Commando swinging arm symmetry

Wouldn't the more important question be:  Is the rear sprocket in line with the drive sprocket?

Mike

My Mk3 has always challenged me, because the rear wheel never seems to line up with the mudguard which is central to the frame, but the distance between the two faces of the rim is equal on both sides.

The other thig to be careful of is looking at the front and thinking the crankcase halfs are equal, the joint is not central to the frame !!

When I had the front wheel built with 18" rim ,to match the back, the wheel builder said that he gave me as much offset as he dared but it was nearly over centre, ie too far to the left...This is because the Mk3 has different front wheel spacers to the others with right hand disc.

All you can do is fit both wheels and get a long straight edge, like a fluorescent tube, and see if they are level. You will have to prop the bike up as you cant do this on the centre stand !

Hi Richard

I have a problem on my 77` Mk3 the handle bar`s when riding seems like they are not right as if I am riding with the forks twisted, it has got new forks and I have undone the pinch bolts and the top Nut`s and twisted them to were I think they are right but go out for a ride and they seem to be the forks are out of line, I just don`t know what to do, also if you take your hands off the Handle bars at around 40 mph it go`s into like a speed wobble, the wheels were done by Devon rim company but don`t know what else it could be ? any help would be a great help, I was going to put my own Thread up to ask this but see who can help here......sorry for the butt in.

Cheers Maurice   

yes I have the right yokes...not had a look at the wheel spaces as I put them back in as they came out so will have to check that one out, when I say twist the forks I mean with the pinch bolts undone and holding the front wheel between my leg`s and twisting the handle bars to Align them, and yes they are new stanchions as the old ones were rusty, but the new ones still do the same thing as the old ones that`s why I thought is there something wrong with the Yokes....I did not know there was a tool to put them in the top yoke as I thought you just have everything lose and Bounce the forks up and down ?

When you have done most of the above, tighten the pinch bolt last. This side should take a natural position on the wheel spindle bolt. The alignment of the hub is taken from from one side only, not the pinch bolt side. 

Distance between the holes in the yokes, and thus stanchions, is often used to centre the front rim, in 99.9% cases it will be OK, but the rim should be checked to the drop of the headstock for ultimate accuracy.  

The rear wheel rim does not sit central to the rear swingarm on a MK3, you will notice this when it is correct, as the gap from the tyre wall to the inner edge of the swingarm is slightly different.

There are some vernier upgrade kits that are installed the wrong way around, this will cause a wobble, and should be spotted when the wheel alignment is checked. Another giveaway is the engine can look central in the frame, as Hans says, it is offset to allow a drive system to be connected to the rear wheel whilst keeping it all neat and tidy. 

Unless the rear loop has had a knock, or been straightened, the tyre should be exactly in the middle, as the rear loop is aligned on the frame which is built using the headstock as a datum.  

After doing all this, make sure your tyre fitter knows how to fit a tyre, despite their attitudes, nearly all don't or don't bother checking. The radial markers or start of tyre wall from the bead should be concentric to the rim on the side it is fitted, most get this right, but they tend to fail get the same distance or radial markers present at the same distance on the opposite side, ie you should have the same amount of concentric bead engaged with the rim on both sides. Just because in is fitted concentric on both sides does not mean it is fitted correctly, strangely many MOT inspectors will let this pass.  

So when you look at all the pieces of the puzzle and the tolerances along the way, you can now see that to get the rear wheel to follow the front was most probably more luck than judgement in the day, OK for road use, but there are many things can be checked to get it better.  

Thanks Richard I will take this all on board and have a good look when I get some time and I will get back to how things go...so Thanks again I wish you lived near to me as I have had this problem since I got the Bike two years ago.

Maurice

I am in Ipswich Suffolk

I am waving can you see me I am the one who is standing under a dull overcast day looking toward you with envy and dreaming of the Sun ;-)

I'm confused (nothing new here) but it doesn't make sense that the front wheel and the rear wheel were designed and made out of  alignment.

I wouldn't think that the bike was designed with the wheels offset at all even if they are parallel to each other.

Perhaps whoever has the original drawings can fill us in on this.........

Mike 

Thanks for the note Richard.

Mike

Maurice, see my reply above. Devon wheel Co told me that the offset on a mk 3 front wheel is so much that the spokes are near vertical. Even with slightly odd offset I don't know why you feel like you are not steering straight. Not being funny  but are your handlebars straight. (you said that it's been like that since you had it). It's a faff but take them off and lay them upside down on a really flat surface like kitchen worktop and see if they rock side to side . Just a thought . 

Hi Hans

Thanks yes that was my first port of call was the handle bars, But Literally you can see that it is the top yoke that looks like it is turned to the right when you are riding the Bike I have tried undoing the pinch bolts and with the front wheel between my legs turning the handle bars to the left and when I think they are straight do the pinch bolts up then go out for a ride and again the yoke looks like it is turning to the right to make the bike to go Straight..... well hacked off as I can`t seem to find the problem :-( 

Just been down the workshop and taken the following Numbers off the back and front wheels of the MK3 if this mean anything to someone in the know.

They are Devon wheel Co. Both back and front have the same Numbers on the Rims

DRC WM2 1.85 x 19 0507 

Hi Maurice, I think that everyone else has given you as much advice as there is out there about aligning the forks , so all I can add is find someone else in your area with a Mk3 and compare parts. Failing that, have the front end right out and check squareness of all parts. Many years ago I rode around with a bent frame for ages after an accident, which I only found after an engine rebuild. Had your bike ever been crashed ...who knows ?

Drop a line through the headstock tube, this should be the exact centreline of the rims. It sounds very much like a bent frame if the wheels are correct. If it is the frame tube behind the gearbox wiil also need checking for cracks, though far from any impact point, it seems to give up there. 

Thanks Ashley I will try the line though the headstock ...... Now I am worried but first things first :-(

It’s possible you have a bent bottom yoke. I had the same problem with the bike feeling twisted and pulling to one side hands off. I tried everything and eventually laid a 3 or 4” alloy bar across the fork stanchions below the yoke. The bar rocked as it was only contacting at 3 points indicating that the forks were twisted. As the stanchions were new it turned out to be the bottom yoke. A new yoke and normal service resumed. - good luck! 

Thanks Ian I will try all that has been said as i need to get to the bottom of this as it makes it handle very badly so need sorting Thanks....

Well I have tried what Ashley said to run a plumb line through the head stock and it should line up with the centre of the wheel rim... well I hope it is good news in respect of the frame as indeed it do line up with the centre of the wheel. so the next thing to find is a bottom Yoke anyone out there in our lovely NOC land have got a MK3 bottom Yoke that is Not bent Please ?

Maurice