250 to a 300

Logan

New member
Bike has 75 hrs on the piston and soon it'll be time to change it. Does the 250 and the 300 use the same crank and rod? Can I just change the jug and the head? How about the ECU? My search didn't reveal much. :(

Thanks for any info.
 
Straight swap. Cylinder, piston, and head. The PV will pull out of the 250 and install into the 300, spigot will cross over too. CDI may have some variances, but if anything the 250 will just be a touch more aggressive. I did the 300 to 250 transition and very happy.
 
Carb jetting sometimes needs to be changed after the 250/300 conversion. On my 07 250 I lost 1-2,000 rpm off the top end after the 300 conversion. Jetting brought it back (thanks RB Designs).
 
Straight swap. Cylinder, piston, and head. The PV will pull out of the 250 and install into the 300, spigot will cross over too. CDI may have some variances, but if anything the 250 will just be a touch more aggressive. I did the 300 to 250 transition and very happy.

I was going to question you about your thoughts, like and dislikes about the 300 to 250? Im thinking about doing this myself? I love the torque of my 300 but im real sick of the vibes it puts out. Sitting on the bike in neutral will vibrate my eyeballs when revved.

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I was going to question you about your thoughts, like and dislikes about the 300 to 250? Im thinking about doing this myself? I love the torque of my 300 but im real sick of the vibes it puts out. Sitting on the bike in neutral will vibrate my eyeballs when revved.

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... that has more to do with your eyeballs than the bike :D:D:D
 
The eyes sound like a sign of excitement to me!

The 250 still vibrates, but its more noticable through the bars at a certain rpm when riding (transport etc). Thats with the super stiff Renthal Twinwalls. I'm sure a better bar would isolate the buzz some more. Its been a while since I rode it as a 300, but from memory it was very noticable both through the bars, pegs, and even the seat. Feet would be massaged and I'd often wonder how long a lady would be able to last when going for a ride.. :D

The 250 still pulls, but its not a 300. It grunts down and chuggs hard off idle and responds well to clutch, but I find it doesn't have the low/mid punch, more of a smooth/violent transition. Things you'd expect from a 250. I like it because it offers 2 bikes to me. I can tractor or lugg it in the nastys and it works just fine (not as aggressive as the big brother), but when I want to blast off I just flick the clutch and off she goes.
 
So Jake. You liking your new 300 better then the 250?

Maybe some Pros and Cons...


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So Jake. You liking your new 300 better then the 250?

Maybe some Pros and Cons...


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I switched from a 300 to 250. I just prefer a more animated ride. Enough so, that I'm considering an even smaller displacement machine. I'll still maintain a 250, it's a ton of fun wringin' the crap out of a 200...even more fun, a 125.
 
I switched from a 300 to 250. I just prefer a more animated ride. Enough so, that I'm considering an even smaller displacement machine. I'll still maintain a 250, it's a ton of fun wringin' the crap out of a 200...even more fun, a 125.

125 is so much fun! Either in the woods or moto....check pads are compressed!
 
My new bike is a 250R :D My old one started its life as a 300 Racing, and then became a 250. The 300 head and cylinder sit in a box with the rest of the spares. There is a new 250 piston sitting on my desk.. Thats a hint to what the next top end will be!

I'd love a 125 but think the novelty would wear off after a while. I'd get sick of having to wring it everywhere and struggling on the big hills. I think it would be a great way to make mundane well known tracks more exciting and challenging though and improve skills beyond the current level. For me the 250 is just the perfect sized do everything bike.
 
Yep 250s are underated, plenty of go still but dont have the same punch when you just get on the throttle, i find it easier to ride than a 300. seems like its all the rage now to have a 300 for the grunt and then and punt around off the pipe I couldnt think of anything worse than shifting when it starts to come pipe all the time except when needed ie technical terrain.
 
My new bike is a 250R :D My old one started its life as a 300 Racing, and then became a 250. The 300 head and cylinder sit in a box with the rest of the spares. There is a new 250 piston sitting on my desk.. Thats a hint to what the next top end will be!

I'd love a 125 but think the novelty would wear off after a while. I'd get sick of having to wring it everywhere and struggling on the big hills. I think it would be a great way to make mundane well known tracks more exciting and challenging though and improve skills beyond the current level. For me the 250 is just the perfect sized do everything bike.

Oh yeah - I totally forgot your new bike is a 250. My bad.

I honestly don't have much vibrations at all with my bike. Jake - you need to remove that cross bar on the rental bars. That alone helps a lot.

I just love the low / mid torque of the 300. That is the only thing holding me back from swapping to a 250 jug.
 
Come on Stu! Give me some credit.. both bikes have had the crossbar removed long ago!

The low to mid torque on the 300 is nice and mighty useful at times. I had no issues with the 300 being a 300, unless if I tried to ride it like a 250.
 
And this is why this is the best dirt bike forum!!

Jake - my bad... I should know better always a step ahead of us all.

Chad - go get your eyes checked...

Not sure about the wt. I would try without it first. But I won't be doing this swap until winter.


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My 03 has the 2k3 ignition(i.e. heavier fw). After getting used to clutching the bejesus out my old KX, I'm looking foward to a bit more FWW.
 
Haha! I'd replace the bars if I wasn't so cheap. They're still stiff even with the cross bar removed, but still strong too!

In regards to the engines. I think less FWW on the 250 is the way to go (as in 2K3 is ok, but I wouldn't be adding more). If you want a smooth engine to fanny about on the 300 is the right bike to be tamed down and still retain the grunt. The 250 is more race orientated/aggressive in nature, but less brutal. To get the best out of the smaller capacity you will be turning the throttle.
 
The 250 2 stroke is historically the most successful offroad racing displacement.From 1985 to current no other displacement has more championships in offroad racing.And flat out exterminated the 500 class in AMA motocross and supercross.Has owned GNCC racing overall since forever.Is the winningest displacement in FIM ISDE for overall victories and top 10 finishers.The 250 2 stroke holds more offroad racing championships period.The greatest offroad racing champions no matter the discipline have all won on one at sometime in their career.And those same racers have won the majority of those championships on that displacement.Look at your own race series in whatever part of the country,or world you live in,Hare and Hound,Enduro,ISDE,Cross Country whatever doesnt matter the top Pros and AA riders are on 250s more then any other displacement.
If you like to putt and chug twist one up once in awhile and basicly ride just about every kind of terrain imaginable and make it easier on yourself while doing so,then the 300 is the ticket.
If you want to get it on the 250 is the only choice.

The 4 stroke revolution in AMA motocross and supercross is a manufacturers game,not the racers choice.
 
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