To rebuild or not to rebuild

[VmaxHush]

Hey fellas, so ive noticed on my new to me Vmax that there was a bit of a fuel leak in the carb (not too heavy but enough to make the front two carbs wet on intake/carb joint and some of the carb body) while reading the forum it seemed checking the wet float levels would be a simple way of eliminating some leak points. So this morning i ran the bike on the centerstand and rigged up my clear line and checked each float level, i did misinterpret how to lay out the measurement marks so ignore those, ill have to redo it another day and mark them properly but the visual should give you guys a ballpark idea of how all over the place the floats were. Here are the pics:


Some of them appear to be close enough to be fine but the LH R and RH Fwd seem to be way off. The bike does run but seems to take forever to warm up and stutters when throttled until its completely warmed but i also have no reference for a "properly running" Vmax. So based on these pictures i would assume i need to remove the carbs and properly set the floats? While i'm in there should i automatically rebuild the carb or should i just spray it out and throw it back together? Thanks

 

[Radioguylogs]

It's normal that the bike would stutter if you run it with the choke off before it warms up.

Those fuel levels do look strange. Was the bike running or just static?

 

[Fire-medic]

Use this once you get them off & opened. Do you have an ultrasonic bath? If I had them off, and apart, I'd give them a trip to the ultrasonic tank.

You know NOT TO USE the all-four carbs brass in one kit from the internet, don't you? Use only OEM Yamaha or K&L (see the K&L # below). The K&L can be bought online.





https://dn790009.ca.archive.org/0/i...ice-manual/yamahavmaxvmx12-service-manual.pdf

I suggest you learn the cylinders labelling in the factory service manual. Draw the capital letter N, starting from the lower left, then the upper left, then diagonally and down to the right, then straight up to the right. That's 1-2-3-4.

The wet fuel levels you're showing are in-need of proper setting. Do the dry-set as shown above, and then synch the carbs according to the factory service manual. Even an inexpensive four-needle gauges set should get them synchronized on the money. The needles should all show the same reading to begin, before they're hooked up.

 

[Parminio]

So this morning i ran the bike on the centerstand and rigged up my clear line and checked each float level,

The problem with that is that the bike isn't level on the center stand. It's leaning forward with the back tire off the ground, so it's not really an accurate way to go about doing it. The best way to do that test is with someone sitting on it on the ground holding it level while you look at the lines.

But, and there's always a but, as Firemedic posted, the only real way to check float levels is actually pulling the cover and checking them.

A very quick thing to do before you get into all that is pull the airbox and make sure you don't have a simple fuel line leak. Get the airbox off then turn on the ignition for the fuel pump to start filling the bowls up and keep an eye out.

 

[VmaxHush]

It's normal that the bike would stutter if you run it with the choke off before it warms up.

Those fuel levels do look strange. Was the bike running or just static?

Bike was running as it didn't seem to draw any fuel out when i was cycling the key alone, in the service manual it does seem to require the bike to be "warmed up" but doesnt say running so im not sure.

Use this once you get them off & opened. Do you have an ultrasonic bath? If I had them off, and apart, I'd give them a trip to the ultrasonic tank.

You know NOT TO USE the all-four carbs brass in one kit from the internet, don't you? Use only OEM Yamaha or K&L (see the K&L # below). The K&L can be bought online.





https://dn790009.ca.archive.org/0/i...ice-manual/yamahavmaxvmx12-service-manual.pdf

I suggest you learn the cylinders labelling in the factory service manual. Draw the capital letter N, starting from the lower left, then the upper left, then diagonally and down to the right, then straight up to the right. That's 1-2-3-4.

The wet fuel levels you're showing are in-need of proper setting. Do the dry-set as shown above, and then synch the carbs according to the factory service manual. Even an inexpensive four-needle gauges set should get them synchronized on the money. The needles should all show the same reading to begin, before they're hooked up.

