XS650 reed valve question

I also have a 70 commando with a timed cam breather. I just recently decided to do the timing chest reed valve modification after researching all the options. Like many people, I didn't want to rebuild my engine and have the added expense of the comstock breather modification, although everything about it seems like the best option.

I have 2 3/8ths holes from the timing chest into the crankcase to allow air movement and a 1/4 inch hole drilled behind the oil pump to allow oil to drain back to the crankcase from the timing chest.

I mounted the mikes's reed valve on a flat blanking plate and replaced the stock dished blanking plate on the back of the timing chest. I routed the the pipe to a Tee so it connects to the cam breather hose right before it enters the oil tank.

Everything works really well so far. I can't believe my bike finally doesn't leak oil anywhere. I always had the typical commando leaks with this bike ever since I rebuilt it 30 years ago. I am pretty happy with the results...

I have pictures of my modification too, let me see if I can upload them...



breather holes are red arrows
oil drain hole is yellow arrow
reed valve hole is green arrow



I have a single question about blocking off the timed breather since I have seen numerous people mention the same advise . My question is, Why do people say you need to block off the timed cam breather once you install the timing chest reed valve???

It seems to me that it's fine just the way it is, as a secondary route for air pressure to escape the crankcase. Logically, I think 2 places to vent crankcase pressure would work better than one...

.... comments please... thanks

Thanks for showing you craft. I approve of your solution which does not need the cam devise which is just along for the ride now with no downsides keeping it nut the ugly hose which can be eliminated if vent hole blocked. I can not think of any reason to worry about it beyond that but watching for rust on dry fasteners.

I would say job well done, there o0norton0o. I have a similar unit milled in that area of the later 72 cases. My differences are that I have yet to drill the low drain hole and that I incorporate a second reed breather from the original location at the lower back left. As you mention "a secondary route for air pressure to escape the crankcase", I have taken this a bit more literally.

I'm just about to make a similar plate to the one o0norton0o made, just wondering about the orientation of the outlet pipe. I was thinking of having it pointing down by about 15 degrees so any condensation in the pipe runs out of the valve not back in. Thoughts?

gripper said:

I'm just about to make a similar plate to the one o0norton0o made, just wondering about the orientation of the outlet pipe. I was thinking of having it pointing down by about 15 degrees so any condensation in the pipe runs out of the valve not back in. Thoughts?

Click to expand...

My main breather come from the lower crankcase and runs to the oil tank.

This breather goes to atmosphere, is a short run and doesn't have the potential residual like the other one might.
I think that if you are not getting it warmed up enough to get the oil good and hot, you will have condensation issue no matter how you run your discharge opening.
That being said, I think you could run your line any which way that will offer the cleanest install.

gripper said:

I'm just about to make a similar plate to the one o0norton0o made, just wondering about the orientation of the outlet pipe. I was thinking of having it pointing down by about 15 degrees so any condensation in the pipe runs out of the valve not back in. Thoughts?

Click to expand...

Gripper, I purchased my blank plate from "oldbritts" who are located near me, and all I had to do is drill the bolt holes and make the breather cutout for the reed in the correct spot. I also drilled 2 out of the 3 holes in the reed valve casting to a larger diameter. The casting was too thin in the 3rd location to drill it wider, so I left that screw diameter alone. (you can see it in the pictures)

If you notice my reed placement, you can see that I needed to use one of the original bolt locations for the blanking plate to secure one bolt in the reed valve block. I didn't think all 3 bolts would fit inside the timing chest cutout without having to grind the existing casting so all the bolt heads would clear. I just didn't want to do any grinding, but it wouldn't have made the modification irreversable if I had done some grinding. If I hadn't used any of the blanking plate bolts to bolt the reed valve block, any orientation of the reed valve would have been possible.

Anyway, I thought about orientation of the outlet hose, orientation of the reed, and had mixed thoughts about it, so it's drilling pattern and what I was willing to consider limited it's orientation. I think that since I was planning to run the hose up to the oil tank anyway, gravity was always going to make oil drain downward regardless of the orientation of the valve. Honestly, I don't really know if it would have been better to mount it oriented in a different way.

What I did think was nice about my chosen method, was that I mounted the reed valve on the timing chest with a full sized cutout for the reed exposed to the whole volume of the timing chest. I didn't have the reed valve far away from the crankcase and have the pulse traveling to it through a length of 3/8" tubing. I heeded Jim comstock's advise about having the valve as close as I could to the case for the best possible result (for my less elaborate modification)

*Hobot, I laughed at the comment about worrying about bolts rusting that are no longer covered in a film of oil... In the past, I have cleaned this bike for charity rides. I was always amazed at how fast the bike recoated itself with film of oil... I've seen 50 year old BMW boxer engines that who's cases were so dry on the outside surface that they looked "chalky". I've always wished my bike could be that "clean"...... this summer's riding should be the test of that.

I am still wondering if there is anyone out there who has a good reason to block off the original timed breather.... anyone??

o0norton0o said:

What I did think was nice about my chosen method, was that I mounted the reed valve on the timing chest with a full sized cutout for the reed exposed to the whole volume of the timing chest. I didn't have the reed valve far away from the crankcase and have the pulse traveling to it through a length of 3/8" tubing. I heeded Jim comstock's advise about having the valve as close as I could to the case for the best possible result (for my less elaborate modification)

Click to expand...

Your may be suprised as to the volume of air that is flowing about the enclosures. When I push may cylinders through, I hear both reed valves croak together, even though t he crankcase valve is up under the seat at the 90degree point heading over to the tank. Even with the redundancy, the reed on the timing side is profoun and the placement, in this regard, can be considered a moot point.

Hi all, and about a Commando with a distributor or an Atlas with a mag , wher could we fit trhe reed valve ??

Thank you for the comments so far. I revived this older thread, rather than start yet another reed valve thread because I didn't want to add another redundant thread on breather modifictions and scatter good information into increasing numbers of redundant threads.

My modification is done, but I wanted clarification of something I read in other crankcase breather threads on the internet, (not so much this one) which stated that I needed to disable the original camshaft breather once I fabricated the timing chest breather modification.

From the responses given here, so far no one thinks the original camshaft breather needs to be disabled and it can coexist with the modified timing case breather without any issues.

I'm really interested in hearing from anyone who thinks it should be disabled, and I'm especially interested in their explanation why they think it needs to be disabled. Thanks again.

I removed the timed disc from the camshaft breather and blanked the threaded hole once I had drilled through to the timing case. My main reason was to do away with the pipe over the LHS of the primary case. I don't think it is important to do away with it if you don't want to though.