tried everything - now what

[t3ttp]

tried everything but still running on 3 cylinders:

drained fuel
changed fuel filter
had Fargo rebuild carb
changed 1 diaphragm
changed 1 a/f needle
shotgun multiple times
changed to cop
changed plugs
changed cdi
155 compression on all 4 cylinders
carb tune still shows that cylinder #2 is not registering until i hit 4-5k rpm and then only 1/5 of what the other cylinders are showing on the carb tune tool.

is there something that i'm missing? how about the magnets?
damn this has been an expensive 6 weeks.

Fargo will check it tomorrow, hopefully we can get down to root issue.

2000 vmax with 43k. :bang head:

 

[PATMAX]

Just thinking out loud. Wouldn't there be carb vacuum even if there was no combustion in that cylinder? As long as piston is moving and valves are opening and closing? Couldn't be as simple as a clogged vacuum port could it?

 

[t3ttp]

Cleaned the port with guitar wire.

 

[t3ttp]

can it be the pick-up assembly behind the crankcase cover?

 

[bazwell]

Vacuum leak.
Split rubber on v-boost or inlet manifold? Inlet gasket?
Try spraying aerosol starter fluid stuff on the rubbers when it's running, and see if the revs pick up at idle.

I don't think the pick up will affect one cylinder. It certainly won't cause vacuum to be low.

 

[twistedmax]

can it be the pick-up assembly behind the crankcase cover?

That would have been my guess.................. but Im a seat guy:confused2:. I do however have a N I B pick up assembly if you find thats what it is I will give you a very good price on it ( there expencesive).

 

[wildweasel_pt]

Did you confirm the plug is sparking? Since you have COPs are them fit snug and contacting well with the plug contacts? You can check that by removing the plug and fire it on the outside being careful for the plug not to touch either you or the bike

 

[one2dmax]

You may need to turn the a/f screw out a little more on that carb too.

 

[sdt354]

Did you confirm the plug is sparking? Since you have COPs are them fit snug and contacting well with the plug contacts? You can check that by removing the plug and fire it on the outside being careful for the plug not to touch either you or the bike

+1 on the cops being a possible problem. Switch them around and see if the problem moves to a new cylinder. My first set had one cop that was bad. My problem was obvious though. It arched. Spart checkers from Harbor Freight are cheap and helpfull with diagnosing. Or,The above works fine too. Good luck with it.
Steve

 

[Fire-medic]

+1 on the cops being a possible problem. Switch them around and see if the problem moves to a new cylinder. My first set had one cop that was bad. My problem was obvious though. It arched. Spart checkers from Harbor Freight are cheap and helpfull with diagnosing. Or,The above works fine too. Good luck with it.
Steve

I have always been told that you need to ground the removed plug if you turn-over the engine or run it, not doing that will fry the transistorized ignition.

Now I do not know if the VMax is an exception to the rule, but it seems like an easy-enough thing to do. Just make sure the side electrode is making a good ground to the frame/engine, or use a couple of alligator clips & a jumper wire to a known good ground besides going to the plug.

If I read that right, the plug will fire at higher rpm's but not up to 4K? Sounds like some idle circuit issue, despite the 'shotgun.' Not being a mechanic, I would guess the vacuum leak would affect that cyl throughout the rev range & not just idle/off-idle & below 4K.

Switching the COP's around to see if one is bad is an easy, quick way to test. ALso, do you use a spray bottle of H2O on the header pipes to see which one(s) aren't firing (cyl's)? The one where the H2O doesn't evaporate immediately isn't firing. Cheaper than a IR thermal measuring tool & easy to 'read.'

 

[06VMAXIMUS]

Is the non-firing plug wet with fuel? If so, your lacking spark...if not wet then you are probably lacking fuel. Compression and timing are good, so spark and fuel are all that's left as possibilities.

 

[wildweasel_pt]

As Bob said above a bike that is kept aside a bit of time may isolate the plugs, especially 2 stroke engines that use oil mixed with the gas for lubing the sump. If thats the case take the plug out and take it to your stove and let the electrode burn a bit to burn off the "coating" then just clean it with a bit of steel wool or scotch brite to remove the soot...

 

[sdt354]

Have you switched the rubber hoses to different cylinders. I know it's simplistic, but it's sometimes easy to over look
stuff when I'm frustrated. It could be sticking-the rod in the tester I mean.
Steve

 

[naughtyG]

One thing I've not seen on your list: have you looked into the fuel tank with a bright light? Looking for rust...

Your problem sounds exactly like what I was getting when very fine rust dust from the tank used to wreak havoc through the carbs..

 

[redneksoldier]

One thing I've not seen on your list: have you looked into the fuel tank with a bright light? Looking for rust...

