TOPIC:

If u guys are pinging, back off the timing, if you lose power, try better gas, if you have a piston kit u have to back timing off, otherwise youll ping (faster burn), get this straight, get it good , change the timing, check it out, then tell the tale. Ill still be here. I, always listening..... im waiting??

Still there?

Sent you pm geek

FWIW:
I put a tank full of 89 octane in on Sunday. I usually put in 87 Regular.
Anyway, I rode 20 miles up the fwy to Rosamond (checked out APE Jay's new place. Nice building, but was closed).
It was a hot day, and during the trip, I tried to get the motor to ping. Opened the throttle when I should have downshifted, mostly.
I listened hard, but could not hear a single ping/knock.
Could it be that simple?

ive been using water for years to de-carbon engines...mainly to lower emissions and help past inspection on autos, my grand father used to do the same on his old tractor. water works extremely well for this ....But you must use small amounts and in short bursts as not to warp the valves...i use a cheap spray bottle with warm tap water on a hot engine...rev the engine to about 2000 rpms..i set the idle screw for this...then spray each carb without the filter till the rpms drop about a thousand rpms the motor will bog and then build back up to the 2000rpm. do this several times. an old windex bottle about half full of water should be plenty. just remember not to spray to much or POUR the water in....if you quench the hot valves to quickly they WILL warp. but it is amazing how well this works..pull the plugs when your done ..they will be clean and shiney like when they were new ...so will the combustion chamber.
in my experiance there is no combustion chamber cleaner that works any better than plain old water.

Maybe practice on the lawnmower till ya get the hang of it...

also...was wondering why temp would change octane requirement?
Ed

EddieBoy wrote:

also...was wondering why temp would change octane requirement?
Ed

My theory is that when the chamber is hot, the chance for pre-ignition is greatest. So on a hot day, the motor's not cooling like it can on a cool day. So the temps in the chamber are higher and the engine is more likely to ping. Higher octane fuel ignites more slowly, so it's less likely to flash before the plug sparks it, fighting the effects of pre-ignition.
Well, that's my theory.

ltdrider wrote:

EddieBoy wrote:

also...was wondering why temp would change octane requirement?
Ed

My theory is that when the chamber is hot, the chance for pre-ignition is greatest. So on a hot day, the motor's not cooling like it can on a cool day. So the temps in the chamber are higher and the engine is more likely to ping. Higher octane fuel ignites more slowly, so it's less likely to flash before the plug sparks it, fighting the effects of pre-ignition.
Well, that's my theory.

I'll agree with that theory...

so would a richer mixture in hot weather effect detonation?

"Richer" just means a higher percentage of fuel in the fuel/air mix.
If it's rich, there'll be left-over fuel because it can't all burn. Will that keep your chamber cooler? Probably, but it wouldn't be worth the poor performance and build up on the plugs and pistons.

good point ltd....
but lets say the motor runs 200 degrees and doesnt ping an a 90 degree day...today...
and tommorow its 130 degrees outside and the motor pings. is it because the outside temp on the motor does not effectively cool the motor at the fins and raises overall motor temp...or the incoming fuel/air charge is hotter therefor leaning the air/fuel ratio? or both? i am genuinely curious about this.

The hotter the air the richer its going to run unless the fuel is evaporating faster (less fuel to air). The air gets thinner and the motor is hotter from the high temperatures, its give or take a little as far as which wat the mixture is gonna go. A bike motor really runs lean in cold weather. If i run lean at 85deg. then at 50deg im looking at scoring pistons depending on the temp of the motor. If im rich at 85deg, at 95deg im leaner because the motor is hotter and evaping more fuel on the way in. My bike runs crazy on a cold day. I gotta jet it down some and see what happens in the heat. Id like to get that cold air power if its possible. Ive tried 89 and plus but it ran slower. 87 is fine for the 180psi 150with cams that im running. If i dont back the timing down from factory it will have loads of torque but fights itself at higher revs. Ill set timing advanced, run it on the road, back it down till the top is clean, smooth and powerful. Then im ready to go fast. And the motor stays cool. If you back the timing off too much, youll lose valuable torque and fun, but you cant have the engine advanced too much and vibrating and hitting the wall at high revs. Its hard on the motor and your corraling all the top end power. An engine actually sounds like its revving quicker with advanced timing, and its very deseptive, its only when you back it off and try it that its noticabley quicker to rev. If it sounds like one big roar its too advanced. If it snaps up fast and then cracks like thunder, its right where it will perform the best on the road.

i like the seat of the pants approach as well...and what you say sums it up....
what i have a hard time understanding is how a few degrees of ambient temp...say the difference between a 90degree day and a 110degree day...all things being the same..would cause detonation. and change the octane requirement. piston slap i could see...but not the octane requirements.
would it be safe to say then that a bike run in the winter needs a faster flame front than a bike in the summer? even thought the operating temp of the motor itself is nearly the same?my kz1000 has a comp ratio of 8.5 to 1...at what temp should i expect that i need a higher rated octane or slower burn?
do the air/fuel molecules in the combustion chamber become so excited and expanded they spontaniously explode?whats the trigger?heat or compression if not the spark...now im talking about a perfect ,new, clean no carbon build up 8.5 to 1 motor...say in a temp controlled room...i sit this engine at say 5000rpms...and start slowly raising the temp in the room to say 200 degrees from 50 degrees. at 80 degrees all is fine with 87 octane. but at 100 degrees it starts to ping? what would happen at 150degrees?
BTW great thread!

you're only assuming engine operating temerature is 'about the same'.

this guy has a different opinion:
www.directparts.com/static/articles/sparkplugs.html

"Unless you live in the desert it should be getting nice and chilly in the winter, and the good high test you run in the summer to keep the engine from hot detonation will now be keeping the engine from reaching operating temp.[ ... ] Regular gas burns hotter than high test [ ... ] "