Gpx 125cc mods

[habib]

currently 26oko & pipe on it which rips, any other simple mods that you could recommend to step it up a touch, cam, head, porting etc.chhers

 

[gottagetacheaperhobby]

If you have lots of money there is a 146cc modernworks head and bore kit available from europe, would turn it into a animal! If your on a budget buy a dremel/rotary tool, pull the head apart, spend some time reaserching the principles behind porting for better flow, and then dive in! You can also buy roller rockers for them through some of the china ebays, but then you would want a roller cam as well to get the best from it. I personally would port the head, find some stiffer valve springs, ti retainers etc and go for rpm. The joy of small displacement engines is their ability to rev to the moon!

 

[habib]

thanks for that...! can i replace the rock and put roller ones in ?

 

[habib]

rockers sorry

 

[my67xr]

Welcome to Minirider's.

First up drop in and say hello in our Introduce Yourself thread

You could fit a big bore kit to your GPX, TB used to do kit but i think you'll have to go to Akunar now they have a 56mm and 57mm kit ? but their site is currently under maintenance
And then you could also add the TB Race head ($760) or port a Lifan big valve head for some more power on top of the big bore.
TB Race Head V2 Kit ? TB PARTS ? Buy Online Australia at DHZ
And the TB300 Race Cam as well, but you might want to change to a PE28 to make full use of the power

Have a read of Timeehs' thread- http://www.miniriders.com/ask-the-tech-masters-/40689-jialing-125-upgrades.html

 

[my67xr]

Welcome to Minirider's.

First up drop in and say hello in our Introduce Yourself thread

You could fit a big bore kit to your GPX, TB used to do kit but i think you'll have to go to Akunar now they have a 56mm and 57mm kit ? but their site is currently under maintenance
And then you could also add the TB Race head ($760) or port a Lifan big valve head for some more power on top of the big bore.
TB Race Head V2 Kit ? TB PARTS ? Buy Online Australia at DHZ
And the TB300 Race Cam as well, but you might want to change to a PE28 to make full use of the power

Have a read of Timeehs' thread- http://www.miniriders.com/ask-the-tech-masters-/40689-jialing-125-upgrades.html

 

[gottagetacheaperhobby]

I enquired about the tb head when I had a gpx 125, I was informed they had been discontinued. From memory the tb valves were .5mm bigger than the stock heads valves, so its gains were probably made more from the ports on the tb head. You can technically use roller rockers on a non roller cam, but gains wont be as noticeable. If your going the roller rocker route then definitely hunt down a roller cam for it. As craig said there is also akunar, they make some pretty large valved heads.. if you upgrade the head, and add a bigger bore then the pe28 would be another great upgrade, a little large for stock head though. Make a build thread and Post some progress shots, always interested to here about upgrades done on these ripper little engines

 

[my67xr]

Thank's Stu,
the TB head's are still listed on TBolt and DHZ site's, maybe they haven't updated them for a while ?

The Akunar head's and big bore kit's are cheaper than you'd expect too, both are around $200 or under inc delivery iirc?
Email them and tell them what you want to do with it and what they'd recommend,
i wouldn't go too full (biggest of each) on unless you planned to drag race it or go for a land speed record, lol

 

[habib]

Ok so done a mild port and polish on the gpx 125 and also had to drop the main jetting and up the pilot and wow what a difference ....! Also looked at the rocker and it a j type so can i just put a j type roller in that i got from ebay.?

 

[my67xr]

Yeah if you change the cam to a roller cam and better valve springs.

 

[habib]

Ok but would it work with the standard cam in and roller rocker?

 

[habib]

Thx but can a standard cam and roller rocker work together?thx

 

[gottagetacheaperhobby]

It may run, but poorly as the shape of the cam is very different. I personally wouldnt...

 

[habib]

Dont undestand why as it had no problems running with the standard rocker and changing to a roller type, its still runs off the same profile and lift but just a roller on the cam.

 

[motodevo]

Only if the ratio of the roller rocker matches the stock rocker exactly

 

[habib]

Its exactly the same size height width just a roller on the tip not flat.

 

[my67xr]

A roller cam has a different profile to a solid cam.
The lobes are rounded on the roller cam so the roller doesn't lift off the ramps
A solid cam has steep ramps.

 

[habib]

Ok thx,so its not going work at all.

 

[my67xr]

You can fit it and try it out just turning it over by hand.
But i dont like your chances

 

[habib]

Ok thx again i just thought adding the roller rockers on it would reduce fiction and giving it that little more as as the gpx cam is quite aggressive.