Vmax running rough at steady throttle

[Max88]

Bike runs rough at steady throttle. Seems bad at any steady speed almost like it's missing or cutting out.. Just had bike at shop for this problem they dyno'd it and jetted it and did carb sync. Told me to come get it but still same issue... Any ideas?
Morleys jet kit
Kerker pipe
V boost disconnected

 

[Fire-medic]

When was the last time you changed/cleaned the air filter? Set the valves? Maybe time for a peashooter or the other procedure, the shotgun.

 

[jfeagins]

Bike runs rough at steady throttle. Seems bad at any steady speed almost like it's missing or cutting out.. Just had bike at shop for this problem they dyno'd it and jetted it and did carb sync. Told me to come get it but still same issue... Any ideas?
Morleys jet kit
Kerker pipe
V boost disconnected

My idea would be to cancel the check you wrote for that service work, or call the bank to initiate a refund somehow. Then I'd look for a different service shop. Somebody didn't do their work properly, or completely.

 

[95spfldmax]

My idea would be to cancel the check you wrote for that service work, or call the bank to initiate a refund somehow. Then I'd look for a different service shop. Somebody didn't do their work properly, or completely.

I agree............"Come pick it up" implies they did everything & all is well...........not "we did as much as we're prepared to do. Now your on your own"......bike should run perfect for the fees that these guys charge....JMHO.......

 

[Fire-medic]

Well they may have told him that they wanted to disassemble & clean the carbs and when they told him that depending on what they found when they did the disassembly, it could cost $$$$. He should have 'dannymax' go thru them for him.

 

[sdt354]

+1 get your money back 1st. Dyno'd , jetted, & sync'd to me means, it should be running right. Our carbs are not that difficult to get running right. And, for a shop with a dyno there is no excuse. Ask for a dyno print out.

 

[Max88]

Have not had time to repair yet but found that right front cylinder intake must be cracked... Sprayed around it and bike picks up rpm.... Could very well be the problem... Will let know how it works out.....

 

[HyperPete]

Bringing it back from the dead...

My 99 has a Kerker with the race baffle and packing in the chamber to soften the loud exhaust a bit.

I had John Furbur work on the carbs a few weeks ago. I had really wanted to replace the mains and go through them completely, (I think that a Stage 1 kit is installed because the previous owner put Dynojet stickers on the airbox) but John said it was running well, and ended up just changing the needles from 3 to 4 and resetting the idle mixture for me.

Unfortunately, now it runs roughly at cruising speed (example - 1/8th throttle.) Instead of a nice "RRRRRRRRRRRRRRRRRRRRRRR" I get a ba-da-da-da-da-da-da-da-da unless I am accelerating. (This looks stupid but I hope you know what I mean.)

I changed the plugs to rule them out. No noticeable difference. The K&N air filter is clean.

Also, if I am cruising at 4K RPM and I whack it wide open it hesitates before kicking in. Almost as if the float bowl needs to fill, because after cracking it open once and accelerating, the next time it's good and does not hesitate.

It does run well so long as I am accelerating, but that rough sound while cruising is embarrassing - it sounds as if it's cutting in and out.

I'm not confident in removing the carbs, but having seen the needle valves adjusted I think I can do that if necessary.

Any suggestions? I know there are a bunch of carb gurus here that won't lead me astray!

 

[scuff]

Bringing it back from the dead...

My 99 has a Kerker with the race baffle and packing in the chamber to soften the loud exhaust a bit.

I had John Furbur work on the carbs a few weeks ago. I had really wanted to replace the mains and go through them completely, (I think that a Stage 1 kit is installed because the previous owner put Dynojet stickers on the airbox) but John said it was running well, and ended up just changing the needles from 3 to 4 and resetting the idle mixture for me.

Unfortunately, now it runs roughly at cruising speed (example - 1/8th throttle.) Instead of a nice "RRRRRRRRRRRRRRRRRRRRRRR" I get a ba-da-da-da-da-da-da-da-da unless I am accelerating. (This looks stupid but I hope you know what I mean.)

I changed the plugs to rule them out. No noticeable difference. The K&N air filter is clean.

Also, if I am cruising at 4K RPM and I whack it wide open it hesitates before kicking in. Almost as if the float bowl needs to fill, because after cracking it open once and accelerating, the next time it's good and does not hesitate.

It does run well so long as I am accelerating, but that rough sound while cruising is embarrassing - it sounds as if it's cutting in and out.

I'm not confident in removing the carbs, but having seen the needle valves adjusted I think I can do that if necessary.

Any suggestions? I know there are a bunch of carb gurus here that won't lead me astray!

sounds to me like you need to get that stage one outta there I have had issue's with mine the needles are not good, how is your air box ?? modified in any way? I talked to traumahawk he helped me a lot, I re-installed the wye in my air box and duct taped the remaining hole closed, put the needles closest clip to the blunt end and while doing this found out I had 150's in my paj2 and 170's in my mains so check that too you should have 170 in your paj2 and not sure what your elevation is for your mains, hopefully the guy you had looking at them would notice that if they were wrong, hope that helps

 

[Traumahawk]

Well stage 1 needles are almost too rich for a stock bike. I ran them....and had good luck. ...but only in the first clip from the blunt end. Thanks for the kind words Scuff.

