Ignition Woes

VMAX535

VMAX535

Vmax-4 Senior Member
I have been having ignition trouble for a while now on my 800 Improver drag drag sled. What is happening is the engine will start up, we heat the pipes, engine engages around 6,000 rpm the sled pulls out of the hole like crazy and all of a sudden the ignition will shut off usually between 100 - 300' out. Once the sled coasts to rest you pull it once and it re-fires and you drive it back to the pits. I have checked for shorts and disconnected the usual culprits like kill switch, ignition switch, tether, vdo and digitron. I have swapped out the stator with my tril sled and this still happens. It seems to be worse in warmer weather. This past winter we made a half dozen 2,000' pulls and it stayed fired. As soon as the wheater got aboce 40C it started to crap out again, it even quit on the rev stand once.

Im using a rpc 10,200, 180* box what do you guys think?? CDI is the only thing I haven't replaced.

Does anybody have one they want to part with or have any other ideas as to what is going on.

/Dan
 

Sure it isnt a fuel issue with being too lean or rich? Had it happen in cars and r/c cars before, but never on a sled.
 
DAN, WHAT ABOUT PLUG CAPS AND EXTERNAL COILS ? LONG AGO, I HAD A 81 SRX THAT DID SAME THING. DROVE ME NUTS. TURNED OUT BEING WIRES OFF STATOR THAT WAS EXPOSED AND CAUSEING SHORT AGAINST CASE. 3:16 (yammie tony)
 
Dus seem like a fuel issue..After it stops on the track you should pull the plugs and look at them...Maybe too lean..What are your mains.?
 
Tony, I changed out the stator and the same thing. I will disconnect the wiring harness and wire it direct to eliminate any wiring harness intermitant shorts. I will swap out the external ignition coils with my stocker and see if it helps.

Good 22, never consider fuel but you might be on to something.

Ronnie, when I was pulling 2,000' I had 170 mains and dial-a-jet set in the middle setting. When we went drag racing I dropped them down to 160 mj and the dial-a-jet was at the leanest setting, this is when it started cutting out again.

Hmmmmmm! Maybe it is fuel, I'm running big pilots so it starts easier and it idles well with the bored carbs and filters but maybe when it comes off that circuit it is lean popping and somehow cuts out??

Thanks for the input.

/dan
 
YOU GUYS SAY FUEL, AS IN FUEL DELIVERY PROBLEM. DAN, NEXT TIME IT HAPPENS, LIKE RONNIE SAYS, PULL PLUGS. MAYBE YA HAVE FUEL PUMP ACTING UP OR SET YOUR NEEDLES IN LAST LOCATION DOWN. THAT WILL TAKE CARE OF A LEAN SPOT. 3:16 (yammie tony)
 
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What carbs are on this...? If they are 33-35.5 do you have Q-8 nozzeles to put in..?? I had the same problem drove me nuts for years..A IMP800 needs alot of fuel than what anyone might think..
 
Tony needles are in the middle. I will pick them up and try larger needle jets as well as the carbs are bored to 35.? mm. Does anybody have any Q-8 like Inline-4 suggests?

/Dan
 
There is a big Mikuni dealer in Toronto. I'll pick some up and try. Will let you know how it works out when we get testing in July.

Thanks,
dan
 
FYI..From what I remember a 1997 700SX either #1 cylinder or #3 cylinder carb has a Q-8..Thats where I got the intel from..So there should be a Yamaha # for it..
 
Nozzle Update

INLINE4 said:
I think it's 89A-14141-58-00
Click to expand...

Ronnie I got some of these emulsion tubes and installed them. They cleared my whole problem up. The sled ran it's fastest et and mph since I've had the sled. Thanks for the input.
 
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