Splitting the Carb Rack

Long time no post, but I'm looking to jump back into my XJ750 Maxim project to get her running again. I rebuilt the carbs a few years back, and had her running, but neglected to run any manner of fuel stabilizer through the bike, or draining the float bowls, before walking away for a couple years. Long story aside, I now need to rebuild my carbs again.

I'm well familiar to RickCoMatic's guide on doing so, and followed it with success in the past, though this time around, I'm considering splitting up the rack for better cleaning (and to fit into the carb dip bucket and ultrasonic cleaner). I understand that splitting the carbs will require that they be properly aligned at re-assembly (I am up to the task), and that I will likely need to replace the o-rings in the fuel rail.

How difficult is it to remove and replace the o-rings. Where can I get them (Len Chacal?)? Any really good reasons to not do this or cautionary notes? My ear and eyes are open.

 

The o-rings in the fuel rail are not the only things to worry about if you plan to "dip" the carbs.

Yes, Len has the parts (the correct ones, no less) and replacing the fuel pipe o-rings is easy.

What's NOT SO easy is replacing the throttle shaft seals. Replacing them requires removing the butterflies and removing the throttle shafts; not something you want to do unless actually necessary. Meanwhile, they're trapped in the carb bodies, and if you "dip" them you can wreck otherwise perfectly good throttle shaft seals.

My point being, unless you're replacing throttle shaft seals, or NEED to replace fuel pipe o-rings, there's no good justification for splitting the rack.

 

Thanks fitz. Good advise there. When I cleaned the carbs last time around, I *did* dip them. No issues were apparent, and I do not want to invite any going forward. I *do* have an ultrasonic cleaner now, where as I did not before. Not sure if the whole rack will fit (it's the 2.5 liter model from Harbor Freight, anyone know if it will fit), but does anyone have any suggestions for the type of solution to use? I've read about "simple green" concoctions and the like, but want to see what's been tried, what's worked, and what has not.... perhaps I should start a new thread....

 

I used 50/50 Pinesol and hot water to clean my carbs last summer, I left all the rubbers on it (i.e. fuel line o rings, shaft seals, etc, even the diaphragm on top of the main needle. I only left them in long enough to use a soft brush to brush off all the crud (it has been sitting for several years and had lots of crud. I soaked all the different pieces I took off for a few hours, but only had the rack in long enough to get it clean and then dipped it in water and dried it off.

It worked beautiful for me, can't promise that it won't affect other people's carbs differently.

BTC

 

You missed my point.

Anytime you submerge a "whole" carb, you take a chance of trapping your solvent of choice IN the throttle shaft seals. Depending on what that solvent is, it may or may not cause immediate issues, or issues further along. Just because you seemingly "got away with it" last time, I'd not tempt fate a second time.

 

the fact that youve already dipped them once, depending on what you used, your throttle shaft seals might have deteriorated a bit. i made the mistake of throwing the float needle seats in some carb cleaner and those o-rings swelled up after a bit.


As for dipping the carbs, i hear boiling them in lemon or lime juice will clean EVERYTHING off, a very slow boil just to be safe. no need to brush anything off, they come out shiny everywhere. You can get a decent amount of it for cheap from a dollar store.

once again though, you'd probably want to completely dissassemble them. even the throttle shafts.

 

Yeah.... Last time I went through this, I did get the bike running again, but had a hard time synching the carbs before the project got back-burnered. Everytime I got close to sync, the RPMS would shoot up through the roof.

At this stage, and after digging through forum posts, I've decided that I'm going to split the rack after all, replacing the fuel rail o-rings, and the throttle shaft seals. I'll make sure that it's done right this time, and hopefully the last time.

I have a PM into chacal for parts and tools. I'm jittering with anticipation.

 

I used the same ultrasonic cleaner but split the rack so I could get one carb in at a time. It worked pretty well that way and you don't have to use harsh chemicals. I replaced the shaft seals while I had them apart - what better time?

 

Sounds like throttle shaft seals. Not completely blown, just weak.
They'll hold at idle, but when you increase the vacuum they start pulling air in. Once i got my carbs cleaned and took it out for a ride it did the same thing. It would idle fine but if I pulled the clutch after moving the idle would stay where it was at when I had it in gear, almost thought the clutch was sticking. Ide have to pull the clutch at the last second before it died to get it to idle low.

 

Tore down and cleaned the carbs last night. Glad I did. As expected, my throttle shaft seals were trashed. I didn't recognize the first one, and thought it was grime. Also, letting the bike sit for a few years with out fuel stabilizer did a number in the float bowls and on the jets. Lesson learned (the hard way):



That jet required a ton of time in the cleaner. The secret formula, other than persistance seems to be a 50/50 mix of isopropyl and distilled vinegar.

Here's a shot of the disassembled rack, after ultrasonic cleaning in a 2.5 liter cleaner I picked up from Harbor Freight. I was able to fit two carb bodies at a time. Each carb spent about an hour in 91% Isopropyl, and an hour in Distilled Vinegar (5% acidity). Everything came out squeaky clean. Was able to get compressed air through all jets and passages, including the little buggers in the float bowl.



For completeness, here's a shot of my organization bin. These carbs are not really as bad as they seem. I probably didn't need bins, but it never hurts to be organized.



I'll update more as the process continues.

 

The reason for the bins is that some parts (enrichment plungers, for instance) become worn in correspondence with the carb they came from. You don't want to mix up parts that are being reused; especially things like throttle shafts and butterflies. They need to go back in the same carb body from whence they came.

 

Good point Fitz. As an extra precaution, I took detailed pictures of the throttle shaft to be sure that I get it back together properly.

 

Is it me, or should those diaphragms not be laying down on their sides like that? I was brought to understand this would deform them, and that was a Bad Thing.

 

I completely rebuilt a carb rack recently, doing ALL seals. I found it quite easy to replace throttle shaft seals.....I just went slow, took lots of notes and made drawings.....and had a second complete rack right next to me to compare with at any given time. Go for it.




've never had a problem with laying the xj slides on their sides. The rubber has gone back to shape easily.

The only time I ever DID have trouble with a diaphragm was on a Honda CL360 carb that I took apart. The diaphragm absorbed moisture from the air and swelled more than half again it's size and would not even get close to fitting where it should have. Everyone including bike shops said I have to replace it. I decided it was a chance to experiment. Thought was - if it swelled with moisture, what would happen if I drove it out? Well.....I know the carb cleaner sprays dry my hands out something aweful, so I sprayed a good layer into a jar, threw the slide/diaphragm into it, covered it tight and let it sit overnight. The next day it went right into place, perfect fit.

Hope I never have to do that again............