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RSRBOB, Technician
Category: Motorcycle
Satisfied Customers: 1078
Experience:  Former Factory Service Rep, Dlr Line Tech, Service Manager, General Manager, Store Owner
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2 problems, 95 Vmax 25K miles ori owner. Cobra pipes. Adj.

Customer Question

2 problems, 95 Vmax 25K miles ori owner. Cobra pipes. Adj. the needle jets slightly per HoleShot Inc. , Bike ran great ! (1.) The bike has some history of suddenly running on less than all 4 cylinders. Sometimes I'd head home but by the time I got there it was OK again. Sometimes just letting it sit for awhile corrected it or draining the carb bowls might help. Once it got real bad and I let a Dealer clean the carbs, (all that did was cause a flat spot on roll on acceleration). But Bike ran OK for 5 years with problem happening maybe once a summer but would clear up "until" this past summer. Could NOT get the Right rear cyl to run right After a great ride and a stop for lunch. Changed plug wires/plugs. No luck. (2.) Now I tried to spray in starter fluid and then plug R/R carb while reving the motor (to suck out any grit) Wrong Move: Because now when I rev the motor and let go of the thottle the revs stay up ! If I force the carb linkage down the revs come back down. Thottle not stuck.
Submitted: 8 years ago.
Category: Motorcycle
Expert:  michael replied 8 years ago.

ok the revs .

diag. on carb


1. pull choke out do revs seems to lower.

2. any popback through carb during start up


diag on runability

1. when was last service mile wise

2. any changes addons ect

3 does it run better at start up or after its warmed and running down road


Customer: replied 8 years ago.
1. Choke not the cause of revs staying high. Choke is in the OFF position. Bike will start right up on 3 cyl. After my screw up the only way to force the revs down is reach down and push the linkage down. Interestingly if Bike is NOT running linkage seems fine, it snaps back immediately. Looking from the top all four butterflys snap right back to position, so the linkage itself does not seem to be binding.But ?
2. a constant, when bike is running, the R/R cyl.(pipe) has a mild popping sound at idle, if riding the bike, it pops a bit, like it is starving for fuel, But ?
1. I change the oil, but I am due for a valve adjustment per Yamaha 24,000
2. The only addon, Cobra Pipes and I do have a switch that turns on the power boost at 3,000 instead of 6,000
3. Really this problem has been a slight anoyance for several years but since I screwed up the throttle nd I can't get it to go away this time. No different if warm or cold. Thank You for your attention I'll pay someone to really clean the carbs but """the throttle has me worried about another expensive fix."""
Expert:  michael replied 8 years ago.

im trying diag with the tools we have .

computer and you ok here is what i want you to do


start bike , pull choke out , im simply checking for a intake leak by doing this we are adding more fuel. if the revs come down with choke out there are a few things we need to check. stick with me 2 things will happen if you do .

1. you will understand your bike better

2. you will prevent spending money on expensive fixes


also sparaying the fluid in did 2 things gave it more of something to burn and also with airfilter off it gave it more air hence hi rev

Customer: replied 8 years ago.
<p>I don't think you are unerstanding my explanation.</p><p> </p><p>I understand what you have suggested but this is not on point,</p><p> </p><p>Lets say the bike is at 1,000 RPM and I rev it up to 3,000 RPM and let go...</p><p>The Bike "stays" at 3,000 until I manually force the linkage down, the air/fuel mixture has nothing to do with this new issue.</p><p> </p><p>If the Bike is OFF and I turn the throttle up and let go it snaps right back the way it should. It is NOT binding in an open position. Curious. </p><p> </p><p>On this issue it was a direct result of reving the bike while cutting off the air input</p><p>(trying to suck out any grit) a tip from the dealer. Did I possibly bend something inside the carb ?</p><p> </p><p> </p><p> </p><p> </p>
Customer: replied 8 years ago.
also sparaying the fluid in did 2 things gave it more of something to burn and also with airfilter off it gave it more air hence hi rev

If you read the initial explanation of the issue this is not on point
Expert:  michael replied 8 years ago.

your right its not the point .


humor me ok. i have been riding for 22 years and wrenched on my own the entire time. also i have spent 42,000 on an education for motorcycles . humor me please. when im dealing with cv carbs i know what im doing . most of the years riding i rode most anything i could get my hands on cheap. inherited alot of problems some one else could not fix ect. there is a step by step method i have to work with carb problems that has been 100% efective . or i can throw you sugestions on whats wrong without diag. your choice.

