trx 90 mod engine suggestions for 90 2s/125 4s class

[Hybrid Iceracer]

Ok, I picked up a decked out trx chassis and need to do something for an engine. I was going to two stroke it for a play bike for my girlfriend and later on build a new chassis for a 150R, but my buddies middle boy is becoming interested in quads and this is the closest $$ wise to ready to race. His two brothers already are on 4 wheels one on a apex shifter (awesome bike) and the other on a 125 raptor Good bike but a Dud in it the power dept.

So I need a LEGAL engine for this trx, are the 114 tbolt's good enough to run with the raptors the 125 just cant take the HEAT form what I see literally they over heat in the woods BTW were running hare scrambles and XC. I have seen a Scott Cain 125 bike it s fast but rarely finishes a race together. I need something semi reliable I understand the nature of the beast ( I ride a lt500 engine in a 250 chassis).


Thoughts good and bad, suggestions

[miniquaddad90]

The 114 kits are good. Ours ran toe to toe with many built raptors running XC a few years ago. I would say the raptors are getting faster and faster since though. A well built Honda 125 (like Scott Cain's) will run right there if youve got a chassis and rider to match. SCR builds his for MX, dont need that kind of power for XC. Can you go with a manual clutch? If so, that opens a lot of doors for reliable 125's

[Hybrid Iceracer]

Ya, I can run a Clutch for sure. Is there a one down conversion for the trannies on them? I wish Hybrids/super minis were legal really that what a Cobra and Apex are. And truthfully these trx s too by the time you get done pimping them out.

So what are my options I was thinking tbolt roller top end?

[miniquaddad90]

The V2 head is a great option. Outside of that, you could go with the standard TB race head (on back order at the moment though), Takegawa, or Kitaco. Weve ran the TB stuff for years, as long as you go with a "matched" set-up the reliability is there like you are looking for. PM me I have some contacts for you to get everything you need for the manual clutch conversion. There is a 1 down tranny but the TRX trannys are bulletproof, I would stay with the stocker.

[bigdaddy77]

I would get ahold of Terry at Firepower minis. You can. Message him through Facebook or Just Google Firepower minis for a phone number or email address. He has done us right along with a bunch of other people in the racing business. Check out what he has going with the Raptor 125. If It's a production class your going to have to stick with the Honda cases. They are more expensive to build than a Pitbike motor,but also you got a little better quality.

[miniquaddad90]

I would get ahold of Terry at Firepower minis. You can. Message him through Facebook or Just Google Firepower minis for a phone number or email address. He has done us right along with a bunch of other people in the racing business. Check out what he has going with the Raptor 125. If It's a production class your going to have to stick with the Honda cases. They are more expensive to build than a Pitbike motor,but also you got a little better quality.

What he said^^^^ That's where I was sending you too.

[bigdaddy77]

I do have a 114cc kit that we had on our Xtreme. It's a Honda bolt pattern and has the trailbike race head. Pro ankh let it go fairly cheap.I would stay away from the V2 head on the 125 motor. It's made for the bigger bores and the one we had didn't make near the power as our Takegawa heads. Call Terry he will get you all fixed up.if your interested in the 114 kit hit me up.

[Hybrid Iceracer]

I switched Gears on this project, I am building it for my Girl friend now and It will have a Crf 150r engine in it. I haven't had a chance to do much more than just tweak the chassis to get the engine between the rails yet but It looks like It will fit in fairly easy. next Fall I will build a new frame for it. Does any one know the wheel base and Swingarm length the Jb, Fischer or Roberts bikes use? I plan to stretch the chassis a little bit but not sure yet how much to go. I guess once its running She will tell me, but be nice to have a starting point to begin chassis layout.

[bigdaddy77]

Roberts mods are larger based off a 400ex. The JB and Fischer's are close to the TRX with a long travel swing arm. If you get it close to a 300ex you should be good. You can probably find 300ex specs online.

[Hybrid Iceracer]

Completely changed direction, just building a new frame. Engine didnt fit no room for radiator. Should have tubing this week to continue.
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[nastynotchback1]

Why do you want to build your own frame?

[Hybrid Iceracer]

Why not, just because I can. I build all my own stuff for my 250s and spring is about a month away here in the NE so I have plenty of time.

[oscarmayer]

Vince at T-bolt really knows his stuff, I would contact him and see what he says. He can probably either build you the engine you need or at least provide all the parts you need. I bet he even has a stroke setup to make it into a 125cc vs. the 114cc. also just an FYI, increasing compression dramatically increases performance int he torque area and response. On the 4-strokes we used to run, I ran up to a 15:1 setup and ti was night and day compared to a 12:1. response was much faster and crisper. you will have to run minimum of 112 but preferably 116 octane race fuel. We accomplished this by using the v2 head with the smaller chamber and had it machined to fit the piston exactly. so with a thin metal HG we got a total of .010 clearance between the piston and the head. I also had to do a lot more custom work than you will with the timing area, but it worked. Also Vince can get you a really powerful cam to go with it. I do also highly recommend getting the head ported to match the intake and exhaust. Run the FMF exhaust setup as it is larger and allows for better flow. BUT, little motors need some back pressure to make power, so ensure you don't try to run w/o a muffler or it will loose all torque and fall on it's face. (lesson learned the hard way during a race when it fell off. lol)

[Hybrid Iceracer]

Making some progress

[Hybrid Iceracer]

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made good progress hopefully after this weekend it will have steering.