Breather again. Newbie needs help.

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Hi all

Sorry to bring this up again but after reading every post I could find on crankcase breathers I'm more confused than ever.

I have a 1968 commando engine # 20M3/1283##. I have the motor completely stripped and I want to fit an updated breather as I understand that the timed breather is not up to the job?

What I want to know is if anyone has modified this type of engine with positive results. What holes to blank, what to drill, etc.

The bike will be used as a street bike for "daily" use so will not be thrashed too often. I also want to keep the "look" of the bike standard.... Love the fastback look.

As this set up has the points at the back of the timing case I won't be able to use that as a location for the breather.

The other thing is I live in the UAE so sending the cases to someone for machining is out of the question but I do have access to a comprehensive machine shop.

Thanks
Dean.
 
I'd say right off, get the comnoz or maybe it's now the CNW sump breather. But if you have the frame brace below the sump, you're out of luck. I've always been confused by the hole drilling too, if it's any consolation. I may be breaking into my crank to re-seal the cases and if I do, I'd like to hear the options too, but I don't have the problem with the timing cover with my '69. Actually I've installed a catch bottle off the oil tank breather and it's pretty much solved my problems, but I'm sure the crank internal vacuum could be better, I'm still using the timed breather, but I rarely go above 5K.

Dave
69S
 
Dean said:
Hi all

Sorry to bring this up again but after reading every post I could find on crankcase breathers I'm more confused than ever.

I have a 1968 commando engine # 20M3/1283##. I have the motor completely stripped and I want to fit an updated breather as I understand that the timed breather is not up to the job?

What I want to know is if anyone has modified this type of engine with positive results. What holes to blank, what to drill, etc.

The bike will be used as a street bike for "daily" use so will not be thrashed too often. I also want to keep the "look" of the bike standard.... Love the fastback look.

As this set up has the points at the back of the timing case I won't be able to use that as a location for the breather.

The other thing is I live in the UAE so sending the cases to someone for machining is out of the question but I do have access to a comprehensive machine shop.

Thanks
Dean.

I can supply a reed breather that will require machining to the rear of one case half. I am sure you can find someone to do the machine work locally. It is pretty simple. Jim
 
Hi there

I have the same engine set up with the points up behind the barrels and a timed breather, and I've never had any problem with oil leaks and such, it breathes into the tank and the tank breathes into the air box. the only place that leaks oil on the bike is from the rubbish set up on the swinging arm!
Are you looking to fit the new breather as a result of a bad experience with the timed one, or are you fitting it as a result of reading all the threads on the subject?
 
Hi

The main reason I'm looking at these mod is due to the many comments about oil leaks. So you are right there Willy. I haven't actually had the bike running as I bought as a barn find in big lumps loosely bolted together. Luckily they never got round to stripping the motor or gearbox. The big end journals are slightly undersized so am grinding -0.010 and the barrel spigot is cracked for the rod relief. Thinking I can sleeve it... Do they take a sleeve ok and will this remove the damage?

The other option I'm thinking is going with the original timed breather and fitting the norvil valve to back it up. I know this May not be the best solution but as it's not a racer I'm thinking it is a good compromise. Also if I go this way should I still blank the big holes and drill drain lower? Thoughts please......

What I'm thinking is while I have it apart I may as well do as much as I can to "make it better"

Thanks Jim for your offer in your reed breather. Can you let me know if I have the blanking / drilling of holes right. Don't know if this pic will open. First time user. Anyway I presume to blank all holes to the timing chest except the small vent hole fwd of the points /mag drive hole and then drill the hole at the aft lower of the oil pump pad? See pic.... I hope.

Thanks again
Dean


[/
Breather again. Newbie needs help.
 
Mine still weeps a bit from the crankcase flanges, but that's because I did a bad job of sealing. All the other engine leaks are pretty much nonexistent on my engine. My problem was the breather from the oil tank to the air breather, with the central oil tank, it's internal to the tank and comes out inside the ham can. I would get lots of oil out of that breather and it would drip down on the gearbox and all over the bottom of the bike. I drilled and tapped that breather tube and extended a tube to a catch bottle and that eliminated that. I've heard some don't experience this dripping from the air filter, but was not my experience. I have another oil tank and was thinking at one time of blocking that oil to air breather and installing another external breather to a catch bottle, it's a pain having a tube come out of the front of the air cleaner when you want to take it off.
 