I bought a kit from ebay that had the K L part number in the listing name, appeared to look the same as the kit shown, when i messaged him he said it was the K&L value kit made in Taiwan? I that another way of saying cheap knockoff or should i be alright? See below

The problem with that is that the bike isn't level on the center stand. It's leaning forward with the back tire off the ground, so it's not really an accurate way to go about doing it. The best way to do that test is with someone sitting on it on the ground holding it level while you look at the lines.

But, and there's always a but, as Firemedic posted, the only real way to check float levels is actually pulling the cover and checking them.

A very quick thing to do before you get into all that is pull the airbox and make sure you don't have a simple fuel line leak. Get the airbox off then turn on the ignition for the fuel pump to start filling the bowls up and keep an eye out.

Doesn't look like a big active leak, more of a seaping and im not seeing anything wet in the airbox but heres a picture i took after i was spraying some carb cleaner in there (the residue you see felt more greasy than gassy but i suppose that could be old gas). I couldn't figure out a solid way of determining level without stripping the top end of the carbs down, i figured if they were "close" i would try a bit harder to make it level but with it being so far off i think the level of the bike was unlikely to be the issue and would require the carbs to be pulled regardless. Also in the service manual to check oil levels it says to level the bike or put it on a centerstand so i figured it couldn't be too far off

So that all said thank you guys for the quick replies, ive ordered an ultrasonic cleaner, a carb sync kit and a carb rebuild set. Looks like ill be getting friendly with this thing real soon. Any recommendations on anything i should have or do while im in there? probably going to take it apart this weekend and have it ready for when the US cleaner comes in. Actually what solution have you guys used?

 

[VmaxHush]

I just ended up messaging the seller to cancel/return the order, bought a made in japan set of 4 with the blue packages for a little more but at least ill have peace of mind that they wont fail

 

[Fire-medic]

Parminio gave you good suggestions. His idea of removing the air filter box and using the six-second fuel pump 'pumping' interval with the key being 'on' should show you if you have any issues. It might take two or three on/off cycles to pump enough volume to make any leakage evident, but with a strong light, and maybe a good flashlight to illuminate around the carbs, you should be able to find any evident leakage, or conclude there is no leakage.

About the 'value' gasket set, I'm not sure if Taiwan is the location for K&L kits now. Those look decent, I guess you can try 'em and see how they perform. The individual single carburetor K&L kits I buy have been printed 'made in Japan,' but I suppose it's possible that K&L has manufacturing in Taiwan too. Do us a favor, take pics of the package, and then compare them to yours. In particular, look at the edge of the jet block gasket of the kit you have, and then the pieces off your bike. Do they appear similar? If you've been wrenching for long-enough, you know that sometimes a gasket will swell from exposure to fuel. One of our members tried the aftermarket 4-in-1 pkg gaskets & brass set and he said that the gaskets swelled significantly, causing issues, and he had to get (I forget which) OEM or the K&L gaskets to replace the ebay crummy set.

Your new tools should allow you to get the carbs rebuilt, saving you considerable $. I believe the $ saved should pay, in one rebuild, for the carburetor tools, themselves.

A reminder, take lots of pictures to help put things back together. Especially the linkages if you separate the carburetors into four separate pieces, you want to be able to make your effort pay-off with properly-functioning carburetors. I do have a suggestion, about the fuel enrichment assembly (the fuel enrichment assembly body is no longer available from Yamaha, it's the not-numbered piece between part #'s 17 and 18, in the fiche diagram below). The starting enrichment piston needs to be worked to purge any water from the ultrasonic soak!

If you do not do this, the starting enrichment piston (called the starter set which is part #20, below) may become frozen in the bore! The stem of the brass starting enrichment piston is a slim, skinny, shank going up to the brass mushroom head (this is a one-piece, machined assembly) where the brass mushroom head sits above the forked stamped steel piece (the starter lever). The forked stamped steel piece (the starter lever) is connected to the rod which is part of the fuel enrichment actuation assembly. See #'s 58 (three pieces, called starter lever, set 2) and #60 (one piece called starter lever) in the fiche diagram (link, below). Those are the forked stamped steel pieces which grab the #20 starting enrichment piston assemblies, there are four required #20 starter enrichment piston assemblies.

