Big bore 125m

[ArizonaATC]

Can you big bore a 125m? anyone done it?

[shortline10]

Ive seen a few kits for the 84-85 back in the day but non were high compression so honestly adding a couple millimeters just for the sake to make it a Big Bore isn't going to make more power, fresh yes .

[John Tice]

Shortline is correct; 2mm doesn’t do much. As far as compression goes, it’s easy to raise by machining the head. The problem with big bore installs is the size of the head bolt pattern. There is seldom enough room to seal the head with the closeness of the hold down bolts. I can do this with a larger sleeve if there is enough room & a suitable piston is available. I suppose at this late date that somebody has already attempted this.

John Tice
503-593-2908 Alternate 541-508-3944
www.smallenginemachineworks.com & www.nwsleeve.com
Turning Custom Cylinder Sleeves Since 1971
http://forums.everything2stroke.com/threads/49513-How-It-s-Done-Projects-around-the-Shop.com

[DohcBikes]

There's always the Lifan/Piranha/Anima engine option. Up to 190cc.

[ArizonaATC]

There's always the Lifan/Piranha/Anima engine option. Up to 190cc.

yeah im still gonna do that but on a 110 frame, i was restoring the 125m to make it look factory new, i just find in mud sometimes the engine gets strained and it wont spin the tires at WOT or move at all so i half to get off and push it, im only 150 pounds also.

[shortline10]

Web sells a performance camshaft and try and find a performance exhaust , that will perk it up a little .




yeah im still gonna do that but on a 110 frame, i was restoring the 125m to make it look factory new, i just find in mud sometimes the engine gets strained and it wont spin the tires at WOT or move at all so i half to get off and push it, im only 150 pounds also.

[oscarmayer]

contact Vince at www.tboltusa.com
he can work with you to get a custom piston and even an upgraded alloy cylinder. he even offers several BB setups that put some of these motors to 140cc. you will need to measure the stud pattern and cylinder height to start as there are a ton of different types on his site. I imagine the one you have is a 69mm in length but double check that. there are some 72mm length cylinders on ebay as well so that is also an option if needed.
here is your biggest issue. the clutch setup, trans and sub trans were never designed for a ton of HP. you will cause those to have failures. if you want more out of your 125 then do this, take the motor out and drop in a lifan, 140cc setup or better yet want to keep electric start?
here
http://tboltusa.com/store/pitster-pro-155-engine-br-fits-pit-bikes-and-other-minis-p-522.html

if you call he can sell you one of his electric start versions of this motor.

[hippyplz]

I have a cam, pipe and little bigger carb on my daughters 125m and it does pretty good for what it is. I looked for a wile and couldn't ever find anything in a performance piston for it.

[oscarmayer]

you will need to measure the stock piston. need piston pin diameter (think 14mm for the 125m but confirm), pin height to piston deck height and diameter if piston. that teboltusa site has a bunch of custom stuff and you can order a high dome piston that fits the specs.

[RUNMEDOWN]

I put a 125 piston (55mm) in my 110 (52mm), did not notice much (3mm diff) other than very thin skirt walls, new cam from Dr.ATV and it did make a difference. The biggest was change was from swapping the rear sprocket (Larger - went up 7 teeth) I was 205lbs when riding it and it would spin the tires in mud easily. just took off some of the top end speed, not that the 110 had much with a 205lb kid on it to start with. Recently went back to the stock rear sprocket for my 130 lb kid, with the cam it still moves me around (280lbs) very well.

[1979atc]

I would say a fresh rebuild if there are no hi performance kits available. And port the head, stage two cam, aftermarket pipe, bigger carb and a uni or K&N air filter. Which would depend n your riding conditions. Dusty Sandy conditions I would recommend a uni air filter.

[greenhuman]

No problems with the 125m clutch and gearbox strength. I ran 310cc with no problems at all.