Starting after 32 years ....
- Thread starter Krazymummy
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rx7171 said:
You want to listen to this guy, he has been there and he seems sane.
Yes, old bikes that have sat for decades can be started, but doing so can damage them. The 850 had the good crank bearings in them and an oil filter so the inside of their cranks are usually very clean. A 750 like yours could have questionable main bearings and there could be debris in the crank just waiting to destroy your rod journals/bearings.
So don't start it, take the bike all apart. Winter is here so it is good timing. Make sure the engine is clean, put it back together with superblend main bearings and you will be doing it a big favor.
While it is apart take your time and research a few options. If you do have a Combat engine you might want to look into putting a standard Commando cam and cylinder head onto it, a combination that can have most of the power a Combat engine has, but will run better on cheap gasoline, run cooler and have power in a more useable rpm range. The carb setup you have would also be much better matched to the non-combat parts. Take a good look at putting the carburettors back to stock. New Amals are available that are of better quality than the originals, fit the bike well because that is what it came with, and they are very easy to find tuning information on.
If you make smart moves and work on the bike two or three times a week, then you can easily have it back together for next summer and you won't be gambling so much on parts and reliability.
Good luck
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Welcome to the never ending tasks of owning and operating a Commando. Take heed of looking in before starting up as may save a blow up or scored bores or rusted valve stem in guide or fracture prone comma oil hole pistons or Al gasket intruding on the pistons - as happened to me on '72 that sat for a decade but started right up and worked a treat of careful easy use for 3 wks then about coasting low 50's mph - tinkle tinkle KaBoom, locked rear and messed up engine to recover. If 2S cam still in good shape I'd leave it Combat spec as the cam over lap allows use on 87 octane no problemo for me in summer heat zooming up steep in 4th. Be ware fiber glass tanks dissolve with ethanol gas to mess up carbs and engine if not caught in time. Beware unknown brake fluid leaks for sudden brake failure and don't get the primary chain too tight when cold as severely tightens up at road temps. Standard Combats 19t sprocket putter around slow and pull as good as any Cdo down low but sure wake up about 90 mph and increase pull to red line and beyond. 1st and 2nd can reach red line in a hurry so pay some attention to tach as there is no power decrease like others to warn ya time to shift. Tranny likely needs new lay shaft bearing as famous for breaking up to lock up so clutch don't release the locked rear slide. Expect a hand full of $1000's to get road worthy presentable.
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I have not the time I thought I would have when I accepted the Norton.. It is on my mind daily .. but slow going ..
Thank you for all your input ...
I'm not going to try and start it , The carb cleaned up nicely and still needs rebuilding .. Not worried about much right now except making it a straight roller.
The 16 inch wheel on the back has to go .. I don't know how anyone could ride this with that wheel it is so cockeyed you would be going down the road sideways like you are in an ever lasting drift .. almost sounds fun ... Anyway I got a WM3 18 inch to replace it .. I'm using the same hub .. I have spokes on the way ..I may try a Size - 120/90H-18 or - 110/90H-18 the 120 I believe will come closer to the diameter of the front 100/90H-19 .. I know that is tight in the rim , but I have been told ether one would fit and work fine . Any input from you guys is very much welcomed .. QUESTIONs : (1). In your opinion would they work and fit in the swing arm ?... (2). Must the wheel be off center when truing for proper alignment ?
Thanks
Thank you for all your input ...
I'm not going to try and start it , The carb cleaned up nicely and still needs rebuilding .. Not worried about much right now except making it a straight roller.
The 16 inch wheel on the back has to go .. I don't know how anyone could ride this with that wheel it is so cockeyed you would be going down the road sideways like you are in an ever lasting drift .. almost sounds fun ... Anyway I got a WM3 18 inch to replace it .. I'm using the same hub .. I have spokes on the way ..I may try a Size - 120/90H-18 or - 110/90H-18 the 120 I believe will come closer to the diameter of the front 100/90H-19 .. I know that is tight in the rim , but I have been told ether one would fit and work fine . Any input from you guys is very much welcomed .. QUESTIONs : (1). In your opinion would they work and fit in the swing arm ?... (2). Must the wheel be off center when truing for proper alignment ?
Thanks
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100 to 120 fits on rim and mounts fine, though the 120 is a squeeze to get past fender and drum. Wear wise 100 gets maybe 3000 miles, a 110 - 4000 and a 120 over 5000, if not feeding full torque full upright most the time, then cut mileage in half. Each tire size up adds a tad more inertia to throttle response and sense of ease to fling around but other wise undetectable. I try to extend my tire by mainly accelerating out of turns or weaving some in lane to reach hiway speed, or feather on power full upright plus avoid much engine drag slowing or I get to change tire too soon again. But if still learning to enjoy the Command thrills, by all means just use the tire up making memories then decide what's cost effective.
