GY6 Honda scooters and the Chinese versions of them.
http://www.ebay.com.au/itm/ATV-Quad-...-/251254862471
here are the various sizes and dimensions
https://sites.google.com/site/motorp...tor/moped-carb
Yamaha SRV250 have 26mm downdraft ones as well.
The 250 Fours have 28-30mm CV carbs
O well, I guess I deserved that. The Yamaha AG 100 piston split in two, almost. After a good hard high speed run. I was trying to get some sort of control before I videoed it but too late now.
Fixes
1 Replace the piston with a forged one
2 Water cool the head as it gets hot. Probably aiding and abetting early combustion as the head gets hotter.
3 Needs the high speed small piston set up ( oval gears ) to get a more accurate combustion point, at the moment it's all happening a bit early but because of the need for high compression I don't have much choice with this setup.
4 I see the crank case is full of oil, maybe as the engine speeds up it's pushing too much oil into the combustion chamber causing it to hydraulic? At first when it stopped suddenly from high speed I thought it had seized as it stopped so fast. Perhaps thats what did the damage? No signs of seizure. A dry top end would be nice (Ryger).
5 Where did I put that supercharger?
I'm sorry, I was so ashamed of that first video I wanted a decient one to replace it, with me under total control, Ha Ha.
Some pictures of the damage, only the Yamaha piston, everything else is still good.
See exhaust runaway gate.
Little tank was full of Kerosene / oil mix, started on CRC spray can.
My pleasure Neil. Here's a version with a couple more functions. Let me know what else you need.
HCCI.zip
Just out of curiosity is the TiN a PVD or a CVD process? Many years ago I was playing with this stuff on piston rings and testing it against arc sprayed / plasma sprayed coatings for cylinder liners
No success, after much thought It would seem I've done the wrong thing. I have a better idea with way more control, I think.
And easy to make. Mark two.
Apart from the exhaust pipe that you're going to need anyway and that would prevent the engine from inhaling oxygen through the biggest port?
A decent pipe can markedly raise the cylinder pressure at exhaust closure and that will change everything that happens further in the cycle.
Like how much compression you need, and when you need it.
PS: after seeing the pictures of your HCCI head I understand why the 30,5 mm bore and 8 mm stroke. I knew there would be a good reason for it .
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