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December 2012 Ask the Experts

Belts, Rings, Chains ... Mr. T would be proud!

Incorrect settings for the oil pump, and/or misguided replacement of oil lines, could be hampering the injection oil efficiency of your 2-stroke.
Went From Semi- to Full Synthetic

Q Why is my 2007 Ski-Doo Summit 600 H.O. SDI harder on oil since I changed from synthetic blend to a full synthetic oil? I did have the engine out, but lined up the marks on the oil injection pump. – Keith Murphy

A There are several reasons why this might be happening. The oil setting could have been easily on the leaner side before removal, and you re-set to the correct setting when you put it back in. Also, it is possible that when re-installing the oil line a slight bend may have been made in the line, causing the oil pump to pull further than the factory setting, thus adding more oil. I would check these areas first. – Jason Houle, Straightline Performance
Check yo chain foo! Every year, whether you think it needs it or not, change your chaincase oil and inspect the chain and sprocket.
Drive Chain Replacement

Q I have a 2010 Ski-Doo Renegade 1200 4-stroke. How often should the drive chain be placed?– John Jones

A Typically drive chains should be inspected for possible replacement on a yearly basis. Chain tension should be checked even more often. When inspecting your chain for changing or replacing there are several things you should look for. 1.) The chain after removal has hard areas that do not bend easily. 2.) There are wear marks in the chain due to the sprockets. 3.) The chain has blue/overheat marks from excessive heat.  – Jason Houle, Straightline Performance
RING FAILURE is not fun, and checking compression every year is a good habit.
E-TEC Ring Failure

Q I have two friends that have Ski-Doo 600 E-TECs and both have had ring failure at 6,800 miles and one at 4,400 miles. I rode for a bit with the guy that had his go at 6,800 miles and I have a 2008 SDI with 8,800 miles on it; we filled up at the same gas stations. I tore my sled down and it had small pitting on the PTO side on the back top of the piston that was maybe ½-inch wide. His had it all the way around on both cylinders with one that failed. I think the direct-injection on the top caused the damage, but mine was able to mix in the ports before ignition. Am I right? – Gary Jensen

A Ignition and compression are completely different on your machine and your buddy’s. The direct-injection did not cause the damage. After trying to understand your entire scenario, it would seem that your engine had more “leak down” due to the mileage, thus having a slightly reduced HP, due to compression. This would have caused your machine to have less damage than a much tighter engine. – Jason Houle, Straightline Performance
Reasoning on an old RMK

Q I have a 2003 Polaris 800 RMK with porting, polishing, reeds, an SLP pipe, NOS and clutching. When I jump or ride deep powder it starts blubbering. I can get it to stop most times by hitting the NOS. I rebuilt the carbs and did a temp sensor and just really trued my crank and put in a fresh top-end and it still does it! I built a box for around the exhaust so it can’t plug with snow and the 40mm flat slide rack carbs are bored. I also checked the TPS and it was in spec. Any suggestions? – Cory Rahnasto

A The most common cause for this would be the seal between the silencer outlet and the bellypan. We recommend running a bead of ultra-black high temperature silicone around the end of the silencer outlet prior to slipping it into place. Where this one is already installed, I would turn the sled up on its side and seal it from the bottom side. The reason this is an issue is that when you dive into deep powder, the snow will cover or partially cover the exhaust outlet. Raw exhaust will then follow the edge of the silencer back up into the under-hood area if there is not a good seal on the outlet. This exhaust will then be sucked back into the engine through the drain holes or other gaps in the air box making the sled run rich (there is little oxygen in exhaust air). If the sled is set up on the rich side on jetting, the problem will be even more pronounced. I would recommend you check the piston wash and jet it so it has about 1/8- to ¼-inch of piston wash extending from the edge toward the center of the piston at the intake transfer ports. Also, if you have a partially fouled plug, a bad cap or sparkplug wires, these would aggravate the problem. Finally, I would be interested to see what kind of box you built around the exhaust outlet. The stock snow deflector on his sled did a fine job of keeping it from plugging in powdery snow conditions. Feel free to give me a call or send me a picture of the box and the exhaust outlet. - Jerry Mathews, Starting Line Products
Belt failure is most often due to a mis-alignment of the clutches. Shim kits are a good answer for many recent Ski-Doo sleds.
Blowing Belts

Q I have a 2009 Ski-Doo Renegade 800 that blows belts every 500 - 800 miles. I am doing mild to slightly aggressive trail riding. I have heard many opinions on what to do, but before throwing money at it I would like to know for sure. –Derek Veale

A There have been typical belt issues with the Ski-Doo XPs since 2008. Most belt issues have been caused by the mis-alignment of the clutches, or chassis flex. Currently the best option for alignment is to buy a shim kit. That allows the jackshaft to be moved into alignment with the primary clutch. The chassis flex can be handled by installing a chassis brace that supports the QRS tower from moving around under aggressive riding. The combination of both produces a more straight, true, and solid CVT system. The shim kits and chassis braces are available from any Straightline dealer. – Jason Houle, Straightline Performance
Editor’s Note:
Each issue we take questions from our “Ask The Experts” forum at, to feature in the magazine. Our industry experts consist of staff from Straightline Performance, Speedwerx, Starting Line Products, Dyna-Tek Racing, Aaen Performance, Hauck Powersports, our editorial staff and other industry pros. If you have a question you can’t get answered anywhere else, try our Ask The Experts forum and we’ll get you started down the right path.
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