Yz250X big bore reviews

I'm about to start the winter rebuild on my 17x and thought what the heck. How much fun to turn it into a 300. Who has done it? What should I watch for? Athens vs other shops. Thanks in advance for ur feedback.

I'm about to start the winter rebuild on my 17x and thought what the heck. How much fun to turn it into a 300. Who has done it? What should I watch for? Athens vs other shops. Thanks in advance for ur feedback.


Jeez dude that thing isn't very old, how many hours you got on it?

I'm headed in the very same direction - would love to follow along as well 

I know Heavy. I have 28 hrs on it. I don't NEED to. But it's pretty fun

I know Heavy. I have about 30 hrs on it and doing my winter tear down, inspect/replace. Figured now is as good a time as any to do it as I was likely going to pull the cylinder and change pistons.

I know Heavy. I have 28 hrs on it. I don't NEED to. But it's pretty fun

Oh sure, I just like my stuff to come halfway apart when it fails, saves some disassembly.

I get it. Old habits for me are hard to break. I always did a winter teardown replace the piston and that was about it. I was thinking of just rebuilding it and looking for a 450 used to tinker with. Haven't got that far in my thinking. Still like the idea of the bb kit and all I've really seen were yz bb reviews.

Mine is out now for a big bore. can't wait to get it back

Cool, want to hear what it did for the bike. Where did you send it?

 

Yes, to hell with the 250!

Once you go big bore (300 or 325) you will NEVER EVER GO BACK!

 

Reference this past thread if you would like to read detailed information on riders experience.

http://www.thumpertalk.com/topic/1020420-yz-325/

 

There is no Replacement for Displacement!!!

Repeat those words over and over because once you feel a 325 Two-Stroke Torque (close to a 450) down low, you will kick yourself for waiting to buy the kit!

In the FIM World Enduro Championship (WEC) the E3 Class (290+ 2-Stroke or 475+ 4-Stroke) with most of the best riders are on 300 2-Strokes. Most of the time, the 300 2-Strokes will be faster than the E1 250 4-Stroke class or E2 450 4-Stroke class. This kit allows you to have 1 Fun Bike with the Broadest (Linear) Power Band for Motocross/Off-Road riding!    

 

Eddie Sanders Racing (ESR) http://www.eddie-sanders-racing.com/category_s/126.htm

 

Options: 325 (option-5 Oversize Pistons) (33% Displacement increase over 250) / 345 (option-2 Oversize Pistons) (38% Displacement increase over 250), Aluminum Cylinder (Can be Re-sleeved), Machined Head, Piston, Adjustable Power Valve and Gaskets a $900 to $1000 investment. 

 

Options: Thinking of buying a 2016 YZ250X ($7,390), YZ250FX ($7,890), YZ450FX ($8,890) Model, if you have the money good for you. Or spend the money on a used Yamaha YZ 250 ($3K to $5K), add a skid plate, front disc cover maybe some other preferred items. After riding the YZ ESR 325 I would say, all the 250’s or 450’s are now second rate compared to the YZ ESR 325! I believe ESR is the best VALUE Big Bore with the BROADEST power band!
Yamaha YZ with ESR 325 Kit - (250 was 212 LBS. Dry - 228 Wet) (YZ 325 - 214 LBS. Dry est.)
Weight Benefit over YZ 250FX, (231 LBS Dry est. – 247 Wet or 16 LBS. heavier) YZ450FX (240 LBS. Dry est. – 262 LBS. Wet) – (30 LBS. heavier) (Note: Fuel weighs 8 LBS. / 1 gal.)

