I have a Combat...help me.

Jeepers! Why do we ride these things!

I would be curious as to what happens if you put on the Comstock reed valve at the back of the case and drill no holes. Wouldn't the reed valve evacuate oil back to the tank?

For the OP. The reason there are a lot of Combats running around unmodified is that if you ride at low RPM with only bursts above 4K or so, you don't end up starving the oil pump. There are lots of unmodified Combats running around because they are ridden on the street and not full out. Not sure how many of them are still around without Superblends. That's another issue.

I have a Combat that is going to be my next tear down. I have been wondering about the current state of what to modify and how myself. For reference read the Old Britts information but realize that removing the weir has come to be regarded as a bit barbaric. http://www.oldbritts.com/n_c_case.html

In fact, if you are new to Commandos, read all of the Old Britts tech articles. They give a lot of good information.

I am going to explore options for cams and pistons and try to decide whether or not I am actually going to use the Combat head. I don't care if the bike is stock or original. This is something each owner has to define for themselves and at what point have they crossed the line.

Russ

Damn.

I have to admit at this point I am a little overwhelmed. Mod this, do that, don't do that read this article. Wow, overload. Lol. Maybe my best bet is to continue with my restoration for now, get her running and then fix or address any problems. I don't plan on racing her but mostly putts around the city. She apparently was working fine before her big sleep in 1987 but that's not saying much I guess.

André Bourbonnais said:

I have to admit at this point I am a little overwhelmed. Mod this, do that, don't do that read this article. Wow, overload. Lol. Maybe my best bet is to continue with my restoration for now, get her running and then fix or address any problems. I don't plan on racing her but mostly putts around the city. She apparently was working fine before her big sleep in 1987 but that's not saying much I guess.

Click to expand...

Might be worth joining the Ottawa section of the CVMG https://cvmg.ca/Ottawa Or just going to a meeting. Sometimes a local eyeball on the project can lessen the frustration level. I almost threw In the towel myself. Hang in there,it’s worth it.

Northton said:

Might be worth joining the Ottawa section of the CVMG https://cvmg.ca/Ottawa Or just going to a meeting. Sometimes a local eyeball on the project can lessen the frustration level. I almost threw In the towel myself. Hang in there,it’s worth it.

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Thank you

Andre,
Like a lot of guys (and girls) here I was forced into an unexpected rebuild. The basic tear down and assembly is pretty straightforward if you read the manual and watch the video. The mods and upgrades are a different thing. What I did was to get a binder and keep track of the “necessary “ mods by category. Then, when I took everything apart I made a mental note of what I needed to do. Take your time and if you get stuck stop and research it. Generally if you post a question here by the time you make a cup of coffee there will be some kind of response.
The limiting factors are your skill set, sometimes tools and definitely your wallet. Good luck, when your done you will feel very rewarded.
Pete

I didn't make any case mods on my 72 and I haven't had any problems in the 6 years I've ridden it. Then again, I rarely thrash it hard. Certainly if you are racing or do a lot of hard riding you probably want to make the mod. If she's a weekend coffee getter maybe not.
I would strongly consider getting a plate to fit under the barrels. This will reduce the compression somewhat and let you use modern gas. Also, it will help with the rocker geometry.

Barrel p

htown16 said:

I didn't make any case mods on my 72 and I haven't had any problems in the 6 years I've ridden it. Then again, I rarely thrash it hard. Certainly if you are racing or do a lot of hard riding you probably want to make the mod. If she's a weekend coffee getter maybe not.
I would strongly consider getting a plate to fit under the barrels. This will reduce the compression somewhat and let you use modern gas. Also, it will help with the rocker geometry.

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Plate for the barrels, please explain.

"Plate for the barrels, please explain."
The combat cam needs compression to work. I wouldn't unless you change the cam. It is a base gasket to raise the barrel to reduce compression.
Cheers,

Tom

https://andover-norton.co.uk/en/shop-details/20527/compression-plate-0-028-750cc
Tom
Can you explain why this doesn't work with the Combat cam. Lost performance or some other issue.
Mitch

htown16 said:

https://andover-norton.co.uk/en/shop-details/20527/compression-plate-0-028-750cc
Tom
Can you explain why this doesn't work with the Combat cam. Lost performance or some other issue.
Mitch

Click to expand...

Yes you just stated it. The Combat cam works with compression.

CanukNortonNut said:

"Plate for the barrels, please explain."
The combat cam needs compression to work. I wouldn't unless you change the cam. It is a base gasket to raise the barrel to reduce compression.
Cheers,

Tom

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Bought one of those but it's more of a copper color. I've seen guys heat it before. Is this necessary?

I ride my ‘72 Combat occasionally... engine bottom end has never been opened .... I put a 34 Mikuni , 21T counter shaft sprocket on , rarely thrash it .... shows 7700 miles now but when I got it no speedo cable , so who knows.... mech. I got it from said (“I freshened up top end , new hot cam everything else in my opinion is good, I raced the big Harley’s up Cape Smokey on Cape Breton Island , if you have trouble let me know and I will give you refund “) so far so good that was circa 1985 .... not sure what to say on this thread
Craig

First thing to consider is that the Combat is kind of a special duck. Some people regard them as hot rods, others as junk. So they require a little special handling on a rebuild. But don't let that get you down. They are still "old school".