Expert:  michael replied 8 years ago.
and yes jaming the linkage down to idle it down can bend the throttle plate
Expert:  michael replied 8 years ago.

and yes jaming the linkage down to idle it down can bend the throttle plate

carb diag 101

does bike idle .......yes but to high of an rpm
intermiten problem with #4 cylinder
possible causes- carb problem and or valve clearence
valves get tighter as you put miles on this is normally most peaple think they get looser
as they get tighter against valve train can cause them not open and close properly.

high idle is caused by to much air.
causes of to much air are sticking slide,intake leak or damage to carb.

if you ride regularly cleaning is usually not a problem its non use that an gum up a carb

couple of things you can do to rule out most anything
1. compresion check
2. leakdown test
3. carb checks and balancing

Customer: replied 8 years ago.
>>> does bike idle .......yes but to high of an rpm
This is incorrect !

it idles fine   if I rev it up it does not come back down as stated before   I do not have to jam the linkage down at all and never did.

high idle is caused by to much air

I give up..

>>> I never said the bike idles too high, I said when I rev the bike up it does not come back down unless I manually push down the linkage ( softly) then it idles back down fine "air has NOTHING to do with this"

I suggest you are a fine mechanic but you have an issue with reading the explanation and applying what you read to the problem at "make up" your own symptoms :^) and then explain that.... not addressing the customers symptoms on point. Thanks for your effort but this is getting no where, let alone a solution.
Expert:  Wayne S. replied 8 years ago.
Good day,

have you tried pulling the plug wire
off the RR cylinder to see if
the engine speed comes down as normal
on the other cylinders?
Perhaps you can isolate the problem
to that carb/cylinder.
If not, then you likely have some other
problem with plugged carb circuits, vacuum leaks or
carb syncronization.
Have you checked the rubber slide diaphragm for holes?
Some pics:
Customer: replied 8 years ago.
<p>Yes I have pulled the plug wire etc. (4 cyl. 4 carbs) I'm very sure the bad cyl is R/R as I've stated early on. Also diaphragms have been checked..they look good. </p><p>All the things you have suggested so far I've double checked, I was looking for some first hand experience of this particular malady.</p><p> </p><p>Overall, I think now I will have some one who is an expert on Vmax carbs clean them and at the same time figure out what the issue is with the linkage or what ever is causing "that" problem. No progress in solving or diagnosing the problem was made on this correspondance.</p><p> Your words indicate that</p><p> >>>> "have you tried pulling the plug wire <br />off the RR cylinder to see if <br />the engine speed comes down as normal <br />on the other cylinders"? </p><p> </p><p>that you still don't understand why the revs stay up "or" you state it incorrectly in your responce.</p><p> </p><p>If I pulled the plug wire on the R/R the engine is unaffected indicating that cyl is NOT firing correctly in some fashion. I tested the spark on that plug wire and it is fine. I feel it is straving for fuel. Early on I would think you would have established that the cyl was getting spark, instead you never really have grasped the 2 problems I said I had.</p><p>The rev problem was a result of trying to troubleshoot the R/R cyl problem. I have NOT received any expertise and fees are not justified.</p>
Expert:  michael replied 8 years ago.
yep your right. thats why i have opted out and opened up the question have a good day
Expert:  michael replied 8 years ago.

im simply going to start over with you.

you chop the throttle and it wont come down on the rpms even though the linkage works properly. you have a bank of 4 carbs and all are cv carbs. im going to be frank and want some one that has experienced this abnormality . with this particular problem . at first you were explaining 2 problems . lets deal with engine first . ok becouse if we do carbs then deal with engine it will change the settings on the carbs then we will have carb problems and your going to be upset with us. so engine first. your due for valve adjustment this needs to be done before carbs . only after the engine has had a valve adjustment can we even deal with carbs.

