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Won't start!!!????

4
Jan 3, 2010
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i got a 2004 summit 800 with a rebuilt bottom and top end early this season.
Here is the problem....
The sled was riding great all day and when i was coming down the trail at the end of the day the sled just died. It felt like it ran out of gas. Then i tried starting the sled for about 20 minutes of pulling and no luck. Let the sled sit for a bit then put full choke and it started but sounded like it was on 1 cylinder. I had to keep a constant 1/4 throttle to keep it alive (sounding like it was on 1 cylinder) then all of a sudden started running great. Then about another 200 feet down the road it started to die again but kept it alive by holding 1/4 throttle. This continued down the trail until it died and pulled for 20 minutes to get it going again. Forgot to mention when i pulled the plugs they were soaked with oil or gas not sure but there was oil all the way up the threads of the spark plug (not sure if that is normal)

The history.
about 250 miles on the motor. The first break in day the sled died similiar to above but all i did was change the pto side spark plug and it ran great all day. The second day the sled wouldn't start when i brought it down the the truck and about to put it on the trailer. Bassically every ride i have had the sled has died within 4 miles of the truck but i have always been able to start it up again without to much grief until yesterday.

things that might be the problem but i am not sure and that is why i am posting this because i am kind of a newbie.

When i take the gas cap off there is a lot of pressure could this cause the fuel no to go to the carbs? maybe i am not getting enough fuel?

I am burning a lot of oil but my oil pump is adjusted perfectly. I am running at like 10 to 1, could this be causing my plugs to foul and cause it to be hard to start?

if you guys have any questions to help better solve my problem let me know.

Thanks in advance
 
F

FNG

Active member
Nov 19, 2008
216
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I'm sure someone with more knowledge than I have will chime in soon here but if you are fowling plugs then your air/fuel mix just ain't right, see here ( http://www.dansmc.com/spark_plugs/spark_plugs_catalog.html ) for a link on how to read your plugs. A few questions to help us help you...

Who did the rebuild, you or somebody else (indicates at least familiarity with your engine not necessarily a better or more thorough job BTW)? If a dealer did the work they should be getting the sled back to you set up very close to correctly for your riding area.

What elevation and conditions do you ride in?.

Do you happen to know what jetting is in your carbs (Main Jets [MJ] and Primary or Pilot jet [PJ]) ?

Are there any other things done to your sled during the rebuild, ie. new reeds or modifications to the air intake system, after market heads or piston kit, exhaust and/or can?

Having a good starting point for this information helps allot in figuring out what is wrong with your set up and which way to suggest improvements, keeping a log of this information is very helpful information to have about your snowmobile.
 
Last edited:
W
Nov 27, 2007
405
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Sounds like ya might have a few things going on here. If your oil consumption is 10:1 you're gona foul plugs.It could be your pump arm is not returning to the idle position.
If your gas tank is not venting your sled will "just die". Check your tank vent line and check valve. Get your oil mix close to 40:1, then check your plugs and piston wash. Aint this fun?:beer;:D
 
S
Nov 27, 2007
419
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Whistler, BC
the sled has a mbrp can and boyseen reeds either than that stock (motor was put together with spi pistons). I am fairly sure that it isn't a motor related problem. I have narrowed it down to... oil pump, the gas tank, spark plugs, and possibly the startor.

I ride in whistler bc so... i start the day at 1500 feet and ride the day in the mountains at around 5000-10,000 feet.

The sled ran great last year until the ring broke when i caught on the exhaust port. I haven't done any mods since then either except new engine.

I did all the work to it.


At first i was confident that it was the gas tank not venting properly because when i unscrewed the cap there was a lot of pressure. But after unscrewing the lid shouldn't it get enough fuel to start right away? after 2 minutes of pulling it will finally start.

I don't no my jetting cause i haven't opened the carb up before. What do you guys suggest as far as jetting. I am thinking about replacing all the jets just to make sure that everything is good there.
 
S
Nov 27, 2007
419
29
28
Whistler, BC
well from the from that spark diagram it looks as though i am oil fouled so i guess that kinda solves that problem. I will work on the sled next week and let you know how it goes. I will also fix that gas tank problem as well cause that could also be a contributing factor.

Thanks a lot for the quick responses
 
F

FNG

Active member
Nov 19, 2008
216
25
28
64
Pull your carbs, find your starting point, may be a good idea to talk to your local dealer (the actual Doo mechanic for the shop if you can) and ask what jetting they suggest for your area, (you can't be the only guy around with your year and model of sled) and pick up a set of those main jets and start from there. It's probably easier to find out what those jets may be and pick them up before you even start as they are cheap, pull the old ones and pop in the new ones while you have everything on the bench and remember to not loose that little brass washer that the main jet sits on.

Also, if your tank is pressurized then you have force (pressure) helping get the fuel at least as far as the fuel pump, still check you vents, but a vacuum would probably be more of a fuel starved problem. There may still be some problems with fuel supply but I'm betting on oil pump settings and possibly carb jetting.

With so much varying in altitude you are probably going to have to optimize jetting for one or the other as 9000 ft of elevation change in a day and being spot on for jetting for the whole ride is quite allot to ask out of a set of jets.

Best of luck and get back to us with the solution.
 
Last edited:
S
Nov 27, 2007
419
29
28
Whistler, BC
K so i adjusted the oil pump, which by the way was way out of adjustment. I checked the carbs and the jets are clean and the proper ones. I tried to start the sled with no luck so i pulled off the head and everything looked good except on top of the pistons there was a bunch of black powder on top (kind of like sand) i dont no what this stuff is maybe burnt oil or something. I have spark and the plugs had unburnt fuel on them????? I am so confused on why this thing wont start, any ideas????
 
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