Big Problem! Need Advice! 650R leak down test!!


9 replies to this topic
  • August

Posted May 26, 2005 - 12:29 PM

#1

Hey ya'll, I hope some of you can offer some advice, qadsan, borynack, you guys out there?!

Some of you may remember I picked up an 01 XR650R a month back or so and I started tearing into it at my friends shop with his help. we took off the forks and swingarm to lube and service. I am also adding a bunch of aftermarket goodies.

Well today when I stopped by the shop we ran a leakdown test on the bike. I wanted to do this to see what kind of shape the engine was in. When I bought it I looked it over a bit and it appeared the bike had been well maintained. It started easy, no steam or smoke on start up, made decent, if not good power.

Well when we run the leakdown it reads 12%, which in itself is not bad...BUT...we are hearing a gargaling noise when air is applied! The wise old man at the shop seems to think it is the coolant bubbling, you can allmost feel it a little in the hose that comes off the head. It is definatly there and noticeable! Does this mean a cracked head or blown head gasket!! :D

The coolant looks fine, the oil is not milky, could it just be pushing air past the rings in teh crankcase and what we hear is oil gugrling?? The bike is an 01 that is uncorked, as far as I know it was never seriously overheated but I just dont know its whole history. I would hate to tear into the engine at this point but do not want to ride it if its screwed up!

Any advice on what to do guys? I am at a loss at what to do at this point!! :)

  • August

Posted May 26, 2005 - 12:58 PM

#2

Thanks B! I was hoping you would chime in, the whole time we were doing the leakdown I was thinking if a 680 kit was in my future! LOL

Well the bike was stone cold when we did the test, no way to run and ride it right now as the swingarm is off awaiting a new bearing and bushing kit (the old ones were trashed due to lack of grease).

So are you saying if I take the Rad. cap off I should see it bubbling up there, we also thought that maybe it was the oil...I guess another option is to take it to a smog shop and see if they can put a sniffer on it and see if they detect combustion gases from the coolant. Well I will keep this updated as to what happens!

THANK YOU!!

  • zx7rye

Posted May 26, 2005 - 01:41 PM

#3

I did the same thing. My '02 has next to no miles on it. I attributed the issue to a timing mark that does not match up exactly with TDC. I was throwing 100 psi into that motor and also had a hard time keeping it at TDC. I think a piston stop would be required to keep it where it needs to be to get a tight reading. Mine was leaking 11%. You can try throwing less psi at the cylinder. You'll just have to refactor the #'s since it's easy to read a leak% when it's based on 100 total PSI. I tryed to follow the path of air flow and had a good deal coming out the exhaust which indicated to me that the exhaust valves were partially open. Knowing the relative history of my motor, it didn't seem to like the conclusion that my motor leaked like a strainer. Finding exact TDC is the game. Throw a degree wheel on it or simply do a compression test to give you a rough idea of engine condition. BTW, I attributed the gargle sound to oil movement.

  • PowerCell

Posted May 26, 2005 - 03:13 PM

#4

Can we get some "L" riders to chime-in with their sage advice... :)

  • XR-Det

Posted May 26, 2005 - 03:25 PM

#5

Can we get some "L" riders to chime-in with their sage advice... :)

Sure, if its a "L" then I guarantee you its definitely not air bubbling in the radiator :D

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  • miguelitro

Posted May 26, 2005 - 03:44 PM

#6

yeah cuz if it was then you'd be in BIG trouble!!!

  • XR-Det

Posted May 26, 2005 - 03:56 PM

#7

I was just wondering how you get to that % reading?? Is that pressure drop over a certain time?? A minute, 10sec or whatever? Or does it measure how much flow/volume it needs to keep the whatever set pressure??

I doubt that that measurement is very valuable unless you want to compare two identical engines or you have detailed specs about leakage at certain pressure values... :)

I would say a compression test is more valuable since you normally get data about it from the manufacturer and if that fails you use the pressure test to find the leak?

I'm not the mechanic but thinking that this would be my logical approach. Just a pressure test has in my opinion way to many variables...

Like August said, oil is not milky and water is OK . Engine power seems normal - compression checks normal then what is to worry about it? No white or gray smoke, maybe keeping an eye on the water level and its OK to go.

But I'm only a "L" rider :D

  • August

Posted May 26, 2005 - 04:49 PM

#8

I hard time keeping it at TDC. I think a piston stop would be required to keep it where it needs to be to get a tight reading. Mine was leaking 11%. You can try throwing less psi at the cylinder. You'll just have to refactor the #'s since it's easy to read a leak% when it's based on 100 total PSI. I tryed to follow the path of air flow and had a good deal coming out the exhaust which indicated to me that the exhaust valves were partially open. .


Thanks, yeah I think we are actually putting 120 psi to it. I will double check TDC tommorow and play with it some more. We dont have any air coming out the exhaust or carb. I personally think this thing is fine, it is a Honda afterall.

  • August

Posted May 26, 2005 - 04:53 PM

#9

I'm not the mechanic but thinking that this would be my logical approach. Just a pressure test has in my opinion way to many variables...


Well the leak down I think is a better indicator of overall engine condition, you can tell what is wrong, valve, rings etc. The compression test on this thing might take a lil, work...am I right in assuming you would have to disable the auto decompresser?

This brings up another question about compression tests. How much variation is there between a warm engine and a cold one? I am doing a check on a big twin right now and I notice a substantial difference between the two cylinders. I am doing the check when the engine is cold.

  • XR-Det

Posted May 26, 2005 - 06:07 PM

#10

Well the leak down I think is a better indicator of overall engine condition, you can tell what is wrong, valve, rings etc. The compression test on this thing might take a lil, work...am I right in assuming you would have to disable the auto decompresser?

This brings up another question about compression tests. How much variation is there between a warm engine and a cold one? I am doing a check on a big twin right now and I notice a substantial difference between the two cylinders. I am doing the check when the engine is cold.


Sure, I totally agree the leak down test is a nice thing to tell/detect whats the problem.

If you have no values to compare it to its not much use to determin if there is something wrong. Thats what I meant. What do you do with a value of 12% at 120psi if you don't have specs of what it is supposed to be? If you get bubbles in the radiator or air blowing out of the exhaust it would be obvious, but I assume you would have noticed that already by a crappy running engine before you did the leak down test.

I don't know about compression tests on motorcycles and auto decompresser either - hmm I think you are right about that but like I said I am not a mechanic. I've only tested and worked own my old cars back then before I could afford the ones with warrantie :D

Hope yours checks out OK on everything :)





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