 

[HyperPete]

sounds to me like you need to get that stage one outta there I have had issue's with mine the needles are not good, how is your air box ?? modified in any way? I talked to traumahawk he helped me a lot, I re-installed the wye in my air box and duct taped the remaining hole closed, put the needles closest clip to the blunt end and while doing this found out I had 150's in my paj2 and 170's in my mains so check that too you should have 170 in your paj2 and not sure what your elevation is for your mains, hopefully the guy you had looking at them would notice that if they were wrong, hope that helps

Yes, the airbox is modified but the wye is there. Also, as I said, I am running a Kerker so it's not 100% stock. It ought to breath a little better.

Quite honestly I am afraid to remove the carbs. Afraid I won't get everything back together right. I also have no way to synch them after I work on them. I read about people pulling the carbs like it's nothing and I am impressed by their skills. I used to work on my old dirtbikes, but a single carb is simple. They were also easy to get to. I don't want to tear it apart and then have to take it to a shop as a basket case because I could not get it back together or I got it back together wrong. I did that once some 30 years ago and learned that it's less expensive to pay someone to do it right the first time than screw it up and then have to pay them to fix your screw-ups. I really wish I had pushed John to do it a few weeks ago when I had it there, but he convinced me I did not need to. :bang head:

I don't suppose there is anyone near Central PA who would want to help me with this?

 

[Traumahawk]

How has the air box been modified?

 

[Dragmaxster]

Yes, the airbox is modified but the wye is there. Also, as I said, I am running a Kerker so it's not 100% stock. It ought to breath a little better.

Quite honestly I am afraid to remove the carbs. Afraid I won't get everything back together right. I also have no way to synch them after I work on them. I read about people pulling the carbs like it's nothing and I am impressed by their skills. I used to work on my old dirtbikes, but a single carb is simple. They were also easy to get to. I don't want to tear it apart and then have to take it to a shop as a basket case because I could not get it back together or I got it back together wrong. I did that once some 30 years ago and learned that it's less expensive to pay someone to do it right the first time than screw it up and then have to pay them to fix your screw-ups. I really wish I had pushed John to do it a few weeks ago when I had it there, but he convinced me I did not need to. :bang head:

I don't suppose there is anyone near Central PA who would want to help me with this?

The hardest part about working on these carbs is putting them back into the intakes (wd-40). You can leave the throttle cables hooked to the carbs but disconnect from the box. You do not have to take the cables off of the carbs.
You do not have to take all 4 carbs completely apart from each other either.
You can take 4 bolts off on each side and split them into pairs and still be able to get to all the bowls and all the jets that you would need to change- putting it all back together is hard to do wrong. You will probably find what is wrong when you take the jet block off and clean the jets inside. I would buy a rebuild kit because that jet block gasket usually tears or is very brittle. O-rings on the fuel bowls will probably need changing too. Look at the online manual for adjust float bowl height-you can just turn the carb upside down to find a close enough mark- The circle height.
Take your time and do it in a proper place. Once you do it you will know it and the next time makes it easier and save you $$$.

 

[HyperPete]

How has the air box been modified?

I'd have to see a stock airbox to tell. It was done by the previous owner.

 

[davesax36]

Post a pic. We'll tell you what's different.

 

[HyperPete]

The hardest part about working on these carbs is putting them back into the intakes (wd-40). You can leave the throttle cables hooked to the carbs but disconnect from the box. You do not have to take the cables off of the carbs.
You do not have to take all 4 carbs completely apart from each other either.
You can take 4 bolts off on each side and split them into pairs and still be able to get to all the bowls and all the jets that you would need to change- putting it all back together is hard to do wrong. You will probably find what is wrong when you take the jet block off and clean the jets inside. I would buy a rebuild kit because that jet block gasket usually tears or is very brittle. O-rings on the fuel bowls will probably need changing too. Look at the online manual for adjust float bowl height-you can just turn the carb upside down to find a close enough mark- The circle height.
Take your time and do it in a proper place. Once you do it you will know it and the next time makes it easier and save you $$$.

You are very convincing, but I'm not going to do anything until after Thunder. With my luck I'd f it up and wont get to go to Thunder!

 

[HyperPete]

Post a pic. We'll tell you what's different.

Well, I think he was wrong about having modified the airbox. I don't see anything that looks hacked.

 

[scuff]

I think he did look under the wye looks modified to me, granted it's not cut like mine was but it does look like he removed some material out from under the wye, i'm sure someone else would be able to confirm.

 

[HyperPete]

oh, that could be. I can pull the wye and get a photo tomorrow

 

[Traumahawk]

I think he did look under the wye looks modified to me, granted it's not cut like mine was but it does look like he removed some material out from under the wye, i'm sure someone else would be able to confirm.

Looks like that to me as well. Unfortunately not at home so can't get a measurement of what it should be. If your flowing more air....that will pull more fuel and make you rich as well.