2018 compression when new?

banditpowdercoat · Jan 29, 2023

Just wondering what these came as new, broken in, for compression? I just got a good tester, finally tested mine 120mag 121pto 4500Km MTN riding. Wondering how much she dropped off? I know I should do top end. But what was the starting point? tested at 1200ft cold engine as well

gedakbx · Jan 29, 2023

Our 1500 mile one has 125 on each side cold this fall.

Tchetek · Jan 29, 2023

banditpowdercoat said:
Just wondering what these came as new, broken in, for compression? I just got a good tester, finally tested mine 120mag 121pto 4500Km MTN riding. Wondering how much she dropped off? I know I should do top end. But what was the starting point? tested at 1200ft cold engine as well

Probably been 120 since new. That’s pretty much spec on a good break in.

+SLEDWRECKS+ · Jan 29, 2023

Best bet is grab yourself a leakdown tester, that will tell the tale.
My 16 Axys (all Mtn riding) made 5,000 km (200 hrs) on OG topend, until PTO side leakdown dropped from 2% to 7%.
Impressed being a Polaris guy.

skid · Jan 30, 2023

Mine has over 5000km and 120 per side, at around a 1000km it was 125 per side. After this year I will rebuild.

ctd · Jan 30, 2023

If it starts, idles & goes in & out of reverse. All of this correctly as in no extra's pulls or cranking, no stalling going into reverse & back to forward compression is good.

Should you want to measure regardless if it passed the start idle test, the position of your RAVE's might influence your numbers. Best to have them full open as is the throttle blade or slide.

If you want to be very fussy do a cold & hot test. Pay attention to pressure on the gauge after first or second puff, then @ ten puffs. The numbers indicated after the first or second puff will suggest how a leak down test may go. If the motor is slow to build compression on the first or second puff the leak down test won't go well. Compare the hot/cold readings, if it's low when hot a freshen may bring it back to life.

The hot test showed bad ring seal back in the 800HO days when the rings flaked. The first or second puff test failed badly as the rings went away.

Trying to compare results with others is similar to comparing different dyno numbers. Many factors influence the results & some can not be controlled. Different elevations such as Edmonton to Malakwa, ES spins the motor faster than a manual crank. Many others.

Our little 2 stroke motor's go away slowly just like clutching. You don't really notice until you freshen it up, then it's OMG Ha!