Topic: CB550 to CB650 cam conversion? Questions

[Hito550E]

All,

I am in the middle of a cb650 cam conversion in my 550.  I wanted to touch base on a couple things.  I am not sure 100% what cam was in the bike or what cam I purchased off ebay...  so lets see if we can figure it out

in this thread: http://forums.sohc4.net/index.php?topic=40369.0  kayaker43 mentions that the 550 has a plastic tach drive gear?  but mine seems to have a metal gear?  and it turns perfectly in the 650 cam's worm gear.  The thread above notes that you have to change the tach drive gear.  Is it an obvious difference?  Because its pretty close as far as I can tell.  I can turn the engine over easily with the old tach drive gear installed with the new cam?  

here is a picture of the tach drive gear that was in the bike.  Definitely not plastic.  What is it from?  there are 10 teeth
http://www.mcmxi.com/~todd_putnam/pict0009.jpg

here's a couple pictures of the cam gear from the cam that I put in the engine.  Does it look right for a 650??
http://www.mcmxi.com/~todd_putnam/pict0007.jpg


Anyone recognize any of these?

The cam that came out of the engine ('74 550) had R11 stamped on the cam that came out of the engine, and a R10 on the one that went in.

Any input would be greatly appreciated!

Todd

[B.O.X.N.I.F.E.]

I've had both cams (550 & 650) in hand, and there is an obvious visual difference between the two. Larger lobes on the 650, you should have no trouble telling which is which by holding them side by side. This is assuming you know one is 550 and the other is def a 650.

[Hito550E]

well looking at the workshop manuels for each bike it seems that the cam gear in the picture is in fact a 650 cam gear, so it seems what I put in was a 650 cam (whew!), but I am still unsure about what came out.  Is there really a plastic tach drive gear in a 550K1?  if so that is there a chance that the bike already had a 650 cam in it?? 

I doubt it but I am still not sure.  The lobes did look different.   It looked like there was more lobe separation on the 650 cam and that the profiles were similar but slitghtly larger for 650.

[FunJimmy]

I think the plastic gear comment was referring to the driven gear, not the drive (cam) gear.
After all, how would Honda engineers have married the plastic drive gear with a cast cam back in the '70's

FJ

[Hito550E]

I think the plastic gear comment was referring to the driven gear, not the drive (cam) gear.
After all, how would Honda engineers have married the plastic drive gear with a cast cam back in the '70's

FJ

I totally agree whith you that the plastic gear in question is the one driven by the worm gear on the cam.  The worm gear on the cam is definitely part of the cam itself.

[paulages]

the cam sprocket you're holding looks like a 650 sprocket. the teeth are blunter than the 550 sprocket, which takes a duplex chain.

[Hito550E]

I am convinced that the cam that I put in was indeed a 650 cam.  mainly because of the cam sprocket more than anything else.  I will take pictures of the cam that came out tomorrow as well as measure the lobes.  I already reinstalled the cylinder head cover over the new cam, but I may remove it to measure the lobes on it as well.  is there anthing else I should measure while I have it apart?

[paulages]

I am convinced that the cam that I put in was indeed a 650 cam.  mainly because of the cam sprocket more than anything else.  I will take pictures of the cam that came out tomorrow as well as measure the lobes.  I already reinstalled the cylinder head cover over the new cam, but I may remove it to measure the lobes on it as well.  is there anthing else I should measure while I have it apart?

Lobe heights will tell you what it is for sure.

[Hito550E]

well.

Mystery solved!

I measured the lobe heights and it seems that I did indeed take out a cb550 cam and installed the correct 1.4/1.39 cb650 cam!

yay!

more good news! the base circle must be the same because my tappet adjustments are still spot on!

As soon as I get my new petcock next week I will post a ride report!!

should I expect to have to change jetting at all?

[Flying J]

How did that cam work out?

[frostyCB]

Second that, How did the cam work out. Did you have to switch the cam chain as well?

[Danno]

that was an early model 550 tach drive gear that was in picture one I don't know if they switched them to plastic later