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jamestnewsonr65
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Compression tests on cylinders
04/24/17 at 09:21:23
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So after a few problems starting my bike (Recent posts) it turned out to be a combination of spark plugs, battery power and needing a general tune up.

The timing was slightly off, but all is working well now and the bike fires up nicely.

I did a compression test to see if this was part of the overall problem and I got results of 55psi on the left and 80psi on the right.

Should I be looking to check the piston rings and tube seals?

I checked this by removing the 3 pin lead under the front cover, removing the spark plugs and then fitting a compression tester to each cylinder whilst cranking the bike for 2/3 times.

From memory the PSI should be over 120psi at least, so this is a little concerning.

Any advice appreciated.

  

1983 R65LS completely refurbished to my liking.
1985 R80 nearly stock rebuild (basically new bike).
1981 R65 (box of bits).
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wilcom
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Re: Compression tests on cylinders
Reply #1 - 04/24/17 at 09:49:17
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Did you hold the throttle wide open?
  

Joe Wilkerson
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Menifee, CA

Present:
1984 BMW R65LS "Herr Head"
past:
1979  R65   
1980  R65          
1982 R80RT 
1974 R90/6     
1972  R75        
1964 R50
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Bob_Roller
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Re: Compression tests on cylinders
Reply #2 - 04/24/17 at 15:37:16
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You need to get at least 10 compression cycles to get a proper compression test .

You can stop when the pressure on the gauge doesn't go any higher .

As wilcom has said the throttle needs to be held full open during the test .
  

'81 R65
'82 R65 LS  
'84 R65 LS
'87 Moto Guzzi V65 Lario
'02 R1150R
Riding all year long since 1993 .
I'll give up my R65, when they pry my cold dead hands from the handlebars !!!!!
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Tony Smith
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Re: Compression tests on cylinders
Reply #3 - 04/24/17 at 15:47:08
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jamestnewsonr65 wrote on 04/24/17 at 09:21:23:
The timing was slightly off, but all is working well now and the bike fires up nicely.

I did a compression test to see if this was part of the overall problem and I got results of 55psi on the left and 80psi on the right.


I checked this by removing the 3 pin lead under the front cover, removing the spark plugs and then fitting a compression tester to each cylinder whilst cranking the bike for 2/3 times.

From memory the PSI should be over 120psi at least, so this is a little concerning.




Firstly I'd be buying a new compression tester. Whilst an R65 engine might run with 50~60 psi compression, you would need ether to get it started.

Whilst I applaud the thought that went into disconnecting the beancan, that didn't really stop the coils from being charged up - next time simply disconnect the positive lead to the coil - which as an added bonus, does not require the removal of the front cover Smiley

In respect to checking over rings etc, my question is "how well known is this bike to you?". If it is an unknown that you have just restored to life then I would have checked valve guide clearance, had a look at valve sealing and, give the relatively low cost, probably thrown new rings (and if an iron bore a de-glazing hone) at it because then I could restart the "counter" to when I next needed to look.

On the other hand, if the bike is known to you and the distance  since last top end refresh is around 50,000km (30,000m) then I'd do the top end refresh irregardless of inspected condition. OR, if it is more than 5 or 6 years since the heads were last off irregardless of mileage.

It may be because the wife's original R65 engine was destroyed by dropping a valve (at 60,000km and 9 years since new) or that my own R65 came to me as a result of dropping a valve (at 52,000km and 10 years) but if I take the heads off an airhead these days I replace at least the exhaust valves - they are cheap compared to new head/piston/cylinder and although I have no "proof" I reckon combustion tempos are a bit higher on unleaded fuel.
  

1978 R100RS| 1984 R65 | 1984 XT350 | 1992 KLE500 | 2002 R1150GSA
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jamestnewsonr65
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Re: Compression tests on cylinders
Reply #4 - 04/24/17 at 17:00:26
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Not sure I had the throttle wide open to be honest. I'll try it again and make sure I do.

I've had the bike for 3 years and restored it apart from the engine. It had been regularly serviced and I have every receipt since new. Covered 18000miles and runs fine. No smoke, oil or anything burning/ leaking.

  

1983 R65LS completely refurbished to my liking.
1985 R80 nearly stock rebuild (basically new bike).
1981 R65 (box of bits).
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jamestnewsonr65
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Re: Compression tests on cylinders
Reply #5 - 04/24/17 at 17:03:01
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Here's a pic for the hell of it.
  

image1.JPG (Attachment deleted)

1983 R65LS completely refurbished to my liking.
1985 R80 nearly stock rebuild (basically new bike).
1981 R65 (box of bits).
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Bob_Roller
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Re: Compression tests on cylinders
Reply #6 - 04/24/17 at 21:09:27
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Unleaded fuel has been mandated here in the US for a bit over 44 years, I have not seen any valve related issues in this time on vehicles here .
  

'81 R65
'82 R65 LS  
'84 R65 LS
'87 Moto Guzzi V65 Lario
'02 R1150R
Riding all year long since 1993 .
I'll give up my R65, when they pry my cold dead hands from the handlebars !!!!!
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Tony Smith
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Re: Compression tests on cylinders
Reply #7 - 04/24/17 at 22:42:05
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Bob_Roller wrote on 04/24/17 at 21:09:27:
Unleaded fuel has been mandated here in the US for a bit over 44 years, I have not seen any valve related issues in this time on vehicles here .


Bob - 44 years? Which parallel dimension is yours in?
  

1978 R100RS| 1984 R65 | 1984 XT350 | 1992 KLE500 | 2002 R1150GSA
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Tony Smith
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Re: Compression tests on cylinders
Reply #8 - 04/24/17 at 23:24:38
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Bob_Roller wrote on 04/24/17 at 21:09:27:
Unleaded fuel has been mandated here in the US for a bit over 44 years, I have not seen any valve related issues in this time on vehicles here .


Bob - that may be the case in your dimension, but in mine I think you will find that mandatory unleaded fuel didn't commence until the 80/90s.
  

1978 R100RS| 1984 R65 | 1984 XT350 | 1992 KLE500 | 2002 R1150GSA
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Tony Smith
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Re: Compression tests on cylinders
Reply #9 - 04/24/17 at 23:26:03
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Tony Smith wrote on 04/24/17 at 22:42:05:
Bob_Roller wrote on 04/24/17 at 21:09:27:
Unleaded fuel has been mandated here in the US for a bit over 44 years, I have not seen any valve related issues in this time on vehicles here .


Bob - 44 years? Which parallel dimension is yours in?



bod, sorry for the multiple messages - the forum is going crazy here and i thought my original post went directly to cyber cemetery.
  

1978 R100RS| 1984 R65 | 1984 XT350 | 1992 KLE500 | 2002 R1150GSA
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