My 80cc HT will be here Friday and once its installed the mods will begin!
First Ill run it stock to wear in the engine but once worn in Ill start modding. The first mod will be to rewire the kill switch with a keyed switch (security) and in a way that disconnects the blue wire instead of shorting the magneto.
Next I will to open up the exhaust by removing baffles, drilling holes and shortening the final exiting tube. In addition the carb will be modded (bore it out - and eventually buy a proper one) and re jet it.
Lastly will be to match cases and clean up transfers/ports and then finally mill the head. From what I understand the compression ratio is determined by dividing the cylinder + head volume over the head volume. Now if the engine is at 6 : 1 now and has a displacement of 65.9cc. I calculated the head volume to be 13.18cc.
This is okay but I was wondering what is a good compression ratio to aim for? Most of the 2T bikes out now use 8.5 : 1 - why this number and not more?
Also if I want 8.5 : 1 on my HT Id need to mill of ~2.625mm off the head (calculated this value). But this seems like an awful lot! And me thinks the HT engines wont even last at this compression. So what my questions are...
What other mods can I do?
Whats a good compression ratio to aim for?
- Why are 2T motorbikes all at 8.5 : 1 and not more?
- What compression ratios are other people running here?
How much more power/revs can I expect form an "derestricted stock" muffler vs say one from a pocket bike with a expansion chamber?
Any help would be greatly appreciated!
First Ill run it stock to wear in the engine but once worn in Ill start modding. The first mod will be to rewire the kill switch with a keyed switch (security) and in a way that disconnects the blue wire instead of shorting the magneto.
Next I will to open up the exhaust by removing baffles, drilling holes and shortening the final exiting tube. In addition the carb will be modded (bore it out - and eventually buy a proper one) and re jet it.
Lastly will be to match cases and clean up transfers/ports and then finally mill the head. From what I understand the compression ratio is determined by dividing the cylinder + head volume over the head volume. Now if the engine is at 6 : 1 now and has a displacement of 65.9cc. I calculated the head volume to be 13.18cc.
This is okay but I was wondering what is a good compression ratio to aim for? Most of the 2T bikes out now use 8.5 : 1 - why this number and not more?
Also if I want 8.5 : 1 on my HT Id need to mill of ~2.625mm off the head (calculated this value). But this seems like an awful lot! And me thinks the HT engines wont even last at this compression. So what my questions are...
What other mods can I do?
Whats a good compression ratio to aim for?
- Why are 2T motorbikes all at 8.5 : 1 and not more?
- What compression ratios are other people running here?
How much more power/revs can I expect form an "derestricted stock" muffler vs say one from a pocket bike with a expansion chamber?
Any help would be greatly appreciated!