What Did You Do With Your Commando Today?

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I tried to correct my wobbly brake drum, after screwing around with the wheel, drum, spacers, cush drive etc. for a few hours I opted to order a new hub and drum from Madass.
It will be great to go to a one piece axle, have a new sprocket, an effective cush drive etc. I haven't built a wheel in years but think I'm up to it, have successfully built a few bicycle and MC wheels in the past. BTW I read here about people installing new one piece axles from the left but I probably will not do that as if a bearing seizes you want it to tighten rather than loosen the axle....not very likely to spin a bearing but I'm OK with a bit more work with it going in from the right (I do the same on my Sportster for the same reason as HD wheel bearing do spin on occasion)

What Did You Do With Your Commando Today?
 

YING

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Well fellas, I believe I've solved the issue with my blown fuse, "pop" sound I heard when I replaced the fuse the first time, and also the corrected wiring of the cluster under the tank.

First off, the Pazon black box is working, at least to start the bike and letting it run. I took it out and performed the troubleshooting process they have on their site, and then attempted to start the bike to test it out.

Well it just would not start after the 10,000 kick. So, I figured something else was amiss. I kept thinking about that popping sound I heard and the little smoke that appeared earlier when I was working through the fuse and inspecting the wiring. It was definitely electrical since wires don't pop and the Pazon was ok. I suspected that mysterious wee assimilator. So, I installed this new gadget that I ordered a while back from a recommendation Batrider made on a thread about assimilators. Picture is below. Wouldn't you know, as soon as I kicked it over, after installing the new assimilator, it fired right up.

So, that "pop" was the assimilator blowing. I figured as much as I've heard capacitors blow before and this was a similar blow. By the way, the old assimilator was the original unit so I'm quite bummed that I blew it up.

Also, Les' suggestion to give my head a shake and replicate exactly the wiring cluster as it was before, with the double commons and not separating the red wires and the white wires into singles, helped as well.

Now the bike is still apart some, but it fires up and idles. Tomorrow I'll zip tie the new assimilator in it's new home and double check my work while I re-assemble the tank and saddle back on the bike. It's supposed to be a very nice latter part of the week and weekend coming and I'm glad the bike looks promising to allow me a nice ride in the country to look at some more colours!
View attachment 100657
Rob,
I had no problems whatsoever with that assimilator
 

Starvingphotog

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Hey guys,
I'm picking this thread up again with the breather setups we all have. This is a photo of my 850 setup. I see large passive hose coming from the timing side of the crankcase, then it takes a 90 degree turn at this junction you can see in the photo (with the X or + mark on the top depending on how you look at it), and leads through a yellow hose to the oil tank. A black rubber hose then leads from the oil tank to the air box, and this completes the system to vent the crankcase with a slight vacuum produce in the air box pulling air from the oil tank and the crankcase via the large hose attached to it. I just wonder from the photo that I've attached whether that 90 degree junction is a check valve allowing air to move toward the oil tank and not back into the crankcase. What do you guys think?

What Did You Do With Your Commando Today?
 

Starvingphotog

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Rob,
I had no problems whatsoever with that assimilator
Mike, this new assimilator is terrific. It actually works like I'm used to with my MG that has a generator/dynamo, in that the ignition light flickers on at low rpm when the alternator isn't cranking out enough juice to charge the battery and turns off at higher rpm. The old assimilator didn't do this. It was either on or off.
 

L.A.B.

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Starvingphotog

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Thanks Les. I figured that but didn't want to disconnect the tube from the oil tank and stick it in my mouth to pull and blow air to check for myself. I don't have any leaking problems anywhere on the engine, with the exception of the primary oil rubber seal that I plan to change this winter. So, I suspect it is a check valve.

The diagram has an interesting twist in the illustration of the return portion of the breather. It looks as though the return hose from the tank can either hook up to the air box or the balance pipes on the manifold using a t-fitting, if I'm seeing it correctly in the diagram. Is that right?
 

L.A.B.

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It looks as though the return hose from the tank can either hook up to the air box or the balance pipes on the manifold using a t-fitting, if I'm seeing it correctly in the diagram. Is that right?

That's the OldBritts diagram showing the 850 Mk3 breather connection from the oil separator that would have originally attached to the black plastic airbox ('34 Assy', in the link) to the carb balance pipe so not applicable to your 850.

OldBritts article here:
>Download
 

Starvingphotog

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This is great Les. Thank you!
So, this setup could be applied to my '74 850 or any Commando really, if we just use the balance pipes to provide that slight vacuum to the breather. This would help us that want to attach those cone shaped filters that I posted a little while back and still have forced breathing of the crankcase. Just need to have a one way valve for the air going to the balance pipes, and a mechanism to provide oil separation. Curious. I think that I would like to look into this setup over the winter in case I want to do away with the air box and mount those wee filter cones and still maintain my current breathing of the crankcase using the balance pipes. Do you think that makes sense as a worthwhile venture?
 

L.A.B.

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Do you think that makes sense as a worthwhile venture?

I suppose you could but the separator to manifold connection is a liquid drain. Air from the oil tank breather is directed into the black plastic airbox via the separator, similar to the previous tank vent system where air from the tank breather is drawn into the engine through the carb intakes and the oil mist it might contain will be burnt during combustion.

