Carb cleaning question (long)

Well, I went home this weekend to work on the bike. I'll try to post photos of it...everything looks great except the tank. Tried firing it up, rebuilt one of the carbs (my first ever!), and bled the front brake.

The engine didn't want to run on its own, but it was definitely firing when I cranked it. When I tore into the one carb, the float was stuck and the slide required prying with a wooden dowel to move it. After cleaning everything in that carb the slide moved like magic, and everything was good except the float pin. I must have bent it a bit during removal and cleaning. I didn't realize those things were so fragile! So my plan is to replace it with the shank of a #39 drill bit as it's a perfect fit. Can anyone comment on this? I am a little concerned with corrosion though, as the original seems to be stainless.

Another weird thing: I couldn't find any way of adjusting mixture on the carburetors! There is one screw next to the slide (under the diaphragm) that the Clymer manual calls out as a pilot screw. When I cracked it loose I tried running it down to seat it, but it wouldn't go further than where it started. When I took it out it looked more like a jet than a needle. My bike has Mikunis, but not the same Mikunis as on Alive's XJ900 in his how-to writeup. Can anyone comment on this?

Last question (maybe this should be a separate thread?): there is a plastic tee that conencts the fuel line to the two middle carbs. There is a crack in mine and it leaks fuel like a seive. I'd just replace it, but everything I've read/heard is that you SHOULD NOT remove carbs from the rack. I don't see any other way around this...what are the risks of taking two of the carbs off in order to replace the tee?

 

The pilot screws, or mixture screws are on the top of the carbs in front of the hats. They may be sealed underneath plugs that you need to remove to adjust them.

The plastic tee between carbs, you may be able to dab some seal-all on it and it may stop it from leaking for now. The tee has o-rings on either end that go into the carbs, those are what leaked on mine. I slobbed some gas-resistant sealer on and it stopped it from leaking, its a temporary fix.

 

I'd be worried about putting any other kind of pin in there besides stainless, as you do get moisture in your gas tank, lines and carbs. Once that thing starts rusting, you might have a bunch of problems.

And your mixture screw is on the top of the carbs, on the engine end. THey may be covered with brass plugs. To get to the pilot screws you'll have to remove these caps. Check out Rickomatic's "carb cleaning: the whole nine yards" (or something like that) in the faq section of the forums for a good way of removing those caps. It's not under the diaphram...it's on the outside of the carbs. What I think you're talking about is a jet...it should have some numbers on the top side.

I've never taken my carbs off the rack so I don't know of any particular consequences or difficulties. But I imagine if you're careful, and note how the carbs come apart, there shouldn't be any real problems. Again, I've never done this, so you should look to someone with more experience than me on these matters.

 

The float pin is stainless to the best of my knowledge. I would only use stainless. The carbon steel will rust and result in a stuck float. Best bet may be to try and straighten the pin.

You found the pilot mixture screw which is the means of adjusting the mixture at idle. {Above that it is not very ajustable except for changing the main jet/needle or shimming the jet needle.} This is what we use the colortune plug for. Your carbs are similar to Alive's 900's in that they are both Mikunis. You have the 28mm and he has the 34's I believe.

The biggest problem with pulling carbs out of the rack is getting them back in right. This is an understatement. Not only do the carbs have to be correctly placed in the rack, the other stuff that comes off in order to pull them has to be right too. This would be the butterflies, the sync springs and screws and the idle adjustment screw. The butterflies must be marked as to carb body, same side, up/down or left right. Easiest way is to draw a line with a Sharpie across the middle of the butterfly before removing them from the carbs. Then write the number corresponding to the carb body on the top or bottom of the line. This tell you which butterfly went where and the correct side to the outside and up/down.
This way when you look at the butteflies while holding the carbs you know that all numbers are up top or on bottom and in their numerical order. If one was reversed you would see the number backwards, upside down or not at all. Which would mean the marked side is turned away from you.
WHen putting the carb bodies back in the rack the throttle shaft needs to be inserted and the carbs placed on a plate of glass. This aligns them. Then turn the throttle shaft to check for binding everytime you tighten a screw. If it binds then they moved and need to be put back. The glass plate will show you which one is up and not aligned with the others.
Of course if you do this the plastic tee can be easily replaced.

 

Hey Blue,

Thanks for the tips. I appreciate the help. The tee is not something I'm looking forward to fixing. The dealer around the corner told me the Yamaha part is $31!!! Ridiculous! But yeah, I'll be very careful to check alignment when reassembling the carbs to the rack. Fortunately my dad has a surface plate, so that should be nice and flat (and stiff) for the reassembly.

-Rick

 

Honda's equivalent is twice the price, be thankful Rick.

 

Yikes! I'd heard that Honda doesn't license other companies to make replacement parts for their bikes. Seems logical that the prices would then be higher.

I may have found a replacement for the float pin: McMaster-Carr sells torch tip cleaning tools that are stainless rods in number-drill sizes! How perfect is that? They want $5 for a set that comes with the size I need. Now I just need to find a local place that sells them. I can't believe the lack of welding shops in my new 'hood!

-Rick

 

Keep looking. Injector tip cleaners are not hard to find at all. Hit FleaBay as a last resort. I've got 3 sets but be darned if I know where they all are (otherwise, I'd hook you up). Moving screws up your filing system but royaly.

