High compression issues

Doo_girl

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2007 Summit X 800, started smoking like it was on fire, compression in one cylinder is 120 the other cylinder tops out at 240, any ideas would be appreciated. TIA
 

Lund

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2007 Summit X 800, started smoking like it was on fire, compression in one cylinder is 120 the other cylinder tops out at 240, any ideas would be appreciated. TIA

Its pumping oil in that cylinder, bet ya the base is full of oil. I would check the oil pump case seal inside the crank case. But first confirm the base is over oiled. There is alway oil in the base, that is normal. What your looking for is the amount compared to the other side, you will probably find that there is too much oil.
 
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Lund

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Thanks for your input, it is full of oil

Ok, going with the info you gave this is what happen. Again without seeing it, this is the internet.

What has happen is the cylinder at fault is pulling in oil from the oil/water pump drive shaft cavity. The crank shaft will have seals to isolate each cylinders, the seal on the fault cylinder closest to the oil/water pump drive has failed thus on the piston up stroke the cylinder vacuum will pull the extra excessive oil in. Here is a picture of your crank. #26 is the seal giving you trouble, #12 is the gear that drives your oil pump and water pump, it is lubed by the oil pump also but isolated by the #26 oil seals from the cylinders.
convert


The repair is simple but expensive, your going to have to replace the crank. Seal replacement can be done but generally your better to replace the whole crank. Plus, you said it is an 07, so i suspect it has mileage on it, so the crank will be out of spec. almost guaranteed.

Hope that helps
 
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