998 engine rebuild

[KnappAttack]

I run a 28 inch snownflap. The longer flap helps with keeping more snow cooling the heat exchanger. Not saying its a cure all but it helps.

I riveted an extension on my flap to help with cooling for that very reason.

My photo bombing pup approves of the work too.

 

[1nc 2000]

I riveted an extension on my flap to help with cooling for that very reason.

My photo bombing pup approves of the work too.

View attachment 161363

28 inch snowflap.

 

[Turboflash]

Probably should have had at least one scratcher down.

 

[jonlafon1]

Tried the extension thing two years ago.. Ran it all year and it did nothing to help temps.. Also tried running MAXIMA coolant.. Only thing that made a difference was this past year running one scratcher off a ski.

 

[sideshowBob]

I was amazed how well my ski scratchers worked on my SW this past season. On one ride the sled went into limp mode, because of temperature, while starting out on a 200 mile ride. I almost turned around to go home and get My Attak but instead let it cool down, dropped my scratchers, and ran the whole day without another temp issue.

 

[yamamarc]

I was amazed how well my ski scratchers worked on my SW this past season. On one ride the sled went into limp mode, because of temperature, while starting out on a 200 mile ride. I almost turned around to go home and get My Attak but instead let it cool down, dropped my scratchers, and ran the whole day without another temp issue.

I run these scratchers and leave the down 100% of the time. I ran them 2 seasons so far and they are still good to go. I haven't overheated at all in 2 seasons with temps always in the 170's

 

[1nc 2000]

Yes, that will take out any weak legged sled! Also I think it is 417 to marquette

I live two blocks of trail 417. Couple sections on that trail to hold it for a couple miles if it's groomed up good.

 

[Todd Beenen]

I live two blocks of trail 417. Couple sections on that trail to hold it for a couple miles if it's groomed up good.

That’s a real nice ripper when you catch it just right

 

[kinger]

Great info Tflash! Thanks for documenting. We're definitely learning about octane and tunes after a few seasons!

 

[1nc 2000]

Or lack of a great working knock protection system!

 

[kinger]

@Turboflash any picts of the swain tech pistons? What are you hoping is the temp reduction the slug will see?

 

[yamadoo]

I run these scratchers and leave the down 100% of the time. I ran them 2 seasons so far and they are still good to go. I haven't overheated at all in 2 seasons with temps always in the 170's

View attachment 161379

Same result for me on a VIper, temps come down to constant 165-170 with scratchers - same as yours- down never tried just one I guess will last twice as long if I alternate- GOOD IDEA

 

[Turboflash]

@Turboflash any picts of the swain tech pistons? What are you hoping is the temp reduction the slug will see?

I'll post pics when I find them.
From Swain Tech (https://swaintech.com/race-coatings/race-coating-descriptions/piston-domes/) site:
Gold Coat™ – This Ceramic Thermal Barrier designed specifically for pistons in extreme environments such as nitrous, turbo, and superchargers. About .003” thick.
GoldCoat™ Ceramic Armor™ Ceramic Thermal Barrier:
As the use of Nitrous, Turbo Chargers and Super Chargers have become common place; Swain Tech developed GoldCoat™ Ceramic Armor™ to protect piston tops in these demanding motors. GoldCoat™ offers the same benefits of TBC™, but adds an extra layer of extra high temperature ceramic to provide even more protection at higher temperatures. GoldCoat™ deals with the heat spikes and thermal shock of boosted motors better than any other piston coating. Now in its 5th generation of development, Swain’s TBC™ uses Swain’s exclusive “Smart Coat” technology which allows the ceramic to expand at the same rate as the piston. TBC™ coated pistons run cooler and retain much more of their tensile strength. TBC™ protects against high temperature oxidation, eliminates hot spots, and encourages proper flame travel. The ceramic also spreads the heat evenly over the entire coated surface reducing detonation, pre-ignition and allowing the use of lower octane fuel. Less heat is conducted through the wrist pins and rods keeping the crank, bearings, oil and entire bottom end cooler.

The don't post exact figures as far as piston temp reduction. On phone, they will often state about a 25% reduction in piston temp. I just figured it can't hurt to keep piston cooler so I went with their Gold Armor Ceramic coating on domes. Also, while it may be tempting to coat the piston skirts with their PC9 super slippery coating, there isn't enough piston clearance in these 998s for it. That coating builds about .0015 per side. Piston clearance in 998 is only about .0025 total so subtracting about .003 would leave no clearance at all. Not good.

 

[sideshowBob]

I have used Swain Tech coatings when replacing pistons on my mod and stock two strokes for a couple decades and have been very happy with the results. The skirt coating can be use to tighten up piston clearances on slightly worn cylinders as well.
Here are pictures of coated pistons compared to uncoated pistons that I recently installed in my 440 Moto Ski engine rebuild.

 

[Crossfire12]

Hey that’s not original clutch, very nice