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Discussion Starter · #1 ·
I just purchase a 1998 ski doo summit x 670 with 2800 miles. I've been riding old sleds for a long time lol. I just rebuilt a 80 kawi invader ltd, but i'm in the mountains now. My questions are:1 This sled has been sitting for about 1.5 years.(no snow) What should i check. It started up in a couple pulls. the gas had been shut off. It seemed to run good on the trailer. I let it warm up then hit the primer to make it idle down and it idled slightly rough at 1500 rpms(a friend said this would show if the crank seals were good,or leaking air). Plugs look nice tan. I haven't drove it yet but I will drain the nearly 2 yearold gas out and replace plugs and change chain case oil. WHAT else do i need to check.I just don't want to mess it up. How about all the electrical STUFF. Does it have a quick check computer hookup thing. Sorry I hate electronics. I may pull the carbs.
2. What does the "x" mean. I know some pipes won't work with it. Is it higher compression. I've heard it has an altitude adjustment for the carb. what is the hp specs for the x.
3 Does the 670 use reeds. The only reason i ask is it almost looks like a rotary valve, and its not listed in the reeds in dennis kirk, but i thought they quit using those in the seventies . I love forums. Thanks.

OYEAH how long do reeds in snowmobiles last. In my KDX and CR they would chip or flake.
 

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treukauf said:
I just purchase a 1998 ski doo summit x 670 with 2800 miles. I've been riding old sleds for a long time lol. I just rebuilt a 80 kawi invader ltd, but i'm in the mountains now. My questions are:1 This sled has been sitting for about 1.5 years.(no snow) What should i check. It started up in a couple pulls. the gas had been shut off. It seemed to run good on the trailer. I let it warm up then hit the primer to make it idle down and it idled slightly rough at 1500 rpms(a friend said this would show if the crank seals were good,or leaking air). Plugs look nice tan. I haven't drove it yet but I will drain the nearly 2 yearold gas out and replace plugs and change chain case oil. WHAT else do i need to check.I just don't want to mess it up. How about all the electrical STUFF. Does it have a quick check computer hookup thing. Sorry I hate electronics. I may pull the carbs.
2. What does the "x" mean. I know some pipes won't work with it. Is it higher compression. I've heard it has an altitude adjustment for the carb. what is the hp specs for the x.
3 Does the 670 use reeds. The only reason i ask is it almost looks like a rotary valve, and its not listed in the reeds in dennis kirk, but i thought they quit using those in the seventies . I love forums. Thanks.

OYEAH how long do reeds in snowmobiles last. In my KDX and CR they would chip or flake.
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Check the chaincase. You will probably want to drain it and put new fluid in. Don't worry about the electronics and no there is no computer hookup. The X is
like a race model of the summit. Don't change the exhaust because its the best
setup you can get for that sled. The x model has 125hp. The 670 does not use reeds and yes that is a rotary valve on the back side.
 

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Discussion Starter · #4 ·
I am going to pull the carbs and clean them. I got the specs from the dealer. Mains 260,240. Power jet, 60,60. and on the third notch. Can anyone confirm this. I am currently at 4500 ft but i will ride west yellowstone which is up to 7 or 8k, and back home at 2500. O yeah is there any complicated hookups on the carbs for the dpm alt. adjust stuff. I talked to the dealer today and he just asked if it smoked on start up.
 

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Are you sure you've got a '98 and not a '99? I didn't know they made an 'X' in '98. Either way, I checked my shop manual for the '98's and they say 380/370 for the main jets, no mention of any power jets, so I think you might have an add-on there, but from what I know of them, I think you got about the right set-up. If you have got a '98, you won't have DPM, you'll have HAC, which is a simple non-computerized version of the DPM. If your sled has the DPM, then my guess is that you've either got a '99, or a late season '98 (anyone know if they did that in '98?) The only problem I can see with your running it at 2500 is that if it is a high compression model (many mountain sleds are) you'll have to run good high octane fuel in it in order to prevent detonation at lower altitudes. Good Luck!
 

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Discussion Starter · #6 ·
It is a 98 its blue. its a summit x and it says dpm on the hood of it. I have heard that the x were a 98.5 model. the dealership looked up the specs for the sled. I think it has 44mm mikuni carbs. one guy said ski doo put the 99 motor in the 98 and that was the x. are you sure it wasn't 270 instead of 300's the dealer ship looked it all up.
 

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Be very specific with what you do to your motor with the Summit X I have a 670HO the exact same motor and they are hard to find parts for. Don't bother piping or putting a can on it you won't get a thing out of it with the X motor. They are fun sleds you will shock a lot of 700-800s out there
 

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The 670 X/HO motor was in production for two seasons.
98 and 99 Summit X 670 and the 99 MXZ 670HO.

The differences between these and the std 670 are:

- flat top pistons
- new head design
- different pipe, y-pipe and silencer
- 44 mm roundslides
- DPM
- DESS
- case porting
- ignition
- rv timing
- etc

The std 670 makes 116-117 HP at 7700-7800 RPM
The 670x/HO makes 124-127 HP at 7900- 8000 RPM
Amsnow rated it at 129 HP ???

The differences between the X and HO are minor:

- different engine mount plate, Mxz motor is lower and tilted
- different y-pipe to accomadate for tilt
- Summitx has more compression for altitude
- different ign timing curve, MXZ has more advance at high RPM
- Different carb specs
- Summit X had short carb boots, MXZ did not
- of course different clutching.

The 98x is a fantastic machine. The seats on the 98 and 99 Summitx are
extremely light. I understand Doo had patent problems and these seats
are as light as they ever produced. The blue looks great on the snow.

Enjoy!!
 

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The 670 X/HO motor was in production for two seasons.
98 and 99 Summit X 670 and the 99 MXZ 670HO.

The differences between these and the std 670 are:

  • flat top pistons
  • new head design
  • different pipe, y-pipe and silencer
  • 44 mm roundslides
  • DPM
  • DESS
  • case porting
  • ignition
  • rv timing
  • etc

The std 670 makes 116-117 HP at 7700-7800 RPM
The 670x/HO makes 124-127 HP at 7900- 8000 RPM
Amsnow rated it at 129 HP ???

The differences between the X and HO are minor:

  • different engine mount plate, Mxz motor is lower and tilted
  • different y-pipe to accomadate for tilt
  • Summitx has more compression for altitude
  • different ign timing curve, MXZ has more advance at high RPM
  • Different carb specs
  • Summit X had short carb boots, MXZ did not
  • of course different clutching.

The 98x is a fantastic machine. The seats on the 98 and 99 Summitx are
extremely light. I understand Doo had patent problems and these seats
are as light as they ever produced. The blue looks great on the snow.

Enjoy!!
Does it take the sled and the key to program a backup DESS key for a 1999 SKI DOO SUMMIT X 670?
 
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