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What are the symptoms of the cam picking up in the head ?

 
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Phil-UK
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Joined: 19 Oct 2006
Posts: 229
Location: ENGLAND

PostPosted: Mon Apr 15, 2019 2:00 am    Post subject: What are the symptoms of the cam picking up in the head ? Reply with quote

Took my CB350 out for the first time this year and after @4 miles at about 50mph it tightened up and felt like it might have seized. It restarted but was blowing a LOT of smoke out of the cambox breather.

Limped it back home and changed bikes and later ( when cold ) put a compression tester on and both cylinders seem OK, the oil level was low.
Havent done anymore and probably won't as half way through another project but I wondered if the cam had picked up in the head ( apparently not unknown on these style Hondas ) would that have caused the "tightness" and the oil blowing ?

Anyone out there had the cam seizure and able to say what the symptoms were ?

thanks

Phil
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Phil-UK
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Joined: 19 Oct 2006
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Location: ENGLAND

PostPosted: Mon Apr 15, 2019 2:03 am    Post subject: Reply with quote

Forgot to make clear, oil level had been on full when left home.
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G-Man
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Joined: 25 Mar 2009
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Location: Derby, UK

PostPosted: Mon Apr 15, 2019 2:13 am    Post subject: Reply with quote

Hi Phil

I don't see why partial seizure of the cam should affect oil getting past the valve guides or piston rings.

More likely the cause of the problem - blocked or reduced oil supply - should have affected the other parts as well as the cam. i.e. if there was no oil getting to the cambox area then the valves and guides would have beem starved also.

The piston gets its oil thrown off the big end so that could mean blocked sludge traps in the big end or blocked oilways in the centre main bearings or centrifuge to the big end.

It sounds like a full strip to investigate.....

G

Phil-UK wrote:
Forgot to make clear, oil level had been on full when left home.

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Phil-UK
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Joined: 19 Oct 2006
Posts: 229
Location: ENGLAND

PostPosted: Mon Apr 15, 2019 9:32 am    Post subject: Reply with quote

Hi Graham

My thinking was that if the clearance between the cam and carriers was too big the oil might have been escaping and over filling the cambox and then crankcase pressure could cause it to blow.

Probably grasping at straws and I agree it will only show up when stripped; I know cam seizures were perceived to be a 70s/80s issue but didn't know what the symptoms were.

The bike is going in the naughty corner for now as I have other things to finish ( hopefully ) this summer.


cheers


Phil
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mike in idaho
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Joined: 29 Jan 2012
Posts: 396
Location: orofino, idaho

PostPosted: Thu Apr 18, 2019 8:53 am    Post subject: Reply with quote

Remove the points cover and back off the valve adjustments to relieve the spring pressure on all the rockers. Now grab the end of the spark advancer and try to move it up and down. If the cam end bearing is still in good shape there should be very little(if any) movement there.
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