Usually the number on the fiche to the right of the fiche price for that part tells you how-many of those parts you need for this page diagram. I am referring to when you use the link below to Ron Ayres Yamaha, to the page for the carburetor exploded diagram. In the example of the starting enrichment pistons, part #20, called the starter set, there is only one listed, but there are four required, one for each body. They are all the same configuration/shape. Why it only lists 'the number of parts of this type required' as only one, I don't know the answer to that. Four carburetors need four #20 starting enrichment pistons (starter set, as they're called on the fiche).





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



A reminder:
The 'starter set,' one piece for one carburetor body, four required, for four carburetor bodies. Part #20 on the fiche. Again, I call 'em the starter enrichment pistons. An example of the starter set is between the bodies, above, and below. $56 apiece, so it pays to treat them gently, and to ensure that you purge the starter enrichment casting of any water after using an ultrasonic soak to clean your carburetors. If you simply break them into pairs, leaving the potmetal starter set/starting enrichment pistons in-place instead of disassembling the carburetors into four separate bodies, you can open the starter set bodies by loosening the hex nuts and draining the piston chambers of any residual water.

If you are removing the starter set (starter enrichment piston) housing which is the not-numbered die-cast piece no-longer available from Yamaha, between #17 and #18 of the carb body, as-shown in the carburetor exploded diagram-fiche, above, in picture #1, then the carburetors need to be separated into four individual bodies so you can access the starter set die-cast housing, mounting screws. A reminder, to take lots of pictures of each carburetor body disassembly. It's handy to use a piece of paper or masking tape to label each carburetor body as you snap a picture of it. That helps you to put things back together properly.



In picture #2, above, you can see that the top carburetors have their starter set (starting enrichment pistons) removed, while the lower pair of carburetors has them still in-place on the carb bodies (detail pic, below). Here you can see the hex nut, the round brass rod going to the piston shape (not seen here) inside the starting enrichment housing screwed to the carburetor body. Directly below the hex nut shape is a rubber cap, and then the forked steel piston lifter which connects via a phillips-head set-screw to the rod which lifts both forked steel piston lifters together on each carburetor pair.

Notes on the starting enrichment pieces:

• in the picture, below, you can see the rod which passes-through the hex nut shape (plumbers would probably refer to the nut as a gland nut) to the starting enrichment piston. Looking at the picture above, you can see the starting enrichment piston is one piece and has a shape of (starting from the right) a narrow short pin, then the piston body, then a thicker round rod, which ends in a shape to accept the individual forked steel piston lifter. Separate pieces are the hex-head, threaded brass nut, the stainless steel spring below it, and the rubber cap above the hex nut.
• if you're careful, you can use a slim wrench to unscrew the hex nut, allowing all the water out, and a few spritzes of WD-40 to purge any remaining water droplets from the casting, and lubrication to permit smooth operation of the starting enrichment mechanism, once it's fully assembled, on each carburetor, and all four carburetors to the starting enrichment lever, This allows you to separate the carbs into two carburetors each, or two pairs of carburetors as seen in the picture #2, above. However, if you want to replace the gasket (part #17 in pic. #1) then you have to break the carbs apart. This is where a lot of pictures taken will allow you to reassemble the carbs properly the first time.
• Having disassembled many VMax racks of carburetors over the years, I have seen some bodges (mistakes) in the 'repairs' done to carbs, and specifically referring to the starter enrichment assembly.
• look at part #63, (the bent bar) which is no-longer available new from Yamaha. This is the malleable rod which connects the starting enrichment circuit mechanisms of the two pairs of carburetors. If you've studied the factory service manual for setting the starting enrichment circuit to properly open and close the starting enrichment system, it mentions bending this arm to make the system work for opening at the same time, both pairs of carburetors. In carburetor racks I've seen, the bent rod has been bent enough that after reassembling the cleaned carbs, the bending of that rod by a prior owner had to be undone. I suspect that sticking pistons in the starting enrichment system were causing the starting enrichment system to not work properly, and that the prior owner bent all-to-hell the rod, trying to make all four pistons operate. Cleaning, lubrication, and proper contouring of the malleable rod so that all four starting enrichment circuits operate together, fixes that problem caused by a former owner.
• I've seen similar issues with the steel forked starter levers (fiche part #'s 58 and 60) where they are bent out of proper shape by a former owner. They required a bit of time to bend them back into proper position so they worked in unison.

