2004 vmax carb problems

[redster55]

Sold bike ... had set a while...cranked and ran on choke but would not idle...did the shotgun and peashooter system and now it idles fine..but...it will not run above idle..it bogs and goes dead.. I have decided the best shot at fixing it is to pull the carbs and clean them good. My question is will gunk soak hurt the little plastic fitting the small rubber hoses from carb drain screw be hurt by cleaner .. I am afraid to try to pull them out. Any suggestions about the not wanting to run above idle is appreciated. I pulled the bowls and made sure the main was not plugged.. and the carbs were very clean in the bowl area.
Thanks for any help

 

[Fire-medic]

You're gonna have-to disassemble the carbs rack into front and rear halves, remove the jet blocks, remove the two jets in the tunnels, and the main jets, to try and get them clean. See if you can save the jet block gasket, they're now about $9 apiece, if you tear them, you'll need four new ones. Don't lose the tiny o-rings under the CV caps when you remove them and the carb diaphragms/slides. The slides shouldn't be soaked.

Be careful blowing-out the carb passages with compressed air as you could damage the diaphragms (see #12: https://www.partzilla.com/catalog/yamaha/motorcycle/2007/v-max-vmx12w1/carburetor).

I don't know what type of carb soak you're using. If the directions mention, "harmful to plastics," don't put the bodies into it (carb overflow fittings), find another carb soak not-harmful to plastics.

 

[dannymax]

Gunk may not hurt the drain elbows but will destroy the throttle shaft seals, don't soak them....it won't work anyway. Your problems are inside the jet blocks, the carbs need to be completely broken down and gone thru as there are other areas that may be affected.

We provide complete VMax carburetor services at The BRC Carb Shop. You can reach me at
[email protected]

 

[Fire-medic]

'dannymax' will clean 'em right-up for you.

 

[Edward]

You're gonna have-to [...] remove the jet blocks

I finally got my carbs running smoothly when I did this.


When you're cleaning them (and do everything Fire-Medic says here) use a single strand of COPPER wire (from a 16AWG primary wire... DON'T scratch the jets) and carb soaking solution (I use GUNK®.) Dribble the cleaner into EACH passageway of the carb and gently massage the jet with the wire until you can see it emanating from the other end of its passage.


Also, there is no substitute for careful study of the carbs and learning everything about them. It can literally take hours.


If you’re going to dissassemble these carb sets, you may need some help getting the base synchronization before you install them and synch them while running.


A throttle that bogs on opening is usually fuel starvation. Mine was bogging down off-idle then “catching up” as engine RPM increased and the engine started drawing fuel from the main circuits.


I know I don’t have to tell you that with a bike having 110 stock horsepower at the rear wheel, it’s a real thrill as you immediately have to crank down on the front brake to keep from hitting the car in front of you. It gets very tiresome in stop-and-go traffic! The surging and uneven running at about 30- 40 MPH spoils the joy of the ride.

 

[Fire-medic]

Sean Morley and dannymax are the resident carb experts, who post most-often, they are pros. I'm just documenting what's worked for me in my own maintenance.

Harbor Freight Tools has a set of very-small drill bits which I've found to be good for use in most places in the carbs. Don't forget the small brass insert on the carb jet block, on the right-hand side. Use an air nozzle to blow-out all the passages from both ends on the jet block. You can feel the discharge of air from the other end as you use a rubber tip to get a good seal to direct the air through the jet block passages. Brass jets which screw-in are removed for this of-course.

 

[Edward]

View attachment 68496 View attachment 68497 Sean Morley and dannymax are the resident carb experts, who post most-often, they are pros. I'm just documenting what's worked for me in my own maintenance.

Harbor Freight Tools has a set of very-small drill bits which I've found to be good for use in most places in the carbs. Don't forget the small brass insert on the carb jet block, on the right-hand side. Use an air nozzle to blow-out all the passages from both ends on the jet block. You can feel the discharge of air from the other end as you use a rubber tip to get a good seal to direct the air through the jet block passages. Brass jets which screw-in are removed for this of-course.

Hardened twist drills can scar brass jets, a small copper wire will not. Slow but sure. If you use great care with the twist drills or torch tip cleaning tools OK, but when the jets are dirty it's often hard to see whether you are causing damage. One small scratch can ruin a jet.

 

[Fire-medic]

Hardened twist drills can scar brass jets, a small copper wire will not. Slow but sure. If you use great care with the twist drills or torch tip cleaning tools OK, but when the jets are dirty it's often hard to see whether you are causing damage. One small scratch can ruin a jet.

Of-course you're right, but I never-use something large-enough to do that. I have an 8X loupe and when I inspect the jet afterwards, I can't see any imperfections. Boring-through the accretions with a twist drill is much-quicker than trying to use a single filament strand of a soft, floppy metal like copper.

I've also used a single steel strand from a bristle brush, chucked-into a hand twist drill, and trial-fitted beforehand in a clean jet, to ensure it fits without any interference.

