Hello guys I had two pistons with signs of detonation. There were some circumstances. The 102octane was out of stock. So i tanked the regular euro95. I was 33Celsius and moisture was high. It happend at the motorway at 120km/h about 6krpm. I noticed the temperature needle was almost out of the green zone. What can i do? Retarding ingnition now 26 deg at 6krpm. Raising barrel by thicker gasket. Modify the head volume. But how much? Yes oringed head and ss GR exhausts, vforce4. If there is someone with experience please some advice. Here some pics.
If it was overheating, then it did at 6krpm and 1/4 open throttle. The needle of the temp gauge was high but on its last bit of the green part. This was at highway sustained 120km/h speed. Kenny tsa also suggested overheating. I asked him were to look for. To complicate things i did 15km to come home with that holed piston. Can the clamping marks cause the overheating?
Never did a plug chop at 6krpm and 1/4open throttle. I will check needle clip position was it 3 or 4?
Hi Marrcel your sum is slightly wrong. The compression ratio 13.1
You have to add your swept volume and the volume measured above the piston together. You then divide the result by the volume measured above the piston.
I always fill direct to the top of the plug hole and take away 2.5cc for the spark plug.
13:1 is doable my bike runs this compression ratio. i am very interested to know about your needle height.
To solve that stutter around 5,500 - 6,000 rpm people drop the needle to make this part more lean. I don't like to do this as just above the stutter range the carburation can be come dangerously lean before richening out for more throttle.
Last Edit: Oct 13, 2019 16:32:24 GMT 1 by Tobyjugs
Yes Kenny is right the O-ring needs to be squashed down into the groove. The groove has to be wide enough to let the O-ring spread out without damaging it. When i was sourcing O-rings for my cylinder head i was advised by a friend in my technical department to use an O-ring with a Shore 70 hardness rating
Thanks guys. My engineer suggested to make a round groove not rectangle. I will post details soon. Another thing is the needle and emulsion tube. Will raising the needle be enough? Clip was at 3 in the middle. Or is a thinner needle or other emulsion tube the way to go? Drilled airbox
Just did some oring calculations. I am not an expert. Can one of you check the calculation? I want to use the same 0ring 72x1,5mm. I have 8 of them see pic. But it gives a caution in the calc sheet about free groove volume at min? My current groove size is 1.15mm depth and 1.4mm wide. Largest outside diameter is 73mm. So according to the sheet my oring groove has to be wider from 1,4 to 1,86mm. Is this ok?