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Discussion Starter · #1 ·
CB175 - points do not turn when attempting to start

Two days ago I achieved a milestone in my attempted CB175 revival. i was able to ride the bike for the first time; running a little rough I was able to ride down my drive way in first gear.

To get to this point I have spent 7 months reading through posts on this site and asking a few questions of members. Without this resource I doubt if I would be this far along.

After the first ride I made a few small changes to the air mixture screws on the carbys and was able to start the bike again on the centre stand.

One day ago I hit another issue and I am unsure of the level of severity.

Attempted to have another ride in the driveway and when starting the bike heard a clunk type sound from somewhere down below. Was attempting to start the bike in neutral with the electric start.
I do not have a kick start as this was sheared off the righ hand side prior to my purchase.

The starter motor spins and whirrs and the bike did will not start.

Back to the centre stand and for some investigation.

Found that the points were not moving - centre part does not turn. Refer image.

CB175 Points do not turn.jpg

They were earlier when test starting on the centre stand.

At this point I am not sure if I should be looking in the left crank cover near the starter motor? Or if the problem is higher up in the engine and possibly internal chain?

Any assistance to guide me on the correct path for trouble shooting would be greatly appreciated.

Thanks Cameron
 

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Discussion Starter · #3 ·
That bit in the middle is the camshaft. It's hard to say what could have caused it to stop moving. Here's a page that should help you to figure out exactly what you're dealing with.

Dan's Motorcycle "Unsticking Stuck Engines" (If it's seized don't use his force methods, they're only for rusted stuck engines)
Thanks I have had a quick scan of the information and will have a look tonight. Suspect that I will need to take the left hand side cover off as a start. . .
 

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Put it on the centre stand.

Take the spark plugs out.

Put the bike in gear and try to turn the rear wheel. Or you could leave it in neutral and turn the engine over using the bolt on the left hand side of the crank.

That will tell you if the engine still turns over, and if the camshaft rotates. If all is OK there, fault lies in the starter clutch.

However, if the engine turns over but the camshaft doesn't rotate, the cam chain has likely snapped or at least come off the cogs inside, bad news.

If the engine doesn't turn over, same applies. Don't force anything ..
 
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Discussion Starter · #5 ·
Hi Richard
Thanks for replying and providing me with this information.
I did not get time last night to have a look. Hoping to do so tonight.
Will report back with my findings.
Cameron
 

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Discussion Starter · #6 ·
Hi Richard,
I think that I have the problem with the cam chain. Suspect that this is a major repair task?
Troubleshooting process followed was as below:
- on centre stand
- spark plugs out
- bike in 1st gear and turned wheel in direction of forward travel (note: also tried in 2nd gear)
- engine turned over and I could feel air coming out of the spark plug holes
- cam shaft did not rotate at all

Looks like time to start breaking it all down again to get the engine out.

Thanks Cameron
 

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Sadly, it sounds to me like either the cam chain is broken or came off for some reason, or the cam itself is broken. Either way, the top end will have to be taken apart. It's likely to have some bent valves, since the valves sit still and usually one or two open while the pistons keep moving.
 

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Discussion Starter · #8 ·
Update on this thread. . . completed prior Xmas 2018. . . . but been away from site etc. . . .

It was the cam chain. Separated at the joint. . . . all pieces (clip, link and cover piece) extracted from bottom of case with telescopic magnet.

Shop completed repair and engine has been started. Mechanics determined valves OK. Root cause was suspected to be cam chain tension too loose initially.

Cameron
 
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