XR80 Big Bore Options?

[Simo63]

This question is for the XR75/80 fanatics 

I'm rebuilding an XR80 for my young fella and wanted to rebore it so figured a big bore would be the go. 

Not interested in going 120cc as it will still have standard carb, ports and pipe, just wanted a bit more grunt.

What are the options?

[Hardex]

leave it stock or buy a 125.Its that simple.

[Simo63]

leave it stock or buy a 125.Its that simple.

Thanks but not what I was after.

Anyone got any helpful ideas/hints/tips?

[smed]

Wiseco & probably some others do a 2mm oversize piston that gives 83cc,I think thats as big as you can go with stock sleeve

[BETRIC]

 Simo you can use a CB400F piston in an XR80, it will take it out to around 98cc, you should be able to use the std carb as a TL125 uses the same size carb, I have a CB400F piston for my 78 XR75, it only works in the 5 speed XR75 if you use an XR80 crank and barrel, (you can't use a 5 sp XR75 crank and barrel as the crank stroke and barrel are to short) the CB400F piston is just over 50mm dia and has a 13mm piston pin, (does not work in a 4 speed XR75 motor)    

[Hardex]

Check these guys out
http://www.big50.com.au/items.php?section=parts&category=XR parts

[ozyditcher]

http://www.socalxrs.com/   http://www.powroll.com/  http://www.webcamshafts.com/  I have built a lot of very fast xr75 80 100 . Do not port the head , the ports are two big for the stock motor.  A good reverse cone pipe, XR200 carb. web cam,  XR50 ignition,

[Dono113]

Simo wouldnt have aspare head mate, just picked up project and it needs a head as the two I have has flogged out cam journals

[35elsinore]

ozyditcher, I have a 77 xr75 [5 speed] bike laying around and a xr100 engine. Is there a good combo there I can mix to make a little rocket.
Cheers Troy

[smed]

The 100 donk will bolt straight into the 75 chassis

[ozyditcher]

ozyditcher, I have a 77 xr75 [5 speed] bike laying around and a xr100 engine. Is there a good combo there I can mix to make a little rocket.
Cheers Troy

The xr 100 will bolt in the xr75. Put a 120cc kit in it  and good reverse cone pipe on it this is a good cheep mod 10 hp. cam carb 12hp $$ . 130cc 14hp$$$,  148cc 18hp$$$$$$$$$.   

[35elsinore]

Just purchased a bbr 120cc kit with cam [$289 incl freight], what carb would be best. Might leave the 77 xr75 alone and convert the flogged out xr100 frame into twin shock and steel tanker. The ideas are flowing now for a fun bike to flog around with the kids.
PS. would the standard ignition be OK.
Cheers Troy

[ozyditcher]

Just purchased a bbr 120cc kit with cam [$289 incl freight], what carb would be best. Might leave the 77 xr75 alone and convert the flogged out xr100 frame into twin shock and steel tanker. The ideas are flowing now for a fun bike to flog around with the kids.
PS. would the standard ignition be OK.
Cheers Troy

                        honda XR 200 

[35elsinore]

Thanks for your help, much appreciated.

[Tony.Brown]

BETRIC can you tell me which head gasket is used with the CB400F piston? Is it XR100? Or is there a different gasket made for the increased bore size?
Tony.