Diaphragm repair update

[clcorbin]

For those of you doing (or WILL be doing!!!) the carb diaphragm repair with the plasti-dip, you can find the 14.5 oz can (not spray can, but dipping can with 14.5 oz of material) for less than $7 at Home Depot in the paint department. That is almost 1/2 the price of Napa...

[James England]

How long does this repair last?

[motoman]

Trust me James, not long,BTDT. Inspecting some 6mo. later, found the material had come off in teeny-tiny flakes of black all over and in every orfice and crack it could find. The vacuum there will for whatever reason will have a fuel reidue present, releasing the material from the diaphrams. I had also cleaned that one diaphram with lacquer thinner prior to appication, but that stuff apparently doesn't like fuel, even in a slightly misty form. Resolved the tiny pinhole using something else. The little pinholes created are from the flexing diaphrams touching the metal sides when collapsed.

[clcorbin]

I've heard from not long to 3 years. At this point, I don't want to wait on new diaphragms coming in and I don't feel like spending $65 on a set. Hopefully, it will last a couple of years and I will replace them properly.

As for the wear pattern, I saw about 8 places around each one with high wear, as motoman says from rubbing the housing. I fixed the tiny holes that I found and reenforced each of the wear points on the backside of the diaphragm. Hopefully, it will keep me going for a bit longer!

[Schming]

If...

...one chooses to do the temporary fix, I have to ask WHY wouldn't one use a fuel and oil resistant gasket sealer ?

Also IMHO the diaphragms are a delicately designed part of the fuel delivery system and any, added, extra weight and stiffness that occurs from this type of fix will cause poorer performance and make tuning difficult.

Has anyone used this vendor...

http://jbmindustries.com/Yamaha650.html

and if so, how are they ?

[crazy steve]

...Has anyone used this vendor...

http://jbmindustries.com/Yamaha650.html

and if so, how are they ?

Yep....http://www.xs11.com/forum/showthread...171#post332171

[Schming]

Thanxs Steve, Good info.

[James England]

Trust me James, not long,BTDT. Inspecting some 6mo. later, found the material had come off in teeny-tiny flakes of black all over and in every orfice and crack it could find. The vacuum there will for whatever reason will have a fuel reidue present, releasing the material from the diaphrams. I had also cleaned that one diaphram with lacquer thinner prior to appication, but that stuff apparently doesn't like fuel, even in a slightly misty form. Resolved the tiny pinhole using something else. The little pinholes created are from the flexing diaphrams touching the metal sides when collapsed.

I thought not. I've never been an advocate of 'temporary' fixes on machines that travel at 100mph+. Especially given the time/effort required to remove the carbs etc.....

The idea of bits flaking off inside the carbs, right above the component which makes the bike go fast, or stay going fast, doesn't appeal to me. The slides are a tight fit and it would take a bit flake of rubbery stuff to make one stick.

Diaphragms have a hard life..... constantly up and down, in contact with air/fuel etc.... they are too important IMO for a bodge-type repair. Lack of money is often quoted as a reason for bodge jobs and I don't personally accept the logic of it. To reiterate... these old bikes are fast and not so easy to stop as modern ones. A sticking throttle slide could be deadly and I wouldn't want to risk spending the rest of my life in a wheelchair in order to save about $60.

[TomB]

. these old bikes are fast and not so easy to stop as modern ones. A sticking throttle slide could be deadly and I wouldn't want to risk spending the rest of my life in a wheelchair in order to save about $60.

Wouldn't you just shut the throttle to slow down? so the BUTTERFLY would shut the fuel/air flow

I've repaired my diaphragms, I didn't class it as a temporary repair, and is still sound after ten years, I think Schming has the answer

I have to ask WHY wouldn't one use a fuel and oil resistant gasket sealer ?

Carbs being out of sync coz of the extra weight? good point, I sync'd mine after the repair and they were a tiny bit out, hardly noticable, probably that far out anyway.

If you are really worried about the bits of rubber from the repair getting between the slide and carb body, you should stop riding altogether coz where dya think the original bits of rubber that come off the diaphragm go

[clcorbin]

A sticking throttle slide could be deadly and I wouldn't want to risk spending the rest of my life in a wheelchair in order to save about $60.

Ok. I have to call BS on this one. The slide controls the rate of OPENING of the throttle but has NOTHING to do with the rate of closure. The only thing a stuck slide will do is either cause a lose of performance (closed) or a cylinder to not transition cleanly when/if you wack the throttle open.

