BMW Service - Airhead Engine Evaluation
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- Опубліковано 7 січ 2013
- Performing a leak-down test on an R90/6 engine that has 70,000 + miles on it. This is the most important test that you can perform before you purchase that used Airhead that looks so good.
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Great to see a working mechanic with used tools not always perfect, doing stuff to worn machinery not just brand new problem free stuff, great job great videos, cheers
Great video and saved me a bunch of money. Had a lot of symptoms of leaking rings and had a mechanic do a leakdown test, and sure enough 23% leakage on the right side, pushing oil out of everywhere on the left at speed. They said they would have no way of knowing where the leak was unless I left it with them to take the engine apart. I used your video as reference, to which they said "we will call you back". Ten minutes later he called and said it was leaking into the crankcase. Bringing the bike home and using more of your videos to start taking the cyclinders apart myself. Keep up the great work! 1975 R75/6
That is a great story Joe and exactly why I do these. Happy New Year, Chris
Every time I watch these clips I learn more. THANKYOU
Yes, absolutely! I usually perform a leak-down test first (after an initial test-ride). Unlike a compression test, you need not have the throttle wide open during the test as with a compression test and you do not need to bother with a compression test at all. The leak-down test is far more precise in determining if you have an engine problem. Thanks for your question.
Chris, your videos are great, cheers :)
Fun video and informative. Thanks. Helps me with my R50US.
You are welcome. To answer your question: You could certainly use the hose from a compression tester (remove the schraeder valve) and add a pressure gauge and a fitting for your air hose to the end. Then just connect the air hose and slowly open the valve on your air compressor to charge the cylinder.
Hey Chris, thanks for all your video posts, they are extremely informative, I have a 1978 R100RS that I am rebuilding and got it finally started today after sitting more than a year and noticed smokin out of exhaust under throttle, I'd like to send you a video clip of it if possible for you to see to get an idea where to tackle it without spending unnessesary money? Thanks again Ray
Thank you!
Thanks for doing this, Chris. It's certainly appreciated by the airhead community. Do you happen to have any advice on making my own device to perform a leakdown test?
Ok Chris ;) thank you for your great job! Bmw Airheads Italia is on facebook if you want you 're welcome!
You'd have to disassemble the cylinder and inspect the rings and piston. I've yet to come across a BMW with stuck rings that wasn't seized, usually from water in the cylinder.
Great vid. Can the leakdown test be effectively executed with the carbs and exhaust system in place? Thanks.
Hi Chris! I’m doing this test with new rings and rebored cylinder. I’m still getting 80% leaks. The ring gaps are 0.3mm, 0.3mm and 0.25mm. Is it possible to seal with gaps that large?
Good video. On the right cylinder where you had the 20% leakage, how do you determine that the rings are worn versus a stuck ring due to carbon build up?
Do you know anything about the 1973 R50/5 it is made in Germany? Is it worth restoring? Are these rare motorcycles?
Yes.
Compressors are not cheap. Where could I get air ? Although making one with a motor compressor from refrigerator is possible I believe, have heard .. Thanks for the test and video -- great idea ! I bought new /5 in `71
Does the 100 lbs pressure apply to all airheads? Mine is a 78 R45/N. Burning oil on the left side. Thanks! Dee
Hey Chris... I love airhead bikes and I've two... This test must be do when engine is hot. In my opinion that test isn't real and sure because rings tolerance when engine is cold are bigger and is a normal leak. You agree? ;)
Hi, I do not agree. You must do this test cold AND hot. If you have excessive blow-by when cold it will most likely be there when the engine is at operating temperature. If you are merely doing a compression test then yes, you'd be 100% correct. A cold compression test = poor results as it will all change when the engine reaches operating temperature. But the leak-down test will reveal, even on a cold engine, exactly where you are losing pressure (intake, exhaust, crankcase). Thank you though, C
Hi, Chris. I've watched your videos so many times over the years, I feel like I know you. I certainly appreciate you. I did a leak down test today with a Lang tester (looks exactly like your SnapOn) on my /5 (~50K miles), and I got just 5% leakage on both cylinders. I did each cylinder several times just to make sure, since this was my first time doing it. I trust the gauge, as it did show a significant leak once when I wasn't on OT, but my only uncertainty is how much it *seemed* like I was leaking from the crankcase. When I'd pull the dipstick, I'd get the same extreme change in tone that you got in the video. No obvious wind on my fingers, though, so I assume I'm good and I'm just overthinking like amateurs do. Do you agree? Much thanks in advance if you decide to reply. Hope you're doing well in this time of pandemic. ~Mark Wicklund
Your 5% leakage past the rings is not a problem. Ride it! All healthy here, Mark, thanks.
Good job on the video. And I don't even own a BMW. :-)
Hi Chris.
I recently bought a 49k mile 1984 r80rt paralevel. It’s been in the previous owner for 5 years. I know I have done a stupid thing since I didn’t try to check it before tearing down the engine to change the piston rings and reseal the cylinders. I believe that I got all of the assembling procedures correctly because I watched your video and performed it myself. I did the compression test (cold engine) and the right cylinder read 125psi while the left side only read 75psi. Then through this video I bought a leakdown tester at harbor freight. Unfortunately it only show 15psi at the input gauge while the leakage gauge reaching 0%. At this tine, both passed the leakdown test, the leaking rate between 5-8% at TDC (still cold engine). Is it because of the cheap tool? I left the rocker cover on the left cylinder (failed air compression test? through the night, and the next morning I see some oil leak from the top rocker arm through the two top stud rods. I couldn’t check the right side (passed the air compression test) because I torqued the rocker cover back. Would you please diagnose what is the problem that I am facing or what did I do wrong at least?
Thanks,
Tri
Tri, I replied to your message. Chris
You’re the best. Thank you so much.
@@tnguyen-jf1pm You are welcome, Tri. I wish you luck, Chris
Do you have to drain the oil first to do that?
To perform a compression or a leak down test; No, you do not need to drain the engine oil.