 

Recent Rides: YZ ESR 325
-MX Tracks, torque out of the turn, nice linear power band (easier to ride), stronger than a 250 could ever hope to be! (Yamaha YZ250X or YZ250/450 FX bikes with wider gearing will be at a disadvantage)
-Off-Road (OHV areas), try to stall my bike you may not be able to! Want to ride Trials like for Extreme Enduro, no problem! (YZ 250 (non X) will have less top end)
Setup: Yamaha YZ ESR 325 - 2007 Model
-ESR 325, S7 Woods Porting, Silver Head, Race Gas Dome, (Use Race/Pump Gas 50/50)
-162 Main Jet (ESR recommended Main) and 42 Pilot Jet, Needle in the top position, to minimize any unburned oil. Riding Altitude 500’ to 4100’
-Maxima Formula K2 Two Stroke Oil – Flash Point 240 Degrees (One of the Lowest) (helps reduce unburned oil) (40 to 1)
-No Fly Wheel Weight needed, but on the 250 engine a 9 oz. worked well.
-Rekluse EXP Core 2.0 Auto Clutch Kit

R side YZ 325.jpg

212 Land - YZ 325 L side.jpg

A friend did the Athena BB kit on his YZ250FX and has mixed emotions, not sure if he would do it again.  He is a solid B rider and thinks the stocker is more fun.

Yes, to hell with the 250!
Once you go big bore (300 or 325) you will NEVER EVER GO BACK!
 
Reference this past thread if you would like to read detailed information on riders experience.
http://www.thumpertalk.com/topic/1020420-yz-325/
 
There is no Replacement for Displacement!!!
Repeat those words over and over because once you feel a 325 Two-Stroke Torque (close to a 450) down low, you will kick yourself for waiting to buy the kit!
In the FIM World Enduro Championship (WEC) the E3 Class (290+ 2-Stroke or 475+ 4-Stroke) with most of the best riders are on 300 2-Strokes. Most of the time, the 300 2-Strokes will be faster than the E1 250 4-Stroke class or E2 450 4-Stroke class. This kit allows you to have 1 Fun Bike with the Broadest (Linear) Power Band for Motocross/Off-Road riding!    
 
Eddie Sanders Racing (ESR) http://www.eddie-sanders-racing.com/category_s/126.htm
 
Options: 325 (option-5 Oversize Pistons) (33% Displacement increase over 250) / 345 (option-2 Oversize Pistons) (38% Displacement increase over 250), Aluminum Cylinder (Can be Re-sleeved), Machined Head, Piston, Adjustable Power Valve and Gaskets a $900 to $1000 investment. 
 
Options: Thinking of buying a 2016 YZ250X ($7,390), YZ250FX ($7,890), YZ450FX ($8,890) Model, if you have the money good for you. Or spend the money on a used Yamaha YZ 250 ($3K to $5K), add a skid plate, front disc cover maybe some other preferred items. After riding the YZ ESR 325 I would say, all the 250’s or 450’s are now second rate compared to the YZ ESR 325! I believe ESR is the best VALUE Big Bore with the BROADEST power band!
Yamaha YZ with ESR 325 Kit - (250 was 212 LBS. Dry - 228 Wet) (YZ 325 - 214 LBS. Dry est.)
Weight Benefit over YZ 250FX, (231 LBS Dry est. – 247 Wet or 16 LBS. heavier) YZ450FX (240 LBS. Dry est. – 262 LBS. Wet) – (30 LBS. heavier) (Note: Fuel weighs 8 LBS. / 1 gal.)
 
Recent Rides: YZ ESR 325
-MX Tracks, torque out of the turn, nice linear power band (easier to ride), stronger than a 250 could ever hope to be! (Yamaha YZ250X or YZ250/450 FX bikes with wider gearing will be at a disadvantage)
-Off-Road (OHV areas), try to stall my bike you may not be able to! Want to ride Trials like for Extreme Enduro, no problem! (YZ 250 (non X) will have less top end)
Setup: Yamaha YZ ESR 325 - 2007 Model
-ESR 325, S7 Woods Porting, Silver Head, Race Gas Dome, (Use Race/Pump Gas 50/50)
-162 Main Jet (ESR recommended Main) and 42 Pilot Jet, Needle in the top position, to minimize any unburned oil. Riding Altitude 500’ to 4100’
-Maxima Formula K2 Two Stroke Oil – Flash Point 240 Degrees (One of the Lowest) (helps reduce unburned oil) (40 to 1)
-No Fly Wheel Weight needed, but on the 250 engine a 9 oz. worked well.
-Rekluse EXP Core 2.0 Auto Clutch Kit
5a00f299555dc_RsideYZ325.jpg.7436c58cda4d40d04ce8187ddb8e154f.jpg
5a00f2a2425e3_212Land-YZ325Lside.jpg.639918065db6615475689da13431f12f.jpg

