Sputter

[brett03]

Hello all. I have a '93 Max I purchaced last month with 19,277 miles on it. I have put about 150 miles on it and it started to run very rough spit and sputter. the bike was completely stock. A/F plugs still installed. I removed the plugs and went to remove the screws and 1 broke :bang head:. I drilled and removed it. i did the Shotgun and Pea shooter. found the diaphrams were cracked and replaced them as well as all pilot screws. started it and no improvement. I thought I may have damaged the carb I drilled the screw out on. I bought a carb body from CaptainKyle (Thank You). I have also done the crimp mod, COP mod Installed a new AGM battery. LED turn signals and tail light while waiting on parts Built up the new carb and installed Synced carbs, set screws at 2.5 turns out. Still no change. Voltage before start up is 12.85v at idle 13.85v at 2500 RPM 13.2v. Sprayed carb cleaner around boots and no leaks. i dont know what else to try or if its Fuel or Electical. Any help would be GREATLY appreciated as I am dying to get back on it.

 

[DMAN999]

Read through this Guide and check your Charging system:
http://www.vmaxforum.net/showthread.php?t=19108

 

[jfeagins]

At what RPM's is it sputtering? Fuel filter OK? Fuel pump OK?

If you have enough tiny crud in your fuel system, even a fresh carb cleaning may not last long before more crud finds it's way into your jets.

 

[m-cman]

Have you replaced the fuel filter? Cleaned a 2002 carbs and it ran great for a few days then started acting up again. Replaced the filter and cut it in half out of curiosity. It was absolutely full of rusty looking particles. Also could see junk in the tank using a flashlight. Had to clean the carbs again and will need to clean the tank.

 

[brett03]

I am currently in the process of the charging system check. I have found the R/R and the black wire goes up to a connector then into a wire harness by the battery. I can not find the Three Black wire splice. does anyone have pics of it?


The bike starts right up and idles good. at about 3000 it starts to spit and sputter. Brand new filter just installed. Fuel pump sounds good from what i can tell. Clicks a few times when turned on then stops.

 

[brett03]

Update : I have moved the Regulator/Rectifier up to the location were the aft left coil was. Ran the red wire to battery pos. & black wire from mount screw to battery neg. Never did find the 3 black wire splice. Idle is 14.33v & 2500 RPM drops to 14.23v. still no change in the way it runs.

 

[Miles Long]

Your charging numbers are good, the sputtering is probably not related to available voltage.
Other know carbs much better than I, but my understanding is that the a/f screws and settings only effect the idle and low speed operation. If carburation is causing the sputtering, it is because of the other circuits involved, or float operation. Have you performed a wet float check, and opened the bowl drains to check for debris?
Does it sputter at 3k plus rpm while on the centrestand, or just when driving (engine under load)
Plugs checked and gapped? Fuel cleaning additive in the tank? (such as Seafoam)
Cheers!

 

[rollin thunder]

I will put my bike on the stand this weekend to see how she runs with the rear wheel up.When I hit 5-6grand she takes right off so I think that rules out the fuel filter.I have new plugs and put on C.O.p setup a few months ago.

 

[brett03]

I have new plugs in and gap was checked. The problem started when i was riding it and now its on the center stand in nuetral. I will pick up some clear tubing tomorrow and check the wet float check. I have drained the bowls a few times and have'nt seen any debris. I have aslo ran Seafoam thru it.

 

[Irtron]

Just to eliminate another potential reason.

Have you checked the vacuum line that connects the second cylinder (front left) body to ignition unit? It has a one-direction flow restrictor on it that should point up as I remember.

 

[brett03]

Checked wet float level. AFT right carb is just a hair below the 17mm mark. i pulled the plug on that cylinder and here is how it looks.

And here is a pic of the FWD right cylinder

I have also just replaced the vacuum advanced line and arrow was/is pointing up.

 

[Miles Long]

You have said that you did a sync., and that the bike starts up fine, and idles well.
In an effort to determine if the problem is fuel or electrical, I suggest you pull your airbox off, and check for even diaphragm/slide action on all four carbs, while the bike is at higher rpms and sputtering.
If the carbs appear to be working in unison, I would then run the bike for a few minutes while it is sputtering, then shut it down immediately. After a cooling down period, remove the plugs to check for one (or two) that appear different. Even new plugs can fail. If the old ones still look fine , try them again.
Do you have one of those spark checkers that can be used at the HT leads, to see if one of the circuits is breaking down, again at higher rpms?
All the above to try to determine which cylinder is not working, either because of fuel or electrical.
Did you remove the front coils when you did the COPS conversion? If not, hook up all the original coils. Was the bike running well before the conversion?


