Boxerworks.com

Hi, i am in the process of getting my 1980 R100RS back on the road again after it has stood for almost 10 years ( in a warm dry garage )

It had been fully restored and is in lovely condition having covered a genuine 55,000 miles.

I have sorted all the brakes, flushed the tank and stripped the carbs , cleaning all jets etc.

The bike starts readily now and seems to run quite nicely but has not been out on the road yet.

I have noticed that when the bike is started and allowed to run for a few minutes a "light tapping noise" from somewher on the right hand side of the engine becomes apparent and when i knock the engine off i get a hissing sound from the right hand side valve cover.

Thinking this hissing may have been trapped water from the bike being washed i was not overly concerened but the bike is bone dry now and it still does it.

After doing searches and also finding an airhead on youtube with exactly the same symptoms i am coming to the conclusion that my crankcase breather valve may be kerfurkled causing the noise and excess crankcase pressure. This would not surprise me with the bike standing for so long.

I will strip the top end of the bike down to have a look but does this sound like i may be correct / likely and in addition am i likely to have the old type valve fitted on my year bike? Motorworks list the new reed valve at £24 so i will fit that.
Is there any way of checking the old valve for malfunction and what is the best way of removing it.
Anything else i should be aware of?

Many thanks Darryl

Your breather if original will be the disc on a post type which was superceded by a reed type breather which is generally considered to be better. On the disc type breather at least, even when it's functioning OK, it's not unusual to hear some noise on the last stroke of engine shut off. Honking or turkey gobble are the usual descriptions rather than hissing or tapping.

It's easy enough to inspect the breather for damage by removing the starter cover and then a small domed cover towards the rear right hand side. Replacing the disc type with a reed type involves devising some sort of slide hammer arrangement to pull the old assembly out.

It's not always a malfunctioning breather that causes noises but rather that the breather is not able to cope with excessive crankcase compression caused by excessive blow by or a leaking rear main seal. In fact it can be the seal that makes the noise rather than the breather itself. If the bikes been stood a long time I've seen cases where the seals improve some just through the bike being used.

below is a link to a procedure on breather servicing.

http://www.bmwscotter.org/procedures/oi ... ervice.htm

I have heard hissing from the valve cover area after engine shut-off as well..........
Don't know what the cause is.

barryh wrote:Your breather if original will be the disc on a post type which was superceded by a reed type breather whuich is generally considered to be better. On the disc type breather at least, even when it's functioning OK, it's not unusually to hear some noise on the last stroke of engine shut off. Honking or turkey gobble are the usual descriptions rather than hissing or tapping.

It's easy enough to inspect the breather for damage by removing the starter cover and then a small domed cover toward the rear right hand side. Replacing the disc type with a reed type involves devising some sort of slide hammer arrangement to pull the old assembly out.

It's not always a malfunctioning breather that causes noises but rather that the breather is not able to cope with excessive crankcase comopression caused by excessive blow by or a leaking rear main seal. In fact it can be the seal that makes the noise rather than the breather itself. If the bikes been stood a long time I've seen cases where the seals improve some just through the bike being used.

Thanks,
can anyone tell me if i have got this right. Presumably, in my photo, the item with the yellow line going to it is the old style breather and this can be replaced with the reed valve type. That being the case, the red line is pointing to the unit with the breather pipe exiting from it.Is it just a housing for the tube to clamp onto.

http://i80.photobucket.com/albums/j165/ ... XER037.jpg

In addition does the starter motor need to be removed to get this old valve out? I have an awful feeling that it does.

Darryl

Darryl -

The yellow line does point to where the breather is. Can't say it's the old or new style...I'm thinking it might even be the newer style with an '80. The starter doesn't have to be removed but it does have to be loosened and shoved over a bit so the breather cover will clear. It will be somewhat of a problem to get to the two rear bolts that hold the starter in...I did it with a 1/4-inch drive and socket...upon reassembly, the bolts can be reversed for easier access. In between the yellow and red line is where the oil mist runs before exiting and coming back to the t-fitting and out to the two carbs. When the breather cover is off, look into the well just in front of the cover and you'll see a small hole in the bottom of that well. Carefully, and don't drop it, but take a small wire and ensure that this hole is clear. It lets oil mist that has converted back to a liquid to drip back into the case. If it's plugged, you'll get more than necessary oil mist into the carbs.

Kurt in S.A.

Many thanks Kurt. Do i still have to remove the front engine cover to get at the 3rd starter bolt or can you get enough movement loosening the two which are readily accesible next to the breather.

Cheers Darryl

Darryl Flynn wrote:Thinking this hissing may have been trapped water from the bike being washed i was not overly concerened but the bike is bone dry now and it still does it.

Don't be too quick to discount this one... It can take quite a long time before all of the water evaporates from this cavity...

Rob

Right, i got the cover off without removing the starter motor and i have found that i do have the old type valve fitted so have ordered the later type reed valve as a replacement.

I can see that i am going to have to devise a puller but would it assist if i use a gas blowtorch to GENTLY heat the alloy housing around the valve itself whilst applying upwards pressure.

Cheers Darryl

No need for the torch. After removing the disc and associated hardware, I used some mild steel wire to make a 12" loop through the openings of the breather and slid the handle of my small sledge hammer in the loop. A couple swings upward and out popped the breather. Note: the new breather gets mounted with the reed facing forward, away from the vent tube and so it clears the casting.

Tim Shepherd wrote:Note: the new breather gets mounted with the reed facing forward, away from the vent tube and so it clears the casting.

I believe on the bmscotter website, he accurately discusses the mounting. IIRC, the screw that holds the metal piece should be at the 5 o'clock position or pointing at the rider's right footpeg.

Kurt in S.A.