300 2t vs 350 4T - pros and cons??

[JimBridger]

Just wanted to throw my opinion out there. I've been riding snowbikes off and on since 2012-13. My first few kits were on 450's and many of my friends currently ride 450's. South Eastern Idaho and Western Wyoming are my main riding areas. I love "boondocking" through the trees, slamming drifts and popping pillows, all while trying to miss the trees. For this style of riding, it is hard to beat the light feeling and almost surgical precision of the 300's handling. The 450's rotating mass and vibration always leave us feeling beat up and overworked to attack the terrain the same way.

We needed to find a way to make the 300's make more power, yet not going so insane on a motor that it ruined it for the rest of the year. Mods needed to be simple and easily reversible for summer riding.

On my 2021 gasgas 300ex, we were able to find that balance. Running a high compression rktek head since our lowest elevation we ride is around 6500'. It is 15:1. Mixing 50% vp110 and 50% 91 ethanol free fuel has been perfect to keep the pre ignition demons away. (Also running premix at 32:1, but bike must be tuned to run this way with some form of tbi) A tuned exhaust makes a huge difference as well. I've had amazing luck running the pro circuit platinum pipe and factory 304 silencer. Next was an issue unique to cold smoke powder and the 2 strokes... icing reeds. As the day progresses, the bikes would run worse and worse, as a small amount of those extra fine particles work through our filters and build ice on the reeds. We were able to solve this with a Two Stroke performance Injector Relocation Kit. The gas in front of the reed cage keeps reeds ice free and adds significantly more revs and topend power. Now the airbox was an interesting problem since the stock airboot has to be used with the TSP IRK. I copied what Regan Seig has done by completely deleting the airbox and stretching and ziptying a filter over the actual boot. I use a stock foam filter and outerwear streched over a cut down cage and the boot, and treat them with "camp dry" waterproofing spray every other ride. A c3 airbox bracket keeps the bike without the airbox looking clean. Bike is on a 129 aro with flipped f/r springs. A few musts for top performance on the newer FI 2 strokes is a wrapped pipe, and good blankets. This keeps the bikes running strong and consistent for on off throttle riding. Keeps the bike happy and keeps response super crisp. (Pic before figuring out airbox)

 

[JimBridger]

A few more photos of my setup. Blanket material draped over subframe, intake setup, radiator blocking setup, and wrapped pipe.

This is the 3rd year on this pipe wrap, probably has around 120hrs on it. I had to touch up a spot right as it bends coming out of the jug, you can clearly see where I touched it up. Biggest thing after getting a nice tight wrap is to stainless zipty it and then spray it with dei heat wrap spray, and cure it in the oven. Makes the wrap hard and stiff, and doesn't get torn up much at all in comparison to non sprayed and cured wraps.

 

[eric82930]

Curious how did you know the reeds were icing up? Did you remove them in the mountains? I've had some weird random performance issues that always happen on deep days but most was due to not enough carb heat, clogged intakes or water in electrical connections. Even a wet spark plug cap was a tough one to figure out. There's a bunch of 2 strokes in our group too we ride near cokeville alot if you want meet up sometime.

 

[Sheetmetalfab]

Curious how did you know the reeds were icing up? Did you remove them in the mountains? I've had some weird random performance issues that always happen on deep days but most was due to not enough carb heat, clogged intakes or water in electrical connections. Even a wet spark plug cap was a tough one to figure out. There's a bunch of 2 strokes in our group too we ride near cokeville alot if you want meet up sometime.

His bike being fuel injected (tpi oem converted to tbi) probably doesn’t need “carb heat” ?

 

[eric82930]

Yes I know fuel injection doesn't need carb heat but wanted to know how to tell if the reeds have ice? Also I know the tpi have the pressure sensor going into the hose by the reeds and it gets filled with condensation and messes up the pressure signal sometimes too even in the dirt.

 

[JimBridger]

Curious how did you know the reeds were icing up? Did you remove them in the mountains? I've had some weird random performance issues that always happen on deep days but most was due to not enough carb heat, clogged intakes or water in electrical connections. Even a wet spark plug cap was a tough one to figure out. There's a bunch of 2 strokes in our group too we ride near cokeville alot if you want meet up sometime.

Coming off a smart carbed 19 300 that ran fine all day, my first thought was electrical, but when everybody's 300's were doing it (we had 3 identical tpi 300s in the group) we started digging deeper. I also pack skid plate foam in every orfice of my bike to try to prevent things like electrical shorts from water and to keep snow from weighing me down. If we stopped, turned off the bikes and let the engine heat warm everything in the engine blankets, and after about 10 minutes the bikes would run fine again for a bit. We took our intakes off and could see our throttle bodies had a little ice starting after the butterfly too, so we had suspicions.

One buddy switched to tbi injection for more horse torques and suddenly his bike quit doing weird stuff, so we all switched over to some form of tbi and it solved the issues.

I also modded my ccps hose to a much larger size and have it as close to the cylinder as possible when I deleted my oil injection. Kinda copied the 23 tbi 300's.

 

[eric82930]

Nice work. You gotta do what you gotta do to keep the 2 strokes happy. I'm not a 4 stroke fan at all. I'll admit the broad power is useful on deep days but a turbo sled would be useful too and you won't catch me riding one any time soon.

 

[JimBridger]

Nice work. You gotta do what you gotta do to keep the 2 strokes happy. I'm not a 4 stroke fan at all. I'll admit the broad power is useful on deep days but a turbo sled would be useful too and you won't catch me riding one any time soon.

Yep. There's no denying that a healthy 4 stroke on a 3 inch track will out climb us, especially on the deep days, but I don't care. We are always less beat up and having more fun on our 2 smokers. Haha. A tuned up 300 on a 2.5 129 goes together like peanut butter and ladies. ?