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View Full Version : so who else has modded there yt 125 Yamaha ?



Ethan1
11-13-2013, 09:38 PM
I picked up a little 125 this summer , and it sort of ran checked compression , 60psi so I pulled the top end off to find some really basic porting so I added triple exhaust ports and raised the main port about 2.5mm, cut part of the sleeve away where the transfer ports begin, and added 4 Boysen ports around the reed cage .then found some KX 80 reeds witch are fiber glass and put those and there reed stops on the yamaha cage. Then the stock 20mm carb was still junk so I put a kx 80 carb and manifold on witch just fit , this just had to have the main jet go up 2 sizes. then it ran pretty good but I wanted more so I scrapped most of the original exhaust only keeping part of the lead in pipe. Then I put the kx 80 expansion chamber on it and it was really snappy but the power band hit in a little lower than a stock blaster. So I cut 2 more inches from my lead in pipe and the little thing screams and dosn't like to keep the front tire down but its a ball to ride .

generallee2005
11-14-2013, 09:50 PM
Sounds nice, I've been on the look out for a Bassani exhaust for about a year for mine. Really I've been on the look for any of the performance geared parts for the little guy.

Ethan1
11-15-2013, 10:30 PM
Boysen lists reeds for it. I had a 84 KX 80 with a blown top and bottom end so I started swaping parts. My stock exhaust was broke where the pipe goes into the big muffler , thats where I put the expansoin chamber. I was told the 175 top end bolts on and from what I have seem a Blaster top end might bolt right on too.

Six Stroke
11-17-2013, 11:16 PM
125 moto mods? Let's get our talk on.

barnett468
11-18-2013, 01:59 AM
hey, you're nuts, very cool. sounds like you know a bit but was just wondering, did you mill your head to increase your compression? you lost a bit if you raised the exhaust port. if you did not increase compression then doing that will really make it snappy.

Ethan1
11-20-2013, 08:42 PM
I wanted to mill the head but I haven't had a chance to, It only has 6.5:1 compression stock so you could mill the head with out .040" with stock porting and only have 7.4:1. I only used Honda bond on the base gasket because I didn't want to buy a new one so that lowers my jug a little. Also I took the stock 3 piece head gasket apart and only used the thinnest center piece this saves about a millimeter. I know this sound like a bad Idea to mod any head gasket but It isn't leaking yet.

Trevor58
02-11-2017, 04:38 PM
Hey I know this post is quite old but I'd like to know more about you cutting away the sleeve by the transfer ports as I'd like to also do this

fishertricar
10-24-2017, 05:59 AM
me too please. Im looking for more power to my trimoto, I wonder how blaster ports compare to it175s...