VintageVmax.com

Please bear w me, I will try to describe the best I can.
Recently purchased sled ran great, 3 weeks ago it died abruptly on the trail, checked for spark, seemed weak, it would pop intermittently, towed it home.
1. New plugs, no change, they looked very wet.
2. Went through the carbs, nothing eventful there.
3. Sled just seemed to soak the plugs, so we removed the plugs, shut off the fuel lines and proceeded to crank the engine w the butane torch over the plug holes to burn off excess fuel.
4. We eventually got the sled to start, it cleaned out and ran decent in the shop, I ran it w the fuel lines off to burn out all the excess fuel.
5. After it quit, I turned on the fuel lines and it wouldn't start, we repeated the burn off procedure w the torch.
6. Got it to start and run w the fuel lines off, after it was running for a few moments I turned on the fuel lines and it quit w in seconds.
7. I bought another Vmax for cheap that I could swap parts from to help diagnose the condition.
8. I brought both sleds in to the shop, turned off the lights to compare spark, both intensity and frequency, they both looked the same, actually the sled that won't start and run had better spark.
9. I swapped the carbs from the running donor machine, no help.
10. Rechecked spark, now spark is weak and only when you pull the rewind briskly.
11. Swapped in a CDI that a friend had lent me, spark looked better.
12. Put the carbs back on, still wont start, it's kind of sputtering but nothing too encouraging.
13. One thing I noticed was w this CDI the spark is only there when you pull the rewind slowly, the other CDI was the opposite.
I'm open to suggestions.

Fuel pump, maybe crankseals..... I would tear down and put all new seals and inspect and check everything for spec. I bought a 93 sx exciter and took it out for a ride brought it in the shop and desided to check everything over and the piston skirts were about to come off as one came off in my hand lol!!! Its march i would check everything over..

duane wrote:Please bear w me, I will try to describe the best I can.
Recently purchased sled ran great, 3 weeks ago it died abruptly on the trail, checked for spark, seemed weak, it would pop intermittently, towed it home.
1. New plugs, no change, they looked very wet.
2. Went through the carbs, nothing eventful there.
3. Sled just seemed to soak the plugs, so we removed the plugs, shut off the fuel lines and proceeded to crank the engine w the butane torch over the plug holes to burn off excess fuel.
4. We eventually got the sled to start, it cleaned out and ran decent in the shop, I ran it w the fuel lines off to burn out all the excess fuel.
5. After it quit, I turned on the fuel lines and it wouldn't start, we repeated the burn off procedure w the torch.
6. Got it to start and run w the fuel lines off, after it was running for a few moments I turned on the fuel lines and it quit w in seconds.
7. I bought another Vmax for cheap that I could swap parts from to help diagnose the condition.
8. I brought both sleds in to the shop, turned off the lights to compare spark, both intensity and frequency, they both looked the same, actually the sled that won't start and run had better spark.
9. I swapped the carbs from the running donor machine, no help.
10. Rechecked spark, now spark is weak and only when you pull the rewind briskly.
11. Swapped in a CDI that a friend had lent me, spark looked better.
12. Put the carbs back on, still wont start, it's kind of sputtering but nothing too encouraging.
13. One thing I noticed was w this CDI the spark is only there when you pull the rewind slowly, the other CDI was the opposite.
I'm open to suggestions.

These two make me go Hmmmm....
#6 Are the fuel pumps leaking by and flooding the crank case by a hole in a diaphram ?

#13 Are the connections at the stator clean, tight and dry ? Have you checked all the coil resistances ?

http://www.vintagevmax.com/1986_service.htm
Electrical- Mfr./ Type Hatachi/ CDI
Headlight/ Taillight/ Meter light Ratings 12v 60-55w/ 12v 23-8w/ 12v 3.4w
Lighting Coil Color Code/ Resistance/ Output Yellow~ Black/ 0.25 Ohms +/-10%/ NA
Handlebar Heater Coil Color Code/ Resistance Yellow-Black~ Blk/ 0.77 Ohm +/-10%
Ignition Coil Resistance Primary/ Secondary 0.12 Ohm � 10%/ 4.0 Kohm +/-20%
Source Coil Color Code/ Resistance Brn~Red/ 245 Ohm +/-10%
White- Red~ Red/ 10 Ohm +/-10%

Pulsar Coil Color Code/ Resistance White- Green~ Black/ 100 Ohm +/-10%
Spark Plug Type/ Gap/ Torque NGK BR 9EV/ 0.7~0.8mm/ 2.75 m/Kg (19.9 ft/lbs)
Ignition Timing 1.6mm BTDC

Pulser coil gave no reading.
I wonder if that fits the symptoms described?

Ya if its not getting proper timing of spark it doesnt matter if its getting spark.