MXZ670Rider

my 99 mxz 670H.o. is actin weird. when u first start her up she runs good put when u hit the gas and she revs up to about 4,000rpms it cuts out and dies till it hits about 1,500 then she picks back up. i wasnt sure if it was fuel or spark, so i got 2 spart testers and started it up n the spark cuts out. and this is 400miles after i put $1200 of electrical into it. and im thinkin about selling it but if i can figure this out ill keep it. soo please help me out

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'02 Arctic Cat ZR800 bored to a 1010cc Psi pipes, vforce reeds, clutched, works suspension.
'96 Arctic Cat Wild cat 700 efi
'77 Arctic Cat Pantera (reconditioning it)
'01 Yamaha blaster 200 with custom exhaust
'06 Arctic Cat 650 Twin
Wheel horse garden tractor w/ 10hp kohler. does 35mph ,2 seats, stereo, wheelies.
racing lawnmower 18hp kohler bored +.025 over, racing cams,egged head. 60mph

mmrosshere

I had simular to this happen to a co-riders sled (also a 99mxz). We were yanking our hair out in the shop till one of the kids yanked the teather and replaced it while it was running up with the same effects we were seeing. We cleaned and spread the contacts for it. It appears that the vibrations at upper rpms as the clutch was hitting shook the teather and made it lose contact momentarly. I hope your fix is as easy as that. Good luck.

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MXZ670Rider

but if that was the problem y would it only do it when its cold? cuz once it warms up its fine. i mean if u was the teather it would do it all the time. right?

__________________
It's a downright joy for a country boy
when he hears them engines moan .



'02 Arctic Cat ZR800 bored to a 1010cc Psi pipes, vforce reeds, clutched, works suspension.
'96 Arctic Cat Wild cat 700 efi
'77 Arctic Cat Pantera (reconditioning it)
'01 Yamaha blaster 200 with custom exhaust
'06 Arctic Cat 650 Twin
Wheel horse garden tractor w/ 10hp kohler. does 35mph ,2 seats, stereo, wheelies.
racing lawnmower 18hp kohler bored +.025 over, racing cams,egged head. 60mph

BRPforlife

I had the same problem. The needle valves were sticking shut.

Start by giving your carbs a good cleaning, and check the needle valves while you're in there.

MXZ670Rider

i did notice that the one exhaust valve is missing a spring. dont know if this would have an effect, and i have no clue how it got outta there. but if u are sittiin on the sled it is the left one.

__________________
It's a downright joy for a country boy
when he hears them engines moan .



'02 Arctic Cat ZR800 bored to a 1010cc Psi pipes, vforce reeds, clutched, works suspension.
'96 Arctic Cat Wild cat 700 efi
'77 Arctic Cat Pantera (reconditioning it)
'01 Yamaha blaster 200 with custom exhaust
'06 Arctic Cat 650 Twin
Wheel horse garden tractor w/ 10hp kohler. does 35mph ,2 seats, stereo, wheelies.
racing lawnmower 18hp kohler bored +.025 over, racing cams,egged head. 60mph

smallengineguy

That will not affect the spark cutting out, but you NEED to replace the spring or it won't run well at high RPM's.

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1992 Ski Doo Mach 1 (SC-10/2 suspended) March '07 SF.com Sled of the Month!
1993 Ski Doo Mach Z 780 triple
2001 Ski Doo Mini Z



Evergreen Valley Snowmobile Club Webmaster

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MXZ670Rider

why would this have an effect on the spark? not saying you wrong im just asking.

__________________
It's a downright joy for a country boy
when he hears them engines moan .



'02 Arctic Cat ZR800 bored to a 1010cc Psi pipes, vforce reeds, clutched, works suspension.
'96 Arctic Cat Wild cat 700 efi
'77 Arctic Cat Pantera (reconditioning it)
'01 Yamaha blaster 200 with custom exhaust
'06 Arctic Cat 650 Twin
Wheel horse garden tractor w/ 10hp kohler. does 35mph ,2 seats, stereo, wheelies.
racing lawnmower 18hp kohler bored +.025 over, racing cams,egged head. 60mph

BRPforlife

Sorry, I didn't see that you already tested the spark.

Exactly what did you do to the electrical?

MXZ670Rider

the plastic wrapping that goes around the copper wire below the magnetson the stator, a piece of that plastic came off and chewed up the magnets. so the stator went and when that went is shorted out the cdi box and the coil. soo i had to replace all that. but what i dont get is after all that is still cuts out like that.soooo

__________________
It's a downright joy for a country boy
when he hears them engines moan .



'02 Arctic Cat ZR800 bored to a 1010cc Psi pipes, vforce reeds, clutched, works suspension.
'96 Arctic Cat Wild cat 700 efi
'77 Arctic Cat Pantera (reconditioning it)
'01 Yamaha blaster 200 with custom exhaust
'06 Arctic Cat 650 Twin
Wheel horse garden tractor w/ 10hp kohler. does 35mph ,2 seats, stereo, wheelies.
racing lawnmower 18hp kohler bored +.025 over, racing cams,egged head. 60mph

smallengineguy

Pick up coil?

__________________
1992 Ski Doo Mach 1 (SC-10/2 suspended) March '07 SF.com Sled of the Month!
1993 Ski Doo Mach Z 780 triple
2001 Ski Doo Mini Z



Evergreen Valley Snowmobile Club Webmaster

If I'm not home, CHECK THE TRAILS!

MXZ670Rider

where and what is that? lol

__________________
It's a downright joy for a country boy
when he hears them engines moan .



'02 Arctic Cat ZR800 bored to a 1010cc Psi pipes, vforce reeds, clutched, works suspension.
'96 Arctic Cat Wild cat 700 efi
'77 Arctic Cat Pantera (reconditioning it)
'01 Yamaha blaster 200 with custom exhaust
'06 Arctic Cat 650 Twin
Wheel horse garden tractor w/ 10hp kohler. does 35mph ,2 seats, stereo, wheelies.
racing lawnmower 18hp kohler bored +.025 over, racing cams,egged head. 60mph

smallengineguy

Under the flywheel, mounted near the stator.

__________________
1992 Ski Doo Mach 1 (SC-10/2 suspended) March '07 SF.com Sled of the Month!
1993 Ski Doo Mach Z 780 triple
2001 Ski Doo Mini Z



Evergreen Valley Snowmobile Club Webmaster

If I'm not home, CHECK THE TRAILS!

Sled Ed

I was doing a search and found this post with the same problem that I'm having with my sled. I need some help in figuring it out. MXZ670Rider If you figured out what the problem was could you post what you did to fix the problem, and by the way my sled is the same as yours MXZ670Rider, a 99 MXZ 670, maybe it's something that happens to alot of these sleds.

Thanks a bunch

Sled Ed

After some seaching on the net I found that the problem is with the spark plug boots, they were defective, so I changed the spark plug boots and the sled runs like new!! 12 dollar fix sswweett!!!

Deano

Snakeman

Too many people bypass the easy stuff when diagnosing a miss.Plug caps are cheap and could be replaced every year as part of the tune-up.OR you could at least check the resistance with a multi-meter.Should be between 5&6 Kohms.It will still run when they are out of spec and run pretty normal,but you will foul more plugs.