Change Gen1 Carb Diaphragms

[Johnwhatsisname]

I am busy doing a carb rebuild.
I need to replace the diaphragms and have seen several posts in this.
From the more knowledgeable contributors here, should I grind off the flange at on the slider to replace the the diaphragm or try the putty knife method?. this seems very dangerous for the new diaphragm.
Any advice or experience would be welcome

 

[one2dmax]

Putty knife method. The other breaks more then it fixes.

 

[Fire-medic]

I've done the grind, and that worked OK for the one time I needed to change some. Sean's done far more than I ever would, so I'd trust his expertise. I think with care and taking your time, you could make the other work successfully.

 

[Jack Hammer]

Putty knife.

 

[StanVM2007]

Could you guys show a photo of what you are talking about? I don't think my diaphragms would need changing from what I saw when I removed the sliders a while back to clean and squirt some Seafoam in there. Mine is 2007 and if true, they were cleaned before I bought the bike in 2016. Bike runs fine but I am thinking I should eventually give them a good overhaul, replace some (especially idle) brass for a fresh clean new life. I've seen idle jets from other bikes under a microscope. They looked fine with a naked eye, but under glass there was a lot of pitting. Changing the jets solved rough idle issues, so I practice at least always changing idle jets when digging into carbs.

 

[Fire-medic]

Rarely have I had to replace carburetor brass on any of my motorcycles. A thorough cleaning in an ultrasonic bath, and yes, I do use a bench-mount florescent illuminated magnifying glass to 'read' the brass. However, if you think it helps, and that the brass is knackered, they yes, that's a good call to do it.

 

[Johnwhatsisname]

Could you guys show a photo of what you are talking about? I don't think my diaphragms would need changing from what I saw when I removed the sliders a while back to clean and squirt some Seafoam in there. Mine is 2007 and if true, they were cleaned before I bought the bike in 2016. Bike runs fine but I am thinking I should eventually give them a good overhaul, replace some (especially idle) brass for a fresh clean new life. I've seen idle jets from other bikes under a microscope. They looked fine with a naked eye, but under glass there was a lot of pitting. Changing the jets solved rough idle issues, so I practice at least always changing idle jets when digging into carbs.

Sorry for the late reply. There are 3 methods to change the diaphragm. 1. To prise the old diaphragm off and then gently insert the new one with a "putty knife" between two very close washers. 2. Is to grind off the flange holding the washers/old diaphragm and then use a RTV sealant to replace. 3. Break apart the plunger with the same intention and result. YouTube explains well.

 

[Fire-medic]

Sorry for the late reply. There are 3 methods to change the diaphragm. 1. To prise the old diaphragm off and then gently insert the new one with a "putty knife" between two very close washers. 2. Is to grind off the flange holding the washers/old diaphragm and then use a RTV sealant to replace. 3. Break apart the plunger with the same intention and result. YouTube explains well.

I see two things I would not do, in this reply.

"grind off the flange holding the washers/old diaphragm and then use a RTV sealant to replace."

Yes, you can use a Dremel or other abrasive tool to do this. I don't recommend using a bench grinder, because if the bench grinder wheel 'grabs,' and launches the slide, when it comes-down, it's likely going to shatter. They are notoriously brittle.

I admit to never having used RTV to re-attach the exposed top of slide ring with RTV, I have used epoxy, namely, everybody's favorite, JB Weld. In my experience, it holds well, it doesn't separate over time, and as in the original method of holding the diaphragm, it's a rigid method of attachment once it cures.

"Break apart the plunger with the same intention and result." No do not do this! The slide will break! As mentioned above, they are notoriously brittle.

That leaves the putty knife method, as a way to accomplish the swap-out, without trauma to the carburetor slide.

Of course, everyone gets to choose their own methods of attachment. I am offering advice based upon personal experience, and I know other members have had success with what was mentioned. If you choose to try what I've suggested, I expect you will have less of a chance of having to replace an expensive part.

Diaphragm Assy

1FK-14940-09-00

Retail Price: $201.99

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https://www.ronayers.com/oemparts/a/yam/50045c0ef8700209bc7942f3/carburetor

 

[dannymax]

There is no 'one method fits all' for diaphragm replacement. How to approach it depends on the slides you are working on.

 

[StanVM2007]

Rarely have I had to replace carburetor brass on any of my motorcycles. A thorough cleaning in an ultrasonic bath, and yes, I do use a bench-mount florescent illuminated magnifying glass to 'read' the brass. However, if you think it helps, and that the brass is knackered, they yes, that's a good call to do it.

