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250 porting - mid/top or mo-better?

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I'm having a hard time deciding what Gorr porting option to go with for my YZ 250..

Trying to choose between mid top and mo better?

Im Riding Fast hare scramble and sometimes track..

I'd like a little more overrev on top, I enjoy the "hit" on a two stroke and the yz is pretty consistant already so I dont want to mellow the mid range too much with mo-better.. but also don't want to sacrifice too much low end with mid/top..

I like the power balanced and want wicked top pull to make me smile when ringing it out..

Has anyone ridden both and can give a little insight? Thanks

-More Low to Mid-Range (Ideal for stadium mx, single track off-road, or novice riders).

-More Mid-Range to Top End (Ideal for outdoor mx, intermediate to expert riders).

-Mo-Betta: a wider, smoother powerband with less hit in the mid-range (This is the best choice for off-road or mixed use riding. It’s the most popular choice by our customers).

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Just ask yourself how much time you spend in what part of the power band.  I would get mid/top if you are wringing the bike out all the time.

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Not trying to hi jack the thread, but has anyone took measurements before and after a mid-top power port job to see what has actually been changed? Any defects or bad areas noted to need open or moved?

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I got mo betta. It sure does work for me with:

   1.60mm squish (single layer head gasket), Fatty pipe, Boyeseen Power reeds, Aus 98 fuel and good carb setup.

Great power across the whole rev range.

Plenty down low. Often too much so I need slip clutch to meter it out.

Ample rev range up top.   Just be sure to retard the timing enough, then it pulls for ages.

Very responsive to small throttle changes. Without a little throttle cable slack it can get away from me.
Bit of an animal with 165 lbs me on it.  Far more punch than any KTM300 I've ridden.

I think mo betta porting is amazing. I'm running 14/48T sprockets and riding in 3rd almost as much as I can on my 450.

If you want to race 4 strokes on 4 stroke tracks and avoid shifting gears, then mo betta is the best porting.

Edited by numroe

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Good question.  Ans: 295 BB from EG.

 

You just made me realise the original poster might not want to go up from 250. 

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Okay thanks I think ill go mo better! Yeah mine is still 250 stock bore.. I'm going to wait till the next replate before I go big bore..

As for big bore options I'm thinking 265..

I'm a lite weight and the 295+ kits might be a little more than I need.

Edited by Chill_MotoX

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I also thought a 265 could be a good option. Slightly more metal thickness beside the exhaust side ports,.  It's only 15cc bigger but you'd also get new plating and nicer port edges than stock.  His porting is good.

 

I tamed my 295 a lot with less spark timing advance. Then the PC Plat 2 pipe tamed it a bucket load. So much I advanced the timing back a little.

 

The type of fuel you run seems to be a huge variable with these things. In Aus our pump 98 stuff seems to work great. 

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Wish we got pump 98 here in the states, best i can find at the pump around me is 93. Most pumps are 92.

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That must suck, and there are a few of those stations around here, i dont even go to them. Any gas vehicle i own gets fuel from the same station. Its the only station in town without ethanol and 93 octane.

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I got mo betta. It sure does work for me with:

   1.60mm squish (single layer head gasket), Fatty pipe, Boyeseen Power reeds, Aus 98 fuel and good carb setup.

Great power across the whole rev range.

Plenty down low. Often too much so I need slip clutch to meter it out.

Ample rev range up top.   Just be sure to retard the timing enough, then it pulls for ages.

Very responsive to small throttle changes. Without a little throttle cable slack it can get away from me.

Bit of an animal with 165 lbs me on it.  Far more punch than any KTM300 I've ridden.

I think mo betta porting is amazing. I'm running 14/48T sprockets and riding in 3rd almost as much as I can on my 450.

If you want to race 4 strokes on 4 stroke tracks and avoid shifting gears, then mo betta is the best porting.

 

1.6 mm squish is huge, are you sure that is what you have?  That is a inefficiently large squish.  Pro circuit race motors had less than 1mm. Heck they even send out cr250 pump gas setups at 1mm.

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1.6 mm squish is huge, are you sure that is what you have? That is a inefficiently large squish. Pro circuit race motors had less than 1mm. Heck they even send out cr250 pump gas setups at 1mm.

It's perfect. It's a 295. Not a 250.

1.60mm. It runs amazing. No detonation, no hesitation, cool and a clean top end.

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Im not saying it doesn't work, just surprised its so large. There is power tobe gained with smaller squish, anything over 1.2 (.050 inch) is to big in my opinion. Race motors built for maximum power are as tight as .025, with a bit of rod stretch the piston is scrubbing the head. Not saying i would put .025 on a big bore 250 2 stroke. Just a fun little fact is all.

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