Steering Issues

I'm getting ready to install new tires and figured this would be a good time to address an issue I've had since I got the bike. My '74 850 wants to go left, that is (I assume) the front wants to steer right, causing the bike to lean left. The rear tire tread is worn to the limit with a fairly flat profile. The front tread is good. Drawing a couple of strings forward from the back tire does show the rear is angled to the right. I'm not able to wrap my head around how a right angled rear tire would affect the direction the bike goes, but I know it's not correct. The other thing I notice is that with the bike on a jack and the front wheel centered, it will fall to the right under its own weight. I'm assuming this is normal, the result of the heavy brake caliper and disk? Is this correct? Later this week, I'm going to attempt to align the rear, install the new tires and hope it solves the problem. Any insight into these observations is appreciated.

Thanks

Your are correct rear wheel cockeyed in swing arm don't affect handing or aim much as front tire just self aligns to automatic make undetectable unless maybe hands off where essentially all bike drift up crown to L. Also the rear wheel center is offset to the LH along with the whole power unit ~3/8". This causes trouble compromising centering the fender in loop with centering for tire spray or viewing.

A very sloppy loose swing arm may contribute its slight effect too but I've purposely tested one with almost 1/2" loose slack and iso's 1/4" gap at front to find it just as fine and smooth as any Cdo I've tried, except for .10 sec twitch on zig zags as slack taken up then smooth stable flyer. I'd be scared to hold it in a longer held sweeper where oscillations can build up though.

Main thing aligning rear is chain runs straight, which I now do after trying all other methods by just sticking fingers between tire and swing arms and diddle close as I can feel while retaining enough chain slack for suspension arc. A few flats away from home render all other methods as just fun and games academics.

Any and every thing can make Cdo's drift more than they should, worn or long stored on side stand tire profiles are famous for this but so is iso doughnuts getting a skewed set. Front should be couple PSI lower than rear tire or fork tends to bother the rear aim, which rules the roost, not the front which is just a rudder to aim big powerful rear and whole bike, witness unicycle stunts.

As rear tire patch is just left of center would make sense Cdo falls to R when let go. A lot of cycles designed with a bit offset rear to center line, non issue.

hobot said:

Main thing aligning rear is chain runs straight, which I now do after trying all other methods by just sticking fingers between tire and swing arms and diddle close as I can feel while retaining enough chain slack for suspension arc.

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Another thing I have trouble wrapping my head around. . . How the heck can you tell if the chain is straight? The swing arm doesn't tell you anything, because it splays out in a different plane than the chain. Sighting down its length, it's difficult for me to tell whether it's straight or not.

Good question that has can be answered by me d/t prior checking with straight edges, string and once even by gravity hanging bike from rafters. You can just trust that Norton made the crank pulley to line up pretty well with clutch when its shimmed out form inner cover not to rub and the main shaft drive sprocket lines up with drum teeth when rear tire is centered in front Vee of swing arm arms. Swing arm is not symmetrical the RH leg splayed out along its length a bit more than LH. Norton spacers place hub where it should be as long as not angled in axle slots. Chains can take the slight inherent mis-alignment of common Cdo's no problemo.

I love your attitude and question as flashes me right back when I got so confused by such a simple machine. I still have episodes after a dozen years
and still tests my sense of manhood will power intelligence and dexterity.

BTW if you can lift chain links out of back sprocket valleys then its that much used up, 1/3 valley lift mean 33% worn before chain fans teeth tips over as chain in use rides that far out of valley robustness. Chain tension has no effect on this.

Steven 'hobot' Shiver
Arkansas Ozarks Dixieland.

Hi Bonwit,
I had a post regarding this subject a few years back, use the search function to find "Pull to the left cured !" which was posted June 21, 2007. Hopefully the discussion/info there will prove useful to you. If you want to discuss it further feel free to email me geo46er@yahoo.com

GB

Thanks everyone for the good info. I'll search for that earlier thread. Glad to know I'm not the only one with the problem.

Bonwit said:

Thanks everyone for the good info. I'll search for that earlier thread. Glad to know I'm not the only one with the problem.

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Indeed you are not! I have the same problem with my '74 built 850 MkIIa and it's really starting to bug me. I've been trying to fix it for nearly four years and though I've made it better, nothing I have tried has fixed it completely. Everything is in line so far as I can tell and I'm coming around to the view that it's the weight of the brake disc/caliper/cylinder all on the right - if I jack the bike up the steering falls hard right and it needs a pull on the bar end of around 1/2lb to hold it straight. I'm going to try weighting the left bar end and if that makes a difference I'll swap the disc to the left fork leg as per geo46er's earlier posts - I intended to do this some time ago but somehow never got around to it......

This seems to be a common 850 MkIIa issue, but I don't understand why the earlier disc brake models don't have the same problem - or do they?

Here's a link to some other posts on this topic:

disc-brake-from-left-right-side-t5611.html

Bonwit said:

Another thing I have trouble wrapping my head around. . . How the heck can you tell if the chain is straight? The swing arm doesn't tell you anything, because it splays out in a different plane than the chain. Sighting down its length, it's difficult for me to tell whether it's straight or not.

