m in sc
Well-known member
So, i was ordering parts for another bike on webike, and saw the 26mm TB for the CT125. it was cheap, 100 bucks and a direct bolt on. calculating the surface area - the throttle shaft, its about 17% larger surface area than the stock one, and with a 143, which is about 17% more displacement, figured it can't hurt, and didn't want to go any bigger w out upgrading the cyl head and an actual fuel controller ( i still have a ported head and 34mm tb leftover fromt he grom.. 
). so i bought it, bolted it right on, stock intake tube and filter etc. so far, zero downside and no weird external map sensor needs or adapters, etc. jut looks to be a stock TB bored out with a larger throttle blade. I did take the intake off behind it, and use my porting tool to match it and blend it, actually has a nice linear small taper down to the head so velicity will stay nice and high.
and, it ran just fine. took its usual 10-15 miles to start feeling any difference, and midrange was again improved, and topend was a hair better. so... as ive said all along, the intake runner from the airbox always seemed to be the bigger restriction, and certainly was now. so, i bought the NK intake from beez, was 68 bucks shipped from the beez site.
so, looking at the pictures, one would assume it would come with a rubber flange or the like to fit into the stock airbox. Nope. of course, zero instructions but it def was made well. i -think- it was developed to just stuff a cone filter on the end, but i wanted to run the stock airbox.
so, i had to cut the front of the airbox, by quite a bit, after i pulled out the rubber runner (which measuring, the size was at 25mm id at some points and its a mile long).
I used a rotozip bit on my dremel and opened up the airbox hole, deburred everything, blew out all the plastic bits. shoving the intake in, it was too long, so i had to cut the last .. 17 or so mm off it to clear the oil breather baffle area. no big deal but still. then it hit the LH frame stay that holds the bodywork on, so, i went ahead and dinged the bottom of the new intake runner so it would set down a bit to allow for the airbox to bolt back in.
I sealed the stainless intake tot he airbox with a thin bead of black silicone, put it all back together. the stock filter element def seems to have enough surface area to slo the nec air, as does the rear snorkel.
i left the pipes 'tumor' helmholtz resonator on, it wasn't as bad as i thought to look at. is it designed to be effective on this thing? probably not but doesn't hurt anything. I also used the stock hose clamps on the blue silicone joint, i just prefer them over worm-screw clamps.
fired it up, sounded a bit throatier but that means nothing. here are some pics:
(none of the TB install, it looks the same as stock)
part i cut off the new intake. i squared up the end and radiused the edge as well.
right here is where i had to dent the intake. thinking back on it, i probably could have taken a bit off the front of the intake and moved it 'in' a bit to clear it. but f-it.
heres where it goes into the airbox, can see the silicone around the hole. it was a tight fit, but still doesnt hurt.
heres a wider shot of it installed and all put together. I do plan on getting a section of black silicone hose vs the blue it came with.
the intake on the small end is ~30mm id. I rode it to work today, and again, after about 5-6 miles i started to feel improvement. by the time i got to work, the last leg i hit 60 w out much effort, 55-58 was easy, and it wasnt really dialed in yet w the ecm adjusting. power was better -everywhere-. but I think the whole combo is a good light upgrade package. If i go any further, it will def get an ecm, and probably a 181 or a 186 with a ported head, but thats doubtful.
also, note i did one upgrade at a time to allow the ecm to adjust per mod, its easier on the motor instead of large swinging changes at one time w/out an aftermarket ecm.
yuminashi 143
238 cam & adjustable cam gear, 2 degrees advanced
150 pcx injector
eife fueling thingy doo-dad
aftermarket exhaust.
intake and tb as listed above.
stock gearing, etc.
). so i bought it, bolted it right on, stock intake tube and filter etc. so far, zero downside and no weird external map sensor needs or adapters, etc. jut looks to be a stock TB bored out with a larger throttle blade. I did take the intake off behind it, and use my porting tool to match it and blend it, actually has a nice linear small taper down to the head so velicity will stay nice and high.and, it ran just fine. took its usual 10-15 miles to start feeling any difference, and midrange was again improved, and topend was a hair better. so... as ive said all along, the intake runner from the airbox always seemed to be the bigger restriction, and certainly was now. so, i bought the NK intake from beez, was 68 bucks shipped from the beez site.
so, looking at the pictures, one would assume it would come with a rubber flange or the like to fit into the stock airbox. Nope. of course, zero instructions but it def was made well. i -think- it was developed to just stuff a cone filter on the end, but i wanted to run the stock airbox.
so, i had to cut the front of the airbox, by quite a bit, after i pulled out the rubber runner (which measuring, the size was at 25mm id at some points and its a mile long).
I used a rotozip bit on my dremel and opened up the airbox hole, deburred everything, blew out all the plastic bits. shoving the intake in, it was too long, so i had to cut the last .. 17 or so mm off it to clear the oil breather baffle area. no big deal but still. then it hit the LH frame stay that holds the bodywork on, so, i went ahead and dinged the bottom of the new intake runner so it would set down a bit to allow for the airbox to bolt back in.
I sealed the stainless intake tot he airbox with a thin bead of black silicone, put it all back together. the stock filter element def seems to have enough surface area to slo the nec air, as does the rear snorkel.
i left the pipes 'tumor' helmholtz resonator on, it wasn't as bad as i thought to look at. is it designed to be effective on this thing? probably not but doesn't hurt anything. I also used the stock hose clamps on the blue silicone joint, i just prefer them over worm-screw clamps.
fired it up, sounded a bit throatier but that means nothing. here are some pics:
(none of the TB install, it looks the same as stock)
part i cut off the new intake. i squared up the end and radiused the edge as well.
right here is where i had to dent the intake. thinking back on it, i probably could have taken a bit off the front of the intake and moved it 'in' a bit to clear it. but f-it.
heres where it goes into the airbox, can see the silicone around the hole. it was a tight fit, but still doesnt hurt.
heres a wider shot of it installed and all put together. I do plan on getting a section of black silicone hose vs the blue it came with.
the intake on the small end is ~30mm id. I rode it to work today, and again, after about 5-6 miles i started to feel improvement. by the time i got to work, the last leg i hit 60 w out much effort, 55-58 was easy, and it wasnt really dialed in yet w the ecm adjusting. power was better -everywhere-. but I think the whole combo is a good light upgrade package. If i go any further, it will def get an ecm, and probably a 181 or a 186 with a ported head, but thats doubtful.
also, note i did one upgrade at a time to allow the ecm to adjust per mod, its easier on the motor instead of large swinging changes at one time w/out an aftermarket ecm.
yuminashi 143
238 cam & adjustable cam gear, 2 degrees advanced
150 pcx injector
eife fueling thingy doo-dad
aftermarket exhaust.
intake and tb as listed above.
stock gearing, etc.