The Mk3 separator, manifold hose connection, T-piece, etc. are often removed because it's of no real value.
 

Starvingphotog

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Ok. So, now I wonder. If you remove those hose connections to the manifold, as you mentioned, how is the minor vacuum produced to help the engine breathe? Is this minor vacuum unnecessary then, so that you allow the engine to passively breathe on its own and with a check valve on their, or reed valve breather, it will just expel air as it needs and carry on? I had thought that a minor vacuum is necessary for the engine to maintain a slight negative pressure or zero pressure.
 

L.A.B.

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Ok. So, now I wonder. If you remove those hose connections to the manifold, as you mentioned, how is the minor vacuum produced to help the engine breathe?

I don't believe it was ever intended to assist breathing but only to draw accumulated liquid from the separator to the engine.

Is this minor vacuum unnecessary then, so that you allow the engine to passively breathe on its own and with a check valve on their, or reed valve breather, it will just expel air as it needs and carry on? I had thought that a minor vacuum is necessary for the engine to maintain a slight negative pressure or zero pressure.

It would still have the apparent vacuum from the tank breather connection to the airbox, similar to the pre-Mk3 tank-to-airbox hose connection.
 
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Not today, but a couple of days ago. Hadn't started the Combat and riden it for about 6 weeks, end of season here so was riding my chop instead. Getting it ready for its winters nap, went to start it. 44 degrees. Turned on gas, tickled it, gave it a couple compression kicks with key off- key on...1 kick.

and sat there and idled like a champ.

I have to say, expected to extend a bit more effort than that...............
 

Starvingphotog

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Hmm, this is an interesting problem, or such, that I think I would like to explore a little more over the winter Les. I would like to try out using those two small cone filters and also have an as effective breather apparatus that is in place at present with the air box. I'll show you guys what I come up with over the winter, as I explore and fidget.
 

Starvingphotog

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I sure hope my Combat does the same thing after sitting behind me in my office for what will be 2 years 6 months when I decide to take out outside for a ride in 2023....:) It has the original points for ignition, and not much else in modifications other than the oil filter kit I plan to install, and the cNw reed breather kit I also plan to install. Other than that, it's stock.
 

Mart UK

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Hmm, this is an interesting problem, or such, that I think I would like to explore a little more over the winter Les. I would like to try out using those two small cone filters and also have an as effective breather apparatus that is in place at present with the air box. I'll show you guys what I come up with over the winter, as I explore and fidget.
Although I have a single carb, with cone air filter, I think the principle should be the same. I have an 850 mk3 with a reed valve (Yamaha xs650 version, I think from HNW) in that pipe, between the case and the oil tank. I have a hose on the second outlet on the oil tank which is directed under the seat and down and round to the end of the swingarm, where it vents to the atmosphere.

It was set up this way when I first got the bike, but without the reed valve. I had all the crankcase pressure symptoms. I added the valve and a miracle occurred. So, I don't think it needs any negative pressure oil tank side of the valve to work. Atmospheric pressure seems sufficient. That little valve, which I knew nothing about before joining the forum, has been the single greatest improvement I've made to the bike.
 

L.A.B.

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I would like to try out using those two small cone filters and also have an as effective breather apparatus that is in place at present with the air box. I'll show you guys what I come up with over the winter, as I explore and fidget.

If they are the usual metal end-capped type then I expect it would be possible to attach a pipe spigot to each filter and connect the tank check valve outlet to each (using a 'T' fitting?), however, I have no idea how successful (or not) that idea might be.

My 850 Mk3 has individual S&B filters and the tank breather is connected to a vented catch bottle. The engine has never suffered from crankcase or other joint leakages so I haven't found the need to fit a check valve (yet).
 

Starvingphotog

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Yep. those are the filters I have here Les. I think I understand better now, after thinking about it some more. It's like the engine is burping out pressure and that's what the breather allows. So, with the check valve in place, when the engine burps out pressure, the engine crankcase goes into zero or negative pressure until the next rotation and it does it again. The check valve prevents back drafting of air into the crankcase once the burp has occurred. So, I can see why the wee vacuum isn't really necessary, as long as the engine has room to burp out the pressure, and this is what the hose leading to the oil tank is for. So, in my case, with the check valve on the breather hose, connecting to the oil tank, and then with an additional hose from the oil tank to the air box, it supplies a little extra bit of vacuum to pull that burp and put it back into the engine for combustion. So, if I do go the route of installing the cone air filters I think I will forgo the reconnection to create a wee vacuum and just put a breather air filter like this to the end of the hose coming from the oil tank and would be going to the air box, to capture any oil mist. Who knows. An idea anyway, that I might try next year.
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Starvingphotog

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Ellis, just picture yourself wheeling the bike out next spring, and dusting it off, and wiping it down. Then of course, putting some fresh fuel in there and kicking it over to hear that all too familiar roar of the Commando! That'll keep you going over the winter mate:)

I changed the fork oil this week. Still amazed at how dirty that stuff can get over a riding season. Mine was close to black. I had put in that Redline fork oil 20wt back then. This time I put in that Silkolene 20wt. I'll see how that fairs next season. I'll take it out for a spin this weekend since it will be sunny and fairly warm in the 20s celsius. Then I suppose I will start getting the room ready to wheel it in next weekend.
 
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