two thunder250 go to work.

[GZBrian]

Great looking rides... GZBrian

[double]

Originally Posted by Water Warrior

Didn't quite understand the bore out statement. Are you saying you bored out the cylinder ?? How much did you go ? Did you need a new piston ? Any other changes to the engine ? And last but not least..........did you get a good return of power for your efforts ?

yes i bore up the cylinder to OS200 or put in a 74mm piston. but i didnt just go with the OEM cylinder, i replace it with cylinder from diesel engine. why i choose diesel instead of bore from current OEM cylinder? because diesel cylinder is much tolerant to extreme heat and it is more thicker so i can bore it again up to OS400 while if i use OEM standard, the cylinder will very thinner and can crack the engine.

for piston, i use from gasoline engine with the diameter i want with the same pin diameter (18mm). since here we dont have privileged for large diameter motorcycle piston, we use piston from car like camry, mercedes benz, daihatsu zebra. sure with some adjustment. and that's about it, no more changes. up till now, i've used the bore up engine for about a year and truly no problem at all.

the effect on my bike? yes it accelerate much faster, more power torque, but of course the top speed still the same with standard. if i want to exceed it, i have to change the stroke, but i will not do that as there will be lots adjustment and can shorten engine life.

[double]

Originally Posted by GZBrian

Great looking rides... GZBrian

thank man! :rawk:

[Water Warrior 2]

Wow, sounds like you did your homework before starting the bigger bore mod. Very impressive.

[double]

Originally Posted by Water Warrior

Wow, sounds like you did your homework before starting the bigger bore mod. Very impressive.

well learn from friends' experience where most engine blown out or crankcase cracked using OEM cylinder. thank man! :rawk:

[RamAir]

Nice bike and welcome. Is that the GZ motor in that thing or another one?? Also more pics of that cooler would be great buddy thanks!!


I posted about an engine cooler idea here viewtopic.php?f=9&t=3943

And ahve this link to a picture of one that would look to work http://img525.imageshack.us/i/enoilcooler.jpg/ but yours looks like a cleaner set-up.

Like I said any pics and info you got on that cooler would be super great! and got any pics and number specs about your big boring?

[RamAir]

Hold on a sec??

Is that a GZ250 motor??

[blaine]

Originally Posted by RamAir

Hold on a sec??

Is that a GZ250 motor??

That is not a G.Z.250 motor.The stamping on the cover says 850ml of oil.The G.Z. holds 1300mls.

[RamAir]

Whats the size of this motor and does it ahve a 6speed????? I mus know for the love of speed!

[double]

Originally Posted by RamAir

Whats the size of this motor and does it ahve a 6speed????? I mus know for the love of speed!

it's 263cc bro...just a year ago i bore up the 250cc engine, from 72mm to 74mm piston..but it is still 5 speed. to add its power, i put fcr carb.. :rawk: