New to me. 1970 750 Roadster (2011)

i thought about it.

but you know, this machine has gone through five owners now, and will be moving onto others when i'm pushing up the daisies.

seemed appropriate to keep the same story going.

A few things: (I have a 70 commando also)

First, that key fob will ruin the paint on your sidecover from flopping in the wind.(ask me how I know that... 8) ) I ground down the head of the key to almost nothing after it gouged my leg while kickstarting the bike, then I drilled a small hole in the little bit of key left exposed and put a loop of a nylon shoelace through the hole.

Second, '70 model frames have the single bolt swingarm tube on the engine cradle. If your handling has a snake dance like feel to it, the poorly designed swingarm tube is most likely to be the cause. The Kegler clamp modification fixed my bike's poor handline to the point where it handles very nicely. (this was my biggest complaint with my '70 that plagued me for decades until I found the kegler modification posted here)

thirdly, awesome purple...

oh, and I've messed with jet sizes and the recommended size (220's) worked best...

I don't have any problem with the key, but I don't hang anything off of it. Doesn't bother me when starting. I don't really see the issue. I agree the colour is great.

DogT said:

I don't have any problem with the key, but I don't hang anything off of it. Doesn't bother me when starting. I don't really see the issue. I agree the colour is great.

Click to expand...

Right, you don't see it.

Do you start your bike with it on the centerstand? I don't, and I wouldn't because I'd rather stress the early model centerstand, which are prone to break, and could use some reinforcment directly between the pivot point arms.



unlike the later model which has a tubular member higher up which cuts down on the length of the leverage arm acting on the frame of the stand. The early stand is no where near as strong as the later model stand pictured below.



I also don't have scrambler pipes pertruding from the left side of the bike which would prevent my inner thigh from contacting the head of the key.

and finally, I have narrow 24" wide handlebars, so I have less leverage with which to keep the bike balanced when I kick it over as I hold it steady. It's a balancing act on a high compression bike. The key had gouged my leg more than once before I decided to make a few copies of it and grind some of their heads down to keep the key from ripping into me... again.

Now you should see...

o0norton0o said:

A few things: (I have a 70 commando also)
Second, '70 model frames have the single bolt swingarm tube on the engine cradle. If your handling has a snake dance like feel to it, the poorly designed swingarm tube is most likely to be the cause. The Kegler clamp modification fixed my bike's poor handline to the point where it handles very nicely. (this was my biggest complaint with my '70 that plagued me for decades until I found the kegler modification posted here)

Click to expand...

i didn't know about that. this machine is completely stable at speed, but hands off at 35 mph it shakes its head a bit. not enough to bring on a wobble, but a definite oscillation. i'll have to look into the swingarm, as i can't tell whether the looseness is front or rear.

o0norton0o said:

Do you start your bike with it on the centerstand? I don't, and I wouldn't because I'd rather stress the early model centerstand, which are prone to break, and could use some reinforcment directly between the pivot point arms.

Click to expand...

no center stand on this puppy. the early stands are hard as hell to find. i thought about drilling the cradle out for the later assembly, and if i simply can't get an early one i may still do that. it seems to me that welding a solid brace across the early stand would help it a lot, but i don't know what would interfere with what until i have on on it so i can see.

and finally, I have narrow 24" wide handlebars, so I have less leverage with which to keep the bike balanced when I kick it over as I hold it steady. It's a balancing act on a high compression bike.

Click to expand...

the bars i have on it now are pretty wide, and feel fairly odd to me. i have some old superbike low bars from the 70s i kept on my bonneville until recently, and i may switch those in.

it's still odd to me how well this machine corners.

i thought that purple paint was an eyesore at first, but i have to admit it has somehow mellowed on me. i'll be keeping it, if only because it was what the machine originally came with.

speedrattle said:

o0norton0o said:

A few things: (I have a 70 commando also)
Second, '70 model frames have the single bolt swingarm tube on the engine cradle. If your handling has a snake dance like feel to it, the poorly designed swingarm tube is most likely to be the cause. The Kegler clamp modification fixed my bike's poor handline to the point where it handles very nicely. (this was my biggest complaint with my '70 that plagued me for decades until I found the kegler modification posted here)

Click to expand...

i didn't know about that. this machine is completely stable at speed, but hands off at 35 mph it shakes its head a bit. not enough to bring on a wobble, but a definite oscillation. i'll have to look into the swingarm, as i can't tell whether the looseness is front or rear.

Click to expand...

