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Old 05-21-2013, 11:05 AM   #61
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Old 05-21-2013, 04:57 PM   #62
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I saw something like this once on an old Guzzi that had been sitting and it was a clogged crankcase breather.
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Old 05-21-2013, 11:32 PM   #63
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Since the jetting, carburetor adjustment, timing .... seem to be spot on I'm thinking a colder spark plug. Right now the motor has NGK BP6ES and I'm thinking about Bosch W5DC's. Thoughts?
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Old 05-21-2013, 11:52 PM   #64
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Originally Posted by bmweuro View Post
Since the jetting, carburetor adjustment, timing .... seem to be spot on I'm thinking a colder spark plug. Right now the motor has NGK BP6ES and I'm thinking about Bosch W5DC's. Thoughts?
First establish detonation, then establish why.

You say there are no signs of detonation? Then don't fool with the plugs.
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Old 05-22-2013, 05:52 AM   #65
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I have a 1981 R65 with a genuine 7500 miles on the clock, on starting from cold the engine is very quiet, when it's warmed up there is a definite knocking sound from what appears to be around the clutch/gearbox area ( not verified as being positively from there ) pulling the clutch in and selecting a gear doesn't alleviate the noise, still there when the revs rise through the range, all oils are new, the carbs. are balanced and the bike runs very well. I'm looking for pointers as to the possible cause of said knock before having it attacked and stripped into pieces.

Thanking you in anticipation...
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mike delacoe (mike delacoe)
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Posted: Sun Apr 21, 2013 11:53 am Post subject:
Hi Terry,

Any chance of posting a video clip of the bike running so we can listen to it?

Mike
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grimreaper (Terry Clark)
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Posted: Sun Apr 21, 2013 1:31 pm Post subject:
Hi Mike

Thanks for the prompt reply, the bike is at present with a mechanic friend of mine, I should be able to get a video of it later this week and hopefully post it.

Thanks again
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bwprice (Brian Price)
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Posted: Mon Apr 22, 2013 9:34 pm Post subject:
.
Hi Terry

It does sound worrying and possibly something worn in the engine but saying that I do of one member who had a similar tail then only to find it was the lock stuffed up the frame tube under the tank.

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John King (John King)
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Posted: Mon Apr 22, 2013 9:53 pm Post subject: Knocking
I will hold my hands up to finding the lock and cable inside the top tube. They say lightening doesn't strike twice in the same spot, but it may be worth just having a look. The knocking on mine kicked in around 3500rpm and went about 4000.

The other thing I thought of in your case was possible worn needle bearings in the rockers. The thicker oil may conceal the wear when it is cold but when warm and the oil thins this can set up an awful din!

Then there is the possibility of a worn cam chain and tensioner blades. The cam chain is tensioned by oil pressure. Again when it is cold there will be enough pressure to keep the tensioner piston hard against the chain but when it gets warm the pressure will drop and the knocking will start.

The needle bearings can be done by a competent mechanic with knowledge and the right tools to remove the old ones and press the new into place, but that is a job I would leave to a specialist, only 'cos I have not got the tools.

Replacing the cam chain and tensioner is a relatively easy job that can be done by someone who knows a spanner from a screwdriver and can work methodically.

I have just re-read your original post and see that your bike has only done what is running in mileage, I would still look at the cam chain tensioner. They are made of plastic and could have broken up with lack of use in the years since it was made.
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grimreaper (Terry Clark)
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Posted: Tue Apr 23, 2013 10:06 am Post subject:
Thank you for your replies, it isn't a lock in the frame tube but my mechanic is going to look at the cam chain and tensioner this week, he is a very competent and trained man, builds lots of engines for classic bikes, road and race, but his knowledge of old BMW problems is limited, he is very well respected and has a fully equipped workshop so needle bearings wouldn't be a problem, anything from piston slap, rocker wear or little ends wouldn't be a problem and would be relatively inexpensive to correct. Thanks to you all for the response and suggestions, I'll keep you posted on events.
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R1100RMAN (David Day)
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Posted: Tue Apr 23, 2013 1:40 pm Post subject:
I helped rebuild an R75 engine of the same era and mileage that had a "big end knock".
It only knocked when warm at tickover and at intial acceleration. The rebuilt engine was no better, and in the end it turned out to be harmless backlash between clutch plate and splines. It sounded more or less the same whether or not the clutch lever was withdrawn.
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grimreaper (Terry Clark)
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Posted: Tue Apr 23, 2013 1:58 pm Post subject:
David,
Thank you for your reply, that sounds to be on the right lines and well worth bearing in mind, same symptoms for me, knocks clutch in or out, I can't actually hear it whilst riding the bike but I can when stopped at lights etc. certainly there at standstill and with rising revs, trying to pinpoint the location accurately is nigh on impossible, I'll certainly put it to my man as another feasible option. Still hoping to get some video/sound footage later in the week.
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grimreaper (Terry Clark)
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Posted: Mon May 20, 2013 10:08 am Post subject: R65 mystery knock update
To all the respondents to my R65 problem, I'm afraid I wasn't able to get the requested video but on the advice received a new cam chain, tensioner and other gubbins has been fitted and hey presto the problem has now gone away. Thank you again for your input, much appreciated...
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mike delacoe (mike delacoe)
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Posted: Mon May 20, 2013 10:24 am Post subject:
Hi terry,

