1972 Roadster Rebuild

Re: New Sign On

I was able to finally squeeze the edge of my grandfathers wonderful old United States Cutlery putty knife under them to break them loose. That blade is almost razor thin and very flexible, I love that tool. Those rings are copper. After that success, I took on the cylinder base nuts, and got them all loose too. Why do they bother even publishing torque values for those? But I actually spent most of the day reading up on Combats. There certainly is no shortage of opinions or info about them on here or in the Norton books I have. The best posts were by hobot, of course. I don't have a vernier caliper big enough to measure my push rods accurately, but I think they are the shorter ones. The cam should decide it. The odometer says 16,000+ miles, so it's hard to believe the cases weren't already split at some point. Although, there are places on the frame where mounts for highway pegs and a sissy bar were welded on and then cut off, so maybe it was just cruised around on? It does seem a shame to miss out on all that Combat fun if it's been dropped in my lap, but is pump premium good enough for 10:1?

Re: New Sign On

pantah_good said:

I but is pump premium good enough for 10:1?

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More than likely not. Many people detune by adding a base spacer and/or thicker head gaskets. But in doing so will hamstring the awesomeness of the 2s cam for it likes the compression and doesn't function as well without it.

Although my 750 is not a combat, I do have a JS1 cam, shaved head and a big ass carb. It does not like pump premium 93. It will knock. I used to get 110 racing gas and mix it 50/50 with 93, but I have recently found a regional airport that I can just drive up to and slide the debit card through and get avgas. I still mix it 50/50 and it has proven to be a good way to go and 2 to 3 dollars less per gallon than racing fuels around here.

Anyhow, you'll just have to wait and see, but in the mean time look for alternatives in you area.

Re: New Sign On

Avgas is a wonderful thing. But last time I went to the local airport, they really didn't want to give it to me because they now have the ground wire they have to attach to something and there's nothing on a plastic can. If I had a Combat, I'd keep it Combat with the proper oil mods. I did find a place that will sell non ethanol gas, but not sure of the octane. I use the avgas because of the F/G tank I have, but it sure runs nice in the bike and doesn't foul up the carbys, it evaporates really fast. But yes, it's approaching $6/G and it's hard to ride from airport to airport. Smells good and has nice blue color too. Not for road usage, no road tax. Oh, well.

Re: New Sign On

pantah_good said:

Yes, thank you, I'm aware of the case oil system issues that will need to be addressed when I get them split. Not sure where to have them worked on yet.

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Well you can't go wrong with thenortonmachineshop aka comnoz here on the forum, just have to mail it to Pueblo Co.

Re: New Sign On

A quater in. wide ( ish ) wood chisel , flat side out - should get under the Copper Rings if you tease it ( a sharp one ) to hook an edge free , without scouring the mating face .

Tightening the ring nuts , when refitting , if your sulubrious ( all faces pre coated ) with Koper Kote , should stopem galling & seizing & falling out . You lean on the wrench
firmly with your palm ( unless your a 15 stone weight lifter - a few fingers'd do ) . Each Heat Cycle you bring them down a bit ( they anneal or suchlike - with the heat )
Some are / were copper wraped asbestos chord . After half a dozen or eight goes theyre down flat and stable , and wont undo unless a muffler falls apart and is loose .

Aligning the pipe so the face is square ( Fit the pipe against the head and see if it needs a tweak to align the mounts ) to the mating face . Get the muffler mounts so everything sits in place
and the bolts push in freely - I.E. its all unstressed fitted . Then supporting the weight while fitting / tightening up , it should be unstressed and stay in place , though the heat at the mount against the muffler & pipe/muffler clamps shpould seem need ' retourqueing ' unless youve played Tarzan on the wrenches initially .

The old JoMoCo NORVIL Valve Springs ( same as Trumpy ones ) or better should see less stress on the Valve Gear . The old Terrys dont last forever , if your giving it a bit of stick .
Shimming the setup to 40 thou. of coilbound & min. 40 thou. valve to piston isnt a bad idea either . Just wind in the adjusters 40 thou , and turn it over , plugs out , somewhat gingerly .
First hint of contact ( lock up ) and go back , and re figure .

