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Discussion Starter #1
Hi all this is my first post here I just recently purchased a 98 xc 700 the only mods are vforce reeds and cages and boost bottle. I took it for a ride over the weekend and it drives fine but after a ride the as it gets hot the idle will start to dropfrom 1700 to 1000 and after a while if turned off when I try to restart it I have to give it gas to start it. I took it across the lake and gotit up to 95 mph and on the ruturn trip it at around 90 it started to dye out and fall on its face almost felt like partial seize. After letting it cool down for a hour it runs fine and the idle is back to where its supposed to be and runs fine I havent tried going over 70 again . Could this be the oil injection not working at high speed causing lean condition ??? the plugs are brown . any help is greatly appreciated
 

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Sounds like you have a cooling problem, whether that's the only problem or not I don't know yet. Probably not oil injection...could be tested by running a tank of light pre-mix tho. That's about all for now...if no one else has experience with this I'll break out the books and see what I can find...
 

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Discussion Starter #3
Thanks for the quick response the heat exchangers are under the running boards I believe if should I check them to make sure they are heating up to temp I was told to put front end in air and let idle for ten mins to warm up and feel the exchangers to see if they heat up . Should I bled the radiator if so any Idea how on the polaris thanks
 

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sounds like you are intermittantly losing a plug. Install new plugs and check from the plugs back. then carefully try again.
 

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Discussion Starter #5
plugs are fine changed them and they are brown . Like I said it feels like it partialy seized it fell on its face and trys to die out. then it will have a hard time idling and I have to give it gas just to start it after it cools down for a hour I can start it no problem without giving it any gas and it will run fine it runs good through the trails no hesitation and it will go fine as long as I dont try to go across the lake at 90mph when I do that it will die out
 

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Well there is a mechanical type sieze(bearings ect.) a lean sieze from not enough fuel which always colours the plugs white or with aluminum dust. Or a cold sieze where the piston expands quicker than the cylinder. You dont seem to fall into any of these catagories. so I guess you will have to wait for some other people to respond. because with the information supplied it doesnt make sense to me. I suppose it could be a cooling problem but I thought that would be evident very soon after starting not just at high speed.
 

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Discussion Starter #7
One more thing the fuel filter in not full it only has a quarter or less even when I give it gas not sure if maybe when I am holding it wide open there isnt eneogh fuel going through
 

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I was just going to mention checking the fuel filter. They are never full, I would change it anyway. There is also a screen type filter in the tank. Make sure the fuel petcock isn't partially closed. I definately think you are running out of fuel when this happens.
 

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I had a similar problem and it turned out that the plug cap on the end of my ignition wires were lose due to vibration. Just turn them and they tighten back up.
 

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Discussion Starter #11
I just changed the plug end caps last week . I am going to cut the wires back and put them back on just to be safe . I checked the fuel filter up top and that is letting gas through fine but I started it with fuel line off and no gas came squrting out like I thought it would seems strange .I am going to check the fuel pump tommorrow .I am just going by my jet ski and it is supposed to pump like a half gallon a minute so why wasnt this one pumping anything I put the line back on and it filled back up again and it starts right up and runs great but still need will do same thing when i take it across the lake . I checked hte compression it is 150 in both cylinders thanks for the all the help and any more idea's are appreciated
 

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If your motor was actually seizing the compression would be much lower from the "meltdown" it would have caused. This is a good sign. It must be a fuel or spark problem.
 

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Discussion Starter #13
I am thinking it is the fuel pump or the oil pump that is cusing it to die out but, why if it is fuel pump does the idle drop until it cools down My buddy's new pro x is so much more responsive from the start he has the ves and I dont but dam its a big difference mine Is like a dirt bike I wait till the power band kicks in. The pro x kicks ass what a nice sled
 

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remember anything to do with not enough fuel should definately show up as light, white or frosted plugs. Thats why Im stumped.
 

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Discussion Starter #15
Nope the plugs are almost perfect but if the lean condition only occurs at WOT held then It would not show up on plugs the plugs allready got there color from the ride I will try a plug chop next time across the lake . The idle dropping is what stumps me
 

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Discussion Starter #16
I am thinking maybe the plugs are fine because the lean condition may not occur until WOT across the lake so the plugs would not show it. I am going to do a WOT test across the lake with new pugs to see if I can get some true results
 

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I would suggest if you are pretty sure its leaning out at WOT that you throw some bigger mains in there first. You usually dont get two chances on a WOT lean out. Usually the front of the piston is melted. Unfortunately talking from experience.
 

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Discussion Starter #18
Yes but putting bigger jets would not stop the sled from leaning out if it is not getting gas the same thing will still happen by putting bigger main jets in .This is the second time the second time the sled has done htis too :) this will be my third chance
 

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The RPM drops with the sudden slow down right? If not it could be something in the drive train slipping because of heat.
 

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Discussion Starter #20
The rpms drop and the engine wants to die out if I stop after and shut it down I can restart but, I need to crack throttle open to start it until it cools down
 
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