CR125 low-end power?

[krasher]

Hullo. Perhaps I am chasing the impossible however, I want more power at the low end. What can be done?

Honda CR125 2002

She goes like stink in powerband but is pretty shy until she hits it.

Also, what gas should I be running. I am currently using 91 and 50/1 fully synthetic.

What options do I have?

[barty5]

most would be usein 96 to start with
what pipe and muffler you got can make a difference

[krasher]

Stock exhaust with a med/small dent in it. Small leak too up by the motor. I think the seal might need doing.

Ok I will change to 96. I just ran out of mixed fuel so that's easy.

[honda_power]

125s are made for top end, a pipes not gonna do fuck all for the cost of them, a flywheel weight would prob help a little though

[Rupe]

Hullo. Perhaps I am chasing the impossible however, I want more power at the low end. What can be done?

Honda CR125 2002

She goes like stink in powerband but is pretty shy until she hits it.

Also, what gas should I be running. I am currently using 91 and 50/1 fully synthetic.

What options do I have?

50/1 doesn't sound right, I'd say you'd fuck it in time running at that. I'd expect it to be 32/1 but wait to see if any owners know.

A pipe (fmf gnarly has great bottom) and muffler would help, and a flywheel weight. But it is a 125cc they don't have much bottom and you have to use the clutch a lot, but master it and you'll be a quick rider.

[driftn]

Buy a 250.

[clmintie]

I always run 32/1 in 96 (TTS with about 20ml of castor per 10l) in the KX125 and 85. My understanding is that less oil = richer mixture, so you may have lost that 'fat' feeling at the bottom. I'm only a slow old guy, but in my favour is the fact I only weigh 66kg, I find the 125 has plenty of mid range (and a clutch that screams "abuse me" in several languages )

The copy/paste from Holeshot below is interesting.....
..................................

Here is what we run in Shaun Fogarty's 2008 KX125 race bike running a FMF Factory Pipe and Powercore 2 Muffler.
Main Jet 390
Needle-jet 6CHJ10-84
Clip 3
Pilot 37.5
Air Screw 1 3/4
Fuel 98 octane
Fuel/Oil 28:1 full synthetic Silkolene

[Buddy L]

I ran my 02 on 96 octane and 32/1 mixture, it had a pro circuit pipe.
One if found out the main jet was too big and replaced it with standed sizing the bike had a heap more bottem end and ran alot better.

[cheese]

I got a flywheel weight if you want one? $100. Its for a 250 though

[Danger]

I always run 32/1 in 96 (TTS with about 20ml of castor per 10l) in the KX125 and 85. My understanding is that less oil = leaner mixture, so you may have lost that 'fat' feeling at the bottom.

Sorry mate you got that backwards, less oil = richer mixture due to the fact the fuel flows through the jets quicker, common mistake. Regardless I would run 32/1 in a 125 and a flywheel weight would kill any bottom end it has so flag that idea too.
If you must ride a 125 but want more bottom end look at the YZ or the KTM, they have the most bottom end out of the 125's. The CR even modified will not run as strong as either of them, although the '05 and up with a FMF fatty and a shorty was better, but still not up to the YZ, RM or KTM.
There are 144 kits for many of the 125's, these will give you more torque.
Other wise make sure your top end is fresh and try going up a couple of teeth on the rear sprocket.

[krasher]

Thanks for the replies! I better look into my mix. Don't want to break my bike!

I know that 125's don't have much bottom end but it seems it has less pep than another 125 that I rode. It has more top end though.

I'll try changing my mix for starters.

[clmintie]

Sorry mate you got that backwards, less oil = richer mixture due to the fact the fuel flows through the jets quicker, common mistake.

Oops, my bad..... Wrong again....:rolleyes:

[vr4king]

Abother 125 rider here........LOVE your clutch but punish it too and keep it on the pipe,If you cant keep it just of the pipe but NEVER let it bog down as it will stop and trust me thats no fun half way up a hill climb

[theblacksmith]

Ive been running 32-1 in my kdx250.
Ive also changed to 95/96 fuel and am now using Maxxol racing castor oil(Cant mix with petroleum based oils).Goes really crisp and heaps more bottom end torque but stinks for miles man!

[theblacksmith]

Buy a 250.

And that will make the 125 gruntier at bottom end?:eek5:
News to me!

[tonyg26]

get a pro circuit system and run 98 octane, 25mls of oil to 1 litre of petrol

[krasher]

Ok, some good suggestions Cheers.

PS. Telling me that its a 125 so get used to it is not helpful. I am trying to see if I can get more out of this because I don't know if its setup right. No point giving up before I start right?!

[Reckless]

Ok, some good suggestions Cheers.
Telling me that its a 125 so get used to it is not helpful.