Dean said:
Hi

The main reason I'm looking at these mod is due to the many comments about oil leaks. So you are right there Willy. I haven't actually had the bike running as I bought as a barn find in big lumps loosely bolted together. Luckily they never got round to stripping the motor or gearbox. The big end journals are slightly undersized so am grinding -0.010 and the barrel spigot is cracked for the rod relief. Thinking I can sleeve it... Do they take a sleeve ok and will this remove the damage?

The other option I'm thinking is going with the original timed breather and fitting the norvil valve to back it up. I know this May not be the best solution but as it's not a racer I'm thinking it is a good compromise. Also if I go this way should I still blank the big holes and drill drain lower? Thoughts please......

What I'm thinking is while I have it apart I may as well do as much as I can to "make it better"

Thanks Jim for your offer in your reed breather. Can you let me know if I have the blanking / drilling of holes right. Don't know if this pic will open. First time user. Anyway I presume to blank all holes to the timing chest except the small vent hole fwd of the points /mag drive hole and then drill the hole at the aft lower of the oil pump pad? See pic.... I hope.

Thanks again
Dean


[/
Breather again. Newbie needs help.

That would be correct. But don't do this unless you do the crankcase reed breather. Jim
 
Jim,

Do you have a picture of where that reed breather goes and the machining?

Dave
 
Hi Jim

Machining looks straightforward.
I would like to go ahead with the getting one of your reed breathers. Let me know how to go about it.

I understand that the timed breather is also blanked. Was just wondering if it is worth leaving the disc and spring out at reassembly?

Thanks again,
Dean
 
Dean said:
Hi Jim

Machining looks straightforward.
I would like to go ahead with the getting one of your reed breathers. Let me know how to go about it.

I understand that the timed breather is also blanked. Was just wondering if it is worth leaving the disc and spring out at reassembly?

Thanks again,
Dean

I would leave the disk out just because I have seen them break up before. It will not matter as far as operation.
PM sent. Jim
 
I used Jims sump breather, and it seems to work great. I'm amazed at how little volume appears to come from the breather outlet into the tank, as its only ever emitting excess gas, rather than pumping it back and forth.
I plugged the holes with threaded bungs, then peened them over, overkill perhaps. Here's my plugged case with new oil drain hole just below and to the left of the pump face:

Breather again. Newbie needs help.
 
Fast Eddie said:
I used Jims sump breather, and it seems to work great. I'm amazed at how little volume appears to come from the breather outlet into the tank, as its only ever emitting excess gas, rather than pumping it back and forth.
I plugged the holes with threaded bungs, then peened them over, overkill perhaps. Here's my plugged case with new oil drain hole just below and to the left of the pump face:

Nice, I'm going to save your picture to show the best way to do it. Jim
 
comnoz said:
Fast Eddie said:
I used Jims sump breather, and it seems to work great. I'm amazed at how little volume appears to come from the breather outlet into the tank, as its only ever emitting excess gas, rather than pumping it back and forth.
I plugged the holes with threaded bungs, then peened them over, overkill perhaps. Here's my plugged case with new oil drain hole just below and to the left of the pump face:

Nice, I'm going to save your picture to show the best way to do it. Jim

I'm honoured Jim,use the pic as you wish!

BTW the plugs were a tapered thread, locktited, and peened.
 
Wait a minute. The 2 pictures have different holes in different places. FE has 4 blanked holes and Dean only has 3. Is that just the difference in models? Which one will my 69 be like? I'm not sure I've got a pic of my inner timing side.

But I do appreciate the info. I may or may not do this anyhow, I don't seem to be having any problems.

Dave
 
comnoz said:
Nice, I'm going to save your picture to show the best way to do it. Jim
That, and the sexy con rods! And no empty beer cans in the background. And a nice engine stand. And good lighting. And, and, and...


Can I bring my bike to your shop?
Nathan
 
DogT said:
Wait a minute. The 2 pictures have different holes in different places. FE has 4 blanked holes and Dean only has 3. Is that just the difference in models? Which one will my 69 be like? I'm not sure I've got a pic of my inner timing side.

But I do appreciate the info. I may or may not do this anyhow, I don't seem to be having any problems.

Dave

The number and position of the holes varies from year to year. The earlier models may only have one hole to plug.

Regardless -you plug all the holes except the cylinder head drainback hole and drill a new drain hole next to the oil pump. Jim
 
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