 

Okay, back at the parents' house, I got to look at the carbs tonight and snap some pictures. Firstly, sunna muh bish, there IS a brass plug just like everyone said! 8O Tomorrow I'll pull that out and see if there's a pilot mixture screw underneath 8) I'll assume the brass plug everyone is talking about is right smack dab in the center of this photo:




Regarding the stainless float pin, my dad bought some .120 brass rod from the local hobby shop and turned it down to .098 on the lathe. I love having my old man retired! So I'm going to try brass for the float pin(s) (depending on how the other three float pins fare).


Finally, I don't see any reason not to separate the carbs from the rack or each other. Here are two pics I took of the linkage between the two middle carbs:





Sorry about the crappy quality, I only have my phone camera. As you can (kind of) see, there is daylight between the throttle shafts. It appears that the linkage of one carb has a tab that gets pinched between the adjustment screw and the spring of the next carb. Throttle shaft alignment doesn't appear to be critical. I will, however, align the throats on a surface plate while re-attaching them to the rack per Blue's suggestion.

Sooooo, my plan is to take two carbs off the rack (and keep them attached to one another) to get at the tee, then copy the design of the plastic tee in brass.

 

Sounds like a plan. Any chance you'll be making extras???

 

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And we can't come-up with a Float Pin Hinge Pin and a Fuel Supply T.
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Take 'em apart. No Problem. Double-stacked O-rings make it a little difficult to withdraw the barrels and T's.

When you're ready to line-it-all-up and tighten-down the fasteners that hold the bodies on the brace ... just perch-'em on the side of a short LEVEL and keep everything squared-up.

I got a Hinge Pin. I know for sure. PM Me.

I also think the Number Drill idea was a great improv fix! I think you could drive the drill into the side of a tree and not worry about it rusting for awhile.

 

Hey fellers,

I took two carbs off the rack this morning, no big deal. Just had to back out the synch screws a bit, store the springs in my handy muffin pan, and pull the carbs off. My dad made a tee out of two slugs of brass and silver soldered them together...we'll see how it goes back together!

I'll ask him if he's interested in a production run. He's got a ton of projects going at the moment so don't hold your breath. At the very least I'll post pictures.

An odd thing though...I had thought my bike was an '82, turns out '81 is on the tag on the stem. When I looked up the tee for an '82, it showed a tee with four o-rings on it. I had assumed my tee was plastic that had cracked, but it turns out it's an aluminum casting with a jacket of rubber over the whole thing! So the aluminum definitely seals, the rubber around it was just dry rotted. I'm starting to think the drip I saw was from stuck floats. At any rate, it will be replaced.

For the float pin, the brass fits well and we'll see how it holds up over time. That stainless pin was so soft I couldn't imagine the brass being much softer. On the second carb, with it off the rack I was able to use a drift and a small hammer to tap tap tap it out. Here's to hoping it fits back in!

I so far have drilled out and removed two of the pilot screw cover plugs using an ez-out extractor. That worked pretty well! Both the pilot screws came out without much hassle, even though I nicked the first one pretty good with the drill bit and the second one a tiny bit. As far as plugging them up when I'm done, I think after tuning the bike I'll spooge a little fuelproof RTV across the tops of the holes; just enough to keep crap from building up in there.

And finally, I'm about halfway through the disassembly/cleaning/reassembly process for the second carb. Sheezus, I hope this is the worst of them! The slide was the stickiest of the four, and the choke (yeah, yeah, ENRICHENING) needle was STUCK HARD in the carb body! I broke the tip off the choke needle--the part the fork lifts up on, so at that point I broke out the channel locks. After galling the crap out of the shaft, I sprayed it with Gibbs and let it sit for ten minutes. After that it came out, but not without a bit more of a fight. My plan is to clean up the shaft so as not to tear the rubber seal, put it together like that, and get it running while I wait on the part. That shaft shouldn't be too difficult to replace on the bike as long as I remove the tank.

Oh, and pulling the tee out of the carb took merely light hand pressure. Methinks those seals had shrunk; they almost FELL out. Really the hardest part of taking the carbs off the rack was unseating four galvanized screws that had been sitting in an aluminum casting for the last 25 years.

-Rick

 

Last night I got last two carbs cleaned and reassembled, then put everything back on the rack. I ended up taking all four carbs off so that I could replace the o-rings on the two fuel joints between each pair of carbs. One of them was seriously loose to start with! I think that could have been a source of trouble soon so I just replaced them.

Sooooo with everything back together, and the throttles bench-synched, I put them in the workmate, leveled them, and tried to check fuel level. One carb showed proper fuel level, but the other three leaked fuel out the throats, so I took them apart, checked that the floats actually float, and checked float height. Float height is the same on all of them. My dad suggested that the needles/seats may be damaged...I'm tempted to put them on the bike to see if it will run. GAH! So close, yet so far...

Regarding the fuel tees, my dad said he'd have to think about how to make them more quickly if he were to produce them for less than the $31 that the dealer wants. He also said that Lowe's has a lot of brass pieces for lawn sprinkler systems that may be a good starting point, removing the need to whittle so much material away and solder multiple pieces together. I'll keep on him.

Oh, and I'm still not sure my fuel tank valve is working--it seems to not always flow when in the prime position. I took it apart, looked for blockages or bad seals and didn't see anything amiss, so I'll see how it drains into a mason jar after lunch.

-Rick