Carb rebuild kit?

[randu]

Total noob getting back at my ‘98 “rebuild “ after taking some time off due to frustration. Finally took the carbs off. Any advice on where to buy rebuild kit(s)? Top jets and main jets clear, but o-rings kinda beat up and screwdriver slots kinda rounded so I’m assuming I should rebuild? Any good links for step by step instructions? Thank you

 

[Fire-medic]

Buy OEM brass, but I frequently use K&L gaskets & rubbers.



For parts, the local OEM dealer, or I like Ron Ayres Yamaha, and have used others.

Photo for setting floats courtesy of other members.



Where brass is hiding.



Old crusty non-functional carburetors often have stuck starting enricheners.




I often can separate the carburetors into two pairs, but sometimes to check/replace the start/enricheners you need to separate 'em into four. Take lots of pics as you do it, so you can get them back together properly. Many of us also replace the screws with allen head cap screws. Have you noticed the OEM carbs have security screws, one apiece, on the float bowls? I have a set of Harbor Freight security screw tips, but you can also use straight jaw Vise-Grips to remove them, or just use a Dremel w/a cut-off disc to slot them and then use a snug-fitting slot blade screwdriver. Beware using a hand impact tool, as you may crack the body, $$$!

 

[3-Max]

Tip for setting the float height. I cut a length of plastic rod (Q-tip / cotton-bud stem) to 28mm then taped on a tap of card to hold it with. Used that as gauge. Carbs need to resting at an angle & upside down (as seen in the pic) so that the float tab is lightly resting on the float needle. If you can just fit that in (furthest point from the pivot) without it touching or just touching the float you should be good.

I've been going through the same thing on my '98. Things were so out of whack the previous owner or builder had the settings all over the place just to get it to run. Of note the air/fuel mixture pilot screws were set wrong & the carb's were well out of synch. If you don't know the bikes history I'd check those as soon as you can after rebuild. Getting them right has made a hell of difference to how mine runs.

 

[randu]

thanks all. one other question-when i took carbs out for first time i realized the carb vents werent attached to any hoses. is that even important? not sure i even know where those hoses are even supposed to run to? does it even make a difference if theyre connected or hoses are even present?

 

[3-Max]

No 'vents' on mine. Not even the one overflow shown in the Haynes manual.
Are you talking about the drain tubes?

 

[randu]

its the curved vent in attached pic, on top of ea carb

 

[3-Max]

Yeah, my autistic brain taking 'vent' literally. These are breather tubes (I know - see 1st sentence). There should be long tubes (7mm bore) that run up the side of the airbox (2 each side) & fit on a small bracket near the air intake opening on the air box. They make refitting the airbox a tiny bit harder as they tend to get in the way/trapped but what do you expect on a Vmax.
How they are on mine. I replaced mine to make them a tad longer so refitting was easier. A 2m length was ample. I initially cut them well over length then trimmed in situ.


Screen shot showing where they run to & the bracket.


I've not personally run without them in place but I recall another thread discussing this & if they're not fitted & aren't positioned in the correct place on the air box it can/will result in the engine running poorly when on the road.

 

[randu]

thank you so much for taking the time to explain that! i knew it couldnt be right. could explain alot of the performance issues. im assuming i could find the proper tubing on amazon? thank you again

 

[Fire-medic]

The float bowl vents allow a measured amount of air to contribute to the carburetors' proper operation. The bike can run w/o them but not as-well as if the tubes are in-place.

Back when the Kawasaki ZX-11 was new to market, one of the things that helped it to operate properly was a similar design for the carburetors, at highly-illegal speeds (not a concern during track days) where the air inlets feeding the carb bellmouths got a 'ram-air' effect from the engineered air inlets, the carburetors also had equalizer tubes like those on the VMax, so the ram-air at high road speeds would have those hoses to provide the proper air pressure to the float bowls, so the ram-air system would work properly. Cheap horsepower!

Sure, you can order almost anything on Amazon, but just measuring the inner diameter and matching it to that size for vacuum tubing at your local auto parts store should work. You could also fabricate some brackets like the OEM ones which are fitted at the front of the OEM airbox. Some sheet steel, and steel tubing, soldered or brazed/welded, wouldn't take much time, or you could see if 'the Usual Suspects' parts-breakers on here have them for purchase, if yours are missing. I use brake line tubing for fabrication like that, a better alloy for soldering/brazing/welding, & thicker walls.

