What next?

[Ash]

Have had my '81 R65 two weeks now - it's got 37,000 miles on it and when I bought it it had no history, but looking at the condition/number of owners etc I am fairly confident the mileage is genuine.

The bike didn't have any major problems - did 300 miles on it within 4 days of buying it.

Serviced the bike a few days ago (changed all fluids, filters and adjusted the cylinder heat nut tightness and valve clearances).

My problem now is this: before servicing I noticed there was a 'loose' sounding (but loudish) tapping coming from the right hand cylinder between 3-4000 RPM. There was also a big 'flat-spot'/weakzone in the engine at this speed (normal for these?).

Post service, the tapping is now constant - although quieter, more regular and 'tighter' sounding (I am 'happier' with the noise than it sounded before) and my exhausts (esp. right) are a bit louder/clearer sounding - again though I think it sounds healthier. The flat-spot has also reduced quite a lot.

When adjusting the valves I peered through the crankcase aperture (rubber bunged hole next  to the oil filler hole?) with a torch and all stages of turning the engine and couldn't see anything!. So I got the cylinders to what I thought was TDC through watching the valves and feel through the back wheel. The clearances didn't seem too far off the recommended and so I adjusted accordingly and now this is where I am.

Should I be worried? I have read about the valves on these bikes needing replacing after 30,000 miles.

[Bob_Roller]

Hi Ash,

If you are new to BMW aircooled motorcycles, they can make some unusual noises compared to other makes of bikes.

Most of the noise comes from the valve area, the 'ticking' noise, kind of sounds like a sewing machine.

There could be more freeplay in the rocker arm end play than is necessary, may want to check out the clearance next time you are in there.

The 'dead' spot could be a rubber diaphragm in the carburetors, if they are original, good chance they brittle or hard, and have a tear or hole in them.

Carbs would be a good place to go next, I'm sure the rubber parts are in need of replacement, as well as the condition of the foam floats that are used, they have the habit of absorbing fuel, especially since fuel these days contain ethanol, that seems to be hard on the foam.

We have a few members here that reside in the UK, may be able to give you local sources for parts and the like.

[trolle]

Hi Ash

Welcome to our little happy forum.

With only 37K miles on the clock, your engine is almost brand new. As you will see, if you take the time to read the postings in this forum, several of the engines have done three or four times as much without any problems.

One of the things to look out for on the '81 to '84 engines is the dreaded valve recessing caused by the valveseats being deformed. The main symptom of this malady is a very high idling when the engine is warm and if you check the setting of the exhaust valve you will see that most of the gap (normally 0.2 mm) has disappeared.

Do not worry, you may have more than 30k miles left before that particular ailment develops; enjoy :-)

greetings from a very cold and white north with dry roads: good riding conditions

trolle

[Ash]

OK cheers - I think perhaps I am being a bit of a hyperchondriac, I did buy the bike because of BMW's 'bombproof' reliability.

I was just a little worried that perhaps I had ballsed up with adjusting the valve gap clearance since I couldn't see anything through the aperature and having never done this job before (or any other on a BMW)!

[MrRiden]

Ash, you probably didn't do any harm but the next time you have a willing mate at hand pull the timing plug, spark plugs and have them turn the rear wheel in short bumps while in gear. You'll eventually find that timing mark. The first time I had a look at mine I couldn't find that rascal but on close inspection it revealed itself. A timing light may also show you what it looks like and then you can always poke a cocktail straw into the spark plug hole to verify the piston position, don't drop it in [obviously].
  Trolle, you've made a wave of fear come over me. My LS is starting to idle high after extended high speed runs. I'm off to the garage to grip my feeler gauges with much trepidation!
rich

[Justin B.]

Rich, this can also be caused by a sticking centrifugal advance assembly...

[trolle]

Rich, I did not mean to scare you, just help you  

If you check the valve settings every 1000 miles and you see that the exhaustvalve setting keeps diminishing, it is time to have a head job (cylinder heads, mind you). If the setting does not change, the high idle is caused by some other strange behaviour of the engine or the carbs.

greetings from a warm (a real spring day) north with wet and slippery roads

trolle

[Ash]

Update:

After spending (literally) hours ploughing through Snowbum's articles on valve and rocker adjustment I decided to give adjusting the valves another go today.

This time I managed to find TDC for both cylinders with no trouble at all - had the back wheel propped off the ground which made it a lot easier. I adjusted all the valves correctly, after checking the play on the rockers (which all seemed OK).

When I last adjusted them, it seemed I had the right cylinder exhaust gap at twice what it should be - hence the loud exhaust I'm guessing.

Put it all back together and it now runs MUCH quiter and smooth - now just need to take it out for a full test-ride this afternoon.

The flat spot has now disappeared - ran a bottle of carb-cleaner fuel-additive through which seems to have done the trick.