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Sounds like a plan .. Thanks hobot .hobot said:
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beng said:
Beng
Thanks for the thumbs up, but I want to comment on your suggesting a Standard head instead of the Combat one.
If the Combat 10 to 1 high compression was your concern I lowered it using a spacer I got from OldBritts under the barrel, so no need to change head.
Part number 11-066591 .028" Thickness. Since the Combat head was a Standard head with intake porting for 32mm carbs and shaved .040", by using a .028" spacer the finished compression ratio is probably about 9.2 to 1 rather than the 9 to 1 of the Standard motor.
I did that because I didn't want possible problem of pinging (pinking) with the high compression, especially since the standard cam may increase that possibility.
The bike really goes with that Mikuni 34mm VM so its low end grunt is really helped with these mods, instead of having to wind the engine north of 4,500 before the 2S cam of the Combat catches fire.
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I thought a bit more about the Combat versus Standard engine outputs and how to decide what is the prefered configuration for what type of performance you are looking for.
I looked at the Torque/Horsepower Chart on page 73 of Mick Duckworths book "Norton Commando".
The Standard configuration produces more horsepower than Combat until 5,300 rpm where the Combat pulls away up to 7,000 red line.
The Standard produces about 2 more horsepower than Combat at the same rpms until about 4,800 rpm, eventually declining starting at about 6,100 rpm until there is a spread of about 7 hp between it and Combat when both at 7,000 rpm.
The Standard configuration produces its maximum torque of 47 Lb-Ft at about 4,900 rpm, with the Combat's maximum of 48 Lb-Ft at about 5,700 rpm.
The Standard torque exceeds the Combat's by about 3 Lb-Ft up until the lines cross at 5,300 rpm.
For the Standard configuration it appears the 4,500 t0 5,500 range would be the rpms to use for spirited riding.[/u].
With Combat, if you want to exceed the performance of the Standard configuration you need to regularly push the rpms up into the 5,700 to 6,000 range where both horsepower is very strong and before torque starts to decline after 6,000 rpm.
I looked at the Torque/Horsepower Chart on page 73 of Mick Duckworths book "Norton Commando".
The Standard configuration produces more horsepower than Combat until 5,300 rpm where the Combat pulls away up to 7,000 red line.
The Standard produces about 2 more horsepower than Combat at the same rpms until about 4,800 rpm, eventually declining starting at about 6,100 rpm until there is a spread of about 7 hp between it and Combat when both at 7,000 rpm.
The Standard configuration produces its maximum torque of 47 Lb-Ft at about 4,900 rpm, with the Combat's maximum of 48 Lb-Ft at about 5,700 rpm.
The Standard torque exceeds the Combat's by about 3 Lb-Ft up until the lines cross at 5,300 rpm.
For the Standard configuration it appears the 4,500 t0 5,500 range would be the rpms to use for spirited riding.[/u].
With Combat, if you want to exceed the performance of the Standard configuration you need to regularly push the rpms up into the 5,700 to 6,000 range where both horsepower is very strong and before torque starts to decline after 6,000 rpm.
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Yea .. I think they were always one or the other :wink: , The thing is I have worked with SS a few times and never came across any that was magnetic . When someone brought up that they may be , I was inclined to look further into the possibility and found that some SS make up is indeed magnetic .. I have not touched them since that time of cleaning off the paint , but I feel now that the possibility of them being SS is strong ..Rohan said:
Thanks for your post and input Rohan .. This really is a great forum .
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rx7171 said:
rx7171 , Thank you for your advice and suggestions .. You and others have given me a good base to start some inner tug-of-war with the direction of my obsession . I know I will be at this for longer than I had thought ...
:shock:
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Them wide ones . Chromed were narrower and less flatted , as in a constant radius cross section .
C O M B A T . a bit of attention to detail . Couldnt possibly detune it . Unless your stuck in the city .
Just Not Done . Have to get TWIN MATCHED 34s on it too . No half measures .
and practise wheel spinning tyre smokeing take offs . Some people think a H2 is faster . Deluded feuls .
Fit a impulse Tachometer , if you follow tis train of logic . And tighten the bolts adequately . :twisted: :wink:
C O M B A T . a bit of attention to detail . Couldnt possibly detune it . Unless your stuck in the city .
Just Not Done . Have to get TWIN MATCHED 34s on it too . No half measures .
and practise wheel spinning tyre smokeing take offs . Some people think a H2 is faster . Deluded feuls .
Fit a impulse Tachometer , if you follow tis train of logic . And tighten the bolts adequately . :twisted: :wink:
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