Big bore kit for honda mtx 125? Help please

[stevenWorthin...]

Hi, I have a 1988 honda mtx 125 and the piston and barrel are shot, does anyone know where I could get a big bore kit for it? Or does anyone know of the 200cc mtx drops straight on? Keeping the 125 gearing etc? Thanks in advance
Steve
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Ride it like you just stole it!

[gbrand42]

I would be inclined to replace the barrel and piston with standard parts and sell it and buy a bigger bike, as you must already have a full licence if you are going the big bore route. It will be worth far more as a 125 than a bigger engined bike.
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Yamaha RD50M, Honda C90, Yamaha RS100, Yamaha RD125LC, Honda XL125 V9 Varadero, Honda NT700VA, Honda VFR800X, Honda CRF1000L, Honda ST1300 Pan European

[stevenWorthin...]

I will agree with you there but it was/is my first bike and I just don't think I could bring myself to getting rid of it.. It will be a good bit of kit once again when it is all done.. And I'll be more of a danger to myself on a bigger bike haha! Cheers
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Ride it like you just stole it!

[moonzoomer]

[stevo as b4]

Keep it as a 125cc or else hope you get lucky with finding rocking horse shit (MTX200R engine+ancillaries)

There is no big bore kits around for the Japanese built MTX's, but the Italian built import MTX125's use the NS125R engine, and for that there is a 190cc Malossi top end kit, and I think there used to be a Polini or Autisa kit available once too?

[stirlinggaz]

Hi,
as others have said, mtx200cc engine with atac valve slots straight in
problem is finding one then getting a carb & exhaust as well.
Turns it into a far better bike, but the 200cc expansion chambers are almost impossible to find. So much so that when I gave my mtx125/200 away (wasnt viable to re mot) I kept the spare one I had.
wasnt deliberate, honest. lol
buyer thought it was xmas when I said "you want some spare bits?." & came out ma shed with spare 200cc engine, 200 carb, umpteen gears,new conrod etc
looked at me like I was mental..
anyway point is, new top end parts were getting impossible to find so bike became non viable to keep running.
the uk learner legal 125 was sh*te to start with anyway, far better options available,

cheers,
GAZ

[stevenWorthin...]

thank you all, if i was to just do it up and get it std 125 again and sell it.. what sort of decent bike could i pick up for about 1000-1500? any ideas? only really want a 125 its only to get me to work and back the big toys can come into play when the weather is better! haha
Thanks in advance
Steve
____________________
Ride it like you just stole it!

[gbrand42]

CG or YBR all the way IMO
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Yamaha RD50M, Honda C90, Yamaha RS100, Yamaha RD125LC, Honda XL125 V9 Varadero, Honda NT700VA, Honda VFR800X, Honda CRF1000L, Honda ST1300 Pan European

[stirlinggaz]

Hi,
forget the boring commuter 4 strokes unless its just for getting to work & back.
if you want any kind of fun or enjoyment, get a decent 2 stroke
race replica(rs, mito or nsr),trailie (dt,rx or ktm) or sm (dtr,tdm) there's fun to be had from them all.
cheers,
GAZ

[stirlinggaz]

oops double post

[Vengy]

If anyone’s still wondering bout the bigger carb on these mtx 125’s. I’ve recently rebuilt the engine on 1. I blocked off the atac valve port with a metal bung and a polymer bush then I ground out the exhaust restriction in the front pipe then welded a 80’s cr 125 silencer on. I then fitted a pwk 28mm carb which fitted the inlet manifold and air box boot with a little heating with a hair dryer. Jetting wise it’s on 125 main (for now poss 130) and a 41 pilot (for now poss 45) also fitted a 1/4 turn throttle and dropped 1 tooth up front. It no longer sounds asthmatic and Revs hard ! If anyone can confirm if a 86,87,89 cr125 intake manifold would fit the mtx reed block that would b appreciated as looking to fitter bigger carb once port works been done. Also if anyone knows which v force reed block would fit ? Thanks