Don't worry about a little shaking at 35mph a lot of commandos do that in my experience of it handles well it's best left alone, don't forget to oil the swing arm bushes don't grease them, cheers

it's handling is perfect. if i push it down into a corner, it stays there, doesn't fight to stand back up. if i pull it back up, it comes up, with zero effort, and then stays up.

in contrast, i have a 97 buell that is vastly more sophisticated but has to be forced into a corner like getting a rottweiler into a bathtub.

if that's relatively normal, i won't worry. since my trident threw a rod, this is my daily rider, at least until the snow flies.

I got my bike in 72 with no center stand. And I also can't start it off to the side or sitting on the seat. I actually have to get myself completely up with both feet on the pegs and push it over from there with my full weight to get it through the second compression, when it then decides to start. But all in all it's been an easy starter and I haven't had any issues with the side stand. I always use a block of sorts under it anyhow to keep it from leaning so much. It's a bit of problem to keep balance correct, but I can do it off the pegs which I can't do standing off to the side or with no stand. Every time I've tried that I drop it because it's not on the stand. I know everyone says not to do what I'm doing but I've been doing that from the get go and there's been no problems, it's a matter of balance and how you can manage it. On my rebuild I put a center stand on it, but I don't use it. I should just take it off. Everyone has their method and none is best for everyone IMHO. Believe me I'm far from being critical of how anyone wants to do it.

I ran into a guy with a BSA 441 that had trouble with the oil tank hitting his leg when he started it. They're not easy to push over either. I had a BSA single 500 and parked it on a hill so I didn't have to kick it. Nice torque though but it put your arms to sleep in about 15 minutes.

the 70 seat is pretty wide up front, which is nice to sit on but contributes to a tiptoe stance at a stop. i don't know what the compression is on this machine, but it's higher than i'm accustomed to.

There's a few subtle differences in '70 commandos which were changed in later production years, so the flaws associated with early bikes are largely ignored in the forum by late model owners which makes those differences, and in some cases flaws, less well known to we '70 owners.

LIke:
'70 commandos have 27 degree yoke angle where later bikes have 28 degree
'70 commandos have less offset on their fork tubes from the yoke pivot than later bikes, which gives our bikes a little more trail
'70 commandos have the marginally effective camshaft timed breather, later models eliminated it in favor of various other configurations.
'70 commandos have a different center and side stands
'70 commandos have a single bolt swingarm tube which can cause sloppy handling, later bikes have dual wedge bolts that eliminate this potential handling issue.

so,... change your main jets out to 220's. I've tried 240's and they were too rich. I couldn't get the bike to go past the low 80 mph's. With the 220's I could hit 100mph if I wanted to do that. (but I don't) Now you know about the swingarm tube flaw, so if any handling issues develop, you know where to look. Ditch the key fob so it doesn't ruin the purple sidecover...

* Maybe think about adding a reed breather to your crankcase. Jim schmit makes one that mounts on the existing timed breather port, which would be the simplest way to add a reed valve to your bike. The sump plug breather that Jim comstock fabricates doesn't fit our '70 commandos because of the location of a tubular frame member on our '70 frames... Another glitch for the '70 model year.

As far as handling goes, my bike handles great now that I fixed the swingarm tube. I'm pretty thankful for the info I learned here that helped me fix that problem, because I rode my bike with it's snake-dance motion for decades before learning what actually was the cause of the problem.

Good luck with MR. Purple

i've already put the key fob back in the tool box to hold the spare keys, and i've a bid out on a centerstand on eBay.

i'll have to look into the breather. i run open tubes on my other stuff:



there's no vacuum produced with open tubes, but then there's no possibility of failure, either.

i'll order the 220 jets. my books specify 180, 200, or 220, depending on what sort of machine you're running, but it's easy enough to see what works just by putting them in, and i know it's not rich.

can you think of any other differences between the earlier commandos and the later ones?

Oil tank is central, not off to the side. Electrical system is different, the key only turns off the rear brake lamp and the ignition.

I'm not sure the JS breather would do much good with the timed breather in place, it really needs to be removed, or a totally new breather installed. I've read that some live with the timed breather with good results. My results are lots of oil leakage through the air filter, I fixed that with a catch bottle, but not simple. Keep the oil level in the tank towards the low level. The front mudguard and stays are too small/short for anything larger than a 310-19 tyre. I'm not sure the later bikes had the amp gauge in the headlamp shell. Early bikes had no turn signals.

I got my swingarm fixed a long time ago with something similar to the Kiegler mod, but no clamps, just bolts at the ends and a new oversized SS rod. The early head steady was prone to breaking, I replaced mine with a home made Keith HS. The way I ride, I really can't tell much of a difference. The engine spring off the head steady will help with the idle shakes. Hemmings vernier iso adjustments are good.

