Quick Q about engine differences

[Honda 250r 001]

Okay, Ive got a 125 dirtbike, and of course, the legendary trx 250r. My R has been down for a while, but finially got it running the other day. Been use to riding my 125. After I got on my 250r and took her for a spin, the power just seems to be weak up top compared to the 125. The 125 just seems to pull all the way to when it just wont physically rev anymore. The 250r, It pulls hard in the midrange and just seems to taper off, I can hold on the throttle and it will keep climbing in RPM's, but just doesn't make power like I want it to up top, I am better off short shifting it. I love the power of my 125 and I want my 250 to perform just like it. Power all the way till it just wont physically rev anymore. Im running a PC2000 265 cylinder on my 250r with a 39mm carb 178 main and a ESR TRX 5. Is this just the difference between a 125cc 2-stroke and a 250cc 2-stroke? or do I need to change pipe/porting? Anyone else ever notice this from a 125 to a 250 2stroke?
Thanks!
Will

[troybilt]

125's were ported for more top end, they have nothing on the bottom that I remember.

[Honda 250r 001]

So basicly what it comes down to here, is im feeling the difference between a midrange ported engine compared to a top end ported engine. Im going to look into a top end pipe/porting set up for my 250r. Thanks for the reply. The 125 suprisingly has good bottom end for a little 2-stroke motor.
Im guessing the principal is, to get power out of a little 125 like that and make it compete with a 250 4stroke, you have to port it for top end so it will really rip, a 125 ported for bottom end would feel slow because you cant make the best power from that small of an engine down low.
I think i may have answered my own question, i just wanted someone else to listen and make sure im not going insane. lol. Thanks troy.

[Burns310r]

So basicly what it comes down to here, is im feeling the difference between a midrange ported engine compared to a top end ported engine. Im going to look into a top end pipe/porting set up for my 250r. Thanks for the reply. The 125 suprisingly has good bottom end for a little 2-stroke motor.
Im guessing the principal is, to get power out of a little 125 like that and make it compete with a 250 4stroke, you have to port it for top end so it will really rip, a 125 ported for bottom end would feel slow because you cant make the best power from that small of an engine down low.
I think i may have answered my own question, i just wanted someone else to listen and make sure im not going insane. lol. Thanks troy.

125s are ported high to make a lot of peak hp. They will zing up top for sure. Another thing is pwoer to weight. Your 250r will have less power to weight ratio than the bike im sure. So naturally the bike will be quicker. Also the 125 from the factory was designed for top performance(race). If your 250r is mostly stock, then its still based on a reliable engine with tons of potential.

[Honda 250r 001]

My engine is pretty heavily modded id say. only thing stock is the bolts holding the cases together. Any ideas on a good top end pipe and porting set up? anyone have any feedback on the TRX 9? Either that or a paul turner high rev, and getting the little 265 ported to match which ever pipe i buy. The ESR trx 11 is a little to bulky for racing MX other wise id pick one up.

[RyanWsly]

If the timing is advanced it will make it sign off early, I have a 2005 RM 125 and a TRX with a LRD Pro X and the both pull similar on top.

[Honda 250r 001]

I have the timing set at full retard on my ESR cr ignition

[RyanWsly]

I would look into a pipe first then. To clarify what I was saying they are similar from bottom to top across their respective power curves, the 125 is designed to rev higher but also comes on at a higher RPM so if you are just strictly looking at RPM you will never get it there.

[k7mm]

From what it sounds like,you would love the Curtis Sparks TT pipe. They are hard to find,but it is the exact power that you are describing you want. I have used one on a MX track and it was perfectly at home. It will rev out all the way to the max. I loved the power and feel of that pipe on a National 265 engine I had. I switched to the Sparks MX pipe because the TT was sketchy on technical hill climbs in the woods,but still missed the TT pipe.

[etccb]

Or a trx9 will give you more of an upper hit that you are looking for. The 125 and 250 are just really different and wont act the same way to work for what you are doing. Look at an 80 vs a 500 as far as how they act and you are playing in between.