Baffled !

S

snowhite

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Mar 18, 2008
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Age
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Location
Flin Flon,Manitoba
Hi guys', I know someone will help out with this one,I have a 700 MM i'm working on,whats wrong is that on the PTO plug she is cold, it is not running on 3 cyl.s.what I mean is that I went thru everything-carbs,elec.,compression, plugs, you name.So whats happening is that the pto has no fire while running the engine.She has all the spark when I check the plugs grounded, but when it's running the plug is soaked with fuel and cold.We went through everything we could think of,has anyone had this happen,let me know as the guy is frustrated as well as myself.Strange or what/
 
did you try plug caps, sometimes they fit loose inside, when you remove them to check spark, lay them sideways, they connect.
also, try other coils, sometimes coils will show spark but when you demand running spark they they wont put out.
 
I agree it could be a coil. My dad and I worked on a yamaha triple for a friend one time, same thing, 1 cylinder no spark. We tried everything before finally borrowing a coil, and that got spark back in all three. The old coil just wouldn't work under any load situation....
 
try a swap ..just put one of the other plug wire caps on that cylinder to see if it fires...simply switch plug wires! if it fires on that cylinder then ,the coil is probably bad
 
Listen guys' I knew i would get a quick answer to my problem, but i forgot to mention these things,the fellow said the motor worked fine till he blew a belt so I got to looking at it and I truly know that a blown belt can send fibre around the crank and take out a seal, popped the clutch off and not a thing around the crank,o.k., checked everything we can think of swapped coils, checked the reeds, swapped them with the other,disconnected TORS switch anything i could think of nothing would change this cyl. from not firing. When I went through the carbs. everything was clean and settings o.k. set everything possible to spec.something is crazy here,compression was like this ;4 pulls every cyl. read 60-90-118 to 120 max.So what the H can make this one cyl. not burn the fuel or I should say run?
 
well then it must be flooded out . float must be sticking or a needle stuck somthin that has to do with the carb. cause if its gettin spark and gas its gonna fire! but if its gettin too much gas ,,,well then its not. you missed somthing
 
1.)do the plug wire swap
2.) pull the reed block assembly in that cylinder and inspect.
3.) look in the cylinder and see if the piston still has a skirt left on the piston, you can use a mirror and look up inside.

If all this stuff is good then you likely have a bad leaking needle and seat in the carbs, just simply flooding it out and washing out the spark or puddling it in the case.
 
Got 'er figured boys'!

;)! Well here we go,did everything possible as anybody would to look for the obviuos why that PTO cyl. would not fire.Well I ohmed the coils, wires caps all checked out o.k.So I sat down and had 2 beer and thought what the ####,went to my sled took off the cdi off it and put 'er on the 700.Guess what all 3 cyls. fired! so I geuss my buds cdi box is toasted.His boy said that he was checking spark the other day and pulled the caps off while the motor was running! I've heard lots of times that this is a NO-NO.So this was a costly mistake on his behalf.Now looking for one anybody have one fora1997 MM 700?
 
bluemonster1 said:
ask viperking,he may have one for you..
Click to expand...
Good eve Bluemonster.I'll give him a shout thanks.Hows the south? Man, did some deer hunting in the early part of Dec. in Sask.(home),lots of snow.Only put on about 30 miles so far,not good have to retire I guess who needs to work lets just play!!!! Talk again...
 
KAPUSTA said:
;)! Well here we go,did everything possible as anybody would to look for the obviuos why that PTO cyl. would not fire.Well I ohmed the coils, wires caps all checked out o.k.So I sat down and had 2 beer and thought what the ####,went to my sled took off the cdi off it and put 'er on the 700.Guess what all 3 cyls. fired! so I geuss my buds cdi box is toasted.His boy said that he was checking spark the other day and pulled the caps off while the motor was running! I've heard lots of times that this is a NO-NO.So this was a costly mistake on his behalf.Now looking for one anybody have one fora1997 MM 700?
Click to expand...


Kinda like using an impact to remove a clutch. You could do it a hundered times without any problem, until... and it always happens to someone else, until...

I'd guess that secondary voltage is at least 15-20KV and if you pull the plug wire from it's ground path, that 20 thousand volts will find another path which is usually through the coil primary... and in you case back to the CDI.

This lesson has been lost on many techs since distributors have become a thing of the past, but was common knowledge since magnitos/exciters and until the late '70s. Carbon tracking inside the cap, at the rotor and coil tower used to be a common occurance on vehicles that were not well maintained. The longer you went without plug and wire changes the higher the resistance would become thus the high voltage from the secondary wires would find the path of least resistance.

Bottom line, if you're going to play with plug wires looking for spark, make sure the high tension lead (plug wire) is grounded somewhere before spinning the engine.
 
Just a shot in the dark here but I just ran into the same problem with a friend’s Indy 500. I checked everything you did, carb, spark, compression etc. All was good. Then I took off the exhaust manifold and took a peek inside the exhaust port only to find a damaged piston. Check out the pic. Who would have thunk it. The sled only has 1500 miles on it too.
 

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