I am surprised by that. I took up this practice based on others, and mine, experience dealing with old bikes, often sitting neglected for not just years but decades. With fuel left in the carbs most of the time, amazing things happen inside the carbs when left like that. Plus of course, when running, the particles which get through the filter (yes) combined with the velocity and atomization with vacuum, can have quite an impact in a bad way over time.

Another scenario is getting used carbs. People stick all sorts of stuff in the jets to clean them. Wires, welding tips cleaning tools etc. They push and pull them, wiggle, often leaving all sorts of scratches and even disfigurations to the fragile profiles. All that will affect the dynamic profiles, quality of atomization.

Of course, I agree with that it's not necessary to always change the idle jets (for example). It is just what I do receiving used carbs for personal use, or for rebuilding and resale. If I was cleaning my own carbs regularly, I wouldn't be changing any brass every time of course. Vmaxes are a dime a dozen, and I'm no expert on Vmax things. I just thought I'd elaborate a bit on this since bikes in general were mentioned and there are many examples known to me when people who struggled with tune up, after a through carb clean up and 'looking good' jets, their problems got solved by replacing idle jets and mixture screws - with genuine brand new ones.

Below, a collage of photos of what the old brass might look on a well maintained motorcycle after being 'cleaned' (photos by Scotch), and an example of what carbs might look like after sitting with fuel in bowls (before and after - one of the non Vmax carbs I bought, new brass) .

 

[Fire-medic]

By all means, if you see worn jets, I would consider it a good thing to replace them. Yes, someone using a welder's tip cleaner on a brass jet may result in a scratched inner passage. I use a florescent round lamp and a large, wide convex circular magnifying glass inside of the lamp ring, to inspect things If I have any doubt. There is also a positionable smaller magnifier attached to swing into play should I need it. I have one of those dental visors too, and a loupe if I feel the need.

I like the grunge-look of those carburetors. I'd like a vapor blaster to do castings and pieces, they come-out with such a good appearance. Usually an ultrasonic cleaner does things good enough for my needs. I've used a soda blaster too. It won't remove metal, and it really scours things clean.

Gold Wing carbs, from the license plate 35 years of idleness. Or, not being able to idle!

 

[Johnwhatsisname]

So having rebuilt the carbs the bike is terrible. I can get it to idle and sync the carbs.
However, when I blip the throttle during the sync process it just dies. When I try to Rev it, it dies. So not rideable.
This is what I have done:
The bike was running but not very well I thought so decided to redo the carbs
I purchased a carb kit on eBay which has everything except PAJ 2 and 2.
I decided to go with the grinding method to remove the slider diaphragms . I was very careful and I think it all went well. I used JB Weld to replace the new diaphragm and washers. I couldn’t find the right tool to try the “putty knife” method.
I am happy to take the carbs off again but would like a goal.

Any assistance or advance would be greatly appreciated

 

[Johnwhatsisname]

An update on this...
Having removed and stripped down the carbs again. I found the problem!
I couldn't believe it. The hole for fuel to supply the needle jet in the new ones had been drilled 180 deg wrong. See pic. So no change of any fuel getting in the motor above idle.
I put back the old ones and all working well. The "carb kit" was not OEM but the gaskets and O rings seem ok.

On the issue of the diaphragms I can totally see why this needs to be a mechanical joint and accept that the putty knife method is best. Having said that, I didn't do this as I mentioned in a previous post. Maybe I'm just not dexterous enough but still can't see how to do that without damaging the diaphragm.
The RTV is a waste of time, it just not strong enough. I have ordered some replacement diaphragms and sliders.
I am now experimenting on using Sikaflex or Gorilla glue. The Sikaflex is much better. Not much to loose here and the bike is working well although not sure how long this repair will last.

 

[Fire-medic]

You learned a lesson on the 'all-in-one' ebay kits.' Friends don't let friends use 'em.' You are just the latest on the forum to find out about them. Common complaints are the gaskets swell, the brass is wrong.

 

[one2dmax]

Were these by chance Keyster kits? We ran into this maybe 20 years ago.

 

[Johnwhatsisname]

No. Labworkauto.
Where can I buy a good carb kit? I’m in South Africa so getting original is difficult and v expensive. EBay works for me

 

[Fire-medic]

https://www.ebay.com/itm/2919073839...d=&campid=5338413729&toolid=10001&mpt=7158084



Jet block rubber caps Found with the search function upper right corner.