[clcorbin]

Also IMHO the diaphragms are a delicately designed part of the fuel delivery system and any, added, extra weight and stiffness that occurs from this type of fix will cause poorer performance and make tuning difficult.

Extra weight? Have you weighed the slide assembly? The TINY bit of extra weight caused by the sealing pin holes in the diaphragm is absolutely trivial. You are talking about less than 1/100 of a percent of the total weight! (estimate based on what the rubber weights, it's volume and the total weight of the slide assembly).

Extra stiffness falls in the exact same category. When I repaired mine, I dabbed the material on both sides of each pin hole and worn spots to reinforce them. That diaphragm has over 3 square inches of area in total. At 2 inches of vacuum (this is venturi vacuum, not manifold vacuum), you would have around 6 pounds of force operating against the diaphragm. That tiny bit of extra stiffness in the diaphragm will make no difference in the operation of the slide. None.

I guess these concerns would be valid if you where to try and build up the whole diaphragm to a 1/4" thickness or some equally crazy. But they simply don't matter when the diaphragm is simply repaired.

[DGXSER]

All I can say is that I have one carb body where the PO had used JB weld to fix a hole where the body stick out in the are the slide diaphram sits in, and did a crappy job at best. So the JB weld rubbed on the diaphram and cause a hole. I put RTV on both sides smeared it good and smooth and even. Have not pulled the carbs off yet, no need to. 4k miles and counting on the repair.

[motoman]

The idea of bits flaking off inside the carbs, right above the component which makes the bike go fast, or stay going fast, doesn't appeal to me. The slides are a tight fit and it would take a bit flake of rubbery stuff to make one stick.

Don't see that being an issue James, as that area is seperate from the slides themselves and there movement. When 3Phase was here visiting a couple summers ago, we pulled the caps off and removed the slides to just double check any possible issues and that's when we saw the mess. The only thing I could see possible would be some of those flakes could possibly restrict a vacuum port, but that hadn't happened in this case. Since just one diaphram was affected with a tiny pinhole, Just out of curiosity I got out the automotive paint store expensive two-part plastic bumper repair stuff. It's like an all in one two piece syringe that uses an attachable gun assembly and works like a caulk gun and tube, rachet style, but a bit more sophisticated(and pricey). The mixing chamber tips are a one-time use as the product sets up in less than a minute when mixed together in the application tips and forced out the end. Wasted one of the tips for just a drop out the end, but since I knew it was impervious to fuels, body work sandable and apintable, so it was worth a try at that point. That's been two years now, and recently just pulled that one outer slide off with carbs on the bike and that drop is still there like it was when applied. With the air box off and dropped down out of way of intake, and seeing how those slides dance a bit from the intake pulses, I'm amazed they're as durable as they are. I'm sure they don't dance like that with the airbox on, as it is by design able to smooth out those intake pulses, something individual pods cannot do BTW.

[James England]

Ok. I have to call BS on this one. The slide controls the rate of OPENING of the throttle but has NOTHING to do with the rate of closure.

In fact the slide doesn't control anything at all; it responds to changes in partial vacuum when the butterfly valves are opened. The rate of opening of the throttle is controlled by the butterflies. I was referring to the possibility of a throttle slide sticking in the open position due to ingress of bits of RTV or whatever it was that flaked off the diaphragm mentioned.

[James England]

Trust me James, not long,BTDT. Inspecting some 6mo. later, found the material had come off in teeny-tiny flakes of black all over and in every orfice and crack it could find. The vacuum there will for whatever reason will have a fuel reidue present, releasing the material from the diaphrams.

I think there is possibily a difference in philosophies regarding maintenance/repair of these bikes. Mucking about slopping goop of one sort or another on a carb diaphragm isn't what I would call a repair, for the very reasons you mention above. At best, it's experimental. OK, it may even be good for a few thousand miles but, when I do a 2-3,000 mile European tour, the last thing I want at the back of my mind is whether any 'repairs' I've done are up to the mark. So, for me, if I have a problem with any component, I want a proper repair, not a bodge (however good). A breakdown in Poland due to a 'repair' that saved me a measly few dollars is not something I want. I need to feel that the bike is reliable and trustworthy.... you don't get that with makeshift repairs. Having said that, they are no doubt up to relatively low mileage, local riding, where there's a support structure if you break down...