Customer: replied 8 years ago.
only after the engine has had a valve adjustment can we even deal with carbs.

You have no ideza if the valves need adjustment and why does the problem go away and come back go away and come back ?
Expert:  RSRBOB replied 8 years ago.
I am going to take my shot at helping you. Understand that we are trying to help, not prove you wrong or us right. My goal is to get your bike running correctly again. To do that, I need your help. Your input is a big part of it, but I also need you to do what I would do if I were there working on your bike myself. Some of it may not make sense to you as to why I would do some things, or some things may seem redundant to you. I aplogize and assure you I would not ask you to do anything I did not consider absolutely mandatory to resolve the issues your bike is having.

My first step is to make sure you have maximum slack in the throttle return cable. If the throttle return cable is too tight, it causes a bind and can produce the symptoms you are experiencing. There is no reason to adjust the return cable to minimal slack, if you ever needed to force the throttle closed, a little more slack in the cable is not going to prevent you from doing what the return cable is designed to do. Turn the adjuster all the way in and lock it down. Leave it there.

Next, I would like you to check for air leaks at the intake manifolds. A lean condition can cause a hanging idle like you are experiencing. Start the bike and let it idle (1000~1100 rpms) then, spray contact cleaner on the intake boots, one at a time. If the engine rpms change in any way, either rev up or die down, you have an air leak and need to investigate the source of that. That probably would include removing the carbs and inspecting the intake boots very closely for cracks.

My next step is to synchronize the carbs. The V Max is a little unique in that you have to sync the left side carbs to each other, then the right side carbs to each other, then sync the left side to the right side.

If we are still dealing with problems idling, my last shot for now is to remove the slides, again, and look at the holes drilled in the bottom of the slide. Compare the location of the holes in the bottom of the slide to the little locating tab on the rubber diaphragm. What you are looking for is to see if one of them, perhaps the cylinder in question, has twisted the slide in the diaphragm, causing the bypass holes to not be in the correct position.

If you have any more questions, feel free to ask.
Customer: replied 8 years ago.
I took the BIKE in to the Dealer to fix what I paid for.
I watched them start the BIKE and pull front right plug wire, bike died.
pull left front bike died.

pull eihter rear plug wire no change in idle.

They definitely said there was no doubt about it carb problem.

I am still not sure but they said spark is OK to all cylinders...

Bike ran bad cold or hot.

I paid them 998.00 to "clean the carbs" so I'm thinking they didn't notice or fix the real issue.

This problem can come and go but sometimes it never goes away thus a repair bill.
Expert:  RSRBOB replied 8 years ago.
I would tend to agree with you. That is an awful lot of money for a carb clean. Pulling plug caps can tell you which cylinders, but not that it is carbs. All it tells you is those cylinders are dead, could be from lack of fuel, lack of spark or lack of compression.
Are you trying to fix it yourself now or what? I am confused on what you want to do with your bike now, other than having running right again.
Customer: replied 8 years ago.
I agree with all that has been suggested. I guess somethings are too
complicated to diagnose unless you have hands on. So I gave up took it to a dealer paid them to FIX IT ! Picked up the BIKE rode home happy. However, The problem came back, and I've had this problem off and on for 3 years atleast once a summer this happens and sometimes it just goes away by itself, sometimes it will NOT go away and I've had the carbs cleaned by 2 different dealers over the last 3 years.

Latest issue: Bike running on only the front 2 cyclinders, smell of gas. I wish a pro would tell me what is wrong instead of guessing ( Dealer Mechanic should be able to do that after having the bike for a week) BUT
I was kind of hoping some one might say, yea I have that same problem and it turned out to be (fill in the blank) a life saver to me.

I am so frustrated $$$ and the bike still runs like crap when it decides to. Like I had this problem went home called the dealer, bitched a bit, went out and the BIKE ran fine for a week before it screwed up again. Dealer keeps saying its the carbs, but I paid them $900 to clean the carbs supposedly so what up with that ?

