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Big Bore Help For Rm125 Please

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First of all let me start by saying I just got back into ridding and don't know alot about motorcycles:o , so you'll have to forgive my ignorance. I have a 2000 RM125 and like it alot. Here is my issue. I read the 144 review but didn't seem to help much. I ride both track and off road with my 125. The problem I'm having is low end torque and getting more of it. Now I'm not dillusional, I'm aware the bike I purchased has great top end speed and very little torque. My question is this, if I bore out my 125 to a 144, will my bike get noticably more low end torque to be able to climb hills better or would I be just wasting my money:confused: ? Any help would be greatly appriciated :)

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First of all let me start by saying I just got back into ridding and don't know alot about motorcycles:o , so you'll have to forgive my ignorance. I have a 2000 RM125 and like it alot. Here is my issue. I read the 144 review but didn't seem to help much. I ride both track and off road with my 125. The problem I'm having is low end torque and getting more of it. Now I'm not dillusional, I'm aware the bike I purchased has great top end speed and very little torque. My question is this, if I bore out my 125 to a 144, will my bike get noticably more low end torque to be able to climb hills better or would I be just wasting my money:confused: ? Any help would be greatly appriciated :)

you don't want to hear this but sell the 125 and look for a 2001 RM250 or newer they have the external water pump

i have a 250 and it climbs hills with no problems most of the riding i do is in the bush but you have to be careful not to grip the throttle high "hand placement" you wont make this mistake much on a 250 or it will toss you off as you off when you hill clime

have a good one:thumbsup:

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just learn how to work the low end lever (clutch) on that thing and you'll be just fine...but yes, generally bigger bore means more torque/low end...its about $500 to have it done the right way though

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We have a 144 big bore in an 03 RM125.

I'll assume you are planning to make due with the RM125 for a while, so here's my feedback on your orig question:

Not all bores are created equal, so if you decide to make the investment be sure to go somewhere good. Eric Gorr at Forward Motion is considered one of the best. Included in the bore work is porting, and that is where your power distributed according to your preference. Also, some motors require bottom end casework to make the 144 fit. This can get expensive. But if you get the job done right, just assume a power increase across the powerband approximately equal to your displacement change of 15%.

Having said all that... from a resale perspective... I would not suggest investing that kind of money into a 00 RM125 unless you plan on keeping it a LONG time, because you will never get it back when you resell. A cheap big bore job will be $500 (if not casework is required) which is about 40-50% of the value of your bike in today's economy, but you only get an appox. 15% power increase.

Depending on your size, you can try a few cheaper things:

More clutch discipline is the cheapest. But let's assume you knew that.

Gearing is the 2nd cheapest. Maybe go up a few teeth on the rear sprocket and see if that helps.

From there, you can try a 7-8 oz flywheel weight. That will give you a little more bottom but your bike will not be as pipey. Search threads of fww's because there is a lot of info out there. This is probably the best VALUE for the bottom end you seek.

Porting, mentioned above, can also be done without a bore job. If you want more bottom end then you could get your engine ported locally by a good cycle mechanic, or again, send it off to Gorr. The downside to porting is redistribute your power so if you want more HP on bottom it comes at the expense of the top end. You also can't easily "unport" your engine if you don't like it. It will take a professional's welding or expoxy work and it isn't cheap.

GOOD LUCK!

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just use a 51T rear sprocket and it will be more snappy, big bore usually doesn't give THAT much power/torque for the money you will invest in it, also remember that 125 engine like the rm develop most of their HP between 8k and 11k rpm, the big bore is going to limit you to 9.5k or close to that meaning you will get less power efficiency.

But that depend on the big bore, big bore for YZ tend to do that A lot, for RM: never heard of

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just learn how to work the low end lever (clutch) on that thing and you'll be just fine...

:thumbsup:

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i also have a 2000 rm 125, i suggest checking your jetting my friend... i spent an afternoon working on re-jetting. and got a bills pipe and silencer for mine. it has some fmf selectable ignition box that came on it... and MAN this thing ripps for a little 125 i can run wheelies around in 3rd easily. and im 165 lbs. that being said. i presently ride a drz400 every day. and trail ride it hard. i used to ride a kx500, yz250, and oldschool yamaha mx175. the power to weight ratio on the 125 isnt bad and torque isnt bad either if you ride it like a 2 smoke, just tune it properly. make sure your reeds arent chipped and it should have plenty of low end. you shouldnt ever get stuck if you can pop a clutch.

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