I found a Combat Cam good - over 3500 its ' on ' , 4S is similar but 20 thou. ' more ' everything . A Early 2S with 20 of the base , according to the lift charts . So the 2S is much maligned .
Better Carbs wake it up too . Works ran 33 Mk 1s , 32 Mk IIs alledgedly flow more . I ran 9 1/4 : 1 Comp . Which was more than enough . Bigger valves out on clean seats ( unrecessed )
help no end .
Valves sunk back flush with the chambers ( Typical OIld Triumph ) do nothing for anything . Except Morons .

The opinions on the case mods for the oiling system are mixed. Some consider it necessay, others consider it butchery. May be a need on a race bike, but the jury is out on street bikes. I never did it on my 72 and seem to have no problems. Never blows much oil out the breather.
There's been plenty of discussion on the main forum about the topic. I'd recommend a search and a look through the topic before you commit.

Thanks to Jerry for moving and renaming this thread. And thanks for the technical inputs, although some of it is a little over my head at present.

I was certainly hoping to be able to ride this bike more than one gas tank full round trip away from home, and that Roadster gas tank is looking pretty small at the moment. Carrying a can of octane booster additive may be a solution, if it works. Does anyone have good experience occasionally using it to get pump premium up near 100 octane?

The forum search feature came thru again. Cylinder now loose without starting a fire or breaking any fins.

Today I drove the scenic route up to the other end of Vermont for my first visit to The Classic Bike Experience shop which was having their open house today, and also see my friends from Fishtail Riding School, who were putting on a track day seminar during the open house. I have to say I was very impressed with the C.B.E. shop and the guys that run it. I brought my cylinder head along on the chance that they might have time to look at it, and on the very outside chance I could get them to do a little service work on it by pulling the valves out. I had gotten a loaner valve spring compressor tool from the local Advance Auto Parts store, but it wasn't the style that could drop down in on the valve tops. Nick Woodbury took charge of my head and right off spotted why the l/h exhaust valve was stuck partially open - the guide was broken. In no time he had all the valves removed, and insisted on not charging for his work. Turns out he is from Springfield and knows the guy that sold me this bike. That shop was reeking of good karma today, so I think this bike has found some new friends to help with its rebuild. They even use the same vapor blaster in southern New Hampshire that I'm planning on taking some parts to on Monday. The most current info on CBE is on their Facebook page.
https://www.facebook.com/The-Classic-Bike-Experience-157556270931714/?fref=ts

That bike had seen a tough life!

That is some serious crud in those ports.

Yep, there is serious crud of all forms everywhere on this bike. The l/h exhaust valve from the broken guide was bent a little (doesn't show well in the photo) and had to be driven out of the guide. Cleaned off the piston tops and there is no obvious sign of valve to piston contact, and the push rods appear to be straight. The engine has turned over ok on the kick starter ever since I got it, which has me puzzled. The top ring on the r/h piston was broken in two, and both pistons were stamped "+030". I see there are both "standard" and "combat" pistons listed in the parts manual. How do you tell the difference?

Those guides need a detail cleaning on the inner halves BEFORE they drive them out of the head. Otherwise they'll scratch/score the bores on the way out. A good shop will know this, but don't take it for granted. Could mean the difference between having to overbore the holes and find oversize guides, or skip straight to dropping in new replacement guides.

pantah_good said:

I see there are both "standard" and "combat" pistons listed in the parts manual. How do you tell the difference?

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I wouldn't worry much about the difference. Both pistons (Combat and Standard) for 1972 have been superseded by the later 750 pistons, now part number 67055 for 73 mm bore, and available in oversizes up to +.060".

Ken

Thank you both, there is a lot to study up on and think about when doing one of these for the first time.
Once I get the engine cases split I am planning on having them vapor blasted, and would like to leave them unpainted. I couldn't find any compelling reasons to paint them while researching on here, did I miss anything on that?
Bill

Paint them carefully if you are going for a concours-correct restoration.

Just rebuilding for a nice rider.

I'd skip the paint.

I've done them with and without paint, and I like the look either way. The modern engine paints are pretty good, probably better than what was applied at the factory. Another option is to send them out for coating by someone like Swain. They do a nice ceramic in silver that makes them very easy to clean.

Ken

I'm a fan of bare aluminum.

Yeah, Cerma coating is real nice, but not cheap!