Hot Misfire Question

[MONTREALMAX]

I am not sure if this is the correct place for this post but here goes

I thought I had all of the problems worked out with the carbs

Has anyone ever experienced sputtering severe misfiring and hesitation after the motor becomes hot enough for the fan to come on? I drove home on a cooler day yesterday without incident, today in rush hour traffic the bike heated up to just above the rivet on the temp gauge the cooling fan started and then all hell broke loose

sputtering severe hesitation misfiring backfiring that did not get better once the bike was rolling and cooled off again

I was wondering if this is perhaps electrical in nature ???

 

[maleko89]

It's possible. When this happens unplug the fan fuse and see if thie sputtering goes away. Also, measure charging voltage before and after the fan comes on. The fan takes quite a bit of juice to run and maybe causing low voltage problems for the ignition system.

 

[MONTREALMAX]

Hey Mark would this not go away after the fan cycles and voltage goes back to normal?

The bike is completely stock, odessey battery new last week

Is any of the electrical or sparking system affected by high temps from the motor? pick up coils etc?

 

[maleko89]

Your charging system might not be able to supply adequate voltage with fan running.

 

[MONTREALMAX]

the bike continues to run like crap long after the fan stops turning and the motor has cooled....it seems to not be able to recover from the cycling of the fan it is very strange because I did 250 trouble free miles yesterday but I did not encounter any traffic as soon as it is hot in traffic fans cycles bang misfire until it is shut off and cooled

I am not sure anymore the symptoms all may be coincidence



It seems to charge normally....what would be abnormal low voltage while fan is running?

the tachometer makes wild swings toward zero as the thing is misfiring indicating electrical problem no?

the season has just begun here and I am tearing into this bike yet again.....

 

[maleko89]

Check your charging voltage when the tach is dipping towards zero. It should be over 13 volts at idle

 

[MONTREALMAX]

have you ever seen electrical problems caused by heat on the max or am I barking up the wrong tree?

 

[maleko89]

Absolutely, especially spark plug caps and wires.

 

[Mad-V-Maxr]

Montrealmax, I have the identical problems with my 85max. It warmed up today in traffic and started slobbering, and wanting to die. I've had this problem since I bought the bike. Ive been thinking in the same direction as maleko, my carbs been cleaned, rejetted dynojet kit, diaframs replaced, airfilter, fuel fitler, synced, new battery, protuned when it was cool out last winter. It is set a little on the rich side, but when it gets hot out it runs like crap. The tach needle dropping off I forgot all about till you mentioned it.

 

[MONTREALMAX]

my bike is a 96 stock

carbs completely rebuilt last year all yam parts sync'd again with carbtune 2 days ago spot on

all new boots for intake circuit

new NGK wires

new plugs

new k&n filter

new odyssey battery

idle set to 1100 rpm

charges at 12.8 to 12.9 volts while fan is running

coils ok on ohm meter



just don't know where to go next

last thing i want to do is remove the carbs again if it is not that


the frustrating thing is the problem comes and goes but the bike definitely does not like to run hot once at that temp it hesitates badly and backfires at the pipe at all engine speeds

it is now parked the plates are due and she is going to sit until I figure this out

montreal traffic is scary enough with a bike that does not stall and hesitate

 

[daves86vmax]

My 86 did what sounds like the exact same thing,turned out to be the wires and boots.I could actually see them arcing off the top of the motor and if I touched the wires and the frame at the same time it would kill the motor,it only acted like this when it got hot sitting in traffic,I could barely keep it running.Replaced wires and boots and problem went away.Good luck....Dave

 

[Dreamster66]

sounds like what mine was doing today.....did we piss the vmax gods off???

 

[MONTREALMAX]

my 86 did what sounds like the exact same thing,turned out to be the wires and boots.i could actually see them arcing off the top of the motor and if i touched the wires and the frame at the same time it would kill the motor,it only acted like this when it got hot sitting in traffic,i could barely keep it running.replaced wires and boots and problem went away.good luck....dave

i changed the wires and caps last summer for ngk ran it in the dark garage last night and did not see any arcing from the wires or caps while it was hot

possible bad ignition switch?

 

[maleko89]

That's possible. Could be engine stop switch too.

 

[MONTREALMAX]

Ok guys thanks very much for your input

i will check electric contacts at the ignition and kill switches and get back to you

 

[jfeagins]

Ditto me on the exact same symtoms in the past. I had put on new wires and caps to go with new plugs.

I didn't get the plug wires deeply enough into the coil. I could see some arcing to the valve covers after dark though. You might double, triple check your connections to your coil.

To this day, I still suffer the same scenerio once in a while, but only after the engine is warmed good and I'm sitting somewhere at idle. I'm thinking I need to overhaul my charging system cause I know it's not charging much above 13v at idle anymore. I believe the low voltage robs the electronics of the necessary voltage to create adequate spark at the plugs. :confused2::confused2:

 

[Dreamster66]

same for me....new ngk wires last year.
I'm wondering if my cdi box is finally going (the guy who I bought it from puttied it up....looked like he tried to pry it apart....that was 3-4 yrs ago tho....maybe its finally shittin the bed)
Anyone on here got a spare one I can borrow to see if thats what it is before I plunk down big bucks?

 

[Mad-V-Maxr]

I should do the wires and plug caps pretty soon, see if that helps. Probably check carging voltage again, and run the meter over the coils just to be sure it isnt old parts causing my problem. The sad thing is I worked on rebuilding and rejetting the carbs last year, then decided to take it to a pro to double check my work, but it was already late in the year so I know it never got really heavy traffic hot for him. That was one of the things I wanted looked at too. My max has had the cdi and boost boxes both replaced. Thanks for the advice guys and best of luck montrealmax.

 

[tvmax]

If you are going to replace your wires and caps I would look up the COP mod on this forum. Replacing coils, wires and caps will give hotter spark and cheaper than buying wires and caps.

.02
Jim

 

[MONTREALMAX]

I am going to take a very close look at the kickstand switch and related relay