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Eric Gorr mo betta

By avisagio,
in Yamaha 2 Stroke

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StillSmoking

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I have a Mo Betta with race gas head and it pulls HARD from right off idle all the way through the top end. The best advice I can give you is pick a fuel and stick with it. Jet and re jet until it is perfect at every range. It will get there. Just take your time and make sure you write everything down.

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primerib108

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The mo-betta porting package is good....real good. Don't get frustrated with jetting these things. Takes a little more time than a stock bore......your patience will be rewarded with tire shredding performance. Works excellent with all your stock components too. I mated my with a RB 39mm air-striker carb and it is a match made in heaven.    

 

I heard the mid-top porting is even better. Plenty down low still and the thing will scream.

Edited by primerib108
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primerib108

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I would love to see the dyno on the EG cylinder vs my HP cylinder....

I wouldn't be surprised that a well tuned 250 head could indeed lay down more hp.....especially an HP cylinder. I would be surprised if a ported 250 could match it in the torque curve. I think the real charm is how hard it pulls throughout the throttle.

Edited by primerib108
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Hans Schmid

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I wouldn't be surprised that a well tuned 250 head could indeed lay down more hp. I would be surprised if ported 250 could match it in the torque curve. I think the real charm is how hard it pulls throughout the throttle.

Sorry, I meant a Mo Betta port job on the 250 cylinder vs a HP ported 250 cylinder...

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primerib108

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Sorry, I meant a Mo Betta port job on the 250 cylinder vs a HP ported 250 cylinder...

 

Lol...I was comparing a mo-betta 295 to a tuned 250 like yours will be. Come down to Cow town for the Red Bull rocks and logs and we could do a butt dyno test on both ?

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Hans Schmid

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Lol...I was comparing a mo-betta 295 to a tuned 250 like yours will be. Come down to Cow town for the Red Bull rocks and logs and we could do a butt dyno test on both ?

Ya, I've already been asked by a few people. I'm just so out of shape at this point that racing seems like a pipe dream...

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harrperf

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I love my HP engine.

 

You mean one that looks like this? ?

 

I've attached what our current package as of about december 2013 is, with an fmf will do (dep and PC dyno better peak on this set up - but fmf was chosen by this customer) vs a popular builders 300 kit a customer brought in to test about two months ago.  Hp 250 on avgas and 300 kit was on vp4.4 as it was delivered, with jetting and timing optimized as per dyno runs.

I've attached two of the same so the peaks (at different rpms) can be shown fairly to both engines. If I click the peak of our engine the other engine is past it's peak and dropping - and vice versa

Screenshot (125).png

Screenshot (124).png

 

The 300 is really hard to get enough exhaust port on since the cylinder design limits the width of the main exhaust port and the auxiliaries can't be made much wider either also from casting limitations.  I've put huge time into our 300 kit trying to get around some of those issues but the good ole 250 mod is really, really good after the years of development put into it.  I finally sourced a place that can do castings on both the quantity we want, and the price that is reasonable enough to be sold - and I hope to release a fully new casting that can finally allow a yz300 to realize it's true potential (and a wicked 250 casting that should see 55 horse easy ?

 

With a little change to the head, and just a quick change to exhaust port on supplied 300, was able to get the following result without much development time into that particular configuration.

Screenshot (126).png

 

Edited by harrperf
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proform

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Yes that bike! Everyone that rides it comes back wondering what I had done to the engine. I was talking to a guy today about it. I just texted him the dyno chart, trying to convince him to stay blue and not go with a KTM 300

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harrperf

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Yes that bike! Everyone that rides it comes back wondering what I had done to the engine. I was talking to a guy today about it. I just texted him the dyno chart, trying to convince him to stay blue and not go with a KTM 300

 

Thanks for the good words.

The sad thing is the ktm 300 runs really really good, especially when tuned in.

In a drag race two months ago for shits and giggles on ashphalt with a new 2014 ktm 250sx, and the posted dyno chart I just put up, the yz won every time.  But the ktm 250 isnt too far off, and has better power from 3500-5500 by a good bit.

In full mod form a ktm can easily make 55 with excellent bottom, and 57 without much loss in bottom.  I love the yz - and with the cylinder casting it will be able to romp the ktm, but good on ktm for a rocket ship with "modern" cylinder port design.

I'm really excited though to finally have found a casting place that's reasonable.  For past couple years I was going to have to finance the farm as they say!

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Apprentice

MASGALOS

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EG295 kit?

I have EG295 Mo-Betta porting pump gas. I love it! I added HP powervalve spring, Boysen RAD valve and GYTR heavy flywheel in mine. I think it runs great more everywhere and the flywheel helps it hook up out of corners.

What do you mean "HP powervalve spring" 

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