How can one have a 50% drop in compression pressure, but still hold 90% of pressure for 10min - that seems not to add up...

 

It was my first time ever doing a compression test however I did it exactly how several videos said how to do it. I had the bike turn over for no more than 10 seconds and by that time, the gauge was already as high as it would go. The gauge always stopped going up before 10 seconds was up. I understand that it doesnt sound like it makes any sense that its not even half of spec compression and it doesnt really lose any after sitting. I plan on takling the valve clearance measurement this weekend.

 

That doesn't sound like it's running on all four - did you check to see if you have a cold downpipe?

 

I know this is a few months old at this point, but I figured id put it on the internet if someone else needs it. Ive since sold the bike and got another CBR but heres what I found:

Cylinders 2 and 3 were cold after riding around the neighborhood. The shop I had brought it to told me the cam tensioner had malfunctioned causing damage to middle 2 pistons therefore creating the low compression condition. At that point, it didnt make sense to repair the engine or replace the engine so I had sold the bike. I dont recall if I had specified this in an earlier post, but the cam tensioner was aftermarket.

Thank you to everyone who helped and Im back with another CBR