Good read. I'm curious about the X though. With its PV and CDI I want something that compliments that design.
A friend did the Athena BB kit on his YZ250FX and has mixed emotions, not sure if he would do it again.  He is a solid B rider and thinks the stocker is more fun.

Not sure I would BB a 4t 250. But a 2t?
20 minutes ago, FITZI6_7 said:


Not sure I would BB a 4t 250. But a 2t?

That's asking for it to grenade imo. 

2t's are funner with a BB kit. 125s are way better, and I'd imagine the same goes for 250s, although I haven't had a chance to ride one.

Can be finicky trying to jet it and tune it correctly. 

I'd imagine a BB 250 with a FWW would feel like a 450-tractor.

This interests me, only problem, I don’t own a yz250 yet lol. I’d personally go to 300 and call it good, oversize pistons will be easy to find and you can replate. I wouldn’t sleeve it, I’ve had a bad experience with a sleeved cylinder for my cr250, had to buy a new cylinder, we’ll leave it at that lol.

5 hours ago, ASP1227 said:

This interests me, only problem, I don’t own a yz250 yet lol. I’d personally go to 300 and call it good, oversize pistons will be easy to find and you can replate. I wouldn’t sleeve it, I’ve had a bad experience with a sleeved cylinder for my cr250, had to buy a new cylinder, we’ll leave it at that lol.

Same here. Sleeves are such a pita to install. 

Replating is here and the future guys!

To answer........I'm curious about the X though. With its PV and CDI I want something that compliments that design.

The Athena is a good (20% larger piston) kit, pricey though. I have not had one but looked at there dyno chart and would still recommend it.

Why the Eddie Sanders Racing (ESR)

I thought long and hard about Big Bores read everything I could and came to the conclusion that the broadest available power band was only going to come from the largest Big Bore available, an ESR 325! Discussions with Eddie brought up the question why not a 300, he stated the 300 just does not come close enough to a 450 in torque, so he designed and built a 325.

So it was advantages to go to a 325 (33% larger piston), in order to have a big benefit and not just a slight benefit. He also produced a 345, but stated it really is a Desert Sled that Revs slower. Based on a Broader Torque Band produced by a BIGGER Piston, this is where you gain with the Eddie Sanders Racing (ESR) 325 kit.

Other ESR guys have run 50+ hours an then installed a new Weisco Piston, so you have 5, repeat 5 oversize Pistons to go to. Guys that want Nickel Seal Plating can still get it by sending the kit off for that.

Note: I am sure the YZ250X provides more torque down low than my YZ250, but a 33% larger piston will do a lot more!

Tony

YZ 325 piston vs 250.jpg

ESR 325 Cylinder R view.jpg

Added riding info..............4 friends have rode my bike, they all want one! Very linear power band with a hit in the last 2K RPM range, put on a G2 Throttle Twist system (10% less rotation) and now your elbow is still up for the rough hang on stuff.

 

Fun!!!!

I got a significant gain from a RAD valve, then I put a RK Tek head on and it’s night and day to what it was stock...   Before this I was considering a big bore as well, not anymore as the power increase across the board is significant.   Just a thought. 

I noticed your at 30ish hrs..  I did the first topend on my 250X at 100hrs and currently have another 90hrs it.  I ride on the pipe a lot here in the high desert and I would say it’s a waste of time changing that piston so early..

good thread 

Have any of you guys noticed any increased wear due to the bigger bore on the bottom end? Just curious.

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