Your problem sounds exactly like what I was getting when very fine rust dust from the tank used to wreak havoc through the carbs..

+1 for sure. Just had this problem last week. Exact same scenario! Freaky. I had just rebuilt the carbs and got them back on the bike. had an issue getting them synch'ed so I ended up pulling the carbs back off to double-check everything. Pulled the bowls off and there was a very fine powder of rust all over everything.:bang head: Had to completely clean carbs again and de-rust the tank. Now, all is well and the Max is happy again.

I would put a clean container under the float drain hoses, drain them and see what comes out. couldnt hurt, and will show you if there is any foreign material in the bowls. I ended up using the Yamaha tank rust remover on mine. Worked like a champ.

 

[redneksoldier]

Upon further reading, I agree with Patmax. Even if there is no combustion in the cylinder, there should still be vacuum at the intake. It will affect synch if that cylinder is not firing, but you should still get a reading. Double check that the carbs are seated completely. Also, check the carb boots to be sure that they are on the right way. They have a right-side-up direction. The side with the depressions/recesses goes down. That is one of the things that kept mine from going together smoothly. I had thought that they were seated completely until I saw how far down they actually go. Be sure to lube up the rubbers before attempting to seat the carbs too. They are a really tight fit and it took a good bit of pressure to get them seated.

 

[Fire-medic]

I heartily endorse the "F-M Squat" for seating the carbs in-place w/the airbox on-top. :rofl_200:

Of course lubing the carb rubbers & the airbox rubbers w/either silicone spray or dielectric grease as others have mentioned will help. And, be sure to tighten the clamps above & below the carbs! If you look at the stock VBoost clamps, you see they have a stop which prevents over-tightening them. You tighten them until you get to the stop, a metal piece of the clamping band which comes into contact w/the band as it tightens from the other side. It's easy to forget tightening one or more of the bands as you try to get everything reinstalled for that all-important "test ride!" The bike will run, but not as-good as it would w/all bands secured.

Upon further reading, I agree with Patmax. Even if there is no combustion in the cylinder, there should still be vacuum at the intake. It will affect synch if that cylinder is not firing, but you should still get a reading. Double check that the carbs are seated completely. Also, check the carb boots to be sure that they are on the right way. They have a right-side-up direction. The side with the depressions/recesses goes down. That is one of the things that kept mine from going together smoothly. I had thought that they were seated completely until I saw how far down they actually go. Be sure to lube up the rubbers before attempting to seat the carbs too. They are a really tight fit and it took a good bit of pressure to get them seated.

 

[wildweasel_pt]

I wouldn't recommend using silicon on rubbers... Silicon reacts with natural rubbers and might with some other kinds (melts the rubber). I prefer to use liquid vaseline that dillutes in water. Thats what i use to recondition dried up o-rings and rubber gaskets

 

[Fire-medic]

Silicone is itself a natural product and the carrying agents, gases, and liquids which allow the silicone to penetrate and do its job after the carrying agents evaporate are the same substances found in things highly-touted in this forum, i.e., "Start Your Engine," "Sta-bil," and "Marvel Mystery Oil." (naptha being a primary ingredient)

The % of silicone in the "Prestone" silicone spray lubricant product is 7% or < as-measured by weight.

Prestone Silicone Lubricant:
http://www.chemcas.com/msds112/cas/2423/75-45-6_115-10-6_64742-48-9_75-28-5_63148-62-9.asp

Minimum 7-13% naptha by weight

Sta-bil:
http://www.chemcas.org/msds_archive/msds_01/cas/gb_msds/64742-94-5.asp

Minimum 90% naptha by weight

Marvel Mystery Oil:

http://www.chemcas.org/msds_archive/msds_01/cas/gc_msds/64742-52-5.asp

Minimum 70% naptha by weight


From consideration of this data source, fears of its causing rubber deterioration are anecdotal rather than being supported by the required scientific data supplied to first responders, chemical poison control centers, hospital E.R.'s, industrial and commercial end-users, and other people who daily rely upon the accuracy of this information.

Vaseline petrolatum jelly is insoluble in water:
http://www.chemcas.com/msds_archive/part2/cas/gy_msds/makingcosmetics_com---msds-vaseline.asp

 

[wildweasel_pt]

I said silicone reacts with natural rubber (latex) melting it don't know about different kinda of rubber (synthetic). Been there done that. If you get silicone oil or grease on paintwork you will never be able to repaint that surface, paint will never attach to a silicon greased surface, and no matter how much you clean it will always be there causing bubbling on the paint/varnish... Regarding vaseline, i use it (at least its whats on the label) and i can wash my hands to remove the greasy feeling on fingers. Might have to do with the soap as well... :ummm::biglaugh: