Looking at a set of spi axys pistons. They are 22 g lighter then stock and have the oil groves on intake and exhaust. Interesting.
Spi Axys pistons
- Thread starter raleigh111
- Start date
Another pic. So Fay they are within .001 of factory piston from top to bottom. I will get better measurements this weekend,
3100 miles on stock cylinders and pistons, cross hatch almost gone. Poor man way to get close to indy dans finish, ride it for 3000 miles and let the rings smooth out that nik. nik looks good. crank rods look okay not a lot of wobble.
Took measurements today on spi piston vs axys piston in 3 different spots bottom middle top above rings. Remember the axys piston i am using has 3100 miles on it and could account for the .001 to .003 I am seeing. Also not sure how thick the coating is on the spi piston.
bottom of stock axys piston measured 3.3385
bottom of new spi piston measured 3.3395 .001 bigger
Middle of stock axys piston measured 3.3355
middle of new spi piston measured 3.337 .0015 bigger
Top of axys piston measured above rings 3.312
Top of new spi piston measured above rings 3.315 .003 bigger
The spi piston is .001 to .003 bigger then the used axys piston.. How much of this is the wear of 3100 miles and the coating on the new spi piston. Seems to me they have the taper dialed in to be very close if not spot on to stock up to bottom of rings.
I would not hesitate to use these pistons and the are 22g lighter.
bottom of stock axys piston measured 3.3385
bottom of new spi piston measured 3.3395 .001 bigger
Middle of stock axys piston measured 3.3355
middle of new spi piston measured 3.337 .0015 bigger
Top of axys piston measured above rings 3.312
Top of new spi piston measured above rings 3.315 .003 bigger
The spi piston is .001 to .003 bigger then the used axys piston.. How much of this is the wear of 3100 miles and the coating on the new spi piston. Seems to me they have the taper dialed in to be very close if not spot on to stock up to bottom of rings.
I would not hesitate to use these pistons and the are 22g lighter.
another interesting find.. Axys wrist pins are tapered at the end and come in around 102 g where the spi wrist pins do not have as much taper and came in the 108 range,
Please keep us posted on these if you continue to be a fan or not.
I ended up using the axys Wrist pins (102 gram) and the spi pistons. Got the pistons down to 410 grams. Coming in 27 grams lighter than stock on each hole. Ran several heat cycles and will do a leakdown test soon. Have not checked compression yet.
Is the general consensus that the Spi hyperdrive or Tmoly pistons are a good reliable alternative to factory pistons?
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in my opinion..........
I don’t think there is a general consensus on any piston selection.
Based on the sheer numbers of oem pistons being used out there????
all my research has pointed to the oem 2015 pro rmk pistons being the best choice.......
We have been selling the SPI kits very reasonably for years. I have no compliants. SPI now is called SP1. But still same product.
https://www.gobigparts.com/Snowmobile-Products/Engine/FIX-IT-KITS-PISTONS/
SP1 is a snow specific lineup of replacement parts, accessories, and after-market tools for snowmobiles and the emerging snow bike industry with reimagined packaging.
https://www.gobigparts.com/Snowmobile-Products/Engine/FIX-IT-KITS-PISTONS/
SP1 is a snow specific lineup of replacement parts, accessories, and after-market tools for snowmobiles and the emerging snow bike industry with reimagined packaging.
OEM 2015 piston better than the last polaris OEM piston?
I'm just looking at different options. Iv used RKtek on my previous sled at around 550$ Cdn shipped plus bearing and gaskets. OEM is 300$ cdn per piston plus bearings/gasket.
I have nothing against wiseco's but I personally wont buy them for a replacement.
These spi's seem to have good reviews/ best bang for your buck. I haven't read any failures with them on axys yet myself
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Boy truer words were never spoken. I think the OEM piston isn't too bad since '13 with the newer thicker skirts and better QC of clearances. Having said that, I have had great luck with Weisco's in the Fix Kit from MTNTK going back to the Dragons.
Last winter I had an engine brought to me with less than 150 miles and SPI's. It looked like the 2012 Scud missile, holes and pieces galore.
Rktech pistons are wiseco pistons.
yes the 2015 pro pistons have a better lock on the ring locator pin than the 16-18 Axys pistons. (Can tolerate more detonation abuse. )
(i’m not positive but I don’t think they have changed since 18+)
same dimensions.
I’ve seen more failures in the dragon, pro era sleds using Spi, wiseco, rk tek, pro-x pistons than with OEM.........
(And there’s a lot more sleds running oem......)
When did RK tech switch to weiseco
A few years ago. 
I was just hoping to hear some real world experience on these updated spi axys pistons.
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I will follow this up as the season goes on. I am leaving the pro out of this. Different engine, different era.
I had indy dan run bore gauge down both cylinders and everything checked within spec. Wish i had a new set of axys pistons to check alongside the spi but i did not. Honestly if we did not bring a backup sled on every trip I would not be trying these. This is obviously a new design with oil groves on both sides and 22 grams lighter then stock until you add the wrist back in which is heaver. ( i used axys lighter wrist pins) The big test is yet to come, we will see how much they grow with heat and if the skirts hold up. The one thing that concerns me is the weight being that much different stock spi to stock poo. Where did the 22 grams go? I could not visual see it.
Do you have any pictures? I thought mine looked pretty good with 3000 miles and was still pulling 120 compression. My pto side had some slight scuffing but i ingested a lot of snow last year with a torn intake screen and a leaky air box. Not the pistons fault.
