Topic: CV Carbs - Diaphragm repair???

[tsflstb]

I'm still screwing around with that 550 Kawasaki I bought months ago for cheap.  I hoped it would just need a quick carb clean and adjustment.  Looks like two of the carb bodies are cracked where the tops screw down.  Probably the reason for the erratic idle and poor throttle response.  They're small cracks so it would run OK when cold.  As it warmed up, I think the aluminum carb bodies expanded and let air leak in.  I've been on those cracks with a Dremel tool and will do some JB Welding to seal them up.

One of those cracks went across the sealing surface of the upper diaphragm and wore a hole in it.  Those suckers are $107 each!  Has anybody used any product to patch a tiny hole in one of these?  They are very thin and have to move, so I probably couldn't just slather on a bunch of RTV sealant and expect it to work.

Anyway, this is my 3rd or 4th time into these carbs and I hope to make it my last.  I'm thinking I just want to get this bike running and get rid of it, so I rather not buy a new diaphragm.  If that's the only option though, I'll have to bite the bullet.

[Dragman836]

I used JB Weld on the float tower pin holders with great sucess

[Uncle Ernie]

Hard to say without seeing, but I'd rther see the cracks brazed.  Smooth out the rogh spot, of course.
Try cleaning the diaphrams very well and use a thin coating of YamaBond.

[nickjtc]

Good luck with any diaphragm repair!! Remember that they nead to be completely air tight.

Anyone got other fix-it ideas?

[CB360T]

If the tear isn't too bad, it can be repaired with Mopar GEN II Silcone Rubber Adhesive Sealant P/N 04883971. This stuff really sticks to nitrile rubber diaphragms. Buy it at a NAPA store.

[Jonesy]

Don't laugh, but I've heard you can patch them with a glue suitable for rubber and a small piece from a condom...

[tsflstb]

Thanks for the responses.  I don't have any Yamabond on hand, so I'll make a trip to the local NAPA and see if they have that Mopar stuff.

If I were really doing this right, I'd send these carb bodies off to the guy who does the laser welding on this board.  For the price I may try the old reliable JB weld first.  It doesn't have to be pretty...just needs to be air-tight.  I'll try to post some pictures to see what you all think of the cracks.

Just saw your response Jonesy...hmmm.  I'd have a hell of a time explaining that one since my vasectomy.  No honey, I need them for the motorcycle.  I do think the ribbed ones would adhere pretty well.

[nickjtc]

I do think the ribbed ones would adhere pretty well.

This could be the start of a parallel thread on how to explain condom use in a motorcycle application!

[Jay B]

I had a small tear in the diaphram of my Yamaha 4 wheeler. RTV works, but not for long. I cut a little peice from the red edge of a tire patch and used regular vulcanizing cement. It's been running that way over two years now.

[tsflstb]

Patched up the carb bodies with JB Weld and the diaphragm with that silicone adhesive from NAPA.  It will now idle nice around 1200-1500 rpm.  Problem is, when I give it any throttle, it goes to 3000 rpm and stays there.  I have to back off the idle adjuster to get it to come down.  It behaved the same before the recent patch work. 

I've checked the throttle linkage and it doesn't seem to be binding.  Throttle snaps back like it should.  Is this a vaccum issue?  I sprayed everything I could get at with WD-40 while idling and didn't detect any leaks.  Any other ideas?  My next move is to try a carb sync since it will idle steady now.

[Uncle Ernie]

I don't know what your Kwaki looks like, but I had a Beemer with an automatic advance that used weights that were thrown out by centrifugal force.  The springs ween't striong enough to pull the weights back in so the bike idled too fast when it warmed up.  In gear, f I let out the clutch a little with the brake on, that would often help pull the idle down some.  I just got used to doing that at lights and stuff. 

[tsflstb]

I've never cracked the cover to see what the ignition looks like, but it's a 1990 model.  Not sure what the status quo was back then.  I did see something in the manual about setting an "air gap" so I don't think there's anything mechanical in there.  I guess that's the trigger for another module that handles the advance?  Never thought to investigate the ignition system though.  Any other places to look?

It's a nice clean bike that was too cheap to pass up.  Right now I'm racing to get it running and sold so I can pick up a sidecar rig that's too cheap to pass up.

EDIT...synche'd the carbs and that didn't change anything.  Crap.  It either wants to idle at 3000 rpm or just sputter and die.  I managed to ride it around a little last night and it runs well once moving, but will not idle.  I'm 99.999% sure all of my slow jet/idle circuit passages are surgically clean. 

My next guess is the air adjustment screws.  I noticed there should be a couple of washers and an O-ring in there.  I've pulled out the screws, but never actually laid eyes on these O-rings.  Guess I'll go remove the carbs again.  Fifth time's the charm right?  Before I do that I will go find whomever designed the airbox on this bike and kick them square in the sack.

[tsflstb]

Well the problem is fixed...from my end at least.  I got fed up with spending so much time on a bike that I didn't plan to keep and sold it yesterday.  Heck of a nice guy was just beside himself to buy it and actually insisted on giving me MORE than my modest asking price since there was so much interest in it.  As he was loaded up and about to drive off, he told me how his autustic son was really getting into small engine repair and how he wanted to work on a motorcycle with him.  I kind of feel like an ass for taking any money from him at all now.  I really hope it's something simple to fix and they get it running without too much trouble.

Anyway, I freed up some time, money and garage space.  I think I'm going to just finish up all the stuff I wanted to do on my 400F before I get another bike.