KX Riders

Maintenance & Technical => KX500 Original => Topic started by: kx666 on October 07, 2007, 03:45:19 PM

Title: High compression
Post by: kx666 on October 07, 2007, 03:45:19 PM
who is running the highest compression on the stock bottom end?

i talked to some one who said they were running 15:1 on the stock bottom end..i dont beleave him...
Title: Re: High compression
Post by: BDI on October 07, 2007, 04:40:39 PM
my bike is 15:1. whats not to believe? I plane to back it down to 10:1 when I run the hydrogen peroxide injection. :lol: :lol:
Title: Re: High compression
Post by: stewart on October 07, 2007, 11:58:55 PM
i have ran as high as 19 to 1  on wiseco ptston but i am running 15 to 1  best all around setup
Title: Re: High compression
Post by: Arigato on October 08, 2007, 01:40:40 AM
i have ran as high as 19 to 1  on wiseco ptston but i am running 15 to 1  best all around setup

What would that be if you converted it to pounds?  I'll test mine tonight.
Title: Re: High compression
Post by: kaw rider on October 08, 2007, 03:31:27 AM
i'm running 15:1 also on stock motor.
Title: Re: High compression
Post by: kx666 on October 08, 2007, 03:12:17 PM
wow.. 19:1 commpression, i am at about 13.5:1 or so, i was told to to go much higher
Title: Re: High compression
Post by: monster malibu on October 08, 2007, 05:14:12 PM
What's the reason you guys want to run high compression on stock motors? Would my 87 KX500 benefit from high compression?
Title: Re: High compression
Post by: KXcam22 on October 08, 2007, 05:47:47 PM
Are you guys calculating with the piston below the exhaust port or above? Cam.
Title: Re: High compression
Post by: Danger4u2 on October 09, 2007, 12:29:59 AM
What's the reason you guys want to run high compression on stock motors? Would my 87 KX500 benefit from high compression?

They run the high compression so only the owner can start the bike.  Less likely to get your bike stolen,  the thief won't know about the high compression.  Thief hurts his leg/ankle, no stolen bike and thief can't run away.  Better chance of catching him.
Title: Re: High compression
Post by: Danger4u2 on October 09, 2007, 12:34:13 AM
More compression = more bang = more power.

With more compression you will have to run a higher octane fuel.  The more compression the greater chance of pre detonation or knocking.  Detroit Diesel engines fire because of compression.  No intake valves, no spark plugs   Air is forced into the cylinder from the blower through the intake ports.  As the piston compresses the air the fuel injector atomizes the fuel right before Top Dead Center.  The high compression creates heat.  Combined with the atomized fuel, it fires.  Most diesels have very big starters and big batteries to combat the high compression.   To shut them down you cut the fuel supply.  Most of the giant motors we had on the drilling rigs I worked on had air starters.  With an air starter you can crank and crank and not worry about running the battery down or burning up the wiring.
Title: Re: High compression
Post by: kx666 on October 09, 2007, 04:21:44 PM
i learned about compression when i was young... with fire crackers...this is why my throttle is on the left side  :wink:
Title: Re: High compression
Post by: FactoryPhil on October 09, 2007, 04:51:36 PM
They run the high compression so only the owner can start the bike.  Less likely to get your bike stolen,  the thief won't know about the high compression.  Thief hurts his leg/ankle, no stolen bike and thief can't run away.  Better chance of catching him.


Hahaha. Nice one dude! I needed a good laugh tonight!
Title: Re: High compression
Post by: BDI on October 09, 2007, 05:10:15 PM
If I catch some one trying to still my bike I'm going to be pissed because I do not like digging holes or dragging bodies.
Title: Re: High compression
Post by: FactoryPhil on October 09, 2007, 05:17:59 PM
Yup, plenty of easy diggin' sand out here in the desert. Rule of thumb....don't f**k with KX500's!
Title: Re: High compression
Post by: Arigato on October 10, 2007, 01:39:03 AM
How many PSI is 15:1?
Title: Re: High compression
Post by: stewart on October 10, 2007, 02:41:25 AM
that would vary some with port timing and  ring seal   but 230 or so
Title: Re: High compression
Post by: doordie on October 11, 2007, 10:36:31 PM
Are you guys calculating with the piston below the exhaust port or above? Cam.

The right way in my opinion and even almost the whole "twostroke-world" is when piston close exhaustport and start begin to compress.


(Look at Kawasaki manual:Low rpm/exhaust porttimes low(KIPS)/more compression) :wink:
                                   High rpm/exhaust porttimes high(KIPS)/less compression

As always: just my 2 cent :-D
Title: Re: High compression
Post by: stewart on October 15, 2007, 01:54:39 PM
doordies right  i was giving  total from 86 by 86 to my 35cc chamber
Title: Re: High compression
Post by: BDI on October 15, 2007, 05:38:42 PM
At some point when the pipe starts working the theoretical compression ratio will become the actual ratio. It is best to build the engine based on the theoretical ratio. If you build the engine based on the exhaust port hight what you think is a safe compression ratio will become astronomicaly to high when the engine comes on the pipe.