Don't think they are being harsh Krasher but they do have a point because there is not to much you can do about what you want to achieve.
So to a certain degree they are correct you have to get used to it or sell it.



Hullo. Perhaps I am chasing the impossible

What options do I have?

If you want a good woods/enduro bike and don't like having to keep the 125 in its rev range and have to clutch it a fair bit in the trees etc you haven't got many options. Many have bought a 125 (including me for my son) then sold it because its just not the sort of bike that suits them. Some love the 125 style many don't!


What options do I have?

I decided not to buy Fatty pipes and try fly wheel weights etc for my sons 2001 CR125 as I didn't think it had the fundamental base to make a good woods/enduro bike for a learner rider. Some say though, if you can ride a 125 fast anywhere, you can ride anything fast. So we decided for his learning curve, and his enjoyment, it was better to call it quits and buy an enduro based bike. So we sold it. You either like a screamer(125) or don't as you are finding out. Sorry mate but the engine size seems perfect for a person buying their first bike but take it to the sand pit as a new rider they are much harder to get through the trees, up those sand inclines, and through the soft sand (like the big Dipper). Also quite a bit harder to ride on wet clay etc. My son liked my CR250 much more than his 125, got to the point he wasn't enjoying his riding, I didn't want to loose him, so I sold it.
Enjoy the challenge of the 125, it will teach you heaps but the struggle may send you to another bike. :bye:
Sorry mate some here will no doubt disagree but that's my experiance.

PS If your out at the sandpit or Thunder I'll let you do a loop on his 200exc if you like. So you can feel the difference. Score a ride on a 250f if you can as well if you like 4 strokes.

[Robert Taylor]

And that will make the 125 gruntier at bottom end?:eek5:
News to me!

Deck the cylinder 0.5mm and sink the head by the same amount. Add epoxy filler ( devcon ) to the two rear side transfer ports ( not the boost port ) so that the flow doesnt deflect forward from the ''hook '' cuts. I.e smoothen out the hooks. Raise the forward transfer ports 0.5mm. Add 10mm into the header pipe, run a short muffler. Add a powerblade for better low end atomisation. This will take a little top end and over-rev away but will give a significant boost in low end response. A flywheel weight will prevent stalling but will also give lazier response, it will also extend over-rev.
If that scares you think about a 250 4 stroke if you are looking for low end torque

[Reckless]

Deck the cylinder 0.5mm and sink the head by the same amount. Add epoxy filler ( devcon ) to the two rear side transfer ports ( not the boost port ) so that the flow doesnt deflect forward from the ''hook '' cuts. I.e smoothen out the hooks. Raise the forward transfer ports 0.5mm. Add 10mm into the header pipe, run a short muffler. Add a powerblade for better low end atomisation. This will take a little top end and over-rev away but will give a significant boost in low end response. A flywheel weight will prevent stalling but will also give lazier response, it will also extend over-rev.
If that scares you think about a 250 4 stroke if you are looking for low end torque

Yep Roberts nailed it! Not better man here to comment actually!
Just add the exc range to his list :girlfight:

BTW Robert do those powerblades really work well. Do you think the 08 Ktm200 exc would benefit. I like the look and theory of what they do!

[camchain]

Transfer ports on my 200 are not a great match. Thought about trying an epoxy job but was worried about how to prep and and how long it lasts? Many seem to use JB weld. What is devcon?

[Pierce]

Thanks for the replies! I better look into my mix. Don't want to break my bike!

I know that 125's don't have much bottom end but it seems it has less pep than another 125 that I rode. It has more top end though.

I'll try changing my mix for starters.


Could also compare your sproket gearing for starters. If they've got dif gearing it will make a difference to your bike.

But yeah I've never owned a 125 but have riden a couple, you realy just need to keep the rev's up and rape the shit out of them haha. I even find on my 250 2T that i'm becoming a bit more of a clutch rider.

[krasher]

Ok. That is cool. I still am not sure if there is something wrong with my bike - I will have to get somebody else to ride it and check the basics out myself.

I know they need thrashing/revs. I just didn't know if mine was especially bad.

I get your points though. More clutch, less slow - or do some pretty extreme mods to make it do what it isn't really designed for anyway.

I have considered lowering the gearing. I am only really using 1st and 2nd at the mo. But it might be cos I am such a noob and cos of where I am riding.

I must admit, I do love it still. I love the rush of hitting powerband. I think I would feel bored on a four stroke now.

[Pierce]

See if you've not been riding long i'd say just stick at it and take your time to learn all the basics first. It's easy to get swept up in riding fast or doing big jumps etc but quite often in doing that you forget the basics or skip learning them all together and wind up with loads of bad habits like I did. Now i'm just trying to concentrate on cruising a slower pace but staying out for longer.

