soft pedal

[rmxtwofitty]

The bike is an 04cr500af and this is my first 500 so bear with me.

After a few good sand dune rides full throttle full load the bike seems easier to kick over, still runs way fast though. I run it at 32/1 and a little rich for sand dunes riding, but I expect some compression loss.

I came online to find about how much compression to expect from the 500, and I came up with about 150 psi. Is this about in the range? Also I read an old thread that I need more information about.

I don't know about theKX but the newer CR500s had a notch cut into the cylinder wall to allow for easier kick starting. Kind of like the decompression levers(without the lever).

Will this affect the way I take a compression test?
Will this affect the compression level?

Thanks for any input.

 

[Papakeith]

I'm no authority, but I never let that stop me :)

With that said here's my guess:

1. no
2. no

 

[AJ Waggoner]

good guesses PK.

and i'm not expert as well ,
and would defer to Eric Gorr for a full and accurate explanaition.

my take though?

150 is "ok" but a bit low..
but honestly typical compression testing is so "subjective" that few OEMS even bother to give numbers anymore.

one guys 150 is anothers 175 or 128,, not enough consistency in the testing method itself, ,(not the individuals,bu tthat variers greatly too?)


the eyebrows ,, do make it slightly easier to kick/ or start.

they do not effect the engines running compression..they are far to low in the cylinder for that as they ar esiomply reliefs in the upper part above the exhaust ports



as for your 04 500AF

whens the last time tghe top end ewas fresh? the run time , a physica linspection of the bore to piston ring clearence,
and wether it sucked up any sand is a better test than compression testing it...

AJ

 

[rmxtwofitty]

Thanks a lot for the input guys.
1. I clean the air filter every ride and am sure that no sand was sucked up.
2. I think there is about 35 hours on the piston and rings so I expect it is about time to do a re-build.
I agree that a physical inspection is better but I wanted to know what to expect compression wise, and after a rebuild I was considering milling the head to compensate for our altitude here about 5000ft.
Im going to take the comp test now and will post soon with the numbers. Thanks again guys.

 

[rmxtwofitty]

Bum deal guys. It tested out at a low 123. Time to pull it apart and see the damage. The plug had black threads and a light tan center so maybe I ran it a little lean.

Off subject How can I post pictures with my threads?

 

[BSWIFT]

Light tan sounds perfect! It sounds like it is time for a top end but an inspection will answer that question. I'm no expert, like AJ, but, 35 hrs and riding sand says top end to me.
PS, AJ maybe called a "crash test dummy" but I don't think it really fits him.