My bike seems to like 240 main jet and 0.106 needle, 25 pilot. Nr 3 throttle and middle notch on the needle position.

There's a few more differenced that I'm aware of, and maybe a few I'm not aware of too.

The 70 commando headsteady is primitive. it was replaced by the "box" style headsteady on later models. (I use a comstock headsteady which is better than any stock commando headsteady)

The 70 commando rear wheel is bolted directly to the sprocket/brake drum. Later models had a crude cush drive mechanism in order to take some of the shock load off the drivetrain.

The 70 commando had 12 volt coils, Later models got better spark out of two 6 volt coils. (I use a single dyna coil with dual leads and a boyer ignition)

The 70 commando has a drum front brake (mine was changed to a late model disc 40 years ago)

The 70 commando has a weaker swingarm. later model swingarms have reinforcement gussets welded where the arms meet the crossmember.

I'm sure there are more differences that I've forgotten about. For the most part I've done all the handling upgrades which are the swingarm tube modification, a better headsteady, koni shocks, progressive fork springs. I haven't done the landsdown fork dampers upgrade, but those are being manufactured again by madass and it's on my list to do someday.

I've also done a timing side reed breather modification because it helps to reduce oil leakage. Unfortunately our 70 commandos can't use Jim Comstock's sump plug breather because the 70 frame has a crossmember that blocks the use of his breather. Recently Jim Schmit introduced a reed breather that bolts on to a 70's crankcase at the camshaft port, so there's that simple bolt on option if you don't want to modify by drilling stuff.

HTH...

edited to add... All good stuff dog posted above me while I was typing...

got this on eBay yesterday:



price nearly doubled in the last two seconds because another norton guy tried to snipe it. but he waited just a bit too long and the auction ended before he could match my bid.

sorry if that was any of you. but these things are genuinely hard to find, used or new, and i was glad to get it.

220 mains are coming from MAP.

i need to look at the headsteady on the bike. the parts manuals versions don't look nearly as sophisticated as the comstock one. i'm interested in looking into the handling, although it's already good. i live within reasonable distance of the mid-ohio racetrack, and i've been thinking of joining the club racing group. i think a firm-handling norton would be interesting to take to the track days there. tightening up the front and rear would really be all i would be interested in changing, except for seating position. i like the rest of this machine as it is.

speedrattle said:

......i need to look at the headsteady on the bike. the parts manuals versions don't look nearly as sophisticated as the comstock one. i'm interested in looking into the handling, although it's already good. i live within reasonable distance of the mid-ohio racetrack, and i've been thinking of joining the club racing group. i think a firm-handling norton would be interesting to take to the track days there. tightening up the front and rear would really be all i would be interested in changing, except for seating position. i like the rest of this machine as it is.

Click to expand...

Well, I would pony up the dough and get the comstock head-steady, it really is beautifully made, and it utilizes the existing mounting hole in the frame bracing tube under the gas tank, unlike some of the others out there that use a clamp around that tube, (I've read here from other members that they had rubbing issues between their tank and the clamp). Regardless of which one you go with, the main thing is for the headsteady to keep the engine in the verticle plane while allowing it to bounce up and down as it is want to do being a 360 degree parallel twin and all. As the older style ones wore out, they allowed the engine/rear drive to cant over to one side, adversely affecting the bikes handling.

RGM used to carry those early center stands. That's where I got mine.

cjandme said:

Well, I would pony up the dough and get the comstock head-steady, it really is beautifully made, and it utilizes the existing mounting hole in the frame bracing tube under the gas tank, unlike some of the others out there that use a clamp around that tube, (I've read here from other members that they had rubbing issues between their tank and the clamp). Regardless of which one you go with, the main thing is for the headsteady to keep the engine in the verticle plane while allowing it to bounce up and down as it is want to do being a 360 degree parallel twin and all. As the older style ones wore out, they allowed the engine/rear drive to cant over to one side, adversely affecting the bikes handling.

Click to expand...

beautiful is hardly expressive enough:



i'm a machine junkie, and this is pretty stuff

DogT said:

RGM used to carry those early center stands. That's where I got mine.

Click to expand...

now that i bought one, there are two more for sale.

okay, got the 68-70 1/2 stand, and the correct spring for it (06-0588):




but where does the top of the spring hook into?

there's a hole up in the center stand mounting plate on the right side, but i'm buggered if i can figure out how to get the spring to hook into it:



it's in the right place, but there's no room to swing the hook on the spring into the hole. if i clip some of the spring off so the curved section is shorter than the diameter of the hole, then i can just twist the hook over and in. is that the correct work-around, or does the spring hook onto something else up there?