 

[redster55]

Thanks for all the replies....Pulled carbs...ultrasonic cleaned..jets were perfect..diaphragms all good..I know sync is not perfect but made sure butterflies opened at exactly the same time..carbs are clean.. It still acts like it is starving for fuel..checked pump output...it seemed strong.. It ran fine a week earlier...going to replace plugs and feed fresh gas from a funnel and hose to see if that helps.
I am at my wits end....I am a retired mechanic and I can't remember one stumping me like this.. Surely someone has an answer...

 

[redster55]

Gunk may not hurt the drain elbows but will destroy the throttle shaft seals, don't soak them....it won't work anyway. Your problems are inside the jet blocks, the carbs need to be completely broken down and gone thru as there are other areas that may be affected.

We provide complete VMax carburetor services at The BRC Carb Shop. You can reach me at
[email protected]

Thanks for help...still acts like its running out of fuel..I pulled carbs, disassembled, ultrasonic cleaned including jet blocks ..then blew air through them...pulled main jet, emulsion tube, and the other little jet with the tiny hole..they were all clean and open.
one fellow posted a picture of the jet block with a small drill in the jet block next to the main jet. I did not check that one...But I blew plenty of air through it.. I must admit this thing is kicking my butt.
I cleaned carb bodies in ultrasonic cleaner with heated 50 50 mix of krud kutter....not supposed to hurt rubber or plastics. I have worked on many many carbs (60 plus years) and this is the first time I have been stumped...bench synced and planned to do running sync when finished. try new plugs and fresh gas from hose and funnel this weekend...if that does not work I am up the creek.

 

[Fire-medic]

OK, try this: Open the float bowl drain tubes one at a time, and with the key on, the float bowls should pressurize, and exit the overflow tubes, as you open the screw to empty/drain the float bowl, one at a time. Measure the output of each carb overflow tube flowing fuel, they should be roughly-equal in time, to flow a similar amount. That would at-least show you the flow is good.

Have you done a leak-down test of the cylinders? Just wondering if there's a leaking valve or valves causing some-type of compression problem.

Have you tried running the bike without the air filter? Or with the air filter in-place, but the Y being left-off?

 

[redster55]

OK, try this: Open the float bowl drain tubes one at a time, and with the key on, the float bowls should pressurize, and exit the overflow tubes, as you open the screw to empty/drain the float bowl, one at a time. Measure the output of each carb overflow tube flowing fuel, they should be roughly-equal in time, to flow a similar amount. That would at-least show you the flow is good.

Have you done a leak-down test of the cylinders? Just wondering if there's a leaking valve or valves causing some-type of compression problem.

Have you tried running the bike without the air filter? Or with the air filter in-place, but the Y being left-off?

This time I ran it with the air box off..I didn't have the manifold screws tightened either....they fit so snug i figured it would really matter for a test run. I will buckle it all down and try it again..with filter and all....going to put new plugs in and see if it helps... bike has 13,000 miles and clean as a whistle...I wouldn't be surprised if they were not the ones that came in it...

 

[redster55]

View attachment 68496 View attachment 68497 Sean Morley and dannymax are the resident carb experts, who post most-often, they are pros. I'm just documenting what's worked for me in my own maintenance.

Harbor Freight Tools has a set of very-small drill bits which I've found to be good for use in most places in the carbs. Don't forget the small brass insert on the carb jet block, on the right-hand side. Use an air nozzle to blow-out all the passages from both ends on the jet block. You can feel the discharge of air from the other end as you use a rubber tip to get a good seal to direct the air through the jet block passages. Brass jets which screw-in are removed for this of-course.

Fire medic....where you have the drill in the picture above i thought that was a brass plug....I guess I will split the carbs and check that part of the metering block...

 

[Fire-medic]

Fire medic....where you have the drill in the picture above i thought that was a brass plug....I guess I will split the carbs and check that part of the metering block...

I've had them plugged before in a tear-down.

 

[Oldawg]

Thanks for help...still acts like its running out of fuel..I pulled carbs, disassembled, ultrasonic cleaned including jet blocks ..then blew air through them...pulled main jet, emulsion tube, and the other little jet with the tiny hole..they were all clean and open.
one fellow posted a picture of the jet block with a small drill in the jet block next to the main jet. I did not check that one...But I blew plenty of air through it.. I must admit this thing is kicking my butt.
I cleaned carb bodies in ultrasonic cleaner with heated 50 50 mix of krud kutter....not supposed to hurt rubber or plastics. I have worked on many many carbs (60 plus years) and this is the first time I have been stumped...bench synced and planned to do running sync when finished. try new plugs and fresh gas from hose and funnel this weekend...if that does not work I am up the creek.

Join the club. I'm also an old mechanic that has never had so much trouble with carbs as these. I've been through them twice now and the only place it seems to run right is full throttle - forget starting and idle. The only thing I failed to do that I know of, is set the float levels, since they looked about right and the new needle valves looked like the old ones. They gotta come off one more time and if I don't get better results it's hammer time!