I never learnt to ride on a 2T so I picked up all of my skills (what little skills I have haha) on a CRF250 4T which is a bike you can tractor round with the fourstroke torque.

What kinda riding are you doing? Trails or MX etc?

[krasher]

See if you've not been riding long i'd say just stick at it and take your time to learn all the basics first. It's easy to get swept up in riding fast or doing big jumps etc but quite often in doing that you forget the basics or skip learning them all together and wind up with loads of bad habits like I did. Now i'm just trying to concentrate on cruising a slower pace but staying out for longer.

I never learnt to ride on a 2T so I picked up all of my skills (what little skills I have haha) on a CRF250 4T which is a bike you can tractor round with the fourstroke torque.

What kinda riding are you doing? Trails or MX etc?
MX stuff so far. Only done 5 rides really. Got the bike just before Chrissy and sprained my wrist a couple months back which put me out for 6 weeks.

Keen to do some trails though. Done a fair amount of dirt jump/mountain biking stuff. Nothing big but I'm not totally new to two wheels. It's just the engine and some extra suspension :)

I was going to get a 200 or 250 fourstroke but it would have meant a much older bike for my budget. Perhaps it would have been better but I am having fun which is the whole point :)

I am keen for thursday or friday rides if anyone is every looking for company during the week. I am self employed and do funny hours and prefer a quiet track at this stage of things.

[tnarg]

I might be heading up to the sandpit on friday, let me know if ya keen and I can show some trails that will give your 125 a good work out. By the way I used to have a 125 and loved it once I got used to the clutching, was thinking of going back to one but will probably join the 200exc club for my next bike.

[Robert Taylor]

Yep Roberts nailed it! Not better man here to comment actually!
Just add the exc range to his list :girlfight:

BTW Robert do those powerblades really work well. Do you think the 08 Ktm200 exc would benefit. I like the look and theory of what they do!

They work better on some bikes than others and can sometimes take away a little bit of top end. They do work especially well on bikes with big lungs ( large bore carbs ) and short stroke i.e every 250cc four stroke mx bike. Not so applicable for pro level riders who always operate at higher rpm with more forward speed but often great for everyday joe bloggs riders.
But heck the golden rule is ALWAYS to get the jetting sorted and the bike handling before bolting on go fast engine parts. So many bikes out there that are either jetted for Mexico city on a hot humid day or conversely for ice racing in Canada. There is so much engine response and power available in correct jetting alone. And I also mean correct jetting for the atmospherics, elevation, track surface / loading, fuel used and a whole host of other variables. ( You will well know that from karting! )

[Robert Taylor]

Transfer ports on my 200 are not a great match. Thought about trying an epoxy job but was worried about how to prep and and how long it lasts? Many seem to use JB weld. What is devcon?

A long established metal epoxy used for decades in the aircraft and 2 stroke tuning industries. Very hard to find.

[Reckless]

They work better on some bikes than others and can sometimes take away a little bit of top end. They do work especially well on bikes with big lungs ( large bore carbs ) and short stroke i.e every 250cc four stroke mx bike. Not so applicable for pro level riders who always operate at higher rpm with more forward speed but often great for everyday joe bloggs riders.
But heck the golden rule is ALWAYS to get the jetting sorted and the bike handling before bolting on go fast engine parts. So many bikes out there that are either jetted for Mexico city on a hot humid day or conversely for ice racing in Canada. There is so much engine response and power available in correct jetting alone. And I also mean correct jetting for the atmospherics, elevation, track surface / loading, fuel used and a whole host of other variables. ( You will well know that from karting! )

Yep Rob agree with all you say and thanks for your opinion on the powerblade, just wanted to get it while the subject was bought up!
Re tuning! agree again, the thing is the kart never went well enough, always looking for more, you know how it goes! With the bike I can't ride the bloody thing to its full potentual so the jetting is set good but a fraction rich for everywhere, shit I've even got the powervalve backed off 1/2 a turn! So I'm happy not to play with it at the mo. Thanks, have a good day!

[krasher]

I might be heading up to the sandpit on friday, let me know if ya keen and I can show some trails that will give your 125 a good work out. By the way I used to have a 125 and loved it once I got used to the clutching, was thinking of going back to one but will probably join the 200exc club for my next bike.
Cheers. I am away on thursday down to Tauranga, but keen another week! Cheers.

That info regarding jetting is good. I need to set my fuel mix right - sounds like 32-40/1 is about right with 96 fuel. Then get my jetting sorted. I have no idea how to do that. Is it a home job or wait till I can get somebody else to help me with it?