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Discussion Starter · #1 ·
I need some advice on how to remove the camshaft from a CB175 (pictured below).

The factory service manual does not specify how to do this. The right side camshaft cap was unscrewed and removed just fine. The left side camshaft cap is sticking. All the screws are removed, but the cam shaft appears to be stuck to the oil seal appears to be stock on the camshaft inside the Point Base.

Question: Shouldn't the Point Base just slide off with some gentle tapping on it away from the center of the engine? If not, how do you get the think off the motor?

I would appreciate a description of how to remove the Point Base from the left side of the camshaft.

Thanks,
Dave


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Post some relevent pictures...

You know of the CMSNL exploded views which will complement the manual nicely...

You have removed the points cover, points plate and the centrifugal advance unit ?

Don't loose that tiny drive pin !
 

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Discussion Starter · #3 ·
Thank you for the response. I have used CMSNL for research and while their exploded diagrams are fascinating, they do not offer experienced advice. The diagram depicts the Points Cap as simply sliding out of the head. The parts in the red oval are at issue:

Organism Font Auto part Circle Diagram


Item 7 is the Points Cap and 13 is the Oil Seal. In the following pictures, the Oil Seal can be seen still on the Cam Shaft.

When I have disassembled other motorcycle heads, the camshaft has been relatively easy to remove (as in it just slides out of the oil seal/bearing with little force. This was the case on the right-hand side camshaft carrier, know as the Head, Side, Cover.

What I am concerned with is not breaking any parts, or damaging parts to the point that they have to be replaced. The top-down close up picture shows that the Points Cover is loose in the Head, but the Oil Seal is not slipping off of the camshaft.

I am considering using a puller, or wedges to pry the pieces apart. What I would appreciated is some guidance from someone who has at least done this before and can share their experience.

Over.
 

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From your photos it appears that the cam lobe is in contact with at least one rocker. Take out the adjuster screws to give clearance. If you look on the removed side you can see the rockers were not on the cam lobes.

Been awhile since I was in a 175 but I believe like the CB350 engines there is a point where all the rockers are loose or very close to it. Usually the spot where the cam chain is adjusted.

You may have already damaged parts so do not use further force.

You will need to reassemble at some point and if done properly no force is used to put the covers on.
 

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I can zoom into the thumb nail pictures but they go very fuzzy lacking good detail. The pictures will not open properly when clicked, so no detail on my mobile.

What year etc is the bike ?

Are to saying the left cover is well and truelly stuck to the camshaft ?

If the end covers are reinserted into the head, will the camshaft rotate within them, subject to rockers and valves opening ?

Ps, 2 bits of wood under the head so no risk of bent valves...
 

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You are doing everything correctly so far. The usual problem with those cam bearings is when folks try to remove them when the head is still on the engine, cam chain connected.

Your points side bearing should just easily slide off now. I wonder if your engine has experienced an oil supply problem on that side, and the end of the cam has seized or melted, in which case brute force might be the only answer.
 

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Discussion Starter · #7 · (Edited)
You are doing everything correctly so far. The usual problem with those cam bearings is when folks try to remove them when the head is still on the engine, cam chain connected.

Your points side bearing should just easily slide off now. I wonder if your engine has experienced an oil supply problem on that side, and the end of the cam has seized or melted, in which case brute force might be the only answer.
Richard, thank you for the message. I appreciate the post. It is good to know that this is how it is supposed to be disassembled. The next post will detail the findings. Best, Dave.
 

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Discussion Starter · #8 · (Edited)
The 1971 CB175 camshaft is now removed from the head. The left side camshaft bearing cup (which also houses the points) had a crack at the edge of the oil seal retainer flange (depicted in the yellow oval below):

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With gentle escalating pressure from 2-leg puller, the cup separated from the flange. The camshaft was removed successfully from the head, with the flange attached. I used a cutoff wheel on a grinder to remove it from the camshaft.

The left end of the camshaft is pictured below:

Automotive tire Gear Gas Suspension Metalworking hand tool


The damage to the camshaft is clearly visible. What is supposed to be a 20-mm bearing area has been gouged and worn away to 18.3-mm at the lowest point.

In the next photo, a close-up of the area depicts a broken piece of the camshaft missing from about 10% of the raised thrust bearing:

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I suspect, as others have opined, that oil starvation caused this bearing to grind itself into a unusable state. The cause may have been a blocked oil port, low oil pressure, failed oil seal, poor maintenance, or other factors.

The downstream effects of this can be seen in the video on my YouTube channel listed here:

Now I need to decide whether to buy replacement camshaft, pistons and rings to rebuild this motor, or part the entire project out. I welcome your thoughts.
 

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Have you checked/did you ever service the centrifugal oil filter cos that will be full !

Setting valve working clearances and points gap must have been fun and a dead give away that something was very wrong, not to mention noise in the cam box area.

Do not scrap the camshaft.....

I suspect you have not had this bike long or heard it running.
 

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The oil supply to the left hand side cam bearing is via a tiny pinhole drilling in the top of the crankcase, then up the outside of the left rear cylinder stud, then through a drilling in the head that aligns with a drilling in the cam bearing.

Two obvious ways this can get blocked, crud in that tiny pinhole ( which is meant to be that size, don't be tempted to enlarge it ), or an incorrectly fitted gasket between the cam bearing and head.

You can check that oil is reaching the top of the head by slackening the two outer rear head nuts with the engine running, oil should escape here.
 
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Discussion Starter · #11 ·
Have you checked/did you ever service the centrifugal oil filter cos that will be full !

Setting valve working clearances and points gap must have been fun and a dead give away that something was very wrong, not to mention noise in the cam box area.

Do not scrap the camshaft.....

I suspect you have not had this bike long or heard it running.
Have you checked/did you ever service the centrifugal oil filter cos that will be full !

Setting valve working clearances and points gap must have been fun and a dead give away that something was very wrong, not to mention noise in the cam box area.

Do not scrap the camshaft.....

I suspect you have not had this bike long or heard it running.
Hello,

I bought this motorcycle from a fellow who had pictures dating to 1983 of the best sitting in the same spot in the yard where I bought it 3-weeks ago! It was there when he bought the place. So, no, I have not heard it run, since we can document it not running for 39-years.

I will be posting videos of the project rebuild (yes, I hit my head and I am going to rebuild it!)

Good news, the oil filter came apart fine. The oil pickup screen is in fine shape as well. Found some shards of what is probably oil ring from a piston in the pickup screen.

Generator side is in good shape too. If I can find some pistons, rings, and a new camshaft, I think it will run again!
 

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Glad your gunna save this little bike.

They were extremely popular in the UK back in the day and went quite well.

Sitting in the same spot for over 30 years, enough said about that.

Take your time and enjoy...
 

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Discussion Starter · #13 ·
I am going to appeal to the Commonwealth of Virginia to title the motorcycle in my name. The title search I had done with a lawyer did not find a previous registration. If it were ever originally titled, it was so long ago that the records disappeared prior to digitization.

So, we will see it Virginia plays ball and awards me a title.

If they do, I will do a full restore to be put back on the road. If not, I will probably fix it up as a trail bike...knobby tires, increase res fork travel, larger rear sprocket, etc. It will be the only over-50 year-old electric start trail bike in Virginia, but it beats walking.

Please reply with other good ideas.
 
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