 

[3-Max]

@randu You're welcome. I got my tubing off fleabay, it's cheep enough. You'll need 7mm bore. I bought 2m which gave me ample for trimming. Note the tubes on the rear carbs will be slightly shorter.

 

[randu]

thanks again. its def confusing for a novice. there are no brackets on my airbox. if thats oem, why would anyone remove them? do the brackets just hold them to the side of the airbox or are they also connected to something functional to bikes performance?

 

[Fire-medic]

the brackets just hold them to the side of the airbox

Yes.

 

[3-Max]

Why remove? People do weird sh-t.
I'll try & remember to take a pic for you today if no one else beats me to it.

 

[3-Max]

Parts 44 & 45. A simple 90deg bracket with a couple of holes to push the tubes through would probably do just as good a job. Let me know if you want an actual pic.



edit: as I was working on it this pm.

 

[Semi239]

Fire-medic 3-Max and randu

I'm picking the thread back up. Im tearing into my carbs to figure out my lean pop/sneeze issue. This is great info. Hoping yall will help out with any problems I run into!

I see you prefer K+L gasket to OEM. Is it really necessary to replace those when taking the carb apart?

 

[Fire-medic]

I usually just split the carbs into two pairs and throw 'em into the ultrasonic cleaner. If you need to service the fuel enrichment piston gasket, the carburetors need to be separated into 4 units.

Buying OEM is always a good move but it can get expensive! The K&L kit I mention allows you to replace what things usually need to be replaced in the way of O-rings and gaskets. I usually don't find it necessary to replace the float needle seats, a good cleaning usually works. However, if you get 'em in a kit, you might as well replace 'em.

 

[3-Max]

My '98 has done 15K so & as far as I can tell none of the jets or other metal parts had been messed with. It had been stood / neglected several times & fuel allowed to evaporate from the float chambers leaving shellac crystals (the size of sugar grains) which were blocking jets etc. I doubt ultrasonic cleaning would have got rid of those.

I also had 2 main jet seats that had come undone & were protruding into the carb intake giving inconsistent lean mixture (sneezing) This wasn't my only problem. These have the main jet needle, on the big black plunger, running into them. If these need re-tightening then you have do so from inside the float chamber. In these pic's the brass bit should barely be visible, not like this.



I didn't do the enrichment pistons (choke) as they seemed fine so only split the 4 block into pairs. Do each carb separately strip & rebuild so you don't get parts mixed up. I took off the jet block, undid all the jets blasted everything, jets & passages, with carb cleaner. Replaced the jet block gasket, O-rings & float chamber cover gasket from cheepy fleabay kit. I kept all the metal bits, jets etc, as they looked fine (& I didn't trust the Chinese kit to be correct sizes - some clearly looked different). Failed to clean the groove for the float chamber gasket from crud well enough & these leaked. Had to re-do & also used V.thin smear of a liquid gasket (fuel compatible - name escapes me) & they're good now. Def had to replace the float chamber gaskets as 1st rebuild I'd had return the carb kit as it was rubbish & tried reassembly with the old ones still in place - they leaked.

Reset the pilot jet fuel/air mix to factory spec (someone had already been at these).

The biggest factor (after removing the shellac) was synchronizing them when back on the engine. All 4 were well out balance with lean & rich mixes going on. Getting them working together - wow, what difference.

 

[Semi239]

The K&L kit I mention allows you to replace what things usually need to be replaced in the way of O-rings and gaskets.

Fire-Medic, I went with the K+L kit as well. It seems to be very good quality. I want to pick your brain on a few things

1. When you encounter a stripped head on an A/F screw what do you do? Leave as it is? Is there a secret to getting them out?
2. On the enricher at what point show the whole thing replaced? Two of mine move freely as they should and two have some resistance. Should I just replace all 4?

3. What is this passage here? It seems to be blocked off on all of my carbs. At first, I found some gunk in their from where the bike sat, but after cleaning there appears to be more blocking the passage?

 

[dannymax]

I remove frozen/stripped mixture screws (providing there are no broken drills or ezy-outs) I'll send you a PM.