MUST READ- Butterflyshaft seals

Our bikes are getting to the age where many of the original rubber seals are dry and in need of replacement, especially the butterflyshaft seals in the carbs. I just replaced mine and 6 of the 8 just fell right out, 1 was rock hard and stuck, and the other was crumbling.
To anybody thinking about replacing these-STOP-PUT THE SCREWDRIVER DOWN!!
I don't know about Hitachi, but on all Mikuni carbs, the screws that hold the butterfly plates in the shaft are peened over so they don't come loose. These screws are harder than the shaft and WILL destroy the threads in the shaft.
Before you can remove these screws, you must first use a Dremel with a small grinding bit and grind the end of the screw flush with the shaft. DO NOT nick the carb bore or you WILL have idle problems.Upon reassembly you must use high strength lock tite to keep the screws in place.
When you put the butterfly plates back in, shine a flashlight through the bore and move the plate around untill there are no gaps or they are even all the way around.
A note about the seals. Do not use O-rings, they won't seal right. Use the real thing, Chacal has them and if for some strange reason he doesn't they can be had at motorcyclecarbs . com.
Sorry for the long post, but I don't want to see someone inadvertently destroy an unobtanium part trying to make their bike run better.
Thanks,James 8)

 

James is absolutely right, everyone please take note. I usually have a couple hundred of the seals in stock, so supplying them is not a problem.

Regarding the throttle shaft screws, yes, they are a BEAST to remove, more so on the Mikuni carbs than the Hitachis (in fact, just about EVERYTHING is more of a beast on the Mikuni's than the Hitachis!). I would also suggest that you make SURE you use a proper sized screwdriver when removing the screws, and the "proper" screwdriver is a JIS type screwdriver (Japanese Industrial Standards), which are different than the "rest-of-the-world" phillips-drive screwdrivers----which is probably what everyone has in their tool boxes.

I sell a complete set or individual JIS screwdrivers, as well as replacement butterfly shaft screws, as you will most probably ruin them during removal....whether you grind that peened area off or not (which is a pretty good idea, BTW). Also, on the Mikuni's especially, I notice that the upper and lower rack screws are loctited in place, and a pair of vise grips is normally needed to remove them. Again, I offer a full variety of stock and aftermarket screws for those, also.

http://www.xjbikes.com/Forums/viewtopic/t=2584.html

and then go to page 13..........

 

Not the case with Hitachi, it seems. The screws came right out on mine. Chacal was right in that the right size screwdriver is needed; I happened to have a flat blade that fit perfectly.

 

The Mikuni's use a JIS screw that looks like a phillips but is not. A no 2 phillips is just a hair loose and will damage the head if the screw is as tight as should be.
I found out the hard way that the screws are peened when I removed the first one. It was coming out stiff and I thought-locktight ?-, but when I saw the chewed threads on the shaft, I thought OH S!!!. You have to look closely, but the ends are peened enough to damage the shaft.
When I reassembled I used locktight on all but the damaged one. That screw barely snugged up so I used high strength sleeve retainer on that one. The next person that needs to remove that screw will need to drill it out because with the sleeve retainer it WILL NOT turn.
Anyways, after working on Holley double pumpers and Rochester quadra jets for years I'm impressed with how simple these carbs are and how smooth and well they work.
James

 

I just went through this process on my XJ1100 that I've resurrected after a 10 year sleep and OMG what a difference! Definitely work the $40.00 for the seals and screws I got from chacal! HUGE difference in starting and idel.

 

I was really not excited after reading this thread. However, I decided to dive in and it turned out to be not as big a pain or as risky as I expected.

One thing that made it a bit easier was a little wedge that I made out of a cross section of dowel. I whittled it to get it to fit, then tapered it some on the end that slides into the throat. It held the butterfly open flat so that I could concentrate on filing.

The file I used cost about five and a half bucks at the hardware store and is made for sharpening the teeth on a chain saw. It's very small and flat and worked well. In case it might be helpful to anyone else, I've attached a picture of the carb clamped in the old Workmate bench with the wedge visible and my file next to it.

