2 stroke yz

41racing · Sep 25, 2016

So the big end rod bearing went on my yz250 last weekend (I also dune ride this bike). So I'm thinking its time for a Esr 345 or maybe the 325. Anyone run this motor? Looking for input on what pipe to run. Obviously I want it all, low mid and top lol. Really though I would like something that makes decent low and mid without killing the top end. Also anyone mess with the timing and see any gains? I'm hoping with the 345 kit to be in the upper 50s possible break the 60hp mark.

RDPSMOKER · Sep 25, 2016

Also want to see what people have to say about this. Any pictures of your current setup?

41racing · Sep 25, 2016

I think I got a couple. Rode it last year all stock right down to the pipe. Loved it. It don't have the 450 power but it feels so light and nimble in the tight trees.

wwillf01 · Sep 25, 2016

I feel the 2 stroke gives you a more exciting feeling with the light and nimble... Spring they are great... I felt it gives up the most in chute climbs and powder.... To me the rpm range is not long enough and you have to be way more select on gears... The lighter you are the less this happens... This was my experience on a ported head cut ktm 300 and cr500 .. again more exciting but less effective in the powder at the end of the day.. I run 10,000 feet and up.

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jskattum606 · Sep 26, 2016

wwillf01 said:
I feel the 2 stroke gives you a more exciting feeling with the light and nimble... Spring they are great... I felt it gives up the most in chute climbs and powder.... To me the rpm range is not long enough and you have to be way more select on gears... The lighter you are the less this happens... This was my experience on a ported head cut ktm 300 and cr500 .. again more exciting but less effective in the powder at the end of the day.. I run 10,000 feet and up.

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Same thing i felt on my modded KTM 300 last year. Definitely seems like its more important to have the gearing right for the type of riding, where the 4 stroke is a little more forgiving.
I think it is mostly due to the shorter RPM range of the 2.(7500RPM VS 12000RPM) Makes the gears feel farther apart

I felt i benefited from the 2 stroke in the deep snow because of the lighter weight. I had the E-start stripped from my bike and all though(IT WAS LIGHT)

In your case the 2 stroke has a disadvantage at that altitude. The 4 is a little more efficient at altitude. Especially when your starting at 10k. IMO snow bikes are WAY more fun when you can ride at 4-5k

byeatts · Sep 26, 2016

jskattum606 said:
Same thing i felt on my modded KTM 300 last year. Definitely seems like its more important to have the gearing right for the type of riding, where the 4 stroke is a little more forgiving.
I think it is mostly due to the shorter RPM range of the 2.(7500RPM VS 12000RPM) Makes the gears feel farther apart

I felt i benefited from the 2 stroke in the deep snow because of the lighter weight. I had the E-start stripped from my bike and all though(IT WAS LIGHT)

In your case the 2 stroke has a disadvantage at that altitude. The 4 is a little more efficient at altitude. Especially when your starting at 10k. IMO snow bikes are WAY more fun when you can ride at 4-5k

maybe in the past the 2 strokes weight was an advantage however the new Iron 2017 450sx on the digital scale was lighter than my 2016 300, the 450 was 223 lbs no fuel.

wwillf01 · Sep 26, 2016

Ya I still think it's the feel with the valve train and center of gravity.. That being said the 16 450sxf I road last year was so nimble it is what brought me to the darkside

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jskattum606 · Sep 26, 2016

byeatts said:
maybe in the past the 2 strokes weight was an advantage however the new Iron 2017 450sx on the digital scale was lighter than my 2016 300, the 450 was 223 lbs no fuel.

True, But Ktm is the only one. Everyone else is 20lbs heavier.
Also, you can strip 15 lbs off of the 300(estart, lights, battery, wiring harness) . Cant on the 450

portgrinder · Sep 26, 2016

stock a yz250 is around 47 at the front sprocket.

pipe gets you just under 50. I like the PC2

.025 slice off the head gets you another 2 all the way through the rpm range.

Porting by a guy that nows what he's doing will get you to 60.

from what i recall on mine, changing the timing didnt do anything.

boysen rad valve doesnt add any peak but adds alot of snap off the bottom line.

i wouldnt expect boring to do very much especially if you don't do the above. no personal experience though

41racing · Sep 26, 2016

portgrinder said:
stock a yz250 is around 47 at the front sprocket.

pipe gets you just under 50. I like the PC2

.025 slice off the head gets you another 2 all the way through the rpm range.

Porting by a guy that nows what he's doing will get you to 60.

from what i recall on mine, changing the timing didnt do anything.

boysen rad valve doesnt add any peak but adds alot of snap off the bottom line.

i wouldnt expect boring to do very much especially if you don't do the above. no personal experience though

The Esr kit is their own cylinder with a much better exhaust path. I can only presume that the intake tract is improved drastically also. Planning on the rad valve and also planning on measuring squish and getting that optimized. I would certainly think (or should I say hope) almost 100ccs over stock would make some difference??

wwillf01 · Sep 26, 2016

For sure will make a difference... A lot more grunt

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Yetiman · Sep 28, 2016

Rumours are it's a smoker!

Someone gone a bit crazy! :juggle::juggle:

Tahoe54 · Oct 10, 2016

41racing said:
So the big end rod bearing went on my yz250 last weekend (I also dune ride this bike). So I'm thinking its time for a Esr 345 or maybe the 325. Anyone run this motor? Looking for input on what pipe to run. Obviously I want it all, low mid and top lol. Really though I would like something that makes decent low and mid without killing the top end. Also anyone mess with the timing and see any gains? I'm hoping with the 345 kit to be in the upper 50s possible break the 60hp mark.

I was debating doing this vs. doing a CR500AF conversion. It looked like a much easier and more cost effective project but I ultimately ended up going with the 500. Good luck, let us know how it turns out!

CATSLEDMAN1 · Oct 16, 2016

yz2

the yz 250 in the snow lacks some in the low mid but

add a boyseen rad vavle ........helps
Pick a pipe, I run an fmf gnarly
a 38 lectron will get you way better gas mileage and the throttle response feels like you added hp down low, helps plowingthrough early deep snow. pulls harder longer..........the stock KH carb on mine is an oddball anyway, best to park it, I run hot water around the bell for icing/ homemade thermostat.

gear it down a little, I am redoing by YZ250 kit right now, spare bike but spring fun, going to 2" 120

7 tooth 3.0 drivers'
18 jack shaft
16 18 in the chain case

it will gear it down alittle more, I rarely have it out on early season road rides, so jumpiing right up the hard snow hills I think this will be better

portgrinder · Oct 16, 2016

Pc2 made the most power when we had mine tied up to dyno in '09. 3-4 gain thought the whole curve if I remember correctly.

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2 stroke yz

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