Hello Theth-Air. You may have already checked through these things, but I thought I might post them for your convenience or anyone else that has had similar issues. There are a few things that we ran into within the first few hundred miles with our 850s. I recommend checking each of them on your sled if you have not already done so. While going through the break-in mode with the extra fuel and oil used during this phase, it is very common to have partially fouled plugs by the time you reach the end of break-in (this is a very simple, but commonly overlooked performance point). Check plugs first and replace as needed. Plugs are cheap, so you may want to just replace them (they are NGK BPR9ES). Make sure if you are running non-ethanol fuel, that you are running in the non-ethanol mode, it is the leaner mapping of the 2 settings. What kind of RPM are you running? You should be between 8150 and 8300 at wide open throttle on the 850 for the best performance and snappiest feel from this engine. It has also been common for these sleds to have belt deflection that is loose straight out of the box. Loose belt deflection will make it feel pretty sluggish on the bottom end. We have seen where belt deflection has to be adjusted several times as the belt breaks in. We like to run our belt deflection tight enough that the track will turn just a tiny bit at idle when on a jackstand (this usually ends up being about 1.25" of deflection). If it is squealing at an idle, you are close, but a bit too tight. Loosen it just a hair and you'll be set. Our 850s have been excellent performers with our silencer and clutching installed once we got them through their break in mode, but we have addressed each of these points on our sleds.
Please call us if you have any questions.
Adam Wood
Sales Manager, SLP
208.529.0244
adam@slp.cc