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1973 Honda CB450
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Discussion Starter · #1 ·
Got a 73 CB450 as a winter project. It had a hole in the right piston. I tore it completely apart and have rebuilt it over the past month. Finally got to that pesky cam/timing chain. I have read other posts and watched videos but haven’t seen one with this issue. After I got the chain on I thought I would turn the engine a revolution or two to make sure things were okay and noticed it hitting the left exhaust valve. So reversed it and turned it clockwise and it hit the right exhaust valve. Can see it through the spark plug hole. Didn’t force anything in fear of breaking or bending something.

1. Am I one tooth off on the alignment in the pictures?
2. Is that enough to make the valve and piston hit?
3. Is there a torsion bar issue I should address?

If I do have to take the chain apart and move it one tooth any suggestions on that procedure?

Appreciate the help and any and all suggestions on my huge learning curve.
 

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Got a 73 CB450 as a winter project. It had a hole in the right piston. I tore it completely apart and have rebuilt it over the past month. Finally got to that pesky cam/timing chain. I have read other posts and watched videos but haven’t seen one with this issue. After I got the chain on I thought I would turn the engine a revolution or two to make sure things were okay and noticed it hitting the left exhaust valve. So reversed it and turned it clockwise and it hit the right exhaust valve. Can see it through the spark plug hole. Didn’t force anything in fear of breaking or bending something.

1. Am I one tooth off on the alignment in the pictures?
2. Is that enough to make the valve and piston hit?
3. Is there a torsion bar issue I should address?

If I do have to take the chain apart and move it one tooth any suggestions on that procedure?

Appreciate the help and any and all suggestions on my huge learning curve.
As I see it, the intake camshaft is 1 tooth of time. I don't see a mark on the exhaust camshaft so I think the timing of this one is all wrong! Riveting the chain is done on the inlet side.If you have an original Honda link you may be able to reuse it. If you have a link of DID, better not reuse the old one! Use original Honda 14410-283-000. Check the timing before riveting!
 

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1973 Honda CB450
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Discussion Starter · #5 ·
I just ordered the original link, actually two in case I need to do this a third time. What is the reason for doing riveting the chain on the inlet side vs the exhaust side?
 

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I just ordered the original link, actually two in case I need to do this a third time. What is the reason for doing riveting the chain on the inlet side vs the exhaust side?
This is stated in the workshop manual and works easier. (the inlet camshaft wants to turn back because an inlet valve is already opened) First time the exhaust camshaft and then you have to turn the inlet camshaft slightly up with a screwdriver until the marks correspond and and then tighten the chain at the top.
Greetings from the Netherlands, Ernie

Honda cb92 Bridgestone gtr350
 

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Got a 73 CB450 as a winter project. It had a hole in the right piston. I tore it completely apart and have rebuilt it over the past month. Finally got to that pesky cam/timing chain. I have read other posts and watched videos but haven’t seen one with this issue. After I got the chain on I thought I would turn the engine a revolution or two to make sure things were okay and noticed it hitting the left exhaust valve. So reversed it and turned it clockwise and it hit the right exhaust valve. Can see it through the spark plug hole. Didn’t force anything in fear of breaking or bending something.

1. Am I one tooth off on the alignment in the pictures?
2. Is that enough to make the valve and piston hit?
3. Is there a torsion bar issue I should address?

If I do have to take the chain apart and move it one tooth any suggestions on that procedure?

Appreciate the help and any and all suggestions on my huge learning curve.
In your photos you are on the LT mark but are looking at the right side intake and exhaust cams in the other two photos. The left side is from sitting on the bike.
 

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1973 Honda CB450
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Discussion Starter · #9 ·
In your photos you are on the LT mark but are looking at the right side intake and exhaust cams in the other two photos. The left side is from sitting on the bike.
I‘m a little confused, Bullfrog. I only have marks/notches on my cam and housing on the right side of the engine. Am I supposed to be looking for notches and marks on the left side of the engine?
 

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I‘m a little confused, Bullfrog. I only have marks/notches on my cam and housing on the right side of the engine. Am I supposed to be looking for notches and marks on the left side of the engine?
Brettly, The pictures are good! The marks/notches are on the right side. The only notch I couldn't find was on the exhaust camshaft. Another reason to time the exhaust camshaft first is that otherwise you cannot tighten the chain! The tensioner is on the inlet side so you can have some slack there. Success with it! Ernie
 

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New to the forum but old honda mechanic. One thing to beware of on the twin cam 450's is that they have other casting marks that will fool you. Back when the bikes were a lot newer I put one together on the wrong marks and it turned over with a end wrench on the alternator bolt head. Barely any resistance but it bent a valve.
I owned and rode at least three CB and CL 450's and even a black bomber with a honda scrambler conversion that had a high pipe down each side. Once had a ural sidecar on one in the early 70's. Here's a fuzzy copy of a film camera snapshot of the CA77 I rode to anchorage alaska and back in 1971.
Tire Wheel Vehicle Motor vehicle Automotive tire
 

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Discussion Starter · #13 ·
I’m still stuck. Attached pics 1 and 4 are exhaust cam in the two positions I could get it to set. Couldn’t get it exactly lined up it seems like it is always that minuscule amount off. Second pic is the intake cam lined up perfect. Third is LT mark for setting chain. Fifth is when I turn the engine over that is the point when the left exhaust valve hits the piston. Is it possible I have something screwed up when I assembled the cams? I messed with this for 2 1/2 hours this morning and can’t get anything to work. What am I missing or doing wrong?
 

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I’m still stuck. Attached pics 1 and 4 are exhaust cam in the two positions I could get it to set. Couldn’t get it exactly lined up it seems like it is always that minuscule amount off. Second pic is the intake cam lined up perfect. Third is LT mark for setting chain. Fifth is when I turn the engine over that is the point when the left exhaust valve hits the piston. Is it possible I have something screwed up when I assembled the cams? I messed with this for 2 1/2 hours this morning and can’t get anything to work. What am I missing or doing wrong?
All the pics upside down?
 

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Just had a look at an engine that I've taken apart and see that the intake camshaft has a "line" as a mark and the exhaust camshaft has a "center point" as a mark!
As a check: there must be valve clearance when timing the exhaust camshaft! Hope you can do something with this.
 

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Discussion Starter · #18 ·
Here’s where I have ended up. I have two engines. I took the cam head (whatever it called) and put in on. Had the same issue hitting the exhaust valves. I think I may be using the casting mark to incorrectly line up the exhaust cam. In the pictures when I have the exhaust cam on what looks like to correct marking (picture 2) the right exhaust valve is slightly open (picture 1). Picture 3 shows the alignment mark and the questionable casting mark. Am I on the right track? Should that valve be slightly open like that when setting the cam chain?
 

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Here’s where I have ended up. I have two engines. I took the cam head (whatever it called) and put in on. Had the same issue hitting the exhaust valves. I think I may be using the casting mark to incorrectly line up the exhaust cam. In the pictures when I have the exhaust cam on what looks like to correct marking (picture 2) the right exhaust valve is slightly open (picture 1). Picture 3 shows the alignment mark and the questionable casting mark. Am I on the right track? Should that valve be slightly open like that when setting the cam chain?
Here’s where I have ended up. I have two engines. I took the cam head (whatever it called) and put in on. Had the same issue hitting the exhaust valves. I think I may be using the casting mark to incorrectly line up the exhaust cam. In the pictures when I have the exhaust cam on what looks like to correct marking (picture 2) the right exhaust valve is slightly open (picture 1). Picture 3 shows the alignment mark and the questionable casting mark. Am I on the right track? Should that valve be slightly open like that when setting the cam chain?
 
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