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With the chain removed, lay a long, fairly small diameter straight edge against the flat of the gearbox sprocket and see how it lines up with the rear sprocket. I use a length of 10 mm square section bar stock, but it must be dead straight. I can just get in behind the inner chaincase and hold the bar against the inside of the sprocket with my left hand. Another way of checking approximately is by spinning the rear wheel on the stand to see if the chain runs noticeably to one side of the sprocket or the other. If it's way out of alignment, it should show up as noticeable wear on one side of the teeth and not the other.

Two Commando quirks... left lean and low speed head shake. Both went away on my 74 MKII when I respoked the front wheel and learned how to align the 2 wheels together.

YMMV

drc

mitchp said:

I'm going to try weighting the left bar end and if that makes a difference I'll swap the disc to the left fork leg as per geo46er's earlier posts - I intended to do this some time ago but somehow never got around to

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A brilliant idea. . . Weight the opposite bar to rule this in or out. As I mentioned, my '74 does exactly the same thing.

maylar said:

Two Commando quirks... left lean and low speed head shake. Both went away on my 74 MKII when I respoked the front wheel. . .

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Please explain the spoke situation. What was the problem with them, and how were they adjusted? How the heck did you know to suspect the spokes!

Bonwit said:

Please explain the spoke situation. What was the problem with them, and how were they adjusted? How the heck did you know to suspect the spokes!

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I didn't suspect them of anything... other than being old and ugly. I sent my front wheel to Buchannans for polished stainless spokes for cosmetic reasons. What I got back was a rim that is laced such that the wheel is centered between the forks. The original rim was centered off to the left by almost 1/8". It came from Norton that way.. I guess there are tolerances.

In answer to your question about aligning the chain:

There are a number of ways to align the chain. One of the best (in my opinion) is through use of a tool designed for the task that mounts to the rear sprocket and assists you in sighting down the chain. There are a number of them out there. The following link should take you to a picture of one:

http://www.rockymountainatvmc.com/p...ype&prodFamilyId=17145&stockId=142934&ref=gmc

Not sure if it works with the Norton though because of the small amount of sprocket that you have available for the mount.

Hi Bonwit & mitchp,
I wonder if I could talk one of you guys into a little experiment. With everything else on your bike set where it suppose to be pull the calipher off the fork leg and take it for a test ride sans calipher. If the veer left problem is due to calipher weight that will test that theory.

GB

Experiment has been done with 850's and they seem to behave same. I rode a lot hands off mostly to investigate this bias of directional ease or hinderence. I think the Cdo weights more on the LH d/t the power plant offset so on the rolls its like slight pilot lean L, takes a moment to to begin L drift, but because of the rear wheel LH offset a still bike will fall to the RH. I think.

I'm glad to know the front rim works best centered, wasn't sure even if suspected. To lace Norton rim centered the disc side spokes must essentially be all tensioned and centered before starting at all on the far side or pulls rim to the side when far side snugged up. Ugh.

I've been at this dozen years and still adding to list of what upset Cdo's, and what doesn't.

The very obvious thing that doesnt seem to have been mentioned on this thread, is whether or not the frame is straight or not?

Ok smarty pants I'll mention it, if power unit can be assembled into frame with less than 3 lb sludge and 4 Ft levers and dose not vibe the noise hairs out of you, frame ain't bent enough to detect riding.

And the relative ISO offset front to rear had a big effect on mine. That was 0.31" front and 0.25" rear. Had 0.06" machined off the right side front ISO tube and added washer to left side. It had always pulled left and weaved at 75mph +. No amount of wheel alignment attempts cured it but correcting offset did. The rear wheel has to sit parallel in the arm anyway for chain alignment and it cannot IMO be forced very much to align with the front since the wheel spacers will naturally want to sit square on the plates when torqued up. Is the frame straight? The front tubes could have been bent to one side in an accident and may not be centred on the rears so twisting the cradle and swingarm one way. Thought that was my problem till I measured the ISO tube stickout side to side and front to back.

Carbonfibre said:

The very obvious thing that doesnt seem to have been mentioned on this thread, is whether or not the frame is straight or not?

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Yes, and that's the million dollar question..... My bike is 36 years old with an unknown history - chances are it's been thrown up the road at sometime in its' life. It isn't obviously bent but this is always a possibility. When I bought the bike, the handling was atrocious with pretty much everything misaligned, including the wheel offsets. I've gradually worked through and corrected everything obvious and to be honest, the pull to the left is now pretty mild but it's annoying me because I haven't been able to fix it completely. To put it in perspective, if I go "hands off" I have to lean my body about 6 inches to the right to run straight. If the weighting / brake swap doesn't work then I've run out of cheap & easy solutions and a full strip and frame check is all that remains. I'm not sure the problem is bad enough to justify the effort.........

Oh, by the way geo46er...... nice idea about taking the caliper off, but with UK traffic density and the hills around where I live there is just one small problem..... :shock:

Mitch

Hi Mitch,
What you are describing is exactly what my experience was before the swap. Oh and I don't know if is obvious to you, but you don't have to disassemble the fork, just drop the whole fork(s) out of the triple clamp and swap sides.

GB