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Author Topic: CB750 K0 camshaft woes  (Read 2741 times)

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kaysystems

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CB750 K0 camshaft woes
« on: January 18, 2006, 12:11:36 PM »
I bought the bike with 30,000 miles on it.

Looks like the chain came off and damaged the rear wheel slightly AND made a hole in the engine case. Lots of black epoxy around the rear sprocket. There are black epoxy bits on the oil strainer.

Took the head off as part of fitting new primary chains and trying to find a loud ticking on the head when warm (valve clearances are fine)

Yikes, I can see the camshaft move up & down in the holders. The clearance between the camshaft and the bearings is between .2mm & .33mm (.008 & .013 inches). Presumably it suffered oil starvation.

Can I fit a pair of cam holders from a later model? I know they won't be matched to the camshaft but should be better that what I have.

Or any other ideas?

thanks

David
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Offline scondon

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Re: CB750 K0 camshaft woes
« Reply #1 on: January 18, 2006, 12:55:27 PM »
Yikes, that does sound sloppy loose. If it's oil starvation damage then both cam towers and cam are toast. Take the bearing caps off and have a look.

Sorry I'm not an expert on K0 engines but I think later model cam towers should work fine. Keep in mind that at some point Honda added two extara bolts to each rocker shaft to stop side to side play. If you use a set of these later towers I'd also use the rocker shafts that come with them(two threads tapped into each shaft for the extra bolts).
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kaysystems

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Re: CB750 K0 camshaft woes
« Reply #2 on: January 18, 2006, 12:59:35 PM »
Surprisingly the camshaft is still round and although a little scorred isn't too bad. I've seen a lot worst being used.

I'll look for replacement holders, and a cam if I can find one. There's an F1 cam on ebay, but I think it has different timing.


David
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Offline MRieck

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Re: CB750 K0 camshaft woes
« Reply #3 on: January 18, 2006, 02:25:11 PM »
Quote from: kaysystems on January 18, 2006, 12:59:35 PM
There's an F1 cam on ebay, but I think it has different timing.
David
  Not enough to make a difference- it will work fine.
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Offline Clyde

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Re: CB750 K0 camshaft woes
« Reply #4 on: January 18, 2006, 07:10:08 PM »
I agree with Mike, and note the K7 and K8 use the same cam as the F1.
I would not use an F2, but anything else would be OK.
A later pair of cam towers would be fine. If they are early ones make sure they are matching or if not use a plastigage/flexigage to check the clearance.
Regds Clyde
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Honda CB750 K0(original and unrestored), K1(in pieces), K2(restored), F1(restored), 76 750a (awaiting restoration), 1966 Honda CB72
Suzuki GT750 1972 (restored), Kawasaki Z1 1973 (restored)

kaysystems

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Re: CB750 K0 camshaft woes
« Reply #5 on: January 19, 2006, 04:27:54 AM »
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Offline Clyde

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Re: CB750 K0 camshaft woes
« Reply #6 on: January 19, 2006, 02:45:17 PM »
Both will fit and work OK.
It would be reassuring to get a photo of the tower bearing surfaces closeup to make sure they are good. At least email the sellers to ask that question.
You may get the two separate listings a bit cheaper than the "but it now " option on the other listing. Out in Oz cams are not worth much, but cam towers can sell for high prices
Regds Clyde
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SOHC4 #1909
Honda CB750 K0(original and unrestored), K1(in pieces), K2(restored), F1(restored), 76 750a (awaiting restoration), 1966 Honda CB72
Suzuki GT750 1972 (restored), Kawasaki Z1 1973 (restored)

kaysystems

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Re: CB750 K0 camshaft woes
« Reply #7 on: January 19, 2006, 04:06:19 PM »
Thanks guys.

This is my first Jap bike, so have a lot of learning to do.

David
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Offline dusterdude

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Re: CB750 K0 camshaft woes
« Reply #8 on: January 19, 2006, 04:10:53 PM »
david,what else have you owned?
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kaysystems

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Re: CB750 K0 camshaft woes
« Reply #9 on: January 19, 2006, 05:17:52 PM »
Started with a small Puch in the seventies then moved to a '66 Ducati 250. Still have that in boxes. I bought the CB750 as a daily rider, but is now costing me a fortune in rebuilding.

The Honda & the Ducati are just so different it's impossible to compare them, but the Ducati is probably more fun. Certainly on the twisty roads. They are both OHC with an 8500 redline and both make quite a lot of noise.

I've ridden avariety of Jap & British bikes over the years, but like a lot of folks had to give up riding when a wife entered the scene.

David
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Offline Terry in Australia

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Re: CB750 K0 camshaft woes
« Reply #10 on: January 19, 2006, 06:24:29 PM »
Damn wives, don't they just spoil everything? No wonder those gay guys are always dancing and smiling, they're not married to women! Cheers, Terry.  :'(
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kaysystems

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Re: CB750 K0 camshaft woes
« Reply #11 on: January 19, 2006, 06:26:12 PM »
Terry

I assume you know why women live longer than men?


They don't have to put up with women!!



David
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Offline Terry in Australia

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Re: CB750 K0 camshaft woes
« Reply #12 on: January 19, 2006, 06:34:49 PM »
Ha ha, I'm not really into this whole pole-smoking Karma thing David, but I applauded you for that! Come to think of it, I have known a couple of old lesbians, and they were cranky ol' beaches for sure! Cheers, Terry. ;D
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I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

"Crazy is a very misunderstood term, it's a fine line that some of us can lean over and still keep our balance" (thanks RB550Four)

kaysystems

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Re: CB750 K0 camshaft woes
« Reply #13 on: January 20, 2006, 05:40:39 PM »
As I get further into the engine, I think the story gets more clear. I find that several of the original "8" bolts have been replaced with later ones that have the circle & a line through it. Looks like the engine came apart & partss were mixed or replaced from another Honda. Thinking that the cam holders may have been swapped. The camshaft is within spec, but there is too much wear on the holders. Shouls be interesting when I split the cases. I know that one primary chain is quite a bit more stretched than the other.

David
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Offline Terry in Australia

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Re: CB750 K0 camshaft woes
« Reply #14 on: January 20, 2006, 05:50:26 PM »
Quote from: kaysystems on January 20, 2006, 05:40:39 PM
As I get further into the engine, I think the story gets more clear. I find that several of the original "8" bolts have been replaced with later ones that have the circle & a line through it. Looks like the engine came apart & partss were mixed or replaced from another Honda. Thinking that the cam holders may have been swapped. The camshaft is within spec, but there is too much wear on the holders. Shouls be interesting when I split the cases. I know that one primary chain is quite a bit more stretched than the other.

David

When you say the cam is within spec David, if the scoring is such that you can catch your fingernail in it, it's just gonna chew through new cam towers, so you may as well junk it, used camshafts are cheap, but good towers are not. How have you determined that one primary chain is more stretched than the other? That sounds interesting? Cheers, Terry. ;D
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I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

"Crazy is a very misunderstood term, it's a fine line that some of us can lean over and still keep our balance" (thanks RB550Four)

kaysystems

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Re: CB750 K0 camshaft woes
« Reply #15 on: January 20, 2006, 05:56:40 PM »
Terry

The Cam journals are smooth with no ridges like you describe. I was very surprised. This is partly what makes me think that parts have been changed. Anyway I'm going for one of the matched sets on eBay and will replace everything.

As for the chains. When I push the tensioner up to try to make the chains tight, I can get a pencil & push one up & down about a quarter inch, whilst the other seems tight. Oh yes it rattles at idle in neutral. I figure that if the engine is out I should look inside (it sat for 20 years) and change the chains anyway. Don't want to take the engine out again if at all possible

David
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Offline Terry in Australia

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Re: CB750 K0 camshaft woes
« Reply #16 on: January 20, 2006, 06:12:45 PM »
Good idea mate, do it right, but do it once! Cheers, Terry.  ;D
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I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

"Crazy is a very misunderstood term, it's a fine line that some of us can lean over and still keep our balance" (thanks RB550Four)

kaysystems

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Re: CB750 K0 camshaft woes
« Reply #17 on: January 20, 2006, 07:00:30 PM »
Quote from: Terry in Australia on January 20, 2006, 06:12:45 PM
Good idea mate, do it right, but do it once! Cheers, Terry.  ;D

Exactly.....It won't cost much to do a little preventative maintennce, but if I don't.........

David
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