I have a 2012 300 that I have the top end off right know. I only have 2 day's to reasemble for a race. Should I do a head mod? Is it a simple mod, shaving the head a little? That I can get a local machine shop to do? I read how to measure squish or is there just a safe amout to shave. Do not want to run race gas.
head mod
- Thread starter bones150
- Start date
Jakobi
Super Moderator
You may find you need to add some base gaskets to the stack in order to get the piston flush with the exhaust port at BDC as well which will increase your squish. The idea is then to bring the squish back down tight and then reshape the chamber to correct the compression ratio for your fuels and altitiude, and then I'm pretty sure RB also does a little work to the band itself.
Last edited:
I just had the head skimmed .The squish measured 2.15mm .THe piston at BTC is pretty well flush with the bottom of the exhaust port(maybe .3mm above the port if that).So that gave me some lee way to add a base gasket if it turned to S#$t .I got a fitter from work to skim 0.9 mm from the head.He made an arbor (threaded rod that screwed into the sparkplug hole that allowed fitment to the lathe chuck.He then used a dial guage to ensure the head was spinning true in the chuck.He started turning from the centre out.
The results were...a noticable rise in compression but is still easy to start and runs great on 98 (Pls note this is Australian crap fuel also)
The thing has the ultimate bottom /Mid and the top still has plenty
It ran cooler.It ran to a peak of 82C but sat at around 72 all ride .It usually sits in the high 80-90's.This was 2nd -3rd gear rocky single track for around 30k's
The best part was the fuel economy. I used just on 3 litres for 30k's.The same tracks /same conditions I used over 4 litres for exactly the same distance and tracks.
The full RB mod would probably show even better results and if you live in the States would be the choice but there are plenty of gains from just skimming the head to give a 1.2mm measurement
The results were...a noticable rise in compression but is still easy to start and runs great on 98 (Pls note this is Australian crap fuel also)
The thing has the ultimate bottom /Mid and the top still has plenty
It ran cooler.It ran to a peak of 82C but sat at around 72 all ride .It usually sits in the high 80-90's.This was 2nd -3rd gear rocky single track for around 30k's
The best part was the fuel economy. I used just on 3 litres for 30k's.The same tracks /same conditions I used over 4 litres for exactly the same distance and tracks.
The full RB mod would probably show even better results and if you live in the States would be the choice but there are plenty of gains from just skimming the head to give a 1.2mm measurement
Harry
Member
Hi Bones,
I have done exactly what you have done, my squish ended up at 1.4mm. My results mirror yours too.
http://www.gasgasrider.org/forum/showthread.php?t=10575&page=2
Where are you based?
Harry
I have done exactly what you have done, my squish ended up at 1.4mm. My results mirror yours too.
http://www.gasgasrider.org/forum/showthread.php?t=10575&page=2
Where are you based?
Harry