 

[sdt354]

Join the club. I'm also an old mechanic that has never had so much trouble with carbs as these. I've been through them twice now and the only place it seems to run right is full throttle - forget starting and idle. The only thing I failed to do that I know of, is set the float levels, since they looked about right and the new needle valves looked like the old ones. They gotta come off one more time and if I don't get better results it's hammer time!

Float levels, sync,and vacuum leaks are everything on these carbs. Eyeball setting won't do it. What do the plugs look like? Sometimes even we old mechanics are better off boxing the carbs up and sending them to Danny.

 

[dannymax]

Float levels, sync,and vacuum leaks are everything on these carbs. Eyeball setting won't do it. What do the plugs look like? Sometimes even we old mechanics are better off boxing the carbs up and sending them to Danny.

Thanks for the mention Steve-o, I've completed over 250 sets of Vmax carb rebuilds in the last 10 years and have most of the 'secrets' figured out. Send me a message or email if you are interested in having carb work done.

Danny

 

[Edward]

Of-course you're right, but I never-use something large-enough to do that. I have an 8X loupe and when I inspect the jet afterwards, I can't see any imperfections. Boring-through the accretions with a twist drill is much-quicker than trying to use a single filament strand of a soft, floppy metal like copper.

I've also used a single steel strand from a bristle brush, chucked-into a hand twist drill, and trial-fitted beforehand in a clean jet, to ensure it fits without any interference.

I understand and I wasn't trying to be contentious. I save that for another forum.

It's been a while since I tore mine down but it seems like I remember a jet that the single strand of AWG 16 primary BARELY fit through. It's admittedly slow but you are absolutely assured the jet (no mater how small) will not be ruined.

Gotta get in Zen mode redster55. Time is no object. Study each and every passage and drilling. Examine where the passages are; how they were drilled; how they were plugged and use X-ray vision (really) to follow every air passage and every fuel passage and every fuel/air mix passage. The first time I disassembled mine, I found a shard of metal left over from the manufacturing process that prevented seating of a jet.

Kicking your butt huh? I am trying to solve a sinking brake pedal on my 1998 BMW 528i that's doing the same to me. Arrrgh! I've replaced M/C, booster, rebuilt calipers, lubed caliper slides, had ABS/T module rebuilt, bled so many times I've lost count using DIS 5.7 BMW software to operate the module and it ... still sinks. I'm not trying to hijack your thread; just trying to let you know, I feel your pain!

Don't rely on ultrasonic cleaning. The only absolutely sure way is to use Gunk® and a wire to physically and mechanically clear the jets and passages. I'm still betting on the jet block.

 

[sdt354]

Guitar wire is rigid and works well on the.0375 jets too. Though a .040 drill bit has crossed my mind. I think it's better than turning the A/F screws out so far they loose spring tension. .040's can be bought too. Though I'm not big on overly rich off idle for my set up., and just off idle in transition to mid-range.

 

[Fire-medic]

Discussing what works for you is part of what goes-one here. I'm always quick to announce that Sean Morley and 'dannymax' are the induction experts here. I'm simply relaying to another member things I've done which have brought me success. Sometimes I forget to mention something, and someone else takes-up the slack. If anyone contributes something incorrect, someone-else quickly offers a correction.

I think Edward's advice is good, though I do rely upon an ultrasonic cleaner where he doesn't favor the use of one. I have a dip bucket that's probably older than many members on-here. I use it with a 5 gallon bucket, when I use it. However, my friend at his shop allows me the use of his ultrasonic cleaner, and I do like the job it does.

It's like a visit to the dentist. First, open wide! That's disassembly.

Second, an inspection as things come-apart, to see if you find any obvious defects: torn gaskets, loose jets, missing parts (from having purchased used carb racks, it happens) bent or misaligned parts; torn/punctured diaphragms, missing O-rings (the small ones under the CV caps, above the air bleed screw); whatever.

Third, a good soak, of your choice, Gunk, Simple Green, vinegar, catsup, or an ultrasonic bath.

Fourth, rinse everything well. Inspect after rinsing.

Fifth, drying and inspecting. I like a rubber-tipped air hose blow-gun, be careful around the CV diaphragms and the small diaphragms on the carb sides.

Sixth, scraping of any residual gasket material, deposits, or anything you know needs to not be there.

Seventh, I use new needle valves.

Eighth, "reassembly is the reverse of disassembly." How-many times have you read that in a shop manual? New gaskets or O-rings where needed. I use WD-40 to make things that should slide, do-so.

Ninth, see that the linkages operate properly, no binding, no excessive friction. Lightly-seat air bleed screws below the CV caps, 2-1/2 turns out as a starting point. Attach the carb cables, ensure they work smoothly.

Tenth, lightly-lube the rubber gaskets to the VBoost manifold, ensure the carbs are fully-seated. Snug-down the boots. You should be able to get the engine started at this point. I would probably attach the airbox first, and snug-down the top of carb bellmouths to the airbox. Ensure the air filter is clean. Now, how-does the bike start and run? Balance the carbs, which should take not-much time.