Running on 3 cylinders, help!?

[kevinllee]

About a year ago I had the carbs on my 1986 Vmax completely rebuilt. About Christmas time or soon after, i forget exactly when, my left rear cylinder quit working. My battery is good. I have switched wires that work from other cylinders, coils, and new spark plugs (twice). I have spark at the plug, but when I take the wire off, it doesn't bring the rpm down like the other three. It's like nothing is there.
What else could be the problem?
What else could I check?

thanks for any help!

Kevin

 

[06VMAXIMUS]

Is the offending cylinder's spark plug wet? I would crack open the bowl drain screw on that carb and check to see that fuel comes out. These carbs are fussy, I have put mine away in the Fall only to find out in the Spring that they needed disassembled and cleaned again. Ethanol can be a bitch. Welcome to the Forum!

 

[kevinllee]

That's probably a good idea. Because I don't think the plug was wet. I'd check it again now but I'm in thr pasture trying to round some horses up at work. I'll probably check tonight and start taking the carbs off.

 

[SpecOps13]

Don't need to take the carbs off to check for trash in the bowl. Drain Screw is about 1/2 way down the right side of each carb and the hose is under, sticking out. Drain by turning the screw out a few turns and hold a white paper cup under the hose. Tiny black particles are what you're looking for.

Using Ethanol? I don't let the stuff touch my bikes or for that matter any of my other vehicles. Using a really good treatment in the Ethanol can help if there's no option.

 

[kevinllee]

Thanks for the advice again. I hope its as easy as that to fix. I really don't want to take it to the shop again, or take the carbs off and apart.

 

[thundermax]

I had that problem with my first vmax, a 98, on cylinder 3. It did not fire at idle but did with any throttle. The pilot jet, af screw was seized and there was a blockage not allowing fuel in for the idle. With throttle the cylinder got gas. This is a dangerous situation. Do you get a jump when taking off? I did. It is the unresponsive cyclinder firing up. The jump can put you down, it did with me. Solution: Took off carb, sent it to Sean Morley. He took out a/f screw, replaced it with a threaded sleeve ( taking out the seized screw stripped the thread in the carb). That solved the no-idle on #3 and the ignition jump on takeoff. This is my experience with a no-idle cylinder. Good luck!

 

[kevinllee]

I have nothing at idle and running down the road. My spark plug was brand new clean when I took it out after riding. So a blockage somewhere.....

 

[fmcandrew]

Could also be getting no spark...electronic components tend to just fail...

 

[MrVmax22]

About a year ago I had the carbs on my 1986 Vmax completely rebuilt. About Christmas time or soon after, i forget exactly when, my left rear cylinder quit working. My battery is good. I have switched wires that work from other cylinders, coils, and new spark plugs (twice). I have spark at the plug, but when I take the wire off, it doesn't bring the rpm down like the other three. It's like nothing is there.
What else could be the problem?
What else could I check?

thanks for any help!

Kevin

Did you ever find out what the problem was ? My 97 Vmax is doing the exact same thing, PLEASE RESPOND ASAP... Thanks alot

 

[MaxMidnight]

You are saying that you have a good spark?
If so you will need to check that you are getting fuel and/ or you have compression.

 

[effingidiot]

My max was running on three,it was a stuck float needle.I removed the air box,tapped the offending carb with a nylon hammer.That freed it off.

 

[Fire-medic]

Sounds like it's time for some fuel additive and changing your fuel filter.

My max was running on three,it was a stuck float needle.I removed the air box,tapped the offending carb with a nylon hammer.That freed it off.

 

[effingidiot]

Sounds like it's time for some fuel additive and changing your fuel filter.

Changed my fuel filter,what additive would you recommend.

 

[gentsvmax]

Same thing this past Saturday, Labor day weekend, swapped out the ignitech with my spare, splitting the rack, cleaning carbs, checking float heights. 3 and four where not firing! I could hear ignition when holding the boot near the plug and see spark when the plug was out and connected!
I soaked the carb bodies in Gunk carb cleaner, probed what I could with guitar string and blew them out after a good rinse out, reassemble, synced, fired up and sounding Goood! A day of good riding ended when I blew away a guy on his twin cam Harley with no shirt on. Stopped at a light, he rode up to bump fists and the max starts that thup thup thup sound ,NOOOOOOO!!!! FU#@KKKKK its doing it again! Why only 3 and 4, never 1 and 2???? I spent Sunday in the garage, same thing, determined to beat this ****** gremlin out of my bike and salvage some of the weekend. I split everything again,(I can do it in my sleep and quick by now.) I thought I would dump each carb over my clean white heavy shop towel and Bam! a tiny bit of black grit out of each carb. I think the fuel level sending unit in my tank may have some corrosion, I dont know, but the grit was really fine. Mod monkey scheduled tank service for this fall. I drainded the tank through the low level sensor hole, flushed it, added two new fram inline fuel filters. Reassembled the rack AGAIN, refueled ,synced the carbs, all four@ 2.5 turns idle is SICK @ 1k! She sounds GREAT!! I go down the alley and its starting to stumble, I remember it has to purge air out if the fuel system right? No the bike is barely able to limp back the block to the garage. I let it die and cycle the run/off switch, the fuel pump runs the 5 or so seconds every time and never pressurizes! WTF!!!!! FUEL PUMP, yup, took it out and after 10 quick minutes of open pump surgery the little rubber diaphragms each had the grit on both sides! Finally about 7p.m. and no issues after a short ride. I took the max out this evening and she's crisp and strong...ITs about frickin time!!!!!!

 

[gentsvmax]

Fuel pump out with grit in the spilled fuel. By the way thats an aftermarket fleabay pump, easily disassembled, easy to clean if unfortunately nessesary.