chilly premix

Andy Kiker · Posted: Thu Oct 25, 2012 11:40 am Post subject:

Ian, Glad to see you back to your usual self. Very Happy

I see you or someone took off the four corners of the piston.
I also had to start doing this with the Honda when I ran it.
Just curious as to why? Did not seem to have to do it until we started turning it above 11,000. Any correlation?
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Andy Kiker #24

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al nunley · Joined: 13 Nov 2006 Posts: 3037

Would like to see a picture of that piston from the top. Even a close up of the head. Do I see detonation on the edge of it? That edge has the look of “sandblasting”. That’s what detonation looks like.
Detonation is caused by excessive heat and/or pressure.
The reason you get peak EGT reading at peak RPM is because that is where the cylinder pressure is the least. The 2cycle reaches peak pressure at peak torque, and that is why you need to watch the EGT coming off the corners. Even thou the EGT reading is less at that point, you can still get detonation if the pressure and/or temperature is above the fuels ability to resist it, caused by a lean mixture. It’s no secret that the KT runs best with a rich low speed mixture.
If the pipe is right, it can produce pressures, at low speed RPM’s, above the fuels ability to handle.
Doesn’t it stand to reason that peak torque is reached with peak pressure in the cylinder.
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If the data does not support the theory, get a new theory. (Al Nunley)
All else being equal; Compression is the Holy Grail.
45 years, in and around karting

Racer Johnson · Joined: 08 Feb 2009 Posts: 116

AL I gotta be honest sometimes when i read your posts I feel like im on LSD..... Surprised

Ian Harrison · Posted: Thu Oct 25, 2012 5:27 pm Post subject:

Hi Guys

Well spotted, Andy!! This was a brand new A cylinder at the start of the meeting, so I cross-hatched the corners with 120's production paper. This gives a little extra in clearance and retains a bit more oil. It's all about the temperature of the piston (i.e. expansion). The higher the revs and the longer you stay on the gas the bigger the piston gets. So the higher revs we use now do put things closer to the edge. I'd say I did a good job as you can see the vertical polish lines have almost obliterated the cross hatch right on the corners and also the 2 x polished "eyes" on the front lower skirt. Without the hatching that piston may well have stuck. After a new cylinder has had 3 pistons through it, I don't cross-hatch any more (with standard Honda 'A' pistons). It can make the exhaust port-bridge scuffing a little heavier in the crankcase induction Honda and encourage rear cracking on the cylinder induction.

Hi Ted, your reply is actually closer to topic tha Al's . . . . well done matey Wink

Hi Al, I'll do a picture when I get to work tomorrow. No det. but right on the limit. 60 taps on the det counter and that's spot on for me in a 35kM race. Suddenly, a change of tack, no comment regarding "gumming" , which, I thought was the topic? but a load of "so what!!!!!" regarding cylinder pressure and KT100's (I guess?). Silly me I thought this was a 250 Superkart Forum. Nobodys attacking you here, just stating a few facts. . . . ease of that throttle a bit and relax Laughing

Of course it's as dry as a knat's scrotum in line with the transfer windows and round the back half. I'll say it again, that's the only way to run with unleaded Laughing

Eric, I know what you mean . . . . sort of surreal . . . peace and love man Confused

Best Regards

Ian Very Happy

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Ian Harrison
Viper Racing UK
www.viper-racinguk.co.uk
sales@viper-racinguk.co.uk
+44 7984 225 564
+44 161 343 2009
Championship winning Superkart race team 1997-2012

Ian Harrison · Posted: Fri Oct 26, 2012 12:57 am Post subject:

Hi Al

Just for you!!

No det . . . . smooth as a babies bottom . . . . but absolutely right on "the nuts" Cool

OH . . . and still no gumming *"%:&^!

Heres a twin straight off the dyno on Avgas 100LL and Castrol A747 Castor.

Not as much running, but just as nice Cool

Best Regards

Ian Very Happy

_________________
Ian Harrison
Viper Racing UK
www.viper-racinguk.co.uk
sales@viper-racinguk.co.uk
+44 7984 225 564
+44 161 343 2009
Championship winning Superkart race team 1997-2012

Sam Zavaglia · Posted: Fri Oct 26, 2012 5:17 am Post subject:

Ian Harrison · Posted: Fri Oct 26, 2012 6:15 am Post subject:

Hmmmm, Sam, A bit of Al reply anticipation going on there. Just surprised you didn't comment on the missing rear cylinder bolt on the SAFE Wink

Chris Reinhardt · Posted: Fri Oct 26, 2012 8:50 am Post subject:

Ian Harrison · Posted: Fri Oct 26, 2012 9:26 am Post subject:

Hi Chris

Yes that's the plan once Sam gets the detto harness made, I'll be wiring in the TPS on the Mikuni TMX as well.

I'm just waiting for the first "I really was flat in top through there". . . . in your dreams, perhaps Wink

Best Regards

Ian Very Happy

_________________
Ian Harrison
Viper Racing UK
www.viper-racinguk.co.uk
sales@viper-racinguk.co.uk
+44 7984 225 564
+44 161 343 2009
Championship winning Superkart race team 1997-2012

Sam Zavaglia · Posted: Sat Oct 27, 2012 3:30 am Post subject:

Gerry MacNutt · Posted: Sat Oct 27, 2012 9:59 am Post subject:

ELF does not sell oil on the west coast of USA or Canada, or at least I've never seen it for sale.

Chris Reinhardt · Posted: Sat Oct 27, 2012 11:58 am Post subject:

Ian Harrison · Posted: Sat Oct 27, 2012 6:07 pm Post subject:

Gerry MacNutt · Posted: Sat Oct 27, 2012 9:15 pm Post subject:

OK, maybe better put, ELF is not highly available at most retail outlets on the westcoast, for what ever reason.

Chris
thanks for the tip!

Gerry MacNutt · Posted: Sun Nov 11, 2012 10:55 am Post subject:

update, temp was around 32 (burr) in the morning, I ended up using Motul 800 roadrace, seemed to work good , motor was making real good power.