Low end

I got my 2002 cr 125 and I'm not sure if this is a common issue but here's my little story that brings me to my angers with this bike... So I have this track built by my house and we got some jumps built but the one thing that bugs the crap out of me is the low end on my bike. My brother has a 2000 yz125 and he can go into a corner second gear and hammer it and clear the double but when I do it, I have to slip the clutch hard and the bike will still die down right before the face of the jump and I cannot clear it to save my life and we both weigh the same. My 1st steps were to soften my rear suspension to soak up some bumps and keep it from kicking out on me and 2nd I moved from a 51 tooth rear sprocket to a 53... Still no luck and it's driving me nuts! I got vforce reeds, pro circuit pipe, pr2 did up the engine... What am I missing here that I can't get the hot my brother gets!? They're both 125s! Is honda a sissy bike for bottom end or what? Do I need to play with jetting? Can someone please point me in the right direction before I whip the crap out of my brother over jealousy! Haha

I got my 2002 cr 125 and I'm not sure if this is a common issue but here's my little story that brings me to my angers with this bike... So I have this track built by my house and we got some jumps built but the one thing that bugs the crap out of me is the low end on my bike. My brother has a 2000 yz125 and he can go into a corner second gear and hammer it and clear the double but when I do it, I have to slip the clutch hard and the bike will still die down right before the face of the jump and I cannot clear it to save my life and we both weigh the same. My 1st steps were to soften my rear suspension to soak up some bumps and keep it from kicking out on me and 2nd I moved from a 51 tooth rear sprocket to a 53... Still no luck and it's driving me nuts! I got vforce reeds, pro circuit pipe, pr2 did up the engine... What am I missing here that I can't get the hot my brother gets!? They're both 125s! Is honda a sissy bike for bottom end or what? Do I need to play with jetting? Can someone please point me in the right direction before I whip the crap out of my brother over jealousy! Haha

Get a KX125 and kick his butt all over the place

Pro circuit pipes tend to be more top end pipes. You might want to try something different. A big bore kit is also an option

Current ride: 1986 TRX250R with lots of mods.

Have owned: 1981 ATC250R with lots of mods, 1983 200X, 1986 250SX, 1991 KDX200

The final version of the HPP engine from 98-2002 has no bottom end and I want to say there isn't a whole lot you can do about it without some machining work. I have an FMF fatty pipe with a shorty and Boyesen carbon fiber reeds and the bottom is still extremely weak. The sweet spot is the mid-range, the top is rather underwhelming and the bottom is non-existant.

Is yours faster on the top end? Can you clear it on his bike?

Yeah my bike is pretty sappy and quick on top and when I do hit it on his bike, it shoots right over it like nothing and his bike is bone stock. Any chance my powervalve is a little gummy and jetting isn't right? Or are the crs just weak on bottom in general?

You said pr2 did up the engine I was thinking maybe it was set up for mid-top and sacrificed even more of the bottom end yet.

 

All the things your listing could be it, air leaks, jetting, bad fuel, ignition timing could be off, low compression, powervalve, the list is endless man lol.  Time to get to work! My guess is jetting or powervalve.  Or both. 

Well a little good news on my part is that I just got my new piston yesterday along with the rings and that good stuff, gotta order a gasket kit though, but I'm not gonna mess with it till after this Friday because I'm going on a rough trail ride with some friends and I don't wanna blow it up upon break in haha. But when I take the top end off, I'm gonna rip it apart and take the power valve to my wire wheel and make it brand new looking and clean the engine out with choke/carb cleaner. But I never thought about pr2 making the situation worse but it would make a lot of sense! Thank! If you got anymore ideas, keep them coming! I'll probably also silicone around the intake manifold and check my reeds aswell. This is the best bike I ever had and it kills me to have a stupid issue like this

Who.knows what pr2 already did to it though thats what im asking.

If you want to transform the performance, read this article:

 

http://twostrokemotocross.com/2009/05/budget-racer-2001-honda-cr125/

 

Porting, and a pwk with proper jetting is about the best bang for your buck.

And those changes resulted in NO low end power increase. 

 

 

 

How was it?

In one word: scary.

In two words: scary good.

This is the bike Honda should have built.  On the pipe its easily the fastest 125 we have ever ridden, and thankfully, after the epoxy work, the mid range picked up considerably and the bike was an all around power package.

How does it compare to a modern Yamaha?

The Yamaha has a potent all around motor, with excellent bottom for a 125, impressive mid, and great top.

Our H.P. Bikes Honda has no bottom, acceptable  mid, but a top end to die for!

In a head on drag race from a clutched start, the Honda wins handily.

In roll on drag race, starting lower in the rev’s, the Yamaha gaps handily at first, then gets eaten up once the Honda hits power.

 

 

Doesn't help him. IMO, go buy a YZ125 if you need bottom or even mid range power in a 125.

Edited by shrubitup

Well I wouldn't argue that the yz125 in stock form compared to the cr125 has better low.  The magazine article references a bike tuned for mid/top.  However speaking from experience, my 05 was greatly improved with the EG144 kit with low/mid porting, and a DEP 144 pipe.  How much improvement came from the porting vs the bigger piston, I can't say, but I'd bet the low/mid porting more significant difference.  The pwk upgrade is a no-brainer for any bike with a mikuni carb, IMHO!

Well I wouldn't argue that the yz125 in stock form compared to the cr125 has better low.  The magazine article references a bike tuned for mid/top.  However speaking from experience, my 05 was greatly improved with the EG144 kit with low/mid porting, and a DEP 144 pipe.  How much improvement came from the porting vs the bigger piston, I can't say, but I'd bet the low/mid porting more significant difference.  The pwk upgrade is a no-brainer for any bike with a mikuni carb, IMHO!

the article talked about 00-04 CR125. Your 05 is a different design. 

the article talked about 00-04 CR125. Your 05 is a different design. 

Yes that is true.  But what is your inference?  Porting doesn't work on an 02?  The 05 - 07 had better low in stock form than earlier models, but not as good as the yz.  I'm saying that even the earlier models can be tuned for a desired performance as the magazine article clearly demonstrates.

If your track riding you should be riding a 125 near the top end rather than lugging it around

Yes that is true.  But what is your inference?  Porting doesn't work on an 02?  The 05 - 07 had better low in stock form than earlier models, but not as good as the yz.  I'm saying that even the earlier models can be tuned for a desired performance as the magazine article clearly demonstrates.

Magazine identified that the stock motor had a short span of upper mid range available power wise. They amplified that and moved it primarily to top end. This is easy to do on a 125 because they're mostly intended for this from the factory unless you get the versatile YZ or Husqvarna CR where power exists more broadly. 

 

Due to motor design I'm saying that porting may not be successful to increase low end power on these models. 

More cornering speed less worrying about power on a 125, game over.

Well what are your overall opinions on what's better on a track? The yz or the cr? Or would they be about even?

Also a bit of an update with what I've been doing with the bike... Rebuilding the top end putting a new piston and ring in it and when I got it pulled apart, I found silicone stuffed all through the ports and all over the base gaskets... Got it all pulled out and perfectly clean but I'm sure that didn't help my situation at all

Gotta thank the moronic previous owners for all that crap...

Edited by Emkjr93

Use an 05 base gasket if you didn't

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