THE NEW BIG BORE 250 2-STROKES
IF YOU DON'T SEE YOUR MODEL LISTED BELOW, CHECK OUR BIG BORE MASTER LIST
The new rules for the 250s by the AMA and FIM give the 250 2-stroke the run of the show. If you want to race 250Fs in the 250 class it has to stay a 250 and we can port it to suit your riding style. If you want to race against 450Fs, it has to be at least 295cc and that kit is $660. If you race dtx, hare scrambles, hill-climb, or ice-racing we can build an “80-over” (2mm) 265cc for only $550 parts and labor.
What's Included?
All of our kits include cylinder porting, head mods, and powervalve service. You get you choice of 3 powerbands and 3 fuel types. All the top end parts are included too like a Wiseco piston kit, top end bearing, alignment pins, and oversized gasket kit.
Powerbands and Fuel Types
The 3 powerband choices
- More low to mid-range with a flatter top end. By concentrating the power down in the lower revs it makes a powerband that lugs without chugging, yet is responsive enough to steer with the rear wheel. Perfect for technical mountain climbing, single-track, Arenacross, ice-supermoto, short-track and TT.
- More mid-range to top end and a bit softer off the bottom end. This choice is best for EXPERT mx, desert, dunes, dirt drags, beach racing, and dtx.
- Wider smoother powerband with less mid hit in the mid-range. This choice makes the power wider like a 4-stroke but without the harsh deceleration. It’s great for off-road, hill-climb, and VET or intermediate mx.
The 3 fuel types
We machine your head flat then machine the squishband and bowl to match your powerband and fuel choices. The fuel types are unleaded pump 92, race gas of 98-110, and E85. Pump gas is the most popular choice because you can also run race gas. E85 requires really high compression, a wide squishband, much richer jetting, and advanced ignition timing.
APPLICATION CHART
KAWASAKI
KX250
265cc 1978-2012 $550
295cc 1993-2012 $660
SUZUKI
RM250
265cc 1987-2008 $550
295cc 2003-2008 $660
YAMAHA
YZ250
265cc 1982-2012 $550
295cc 1999-2011 $660
GASGAS 250
265cc 1995-2012 $660
HUSQVARNA
CR/WR250
265cc 1998-2010
KTM
250SX/EXC
265cc 1990-2012 $550
TM 250
265cc 2000-2009 $550
HOW TO GET STARTED
Just CLICK & PRINT a copy of the Service Order Form and follow the directions on packaging your parts for shipping. All the options are listed for services, powerband choices, fuel types, spare parts, shipping methods, and payment options. Click here for the service order form
FAQs on 295 Kits
Does the power hit really hard in the mid-range and flatten-out quick?
Typically big bores hit hard and flatten-out and that’s what magazine testers have complained about. The reason is that tuners cheap-out and skip a step, cylinder porting. We include porting with all of our big bore kits and YOU CHOOSE the powerband type. We have a wide variety of customers using 295s for everything from mx to beach racing at 100 mph, to technical mountain climbing, hare scrambles, and dtx.
Does the crankcase need to be grinded to accept the bigger piston?
No, there is plenty of space in the cases.
Will I need to buy expensive aftermarket parts to make the kit work?
Our kits work with all stock and aftermarket parts except FMF SST pipes which make big bores run hot, but Fatty and Knarley pipes work great, and DEP SPORT makes pipes for big bores. A Boyesen RAD valve works great for all-around use. Steahly flywheel weights from 8-11 ounces work well for single-track off-road riding. If you’re thinking of a wide ratio transmission mod, the 295 pulls the bigger gear with no worries.
Will a 295 pull a 450F?
Our 295 ported for mid-range to top end has more peak power than the average 450F but the four-strokes still have a bit of an acceleration advantage in hard dry conditions. The main advantage of a 295 is the bike is much lighter, there’s no brutal deceleration, and its easier to ride.
Will the 295cc piston make my bike vibrate? Does the crank need to be re-balanced?
Our custom Wiseco Pro-Lite forged piston kit is the same weight as a stock cast piston, so there are no vibration problems caused by the 295 pistons.
Will the engine wear out faster or be less reliable?
We build-in reliability with thicker cylinder plating, a 2-ring coated forged piston, and polished port edges. Our 295cc kits are more reliable than a stock 250.
Is the price of the 295 pistons really expensive?
The price of the 295 piston is the same as a 250 piston, plus our custom Wiseco has anti-wear coatings, 2 rings, more surface area to transfer the heat, and a smooth intake to boost the engine’s over-rev. Replacement cost is $160 and average service life is 50-100 engine hours.
How fast can I get my kit and do you have core exchanges?
Turnaround time is based on the month of the year and if you choose an exchange core or want to retain your original cylinder. Turnaround times are fastest in the fall months and the prime season is from January to August with a peak demand in March and a wait of as much as 8 weeks.
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