here has BROKEN off the mounting boss ...