Clearance

I hung the exhaust system on my '75 Mk III a few weeks ago and had to walk away to start a new contract. I got back to it last night and noticed that the right side, as seen from the rear mount, had much more clearance to the swingarm then does the left; in fact the left is so tight (close) I am concerned that the exhaust mount and the swingarm will hit eachother during spirited motoring.

There is no sign of damage that would have brought these two area together; the exhaust, the "Z" plate, the rear peg all mounted and bolted up just fine and feel solid. I have all the spacers in place, the "Z" plate is flat.

Is this all normal?

RS

Just checked my own, Mk3, on the left hand side between the arm and the end of the threaded portion of the rubber bush that holds the silencer plate, (peashooters fitted), is about 4mm and on the right about 6-7mm, but it is below the swinging arm so I don't see them coming together as when the bike is loaded the arm will push up slightly.

RoadScholar said:

the right side, as seen from the rear mount, had much more clearance to the swingarm then does the left; in fact the left is so tight (close) I am concerned that the exhaust mount and the swingarm will hit eachother during spirited motoring.

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I had exactly the same concerns with my MkIII, so I shortened the thread on the upper rubber mounting and used a thinner nut.

Thanks gents!

I had this sneaking feeling that the PO may have bent something, so it was very relieving to hear that its tight there.

The last time I worked on the bike I managed to pull the horn wires off the prisoner below the battery box, behind the transmission and in front of the rear fender. Today I pulled everything out of the way, rear wheel out, I disconnected the rear shocks and moved the swingarm up and down and saw that I have clearance, probably something like the 4mm rbt11548 had suggested earlier. I too cut off the extra threads and ground thye fastening system down as much as I could for the extra clearance. The next time I do any major dissassembly I'm going to add spacers behind the "Z" plate.

RS

RoadScholar said:

I had this sneaking feeling that the PO may have bent something, so it was very relieving to hear that its tight there.

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I think the reason there's more clearance on the right side than there is on the left is due to the fact that the engine cradle centre is placed 3/16" (approx.) over to the left side of the frame centre line, so the swingarm pivot is also displaced over to the left by an equal amount.

Because of this, the swingarm is not symmetrical, as the right hand swingarm tube splays out more than the left side does, and so compensates for the cradle being offset to the left, which places the rear wheel mounting plates an equal distance from on the frame centre line. So the increased bend of the swingarm tube on the right side gives slightly more clearance for the exhaust mounting.

L.A.B. said:

RoadScholar said:

I had this sneaking feeling that the PO may have bent something, so it was very relieving to hear that its tight there.

Click to expand...

I think the reason there's more clearance on the right side than there is on the left is due to the fact that the engine cradle centre is placed 3/16" (approx.) over to the left side of the frame centre line, so the swingarm pivot is also displaced over to the left by an equal amount.

Because of this, the swingarm is not symmetrical, as the right hand swingarm tube splays out more than the left side does, and so compensates for the cradle being offset to the left, which places the rear wheel mounting plates an equal distance from on the frame centre line. So the increased bend of the swingarm tube on the right side gives slightly more clearance for the exhaust mounting.

Click to expand...

Not trying to hi jack thread, when I put my rear wheel in last week and aligned it I ended up with the adjuster bolt on the left side screwed in a bit further than the right, could this be due to the fact that the swinging arm is not symmetrical?

rbt11548 said:

I ended up with the adjuster bolt on the left side screwed in a bit further than the right, could this be due to the fact that the swinging arm is not symmetrical?

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hi rbt,i dont think that would be the case ,if you draw a line through the swing arm spindle and one through the wheel mount slots they should be the same measurement each side