I hope this helps you in your repair efforts. Once you're done, maybe post some things you discovered along the way, along with pictures to add to the hive knowledge. I just watched Jason Statham in The Beekeeper and the hive possesses much unity to achieve a goal.

 

[VmaxHush]

Parminio gave you good suggestions. His idea of removing the air filter box and using the six-second fuel pump 'pumping' interval with the key being 'on' should show you if you have any issues. It might take two or three on/off cycles to pump enough volume to make any leakage evident, but with a strong light, and maybe a good flashlight to illuminate around the carbs, you should be able to find any evident leakage, or conclude there is no leakage.

About the 'value' gasket set, I'm not sure if Taiwan is the location for K&L kits now. Those look decent, I guess you can try 'em and see how they perform. The individual single carburetor K&L kits I buy have been printed 'made in Japan,' but I suppose it's possible that K&L has manufacturing in Taiwan too. Do us a favor, take pics of the package, and then compare them to yours. In particular, look at the edge of the jet block gasket of the kit you have, and then the pieces off your bike. Do they appear similar? If you've been wrenching for long-enough, you know that sometimes a gasket will swell from exposure to fuel. One of our members tried the aftermarket 4-in-1 pkg gaskets & brass set and he said that the gaskets swelled significantly, causing issues, and he had to get (I forget which) OEM or the K&L gaskets to replace the ebay crummy set.

Your new tools should allow you to get the carbs rebuilt, saving you considerable $. I believe the $ saved should pay, in one rebuild, for the carburetor tools, themselves.

A reminder, take lots of pictures to help put things back together. Especially the linkages if you separate the carburetors into four separate pieces, you want to be able to make your effort pay-off with properly-functioning carburetors. I do have a suggestion, about the fuel enrichment assembly (the fuel enrichment assembly body is no longer available from Yamaha, it's the not-numbered piece between part #'s 17 and 18, in the fiche diagram below). The starting enrichment piston needs to be worked to purge any water from the ultrasonic soak!

If you do not do this, the starting enrichment piston (called the starter set which is part #20, below) may become frozen in the bore! The stem of the brass starting enrichment piston is a slim, skinny, shank going up to the brass mushroom head (this is a one-piece, machined assembly) where the brass mushroom head sits above the forked stamped steel piece (the starter lever). The forked stamped steel piece (the starter lever) is connected to the rod which is part of the fuel enrichment actuation assembly. See #'s 58 (three pieces, called starter lever, set 2) and #60 (one piece called starter lever) in the fiche diagram (link, below). Those are the forked stamped steel pieces which grab the #20 starting enrichment piston assemblies, there are four required #20 starter enrichment piston assemblies.

Usually the number on the fiche to the right of the fiche price for that part tells you how-many of those parts you need for this page diagram. I am referring to when you use the link below to Ron Ayres Yamaha, to the page for the carburetor exploded diagram. In the example of the starting enrichment pistons, part #20, called the starter set, there is only one listed, but there are four required, one for each body. They are all the same configuration/shape. Why it only lists 'the number of parts of this type required' as only one, I don't know the answer to that. Four carburetors need four #20 starting enrichment pistons (starter set, as they're called on the fiche).


I hope this helps you in your repair efforts. Once you're done, maybe post some things you discovered along the way, along with pictures to add to the hive knowledge. I just watched Jason Statham in The Beekeeper and the hive possesses much unity to achieve a goal.

Wow I am loving the level of detail you guys are going into on this, the more the better. I did do a test similar to Parminio's suggestion by shining my light into the carb area and looking for anything actively leaking while the bike was idling and didnt see any active leaking it mostly looked like an old leak that soaked into the dirt/dust on the rubber/carb body, but the airbox was on at the time so when i do my tear-down ill try again for ***** and giggles with the airbox assembly removed and maybe i missed something.

