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DAVE BOOS (Offline)
  #1 11/25/14 12:08 PM
I've got a 08 R-1 that just started smoking last time we raced it, my son got it to 280 degrees in Dodge City over the 4th of July, melted the stator, I replaced it has run good since then.So I decided to do a compression test on it last weekend before I put it away for winter #1 cyl 165, #2 cyl 155 #3 cyl 162 #4 162, I shot a little bit of oil in lower cylinder next test it shot up to 180, obviously ive got a ring problem. Two guys that we race with that I trust there opinions said to rering it or get another motor, which I am planning on doing. My question is how much variance should there be between cylinders before I become concerned? And also keep in mind that we are at 5600 feet elevation were it was tested at and raced not much lower than that, is there any kind of corrected formula for figuring out what this motor should pump up to (if it was healthy) here at this altitude vs. sea level? I know a lot of guys say they should hit somewhere between 180-200psi? Is it because of altitude that my readings are so low or is this thing just a sick pig? Thank You In Advance! Dave
TQ29m (Offline)
  #2 11/25/14 12:37 PM
Can you do a leak down on it, that would leave out the altitude question, and also tell you if, and where it's leaking, I consider a good leak down anything less then 10%, and, if it has sat for a while before you ck'd it, and you are running alcohol, it tends to dry things out, and may give you some unusual readings, lots of things can make a big difference, and still not be an issue to ring one. Bob

"Being old, isn't half as much fun, as getting there"! Ole Robert I!
Likes: DAD
badcoupe (Offline)
  #3 11/25/14 1:23 PM
Rule of thumb is 15% variance between highest and lowest. Those number don't seem that far to me. Oil will raise reading on any motor regaurdless of condition. If you had a cylinder that had say 90 psi and adding oil brought it up then yea ring issue
Likes: Wayne Davis
DAD (Offline)
  #4 11/25/14 2:40 PM
Dave

I don't put much faith in compression readings. As you crank the engine you tend to dissipate the oil film on the cylinders making uneven readings. (Were Your throttle wide open) (Did they all jump up equal with oil).

Ditch the compression gauge. Get a good leak down gauge, and don't overuse it. You should be 5% or less with a stock virgin motor. I have an old 2000 R6 that still pulls 3% and really 10% ain't too bad to race on. With the leak down you can also take a small piece of tubing and stick in your ports, crankcase breather and determine where the leak is. Look in the radiator for bubbles.

A good leak down gauge is a must have tool for a racer. When you move up in class you use it to adjust the barrel valve in the mechanical injectors.

When they sit over the winter the Titanium valves tend to corrode and will screw up your leak down #s. They gets better the first time you run the motor. A squirt of oil mixed with Lucas oil treatment down each intake port followed with a short crank seems to help a little (don't over do the squirt). Take off your injectors clean out the fuel rails with air and then put some Marvel Mystery oil in the rail to help keep injectors from corroding. Take your battery out and put in on a battery tender. CHILL and start getting ready for Florida.

Honest Dad himself
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