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Cam timing question

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GG
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Posts: 144
Joined: Tue Apr 13, 2010 10:45 pm
Location: Costa Rica

Cam timing question

Post by GG » Sun Dec 11, 2022 7:48 pm

Hello! I have a question on the cam timing, Superhawk, cb77 305cc. I put the motor together some months back, but I have no power at all at low rpm's, mixture is rich with smallest jets possible and everything else in perfect / new condition (condenser, coils, carburetor float needles, etc) If the motor was one link off on the cam timing, would it run? My bike starts and idles just fine. But no power down low, and rich condition.

When I set the magneto mark on "T", the little mark on the points shaft is not exactly 12 o'clock, but about 11:00 or 11:30. Is this correct?

Would the bike run okay if the cam chain was one link off?

Any help appreciated!!

GG

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Tim Allman
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Location: Guelph, Ontario, Canada

Re: Cam timing question

Post by Tim Allman » Mon Dec 12, 2022 12:51 pm

When I set the magneto mark on "T", the little mark on the points shaft is not exactly 12 o'clock, but about 11:00 or 11:30. Is this correct?

Would the bike run okay if the cam chain was one link off?
In a word, no. I just checked on my CB77 and the line on the end of the camshaft is, as far as I can tell, at exactly 12:00 when the crankshaft is set to "T". I'm not sure just what the symptoms of being one tooth off would be but your symptoms sound like they could reasonably be caused by a missetting of the camshaft. Fortunately you need only drop the engine and remove the top (cam) cover in order to reset the alignment.

GG
honda305.com Member
Posts: 144
Joined: Tue Apr 13, 2010 10:45 pm
Location: Costa Rica

Re: Cam timing question

Post by GG » Mon Dec 12, 2022 1:05 pm

Thanks Tim! I suspect you are right. What a shame with this site, because in the past it was great and saved a lot of people! (Like me) :-)

The issue I had with the chain is that you have to remove the tensioner in order to be able to pull the chain tight enough. When the tensioner is applied, things "move". So I think I'm one tooth off. Oh well. Live and learn.

Have a great day.

GG

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Tim Allman
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Joined: Tue Dec 02, 2014 9:25 am
Location: Guelph, Ontario, Canada

Re: Cam timing question

Post by Tim Allman » Mon Dec 12, 2022 1:47 pm

If your chain is worn enough that it easily jumps a tooth when not tensioned, it might make sense to install a new one while you're at it. They're still easily available at reasonable cost. You can pull the master link and use it to attach the new chain to the old after which you just turn the crankshaft until the new one is on the sprockets and the old one isn't. Of course you have to be very careful not to drop an end.

I hope it goes well. At least you have the winter to get it done without missing riding days.

GG
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Posts: 144
Joined: Tue Apr 13, 2010 10:45 pm
Location: Costa Rica

Re: Cam timing question

Post by GG » Mon Dec 12, 2022 4:50 pm

No winter in Costa Rica!!! (I live in Costa Rica - only lots of rain 7 months of the year) But no cold, thankfully!

Ok, I'll see if the chain looks worn too much.

I appreciate your help! Have a great afternoon,

GG

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Tim Allman
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Joined: Tue Dec 02, 2014 9:25 am
Location: Guelph, Ontario, Canada

Re: Cam timing question

Post by Tim Allman » Tue Dec 13, 2022 9:55 am

No snow! I've lived places without decent winters and I'm always happy to come home. Today is about -10C and brilliantly sunny as happens only in winter. We get slightly smoggy summers because we are downwind of a lot of heavy industry in the US. In winter we often get arctic air which is much cleaner. In a few minutes I'm going to hike a trail and enjoy it. :-)

The owner's manual tell you how to adjust the cam chain but generally there isn't much travel in the tensioner if the chain is new. Sadly they don't give a specification. Generally chains should lie tightly against their sprockets. If you can pull it up off the sprocket (while installed normally) more than about a mm or two it's worth replacing. Some people just consider cam chains to be consumables and replace them whenever it is easy.

Enjoy the rain.

Edit: My shop manual says that the length of the chain should be 723.0 to 723.8 mm long with a repair limit of 728.0 mm. That strikes me as a lot but it's something to look at.

GG
honda305.com Member
Posts: 144
Joined: Tue Apr 13, 2010 10:45 pm
Location: Costa Rica

Re: Cam timing question

Post by GG » Tue Dec 13, 2022 6:46 pm

:-) All the Canadians I know love their winters !!! Not me! I love my tropics. Haha.

Ok - great info on the chain. I'll have to see how it looks. Gracias!

GG

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