Power Options To Upgrade A Honda Xrm125

[dalidali]

With 2 up, I am hauling around 300+ lbs on this motorbike.

It's a little weak when passing, when I need a good jolt of power.

 

I don't want to do any internal engine mods but would consider trying an after market exhaust system to "maybe" boast the acceleration a little bit.

 

I have seen in motorbike accessory shops, the full system including the header pipe, exhaust pipe and a muffler. Bolt on seems easy enough.

 

Missed the pricing while I was scanning the different systems... :bash:

 

Would anyone have any thoughts on these systems, including a ball park cost?

 

Mind you....I am NOT looking for more noise.....just a little bit more power, but at what cost?

[gapotwo]

With 2 up, I am hauling around 300+ lbs on this motorbike.

It's a little weak when passing, when I need a good jolt of power.

 

I don't want to do any internal engine mods but would consider trying an after market exhaust system to "maybe" boast the acceleration a little bit.

 

I have seen in motorbike accessory shops, the full system including the header pipe, exhaust pipe and a muffler. Bolt on seems easy enough.

 

Missed the pricing while I was scanning the different systems... :bash:

 

Would anyone have any thoughts on these systems, including a ball park cost?

 

Mind you....I am NOT looking for more noise.....just a little bit more power, but at what cost?

Dalidali,  your HP. problem sounds familiar. i bought a china made quad, secound hand and did not like the power, (none) so i stripped it down, rebuilt it with new everything. it came out nice and to my likeing. but the China motor was a 110 cc honda copy of the 110 wave. tossed that engine and put in a honda 125 xrm motor. i was not impressed with the motor, so i punched out the stock muffler with a #10 rebar, got some power, but was noisy, so i bought a aftermarket tuned exhaust. big differance. then i pulled the throttle slide on top of the carburetor and adjusted the needle stopper( c clip) to two slots down to enrichen the fuel to air intake ratio.Tossed the stock air box and put a K&N freeflow air filter. i wes amazed how much more power i got, my final mod. was to swap out the rear sprocket with a larger one, about 5 tooth more on the final drive. Reason was for higher rpm. delivery to the rear wheels. total cost for parts locally here in olongapo was about 2,500 pisos. Not including the motor that was 5000 pisos used. so now i have a quad with no reverse gear, cuz the reverse gear on the china motor wont fit the 125 xrm motor. i just pack around my BOOM BOOM GIRLS ...er....uh.. :no: ..ooooopps, i mean my wife, to push me back.... :) .he he he.          Good boy ako ngayon.....tanks ej.

[robert k]

If you don't want to get too deep into it, I would suggest 57mm bore. Re-jet to suit. There might be something to gain by derestricting the exhaust but a certain amount of backpressure is necessary to keep the engine even tempered, especially a small one. If you are drag racing, a straight short tube is the ticket but on the road it can cause bogging and flat spots at less than a full throttle launch. Not to mention the noise. There is something to be said for the old saying there is no replacement for displacement. The 57mm bore would take you from 125cc to 150cc a 20% increase. Drilling the stock muffler baffles with a long 3/8 drillbit could derestrict it somewhat. Some aftermarket mufflers are louder than stock and are more restrictive at the same time, expensive too.

[Bruce]

Why reinvent the wheel? With the costs of parts and the labor and then added in any unreliability issues from changing to a modified engine, why not buy a 155 Honda? I have a 153 Yamaha because the seat was much softer for long rides. Also have a Yamaha 135 Sniper that was powerful but not comfortable on longer rides for my old ass. I found that the more times I visited the Philippines, my travel radius grew and grew.  

 

Sure new may cost more, but there is no down time, no opinions to wade through as what to do. Check your monthly budget and see what the payments would be for certain time frames. Sell your 125 to offset the costs of a new bike. Are you that far apart to make it a no go?

[i am bob]

Now I haven't been on anything I would consider a small engine (175) for at least 40 years. And even then. 300+ lbs would be hard to get my old bike to really spike. Of course, after 40 years, I imagine power efficiency has improved several times. Still, to pump out enough power for passing with a 300 pounds+ load? Anyone know about this? This info might help out our OP as well.

[Curley]

Why reinvent the wheel? With the costs of parts and the labor and then added in any unreliability issues from changing to a modified engine, why not buy a 155 Honda? I have a 153 Yamaha because the seat was much softer for long rides. Also have a Yamaha 135 Sniper that was powerful but not comfortable on longer rides for my old ass. I found that the more times I visited the Philippines, my travel radius grew and grew.  

 

Sure new may cost more, but there is no down time, no opinions to wade through as what to do. Check your monthly budget and see what the payments would be for certain time frames. Sell your 125 to offset the costs of a new bike. Are you that far apart to make it a no go?

 

Good idea because don't forget if you tune up the engine to give more power you're still working with the suspension and brakes of your less powerful bike.

[dalidali]

Let me clarify what I am hoping for and thank you for the suggestions.

 

The "passing" power I am looking for is not highway, high speed stuff.

I just need a short burst of power to get around a tricycle or multi-cab who is jamming up the lanes.....do the pass thing, normally in second or third gear, then get back in the lane and turn down the power.

 

I am perfectly fine with the open lane cruising power. This moto moves along fine in this urban setting, where highway speeds are non existant. 4th or high gear rarely sees any action.

 

I don't want to, nor would I, tear into the internal engine to make mods, nor would I consider buying a bigger engine moto.

This isn't going to happen. Taking a multi-thousand piso hit on resale won't happen just to get a little more power on acceleration.

 

I can handle just a little bit of increased noise through an after market exhaust system, if I could find a reasonably priced one and get an honest opinion out of the selling shop about the noise factor.

Maybe that new exhaust system could be bolted on and I could give it a whirl for a noise test and the small power jolt I am looking for?

[robert k]

Dalidali, I think what you are looking for is going to be found in the rear sprocket, luckily, that will be cheaper than a good exhaust that wouldn't help until you were wound all the way out anyway. I would say about 10% bigger rear sprocket.

Edited August 31, 2013 by robert k

[dalidali]

Dalidali, I think what you are looking for is going to be found in the rear sprocket, luckily, that will be cheaper than a good exhaust that wouldn't help until you were wound all the way out anyway. I would say about 10% bigger rear sprocket.

I like it Robert....with my normal low speed useage, losing some top end (4th gear) shouldn't be much of a concern.

What I need is a little more low end torque for those quick bursts of power for passing quickly in traffic.

 

I am not a gearhead so I can assume what I would need is a sprocket with more teeth or is it just a larger diameter?

Edited August 31, 2013 by dalidali

[gapotwo]

Dalidali, I think what you are looking for is going to be found in the rear sprocket, luckily, that will be cheaper than a good exhaust that wouldn't help until you were wound all the way out anyway. I would say about 10% bigger rear sprocket.

ENLARGING THE REAR SPROCKET  is good for gear reduction, But if you choke the motor with a stock exhaust and air breatker, you just defeated the whole purpose of higher RPM. on demand.  look into a crankcase breather too. the xrm 125 cc motor is a damn good and reliable motor. ive REDLINED my quad quit often. it takes a beating when i pass the trikes and jeeps on a moments notice. ive pulled the front end up to a wheelie on a secound gear power shift, A knowledgable auto clutch band adjustment always helps too.  good luck my friend on your need for speed.   In da wind.....ej. :cheersty: