Following a rear chain breakage (a long story for later) I decided to check chain and wheel alignment. as for many years I have been doubtfull of the rear wheel offset and the tendency for rear tyre to rub the chainguard fittngs . A straight edge along the wheels appeared to show the rear rim to be offset to the chain side by 2-3 mm at least . The rim measures central to the rear suspension units and the bike handles fine.A further check shows the front and rear wheels are not plumb to each other although the front shows plumb when the top of the frame (behind the tool tray ) is level. Would seem to indicate a twist in the swinging arm.The bike was hit from behind 50 years ago with the DL body work taking a real beating .My question is , can the top frame tubes be relied upon for a datum ?.It will be a fairly simple matter to get the swing arm trued if thats the issue.
After plenty of cross checks…
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Hi Robert, I would highly…
Hi Robert,
I would highly recommend Motoliner as they have sorted out several issues for me and to perfection. The only downside to using them is that during the off season, they are inundated with race bikes and there can be a several week wait - best to give them a call to see how busy they are. It's a father and son business and both of them are extremely knowledgable and easy to talk to.
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It sounds like your prepared to strip it down
This is outside my knowledge level Rob, but If your going for an alignment job…
I remember reading about the Italian framed commandos that were checked on the donkey nob, to align the primary frame with the headstock. This item being an accurately positioned Steel that was inserted in the headstock to determine the status and twist to suit.
By removing your forks you could insert appropriate size mandrill through the headstock and measure?
What I don’t get is the rubbing on the chain guard if the backend is true?
curios as to what you find
Cheers
Jon
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Hi. The spring link is worn…
Hi. The spring link is worn although the chain is not, It has always been recommended that the spring link be replaced during the life of a chain. With the DL chain enclosure there is more scope for the spring link to get flipped off (especially if the chain is a bit slack) . Another possibility is for the gearbox top clamp bolt to corrode to the shell and when the gearbox is moved it tends to twist between the plates which puts a side load on the chain.similar to what can happen with a belt drive. If the sprockets are in line I will move the rim over 3-4mm as there is too little clearance between tyre and chainguard mounts. Am also suspicious of the axle spacers which may be wrong . Having the wheel out also allows access to electric able connections etc.
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After a whole lot of faf ,…
After a whole lot of faf , I have decided its pointless trying to get the wheels in line and that will have to come later. Its clear that the sprockets are not where they should be ,so a bit of shuffling of wheel spacers and washers will get me back on the road. Why the sprockets are wrong is another mystery as they are all orriginal stuff from 1960 and amazingly not worn. I think a complete removal of the primary side will reveal all, but it will have to wait till the season is over.
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Hi George , To check the…
Hi George , To check the sprockets are in line I usually just spin the assemblies both ways and watch what the chain does ,if it sits happily with a little clearance both sides of the teeth then all must be well. Thats not happening now !. As for handling the Atlas just likes to run wide on corners , always has . Captain sensible (oldest son) rides it and does not seem to mind at the speed he rides!. Would drive me mad. Will take the 99 down to Motoliner to see whats the score.
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Found the reason the…
Found the reason the sprockets don't want to line up, the drive side top gearbox fixing has a collar that bites into the eng/box plates mine does not want to slide to allow the box to move ,so the box twists instead . Ho hum . The well of the wheel rim is a bit flakey, so a wire brush some jenolite and a couple of coats of paint may stop rust flakes from puncturing the tube. Have read that WD 40 makes a good tyre fitting lube , has to be better than rust making washing up liquid and water !.
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After plenty of cross checks I now think the swing arm is reasonably square to the rear top frame tubes ,so it seems more likely that the headstock is slightly twisted. I am going to concentrate on chain lines and getting the rear rim centralised between the hub flanges , which is where it is now and I understand is the correct position. This will still leave me with wheels about 3-4mm out of line.Possibly due to the head twist. Perhaps I can get the head twisted back without a stripdown ?. Motoliner?.