what can i safly bore my bike to ?

[Guest]

hi guys i have a gy 125 and i would like to know what size i can bore my bike to to get the highest and best performance cheers guys.

[Guest]

as a learner ... and if it is a 2 stroke then only a rebore for a scored piston etc will do i.e 0.5mm oversize.

anything over 125cc requires a full /restricted Licence

[Guest]

its a four stroke and has no guts wat so ever i have my full licence but am still restricted to 33 bhp an my big has at best 15 bhp

[Guest]

you'd be better off getting a bigger CC bike..

[cyberwolf]

for what it cost to rebore you would be better of selling you bike and buying a cheap 500cc

[Guest]

yes ino its not really the cost its because my friends all say its crap an i cant make it faste rand i know i can prove them wrong its sort of a project to get it as fast as possible to shut the people up who have cars an think bikes are shit

[eastanglianbiker]

you would need to bore the cylinder out rework the valves in the cylinder head new exhaust and rejet the carb ........= not worth the effort

[Guest]

money is no object i just want it to show off but i want to know to what mm i can bore it to so it still lasts a while

[caretaker]

yes ino its not really the cost its because my friends all say its crap an i cant make it faste rand i know i can prove them wrong its sort of a project to get it as fast as possible to shut the people up who have cars an think bikes are shit

 

I would think you need to talk to bike tuning shop..as the would also know what size pistons etc are available and possibly suitable..I imagine there will always be a trade off with future performance v long life

Sounds a fun project.......

[Ingah]

Before i start (to save you disappointment), i don't know the answer to your question - but despite this i want to share as much with you as i can. BTW, I'm going to apologise in advance if you happen to be aware of this stuff already:

You'd be better off asking that question on an owner's forum if you haven't already (if there's one for your bike, as i haven't heard of GY125's before). If it doesn't, find out what bikes if any share the exact same engine (don't make any guesses or assumptions here, even the smallest-sounding changes can make all the difference), and go check out the owner's forums for the same-engined other bike.

That said, may i suggest that before you even seriously consider re-boring, that you do everything else basic servicing-wise to enhance and tweak the performance of your bike. The older/more neglected it is/has been, the more effective this could prove to be. And best of all, it's cheap stuff and is least likely to damage your engine (in fact, much of it is likely to improve longevity), whilst providing modest performance increases at the very least. Pound for bhp, it's probably the cheapest upgrade you can do (servicing, that is). It's all been talked about on this thread, so have a read through before trying to re-bore: http://www.themotorbikeforum.co.uk/viewtopic.php?f=3&t=33054&p=586131

You should also consider making the most of what you already have in the engine (i.e. get a more free-flowing exhaust and air filter - Note: If your bike is carbs you will probably need to change the jets to make sure the bike doesn't run lean due to the extra air getting in. Don't neglect this, or you may seize your engine or reduce its life needlessly due to the extra build up of heat you get with a leaner fuel/air mixture)

I suppose you're well aware of the insurance and DVLA implications of a re-bore too? And the fact that unless you push the boat out and hence vastly decrease your engine life (you can't really do both reliability, and speed - without completely re-designing that is - as the whole process is a huge set of compromises), you're unlikely to get more than a moderate peformance increase.

If you want to show off the capabilities of bikes to your friends, then a 125 isn't really the type of bike to be showing them off with - they're generally designed to be limited well below what the manufacturers would've liked (i.e. to the learner-legal limits - which are arguably far too low), making them little more than cheap commuters and learner machines (a few noteable examples aside. But those are all 2-strokes).

Obviously as other people have said, you can contact a tuning company too. I remember doing this when i wanted my CG125 to go faster. But after a local company offering me a price to do it, but refusing to say exactly what they were going to do (i managed to get them to admit they were planning to change the sprocket as part of it, as i had guessed/asked if that was part of it - but that was all i could find out), i rather quickly dropped the idea . I'd want to know exactly what they planned to mess with and the possible repercussions.

[dex]

money is no object i just want it to show off

 

Money is no Object and you're riding around on some dog sh1t Hongdou GY125?

Seriously?

Trade it in for an MV Agusta F4 CC - I believe there's a few on sale at the moment with £25k off list price - so they're only £50k now. That will shut you mates up.