Thanks for the update, always good to hear a successful outcome.

Mike
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jonah (glyn jones)
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Posted: Mon May 20, 2013 7:49 pm Post subject: Worn - possibly not
I've tried,not hard enough,to stay out of this conversation. What on earth has worn in an engine only 7,500mls old? Glyn

It is probably down to the plastic/rubber components degrading or even breaking up over the time it has been in the engine and that will accelerate the wear.
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grimreaper (Terry Clark)
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Posted: Tue May 21, 2013 9:48 am Post subject:
I must admit I found it hard to believe that anything should be worn out at that mileage, I think age is the problem, there were grooves in the tensioner and guide that's all, the fitting of the cam chain kit has sorted it out, very happy with the result..Cheers..
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Mike Fishwick (Mike Fishwick)
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Posted: Tue May 21, 2013 3:40 pm Post subject: Wear Rate
This sort of life is not unusual - my 1981 R100 started to make noise at about the same mileage, and by 10,000 it sounded like a big end!

The chain was almost unworn, but due to the poor design of the tensioner it only took a little wear - and shallow grooves forming in the plastic tensioner blade- before the noise became unbearable.

The basic problem was that the tensioner profile was incorrect - it only took a little wear (mainly of the tensioner) before the tensioner pressed the chain against the crankshaft sprocket, and all tensioning ceased.

The older engines, with a duplex timing chain, have a similar problem, but at a much higher mileage (probably due to the use of an all-steel tensioner, which wears much more slowly) in that they eventually pressed the chain against the camshaft sprocket.

Anyway - my answer was to carefully bend the steel part of the tensioner, so moving the contact patch to a point midway between the sprockets. This made the new blade into a fit-and-forget device.

During 1992 BMW finally produced the all-plastic tensioner - which had the same profile as my modified version . . . it only took them 11 years!
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grimreaper (Terry Clark)
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Posted: Wed May 22, 2013 12:30 pm Post subject:
That's a very comprehensive and informative explanation as to the cause of the problem, I'm afraid I'll be leaving mine until it starts to knock again, hopefully a good few thousand miles down the road from now, then, when it does I've got the answer at hand providing the cam chain kits are still available!
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Old 05-22-2013, 08:56 AM   #66
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Originally Posted by Plaka View Post
First establish detonation, then establish why.

You say there are no signs of detonation? Then don't fool with the plugs.
I never said thee was no signs of detonation. I have ruled out everything else and the spark plugs as pictured earlier are very light in color after riding around the parking lot when they be a little on the darker side.

Quote:
Originally Posted by chasbmw View Post
I have a 1981 R65 with a genuine 7500 miles on the clock, on starting from cold the engine is very quiet, when it's warmed up there is a definite knocking sound from what appears to be around the clutch/gearbox area ( not verified as being positively from there ) pulling the clutch in and selecting a gear doesn't alleviate the noise, still there when the revs rise through the range, all oils are new, the carbs. are balanced and the bike runs very well. I'm looking for pointers as to the possible cause of said knock before having it attacked and stripped into pieces.

it?

Joined: 07 May 2007
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Posted: Mon May 20, 2013 10:08 am Post subject: R65 mystery knock update
To all the respondents to my R65 problem, I'm afraid I wasn't able to get the requested video but on the advice received a new cam chain, tensioner and other gubbins has been fitted and hey presto the problem has now gone away. Thank you again for your input, much appreciated...
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Thank you for this post. I have never seen a 70-78 double row chain have any issues other than when worn they will slap against the main bearing holder and the timing moves around a bit. The 79-95 chain tensioners rely on oil and the pre 78's have a spring.
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Old 05-22-2013, 09:15 AM   #67
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I agree, but did not know what motor you were writing about
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Old 06-09-2013, 10:56 PM   #68
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Originally Posted by chasbmw View Post
I agree, but did not know what motor you were writing about
1976 R90/6
9.5:1 compression
crank fired ignition with26 degrees total advance
BP5 Bosch plugs- plugs look great
40mm Bings
170 main jets
45 idle jet
Needle position is second from the bottom
Lightened flywheel
308 camshaft
New rod bearing and rod bushings sized to the wrist pins
20/50 BMW oil
Cold oils pressure is 70-80 at idle or under acceleration, hot is 30 at idle and 60 under acceleration
timing chain is good
stock BMW headers with dual Hookse mufflers


...and my noise is still there. I even moved the coils from under the gas tank(thought they might be hitting the tank) and schanged the week starter out.

Still puzzled.
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Old 06-10-2013, 12:04 AM   #69
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Quote:
Originally Posted by bmweuro View Post
1976 R90/6
9.5:1 compression
crank fired ignition with26 degrees total advance
BP5 Bosch plugs- plugs look great
40mm Bings
170 main jets
45 idle jet
Needle position is second from the bottom
Lightened flywheel
308 camshaft
New rod bearing and rod bushings sized to the wrist pins
20/50 BMW oil
Cold oils pressure is 70-80 at idle or under acceleration, hot is 30 at idle and 60 under acceleration
timing chain is good
stock BMW headers with dual Hookse mufflers


...and my noise is still there. I even moved the coils from under the gas tank(thought they might be hitting the tank) and schanged the week starter out.

Still puzzled.

Hmm. You seem to have done everything that makes sense.

Piston slap?
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Old 06-10-2013, 03:47 AM   #70
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Old 06-10-2013, 04:19 AM   #71
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Quote:
Originally Posted by bmweuro View Post
Since the jetting, carburetor adjustment, timing .... seem to be spot on I'm thinking a colder spark plug. Right now the motor has NGK BP6ES and I'm thinking about Bosch W5DC's. Thoughts?

The BP6ES plugs cross reference to Bosch W5DC's which indicates they are the same heat range. I would try NGK BP7ES (which is the next colder NGK plug) and see if that helps or tends to foul out. The knock described could be from detonation - in which case the colder plug should help. Good luck!
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Old 06-10-2013, 06:05 AM   #72
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Did we ever determine if it was a mechanical knock under load or an ignition ping/detonation (AKA "spark knock") under load?

--Bill
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Old 06-10-2013, 06:20 AM   #73
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Originally Posted by Stan_R80/7 View Post
The BP6ES plugs cross reference to Bosch W5DC's which indicates they are the same heat range. I would try NGK BP7ES (which is the next colder NGK plug) and see if that helps or tends to foul out. The knock described could be from detonation - in which case the colder plug should help. Good luck!
Quote:
Originally Posted by Bill Harris View Post
Did we ever determine if it was a mechanical knock under load or an ignition ping/detonation (AKA "spark knock") under load?

--Bill
Stan I believe the cross over is at the BP6ES and WD6DC being the same heat range.

Bill we have not. I have not ruled out detonation but it is hard to tell.
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Old 06-10-2013, 08:38 AM   #74
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Chris,

Since you are not sure where or what it is, try using one of those stethoscopes with the long rod on the end. You can hear much better with that than anything else. It might at least help you narrow down the search.

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Old 06-10-2013, 10:24 AM   #75
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Here is where I got the NGK BP6ES cross references to a Bosch W5DC: http://www.sparkplug-crossreference.com/

Upon closer examination of that site, it shows both the W5DC and W6DC cross reference to the BP6ES. So, it looks like you need to examine the current plugs used to choose one heat range cooler. Higher numbers refer to colder heat range for NGK and Bosch it is vice versa (i.e. lower numbers). For my airhead ('78 R80/7), the Bosch plug is W5DC. However, if you are currently using a W6DC then going with a W5DC (which is one number cooler) may help. Good luck!

Stan_R80/7 screwed with this post 06-10-2013 at 10:29 AM
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