 

Thanks guys.
I'll file it for later.
What a great site! can't imagine how I would do this
stuff without you and all the others that post.

 

baytonemus GOOD POINT. I prefer that method as well, it's just TOO easy to slip with a Dremel and wreck a carb body.

What did you clean the carbs with? Looks very nice...

 

Bayt, I think that is a points file. It is definitely NOT a chainsaw sharpening file. They are always round not flat.

Good technique!

Loren

 

I called around and asked a couple friends if they had a Dremel, but nobody did. Then I priced them out and was surprised at how expensive the cheapest ones are. It's not as though it wouldn't be nice to have one, but I've got lots of other things to spend my money on at the moment. This method is definitely safer but much slower.

As for the cleaning, I just used spray carb cleaner and a toothbrush. I did spend some time on it, though. I do worry a little that the plastic of the toothbrush may be breaking down and leaving some residue, but I can see no evidence of that. Used a very small screwdriver to carefully remove the bits of old gasket.

 

I don't own a chainsaw so you're probably right. There was a picture of the file being used on one on the pkg so that's what I was basing my statement on. Whatever it's made for it shouldn't be tough to find and it's cheap!

 

-Re: a Dremel: Be careful. They sell "vendorized" models, the ones you get at Lowes or Home Depot are different than their "mainstream" models, and often a lot more expensive. I went on their website, figured out which one I needed, and shopped online. Paid about half of what I'd been seeing them for elsewhere. A very worthwhile investment for this stuff; quite useful for brake caliper and petcock rebuilding, as well as polishing the edges of the wheel spokes.

-I use a dull chisel-blade Xacto knife as a precision mini gasket scraper.

-I feel bad for the people who manufacture those files-- it IS a "points file" but what has points anymore? Not even lawn mowers; talk about grasping at marketing straws...

-If your carb bodies look THAT good just using spray carb cleaner and a toothbrush, you are indeed fortunate. Quite often they are seriously discolored and stained, as well as pitted from corrosion and hard to get that clean. They look as though they had been soda-blasted.

-I'm impressed by your progress, you seem to be taking your time and being almost anally thorough. That is the ONLY way to succeed at this, a lesson oft hard-learned (or never learned) by some of our compatriots. Good on ya, mate!

 

Thanks for that, bigFitz. It's a quality my wife just loves! (Or maybe not so much...)

 

Seriously, it's worth it. Check my gallery. The white bike is my commuter; 120 miles every time I ride to work and back. NO ISSUES. (An occasional rude surprise, but that's to be expected.)

YOU are in charge of your process, the bike isn't. And that's what counts.

 

Beautiful! I can tell you're fussy (meant as a compliment) and your bike shows it.

 

Bayt, I think that is a points file. It is definitely NOT a chainsaw sharpening file. They are always round not flat.

Good technique!

Loren

 

thankfully i've found this help but as my other forum i recently created "enough rubber?" asks... what were you able to do with the threaded portion of the screw still stuck in the throttle shafts? just curious how the job was finished baytonemus since I'm gonna have to do the same thing on just 2 out of the 8

 

Look for a set of jewlers files sets come in different shapes round flat oval triangle just about any shape you can think of. Picture of a set
http://bit.ly/gXEx0I

 

That file is a chainsaw file, not for filing the teeth but for filing the rakers between the teeth. They are available at any chain saw shop. Hope this helps, Jack

 

Hey guys, must one take out the butterfly at all when rebuilding the carbs?
Seems to be that it could be that the benifit is weight over by the difficulty and risk.

This is what my rack looks like at the moment.



I have given the screws a nudge and can see that these would be a mongrel to get out.
I got some burn marks on the cylinder and the butterflys also have some soot on them.

Me thinks it would be easier to release the spring loading on the butterflies and then work on them and the bore without removing them.
Has anyone tried this or is it just a given that they are removed during a rebuild?

I just had a thought!
Will it become necessary to loosen the screws in order to realign the butterflies after lightly sanding the bores to get the soot off?
If not then that could constitute another reason to avoid removing the butterflies.

Any comments?
Am I missing something?

A