As I said previously, I'm not a carb guy... I'm just thinking of easy things to check, to narrow down the sputtering to one cause.
Cheers!

 

[brett03]

Ok, The problem started before the COP mod. I'm going to guess that the problem might have been wire connection on the AFT right coil. I reinstalled the 2 plugs I removed and checked the COP wire connections. When I started it and went to 4000 RPM to check if the slides were the same and they were but had no sputter. Blipt it several times then to 5000 RPM and no sputter just a little back fire on deacceleration. Put everytihing back together and went for a short ride, filled up with gas and added some Seafoam. Runs good except when I go WOT it hesitates then goes then hesitates the takes off like it should. Might be the carb that is a hair low on the wet float check..? Any ideas?

I would like to Thank everyone for there input. I have now fixed several little quirks on the bike with all your ideas and have improved it greatly.

 

[Miles Long]

Sounds to me like carburation, i.e., dirty circuits. Sputtering is starting at higher rpms than previously, and not as severe?
In this case, the simplest thing to do is give it a "hot supper" ......take it out for a good run, spool it up to the rpm where it starts to sputter, and keep it there for awhile. No need to speed, just drop it down in gear. Let the Seafoam works it's way into the circuits involved that were causing the problems.
Chances are that following this, if there is still hesitation, it will start at an even higher RPM.
No guarantees, just another easy (and fun!) unk:diagnostic check you can do.
Keep us posted!

 

[brett03]

Sputter has stopped and just a hesitation when I go WOT. I will keep adding Seafoam and try to put some miles on it. Damn Rain. Will let you know. Again Thanks to all for the help.

 

[brett03]

Time for an update: I'm about at my witts end on this:bang head::bang head::bang head:. When I snap the throttle and hit 7000RPM it falls on itself. Feels like it drops a cylinder. After about 5 sec it will sometimes recover and take off. It does it when climbing thru all gears each time it hits 7000-7500RPM. Sometimes it will not recover and I have to let off the throttle then get back on it. If I roll thru the throttle it will not do it at all. Straight thu 700RPM no problem. I have tried three different sets of C.O.P's, Cleadned carbs 5 times, set wet float hieght at 17mm, replaced carb boots, synced carbs 9 times, shimmed needles, replaced all 4 A/F screws, A/F screws out 4 turns, replaced all vacuum caps on carb sync ports, taken fuel pump apart and cleaned, replaced vacuum line on #1 carb to controller, changed fuel filter, changed plugs 5 times and set at differnt gaps, new battery and ZX-14 R/R installed. Last night I found vboost self test works but does'nt when running (maybe because of C.O.P's. No resistor installed) so it is now open all the time. Went for a test run and still does it. Bike starts, idles and runs good other than that.

 

[Miles Long]

Yes, easy to see why you are discouraged.
Only thing I could suggest is to disable the v-boost function(electrically), and see if that makes a difference. And as you probably know, stock a/f setting is 2 1/2 turns out.
Cheers!

 

[jfeagins]

Could this be a transition thing happening when the carbs are going from needle jet assy fuel to full-on main fuel jet activity? I'd think that happens at a lower RPM than 7K, but ???

Could the fuel pump be having trouble keeping up with RPM's, momentarily running the carbs low, then catching up?

Normally, if the pump is having difficultly, it will show up by having to pump extra each time the key is first turned on, BUT...you never know. Might be worth a quick inspection.

My only other 'thought' would be that perhaps at that precise RPM, your engine has its' most vibration, and could in some way be interfering with the pick up coil only near that RPM, and anything above there smooths out and self corrects. (If that's even possible)

 

[brett03]

I disabled the Vboost in open position same result. Then disabled Vboost in closed postion. Same result. Also tried A/F screws set at 2.5 turns both ways and same. Also the pump does'nt seem to run any more the usual from what I have read. I pin the throttle at 3-400RPM and it does'nt do it till I hit 7-7500RPM

 

[Miles Long]

Let's assume that it's not an fuel problem - have you trimmed the HT wires to the plugs? Many previous posts have suggested that the wires corrode (turn green), and that trimming them (cutting off 1/4" or so) improves performance.
What about voltage to CDI (or battery voltage) prior and after 7k rpm? Any decrease? Probably the easiest way to determine this would be to use a clamp-on meter, while you spool up the rpm's.
.... but I'm still thinking this is a fuel issue. I know you have worked on the idle circuits, but did you clean the jet blocks? This involves taking the carb rack completely off. The carb gurus can fill in the details.
Cheers!