Bike won't run without choke. Rough Idle

[Leepbrochill17]

Hello All,

I am new to the site, and I love it so far. Everyone is very helpful.

I am having a pretty serious problem with my 91 Vmax. I am assuming it is a fuel or air issue, or both. The bike will not start without the choke, cold or warm. It will idle, but only with the choke on. As soon as you turn the choke off it stalls. I am able to rev the throttle but only at high rpms. A slow roll on the throttle to about 1/4 throttle it bogs down and wants to stall. If you quickly release the throttle the rpms will rev back up to 3000 and then back down to 1000. The left rear carb will also backfire every so often.

I did do a shotgun carb cleanout and added sea foam to the tank and directly into the carbs. It seemed to make no difference. The throttle may be slightly more responsive but it still wont start without choke and will not roll on in low end.

I had it serviced back in February. They synced the carbs and checked the floats and all that and it seemed to run fine. I have been busy and it has sat for about 3 months, but I have been starting it on occasion and letting it warm up in the garage. I had also put some stabile in the tank. I wouldn't think 3 months of sitting the carbs would gum up already but I don't know what else it could be. Please help! I don't want to pay another 1000 to get it serviced.

One other thing I have been running premium gas in hopes to keep this from happening, could this have helped to cause these issues?

Many thanks for any help or advice.

 

[davidon]

1. Don't use premium gas..you're adding more carbon deposits..sounds like you still have to disassemble carbs and take out jet blocks and pull out pilot fuel jets and spray them out with carb cleaner.

 

[CaptainKyle]

3 months with todays gas Is plenty long enough for the carbs to gum up with todays fuel. Your jet blocks are most likely clogged up. if you have a few tools & are a little mechanically inclined we could walk you thru cleaning them. If not you could send the carbs to me or one of the other guys here that do carbs & we could fix them for a lot less than a dealer.

 

[dannymax]

It sounds like your carbs are in need of a good cleaning. You can try the shotgun again and maybe get lucky, if not you will probly have to pull the carbs and go thru them. If you decide to farm the cleaning out there are some guys here on the forum that provide that service and have way more experience at it than most of the local dealers, I would urge you to check here first.

And yes, 3 months is plenty enough time for gerb to form in your carbs....the gas we're getting these days is real junk, I'm amazed it even burns!

 

[Leepbrochill17]

Thats what I was afraid of. I work on my dirt bike carbs all the time and am sort of mechanically inclined but I have never tackled and carbs this complicated looking. Any help you could provide would be much appreciated. I also have a service manual but it is not very descriptive when it comes to the carbs. I am afraid of messing anything up to the point where I have to trailer it to the shop and pay a fortune.

I guess the first step would be to take the carbs out of the bike. I think I can get most of the way there but just to be safe how should I do this. Specifically detaching the throttle cable.

 

[CaptainKyle]

pretty simple to get the carbs off . remove the scoops, air box , Chrome intake covers, left plastic neck cover , to get to cables & cable junction & undoe the cables there & just pull the lower cables out with the carbs. The rack of carbs is also pretty simple to split.

 

[dannymax]

-Remove the airbox cover
-Remove the scoops, both sides
-Remove the 3 screws holding the left side steering neck cover....the one with the electrical components, move it out of the way
-Remove the throttle cables from the cable block
-Remove the vent hoses from either side of the 'Y' peice
-Remove the airbox
-Disconnect the fuel line
-Loosen the top clamps on the (4) rubber boots under the carbs
-Pry the carbs out of the boots and remove out the left side of the bike

 

[davesax36]

Use two broom handles as levers on the cylinder heads to get your carbs loose at least the first time. Tear them all the way down to the jet blocks and inspect your pilot jet (37.5) it's got a super tiny hole, and when it's clogged you have a frustrating mess with hanging revs (don't ask how I know this at least three times)... When you're taking things apart, get a cheap baking pan or something else and mark off four distinct areas to keep all your parts in. It will make reassembly easier.

Remember, no matter how far in you get, there are guys on here that can get you out. Everyone is super helpful especially with these carbs. They're finicky, and really don't love ethanol gas. You might also take apart your fuel pump and clean it out. I think there's a sticky about it now, as with carb disassembly.
This might help http://162.210.36.140/showthread.php?t=5830&highlight=carburetor+rebuild

That's got pics of everything you need to know as far as where stuff goes, you might have to do some parts in reverse because it starts with everything already disassembled.

 

[Leepbrochill17]

Thanks for the link to the guide. How much would we be talking to farm it out? This may all be too much for me. What I most afraid of is tearing it all down, pulling my hair out putting it back together and then I go to start it and it either doesnt fix it or wont start. Local service guys here are jerks ad Ive already spent alot of money doing this once.

Also, to get the throttle cable out whre should I start? Sorry I have had bad luck with these fraying and dont want to start pulling on it. I can see down near the carb where I would slide it out but I dont have enough slack.

 

[davesax36]

PM Dannymax. He built me a whole new set of carbs using my internals for what I consider a very reasonable price. His "basic" clean/fix-up is VERY reasonable and top notch. Easy to talk to and great with contact if you have things that are not normal or whatever. Mine had some stuff done to them by the previous owner that was pretty dumb.

Disconnect the throttle cables in the rectangular plastic box that's behind the left scoop's electrical panel. It's white on one side and black on the other - has three? tiny screws in it. Leave the cables connected to the carbs, but pull the carbs off in order to have slack to disconnect...

 

[CaptainKyle]

Maximum charge if all your diaphrams are in good shape & they needed completely rebuilt would be $ 375 from me . To get the cables loose you need to go thru the steps me or Danny max listed & undoe them at the junction block under the neck cover. If every thing was replaced when they were in the carbs before it would be cheaper. Feel free to call me but not tonight as I am headed to bed. 813-270-0000

 

[mitchelljd02]

@dannymax.

Can you put me in touch with a forum member who I can ship my carbs to for inspection and proper reassembly?

 

[davesax36]

@dannymax.

Can you put me in touch with a forum member who I can ship my carbs to for inspection and proper reassembly?

Send a PM to dannymax or CaptainKyle or sean (one2dmax). All those guys (and some others) could rebuild your carbs. If, for some reason you can't send PMs due to low post count right now, I'm sending you a PM ...

 

[Rusty McNeil]

Local service guts can be jerks, and dealer prices are way too high.

That's not the worst part tho'

The worst part is that on top of being expensive jerks they rarely have the slightest clue what they are doing with these carbs.

They'll charge you $700 without even being embarrassed that the problem is not fixed.

 

[davesax36]

Local service guts can be jerks, and dealer prices are way too high.

That's not the worst part tho'

The worst part is that on top of being expensive jerks they rarely have the slightest clue what they are doing with these carbs.

They'll charge you $700 without even being embarrassed that the problem is not fixed.

This...

I think the highest that's been mentioned on here recently was something crazy like $1200 for a complete rebuild. That's nutty. I'm sure you could buy all new OEM parts including the carb bodies for less than that. And the dealer probably screwed them up. I don't know why these carbs seem so bad, though. They're just carburetors, it's not rocket surgery.

 

[dannymax]

@dannymax.

Can you put me in touch with a forum member who I can ship my carbs to for inspection and proper reassembly?

PM sent

 

[dannymax]

This...

I think the highest that's been mentioned on here recently was something crazy like $1200 for a complete rebuild. That's nutty. I'm sure you could buy all new OEM parts including the carb bodies for less than that. And the dealer probably screwed them up. I don't know why these carbs seem so bad, though. They're just carburetors, it's not rocket surgery.

There is the flip side to that also....had a guy tell me I was too high, that he could get them completely cleaned/rebuilt locally for $45!!

Watch out for that scenario too....there's a guaranteed rip-off if you deal with one of those guys.

 

[davesax36]

There is the flip side to that also....had a guy tell me I was too high, that he could get them completely cleaned/rebuilt locally for $45!!

Watch out for that scenario too....there's a guaranteed rip-off if you deal with one of those guys.

We know how those end up... It just ends up being $45 flushed down the drain instead of spending it on shipping to one of the guys on here that actually does them right.:bang head:

 

[Leepbrochill17]

Thank you all so much for the reply. I am going to attempt the shotgun method one more time in an effort to avoid having to tear everything off. I am not sure if the gaskets and o-rings were replaced when it was serviced, but I am pretty sure they didn't replace anything, only cleaned.

I have drained the gas tank and put new fresh gas in it with sea foam and replaced the fuel filter to hopefully prevent this from happening again.

Tomorrow I will take the carbs off if after today the shotgun doesnt work.

My only fear is that I will get the carbs back and it turns out they werent the problem. I was thinking possible fuel pump could be causing some issues as well because it died on me today while I was doing 60mph on the highway trying to run some fresh gas through it. Still wont idle/run without the choke.

Thanks again for the reply.

 

[davesax36]

Take apart your fuel pump, too. It's super easy. Two nuts and six bolts. You can clean any rust with a pick, dish soap, toothbrush, whatever. I still don't know why they'd put the pump after the filter...