Looking for a miracle from Just Answer I guess.

Bike runs bad in all situations OR runs good in all situations and can be running good then bad or vice versa.
Expert:  RSRBOB replied 8 years ago.
It sounds like you are assuming there is one thing and one thing only that can cause your problem. The reality is, there is not. That is why figuring out what is wrong requires a diagnostic process.
If you do not want to do any work, just have someone tell you to throw one part at it, and it will mystically be fixed, then I can not help you. If that was indeed what you expected, then I misunderstood your intentions.
If you did actually want to work through this and diagnose as a professional technician would, then I can help you.
I would offer this to you, if it were an easy problem, one of the two dealers you had it at would have fixed. If nothing else, dealers are usually really good at fixing easy problems.
I can appreciate your frustration and certainly agree that you only want to get what you paid for at the dealer, a professional repair that resolved the issue.
If you do not want to work at it yourself, there is a second option. Take it to a dealer and have the dealer come in and assist them with the diagnosis and repair of your bike.
If you are dealing with an intermittant problem, that can make it more difficult for a dealer, but by the same token, it also rules some possibilities out, because some problems are not intermittant.
Also, if you let me know geographically where in the US you are, I might be able to help you find a really good dealer that should be able to resolve the problem for you also.
There you have it, 3 different options. None of them miracle cures, but all viable.
Let me know what you want to do.
Customer: replied 8 years ago.
Problem: 1995 Yamaha VMax can be running fine and then seems (and is) to be running on 2 or 3 cylinders. I would head home concerned. I would remove the seat and check the spark plug wire connections make sure they are tight. Sometimes I would also drain the carb float bowls. Often the Vmax started up and ran fine for days / weeks wihtout a problem. During this time I might also add some carb cleaner in the gas mix just to be sure. That didn't seem to matter one way or the other.

About 5 years ago I had a dealer clean the carbs, upon pick-up the bike did its normal bad performance, mild backfire, but then it started running better and I let it go and wanted to ride. So the bike was OK the rest of the summer.

The latest issue was, I rode about 35 miles and the bike ran great.
I stopped to have a burger and on start up I knew only 3 cylinders were up. The Right rear was backfiring a bit. So I went home and took it to my local Yamaha Dealer and said fix it PLEASE. Anything just fix it. They said $500 to boil out the carbs etc. I said fine.

I did add mounting a new tire and fixing a leaky gasket issue, but the bill was $998.00 I've only had a few days of riding the bike without the exact same issue returning.

The Service Manager said bring it in when the problem is actually occuring and we'll look in to it. I brought it in and after pulling plug wires it was determined that the rear 2 cylinders were not doing anything.
(Compression is fine, spark it fine according to the mechanics.)
But they said "there was spark" and it was carbs problem. AT THIS POINT I HAVE NO IDEA. But I getting the feeling the Dealer has his money and now does not want to deal with it. My bike has been there all week without any progress. So as you may understand I do not want to pay for ideas of what could be wrong, ( I have that already) but what is wrong. If my dealer has incompetent mechanics then I guess I'm screwed. On the other hand my Ford Lightning was droping 2 cyclinders, took it to FORD, they said I had 2 bad coils and replaced them, the truck runs great now. Wham Bam done fixed.

I guess the botXXXXX XXXXXne is that I am beginning not to trust my dealer and believe everything he is telling me about what reapirs were made for the 998.00 dollars. If the bike started running fine, (which it can do by itself) then they may have not done anything and charged me for do nothing.
Expert:  RSRBOB replied 8 years ago.
I offered you three different options.

1. Work on it yourself, which would involve doing what a professional technician would do to diagnose your bike.
2. Tell me what city in the US you are closest to and let me find a capable tech for you.
3. Take it back to the dealer and get Yamaha's national service department involved.

All viable, all capable of resolving your issue, none of which you have tried, nor have you responded. Is there a reason for that? The only reason I could imagine is you are hoping someone will come up and say Do this and that will solve it. Statistically, that isn't looking good.