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Tru_Tension Laser Monkey

Richard Pitman

Veteran Member
Joined
Jun 1, 2020
Total Posts
2,526
Total likes
632
Location
Worcester, England
I bought one of these to use on my CB600, because I felt that the drive chain seemed very noisy and I wondered if it was slightly misaligned. Apart from alignment, getting the tension correct on the CB600 is a pain. It needs 30-40mm free play when the bike is on the side stand, suspension slightly loaded. If adjusted to those figures with the suspension fully extended, bike of my ABBA stand, the chain is bow string tight when back on its wheels. Not helped by the rear axle, with this loosened chain is slack, torqued up the chain tightens. So chain adjustment involves a lot of trial and error.

Anyway, back to the Laser Monkey. This sits astride the rear sprocket and clamps into position. Move the laser head down until the red dot is central on a chain roller close to the rear sprocket, then raise the laser head so that the dot shines on roller at the engine end of the chain. If alignment is correct, dot should remain central. If not, use the chain adjusters to centralise the dot.

Sounds easy, brilliant idea. In practice, I found it to be not so simple. First off, the rear hugger or chain guard has to be removed. Not a big issue, just 3 M8 screws on my CL 175. Then the tool has to be clamped onto the rear sprocket, which is where I ran into problems. Probably on an MX bike, with a large rear sprocket with plenty of clearance around it, this would be easy. Obviously, the tool has to sit parallel with the chain run. My CB600 has a Supersprox rear sprocket, steel chain wheel riveted to an alloy centre. It was very difficult to get the tool to clamp evenly, avoiding rivet heads and step where steel met alloy. After several false starts, I concluded that the CB600 swing arm adjustment marks are actually spot on anyway.

On my CL175 K7, it has the same rear sprocket as a CB200, with that chain wheel protector thing riveted on. That also interfered with getting the tool to sit nicely. Turned out that my chain alignment was perfect already, no adjustment required. By this time, the once bright laser dot had dimmed, don't think battery life is that great.

I will get around to testing it on my CB175, which has a conventional rear sprocket. However, on that one, looks like there's not much clearance to the rear hub with the CB smaller rear sprocket.

In summary, I could not whole heartedly recommend this tool. It's a nice idea but falls down in practice.

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Easier way to check the chain alignment is remove the front sprocket retainer and liberally oil the shaft so the sprocket slides in/out easy. Now spin the rear wheel a dozen times or more. If the sprocket creeps out past the retainer slot or where the retainer won't go in w/o moving the sprocket the wheel is canted left. If the sprocket tracks inboard to where the retainer bolts barely or won't reach the wheel is canted right. If the sprocket remains in it's normal retained position the chain is aligned.
Front sprockets and retainers are designed to be self aligning to a degree, that's why they slide on the shaft a little with the retainer secured.
 
That's a great idea. If only you'd told him before he spent $45 on that monkey... :dizzy:
 
Thanks. That would work on the 175, and I will definitely give it a go. On the 600, the front sprocket is retained by a central bolt, done up very tightly, so it wouldn't be a trivial task on that bike, especially as the range of movement on the front sprocket splines is very limited.
 
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