Leak Down Test Results


9 replies to this topic
  • kdtg

Posted December 14, 2005 - 04:02 PM

#1

I've got a 1995 XR600R that is having some issues and I took it to a local bike shop. I just heard from the shop and they had a 35% leak down test result. He said that was quite a bit but not terrible for this bike. I'm having trouble with the cough and die at idle syndrome. Could a poor leak down test contribute to my problem?

  • J_Daniels

Posted December 14, 2005 - 04:29 PM

#2

I used to be an auto mechanic, and I seem to remember that 5 to 15% leak down were good numbers. I would expect an air cooled motor to have higher numbers based on the increased clearances needed to allow for expansion, so your 35% is probably still pretty high. Keep in mind that these numbers are based on a warm motor, and will increase quite a bit when the motor is cold due to contraction of the parts allowing a looser fit, as well as the reduction of engine oil around the rings if the motor has not been started recently. With a leak down test, the mechanic will typically use a stethoscope to listen at the air intake, exhaust, and crankcase (oil fill point on wet sump engines, crank breather hose on dry sump). By listening carefully at these three points, the mechanic can pinpoint whether the leak is occurring from the piston rings, intake, or exhaust valve seats. Sounds like your shop can do a bit more to narrow down the cause of these numbers and help point to where the problem lies. I would be concerned about a 35% leak down number, but there are many factors other than low compression that could be causing the problem you describe.

  • kdtg

Posted December 14, 2005 - 04:44 PM

#3

The compression test result was 155lbs.

  • Xr650rhonda

Posted December 14, 2005 - 04:52 PM

#4

The compression test result was 155lbs.


Now that seems low, It should be 185.8-214.2.

  • kdtg

Posted December 15, 2005 - 05:00 AM

#5

I don't know if they listened with a stethascope or not I'm going to pick it up tonight and will get to ask the tech some more specific questions.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • creeky

Posted December 15, 2005 - 05:32 AM

#6

35% is a little too much and the compression pressure is low. If the shop hasn't done it already, I'd go for a valve adjustment in hopes that one of the valves is a little tight. If that doesn't help, new rings and a valve job should do the trick.

  • bootlegger2

Posted December 15, 2005 - 08:32 PM

#7

dont forget to let us all know what the verdict is.

  • bork

Posted December 16, 2005 - 07:19 AM

#8

How is a compression test done with an auto-decompresion on a stock bike ?

  • mtrhd101

Posted December 16, 2005 - 08:37 AM

#9

Consider too that cough and die is usually related to a lean condition.. Be sure and check for air leaks and a pilot jet partially clogged, along with the valve adjustment.. 155 is not great compression, however, it should run for sure.. Furthermore, whatever shop did the work should have already checked for a tight valve if they were at the point to even consider doing a leak down test.. You check the valve clearance before you do a leak down test... :applause:

  • Xr650rhonda

Posted December 16, 2005 - 06:46 PM

#10

Do you ever hear any piston slap at idle?





Related Content

Forums
Photo

ignitech programmable XR650L CDI by brianhare


Dirt Bike   Make / Model Specific   Honda   XR600/650
  • Hot  60 replies
Forums
Photo
Washington

Cle Elum Sunday 5/29: Looking for dual sport tips by TigerTanker


Dirt Bike   Dirt Bike Regional Discussion   Northwest
  • Hot  32 replies
Forums
Photo

Post Apocalypse, ThumperTalk style! by Justin Pearson


Dirt Bike   General Dirt Bike Forums   General Dirt Bike Discussion
  • Hot  35 replies
Forums
Photo

Wiseco 101MM Spark Knock Low Engine Temps by imandrewparks


Dirt Bike   Make / Model Specific   Honda   XR600/650
  • 7 replies
Forums
Photo
Supercross

Supercross Preview 2017 Part 1: Championship Contenders by Chris Cooksey


Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  132 replies
 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.