One of the things that was done to them was that the head was "milled" to increase compression. They shaved off some of the metal at the interface to the cylinders so that the pistons would have a smaller space to pack the contents of the engine. Some people put in a thick head gasket to put some of this metal back. Most likely made of copper (copper can be softened thru heating and quenching and yes it is a good idea). Some people put an aluminum gasket (spacer) under the cylinders to move them higher and achieve the same effect. Some have done both.

It is probably true that this defeats the cam used in the Combat. That cam opens the valves wider than normal. But apparently people are riding around with these and the bike runs and they smile when they twist the throttle. That last part is what you are trying to get to whether you keep the bike stock or not. If you remember that smiling while you ride is the end result and work toward that goal, all this other stuff becomes a little easier.

If you have no interest in learning about this stuff, you might consider not rebuilding an old Commando and getting a Honda. No joke. Or start with the Honda and put the Norton in a box for a while. They aren't hard, but they do require some immersion. There are certain topics that are controversial and have created a number of arguments here. Learn what they are and avoid posting about them until you have read old threads. Then the barrage of remarks about them will not be as confusing. There are people here, to whom you should pay attention regardless of whether you agree with them. I am not one of them. But Dyno Dave is. So is Comnoz. They have both been at this a long time and have more experience than bus load of the rest of us combined.

And to whomever is still reading this thread, I was serious with the question about the Comstock Breather. Seems to me it would help evacuate the oil without changing the case. (Note to OP, your case is already machined for this breather).

Don't let all this get you down. But you are gonna have to go to school on some of this stuff. If the end result is that you have a stock Combat with the only upgrades being crank bearings and layshaft bearing then that is all fine. (Your engine may already have Superblend bearings but the layshaft is an important one to change)

You should spend the coin on the Mick Hemmings DVDs on engine and gearbox rebuilds.

Are your cases open now? How many pieces is the bike in? If you are going from the ground up, you might as well start with the frame. You will put a bunch of hours into it and reading about this other stuff will give you a break from it!

Besides the Comstock breather you can also fit a reed valve in the breather line. I go mine from Mikes XS. Less than 20$ and easy to fit as the line is accesible.

Combats definitely wet sump away from front pick up on their strong acceleration and then crank sling at hi rpms which Combats made for. Dynodave forgotten more than most of us together have learned, but easiest most logical solution is leave DS alone and just drill/grind the TS case to expose the oil passage directly into pump as is lowest point and leave the front sump hole open a any oil entering that will drain &/or be pulled out by pump along the rest of the oil puddling at rear. Make sure TS case passage into pump is cleared as swarf can get trapped to block full oil flow even though solvent pours/sprays right through on bench.

Extra credit mod would be a screen to protect oil pump teeth in rare case of engine seizure destruction. Only way I can think of is drilling a bunch of small holes along internal oil passages.

The crank internal oil dynamics will accumulate an 1/16" layer of nano metalic dust from the centrifugal forces, until best streaming obtained then remains self clearing for life of engine even w/o a useless filter that can not trap the nano size stuff settling out.

While frame at hand re-enforce the read loop via external gusetts or slice off a few inches behind rear frame plate for internal tubes jammed in, tack weld through drill holes then loop jammed on and welded ground back to finish.

If you do a forum search, there has been a fair amount of discussion on here about gas and Combat tune engines and avoiding pinging or detonation. By lowering the compression you can mostly avoid those fuel issues. Some of us might think that would be a silly choice, and some maybe not. It's basically your preference.

For clarity Dre , I have rebuilt my gearbox with the new lay shaft bearing also I have upgraded breather .... I was just trying to point out that sometimes everyone gets excited when they hear Combat .... and kinda dump ideas and theories on the unexpecting new owner .... very good advice above bout reading as much as you can on here about your bike , relating to what to do with it .... for many years I tried to do an improvement each winter and ride it each ride season .... to the point where I am now .... with great pleasure surprisingly only area left untouched is the bottom end ....
Craig

I don't think a more simply complex motorcycle every sold so to acquire the skills and tools to measure access and repair replace could take years.

If reducing CR for some reason, as 2S cam over lap lowers low rpm CR to resist ping/detonation lugging around better than standard cam, >> Do Not use soft Alu gasket or spacer good with copper or steel. DAMHIK or why Norton discontinued to sell them. Also Combat pushrods were not shortened to compensate for the .040" shorter milled head, so bit of spacing helps the valve geometry or seek out someone to trim pushrods while retaining the responsive better sounding 10:1.

Btw all Cdo's came with police level wire looms, radios/lights/siren, for about a shoe box worth of unneeded/in the way/ground fault prone clutter that could/should be eliminated when down for the count. Don't know if cleaned up looms sold or not. Glass fuse & holder is common weak link in electric flow so use blade type.

yes , good point on electrics .... I run a halogen high/low beam headlight , brake light and a horn ..... made up my own wire scheme .... with one blade type fuse .... not much wire .... but not original either .... probably got some grief coming ... wasn't difficult to do and very simple to trace troubles ... I "ll take that over original every time ....
Craig