GP head
 

Is there any big difference between GP head and std head on -18 ?
Particular in squish? Have problems with detonations and my thoughts are maybe the head or timing😳

Check and see if the CDI mapping update is also for the GP edition. One of the guys here had a little detonation and had the CDI update on the regular XC and it cleaned things up.

The GP head is different but I’m not sure about the squish. My guess would be that it’s still a pretty big gap. My detonation issues were solved with proper jetting. The stock needle in these bikes is garbage


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It is the new mapping and it get worse after that, all people i have spoke to have GP head and it runs ok with smal detonations some time. So my thought are that std head is maybe te problem for me?
Have tried all kind of needels rum and yz needle and Main jet.
It runs perfect in 1?3 gear in tight enduro but in 4-5 gear under a while the detonation starts.
Currently have stock jetting but it goes crap but detonations is a little smaler with thath

Do you have better gas available? No air leak on airbox/filter yo make it lean?

Measured the squish on my GP300 and it was 1.8mm at the narrowest point at the cylinder wall with the standard 0.5mmm base gasket & 160psi compression at WOT. The squish band has a fair amount of taper on it.

I tried a 0.15mm gasket to replace the std gasket for 1.45mm squish and it was pinging with 98 RON fuel. Compression increased slightly to 165 psi.
Next I put in a 0.3mm gasket for 1.6mm squish & it seems better, with no pinging and running cleaner with 38PJ NECH# 2 172M.

My squish measured in at 1.8mm as well, I put it in the lathe and took .5mm off. this made a fair difference to the bottom end. I had had the detonation problem as well but found that the suzuki necj needle (that was installed on the gp when i purchased it) was causing the problem as it creates a lean condition at 3/4 throttle opening. I have a ktm needle installed now that has greatly improved the detonation problem and have the standard needle ready to try with a leaner straight section. so will report back with findings

Jetting
 

I used the jetting off the Beta 300 chart and have not had any problems.
bike is very crisp fom idle to WFO.Use the Beta needle and their pilot and main jet recomdations and the bike will run like it was ment to. the stock needle has never worked in the gasgas, you nedd to throw it in the garbage.