Ill definitely be comparing the Taiwan gasket to the made in Japan gasket before returning the Taiwan one, because i'm curious myself as I also saw that K&L has manufacturing facilities in Taiwan as well and i wonder if they are able to maintain the same level of quality at the two locations, ill update my post with that for sure.

Regarding doing the carbs in pairs or individually, i watched some videos where the guy split them into 4 and it didnt seem too hard to reassemble, he basically put the brackets and linkages on loosely and then had the carbs lay flat on a piece of wood to ensure level; should i avoid this if possible or is it pretty straightforward to reassemble?

As far as the starter set goes should i avoid removing it or are you basically saying to be careful with it as its casing is irreplaceable? My plan was to take apart the different assemblies to wash them and then blow them out/lube before reassembly but if there are things that are better off untouched then i will leave them alone.

I plan on taking a ton of pictures because ive been in that situation where i wished i had taken a few extra pictures from different angles, hopefully no regrets this time. Might even set up my gopro to reference back to if i have issues, the good thing is that there is no pressure to get it running so i can really take my time and be picky.

 

[VmaxHush]

Alright so heres an update:

A few days ago I had a chance to tear down the airbox and ran the bike for a few minutes to see if there were any obvious leak points, nothing pissing out too much so my guess is its a slow leak caused by the float or a pooched o ring somewhere. I did notice someone discoloration in and around the valves (carbon buildup?) and i'm curious if its normal for these bikes or a symptom of another issue? (picture below) Anyways i then took out the carb (way easier than i expected) and prepped my bench for teardown.



Earlier today I separated the four carbs and tore apart/cleaned the first two, carbs didn't look too bad but there was some crud here and there. First float level was perfect and the second one was a little rich which explains the wet float level test i had for that carb, otherwise everything looked great. Going to leave the other two until i get parts because its looking like it will be another week or two before i see the rebuild kit and i think it will be smart to wait until i reassemble the first two that way if there's any issues ill have the second bank for reference.

Oh I did notice the oring under the brass screw plug on the float bowl cover was pretty dried up so i have those on order.

Ill update when the rebuild kit comes in

 

[VmaxHush]

Another update:

Received my rebuild kit a few days ago, couldn't wait to tear into it so i spent the last two days working on that. I've learned a few things; It isnt hard to rebuild the carburetor itself, i actually enjoyed the process overall (other than that ****ing airbox hose, i wish i had skinnier fingers for that one)

I also learned that whoever had the carb apart before me did not do a good job, there was multiple o rings jammed into the A/F mixture screw holes on one of the carbs, a stripped out float bowl cover screw on another carb and the main nozzle cap screw was loose on another, so im pretty glad i took the time to tear the carbs down. Also i found out the the fuel drain hoses on two of the carburators were 80% blocked with what looked like roofing tar which explains the wet float being so off so i went through and reamed out all of them/inspected the insides.

With that all said i got the bike running well at 1000RPM with the A/F screws out about 2 turns and the carbs synced. Also lubed the throttle cables and went through the adjustment procedure in the manual which led to wonder if ive done something incorrectly; is it normal for the throttle to have "forward/clockwise" movement from the throttle grip released position? i seem to be able to roll the throttle clockwise enough to actually reduce the idle of the bike, is that normal? The only thing im questioning is that there is a brass "weight" or stop that is set screwed to the end of the throttle cable, and it seemed to be floating between the slot at the end of the cable and the bracket that the metal cable sleeve sits in, is this brass piece supposed to be adjusted as a throttle stop?

After doing the throttle cable adjustment i noticed that my plastic blocks in the slider are not within the indicated lines (pic included) and the service manual recommends replacement, should these be replaced based on this or is that a feature .



One last question; should i bother going through the adjustment/inspection procedure for the Vboost linkage or should i only worry about that when theres an issue with it.

Also im not sure if this has been mentioned before but if anyone else has trouble getting thier fingers in the carb to fit the main nozzle through the float chamber opening, i found a piece of string ran through the piece and out the opening made it easy to guide the nozzle through (pic included)




Thanks guys.