Topic: Sport cam?

[Loki]

hey there guys its been a while since iv been on the site. im finishing up a school for my electrical course and i want to get back inot my cb 550 k. i was talking to this guy a while back that said you could get sport cams for the motors? it would increase power a bit, is this something i can get my hans on or should i avoid it?

[KB02]

Grab a cam from a 650. It's a nice little upgrade. 

[Loki]

but would a 650 cam fit? and line up to everything?

[NickC]

but would a 650 cam fit? and line up to everything?

Bolts right in! Some may have to clearance the head to clear some of the lobes. It was close on my 75, but I didn't need to do any work. The only other thing you need to get is a cb650 tach gear to match the cam

[Gordon]

but would a 650 cam fit? and line up to everything?

A lot of us here have done this mod recently with great results.  Do a search for "650 cam 550" to see several previous threads/testimonials on the subject.  It's a straight swap for most.  It seems there is the occasional issue of clearance between the 650 cam lobes and the 550 head, but that appears to be the minority, and can be fixed by removing a little metal.  You'll need the tach and tach drive gear from a 650, too, if you want a working tach. 

[Loki]

so id just have to replace the little tack drive and tack meter?...not the hole upper casing of the motor?also what in some cases does not clear...i didnt get what was said? thanks!

[NickC]

I'm pretty sure all you have to replace is the tach gear.

[Loki]

also what year of a 650 cam would fit in my 77 cb550 ?.....does it matter, because i see a bunch for sale form nighthawks and what not alswell?

[NickC]

Nighthawks are DOHC. Any SOHC 650 will work

[Loki]

know any where i could look, i tried ebay but im always a little sketchy about the products i buy from there, and the honda dealer said they have been discontinued.

[Gordon]

I'm pretty sure all you have to replace is the tach gear.

You have to use a 650 tachometer if you want it to read correctly. 

The 1982 CB650SC Nighthawk is a sohc4, too. 

[Loki]

does anyone have a good site or place i could pick up the 650 cam and tackometer

[Gordon]

does anyone have a good site or place i could pick up the 650 cam and tackometer

Yes.  Ebay and this forum are the best places to look online for used sohc4 parts.  If you have a motorcycle salvage yard in your area that would probably be a good place to look, too.  You should really get over your fear of buying on ebay, though.  It's easily the best resource available for getting hard-to-find and/or cheap used parts for these bikes.   

[NickC]

I'm pretty sure all you have to replace is the tach gear.

You have to use a 650 tachometer if you want it to read correctly. 

The 1982 CB650SC Nighthawk is a sohc4, too. 

Elaborate please

[Gordon]

I'm pretty sure all you have to replace is the tach gear.

You have to use a 650 tachometer if you want it to read correctly. 

The 1982 CB650SC Nighthawk is a sohc4, too. 

Elaborate please

If you want a working tachometer on your 550 after doing the camshaft swap, you need both the tach drive gear and the tachometer from a 650.  You can still run the 550 tachometer with the 650 cam and drive gear, but it will be wrong.  The 650 tach runs on a different gear ratio than the 550, which is why you need the 650 tach drive gear to match the camshaft worm gear, and you then need the 650 tach so everything matches up.

As far as the '82 650 Nighthawk being a sohc4, there's not really much to elaborate on.  It was the last of the sohc4 Honda motorcycle engines. 

[NickC]

So the gearing in the tach is different also?

[Gordon]

So the gearing in the tach is different also?

Not gearing, per se, (it's just a rotating magnet and a spring) but the rpm shown on the 650 tach for a given input revolution speed of the tach cable will be different on a 550 tach with the same input speed.  So now you have the 650 cam with the 650 tach drive gear that turns the tach cable at a different rate for a given engine speed than the 550 cam with the 550 tach drive gear would, and so you need the 650 tachometer which is calibrated to to the speed of the 650 cam/drive gear combo in order to have an accurately functioning tachometer. 

I feel like I'm making this sound more complicated than it needs to be.    

[NickC]

Makes sense, seriously! Thanks!

[Gordon]

Makes sense, seriously! Thanks!

Cool!

Luckily, even though the individual components of the 650 tach drive gears and the tachometer itself aren't interchangeable with those of the 550, the parts themselves are all exactly the same size so there are no issues in simply swapping them out for each other. 

[fastbroshi]

   For anyone searching later on, here's what he means by the 650 tach being geared differently.  Here's the tach ratios for the different bikes (from the FAQ).

CB750 Speedo  2240:60(112:3?) Tach 4:1
CB650 Speedo  2240:60  Tach 4:1
CB550 Speedo  2240:60  Tach 20:3,
CB500 Speedo  2240:60  Tach 20:3
CB400 Speedo  2240:60  Tach 20:3
CB350 Speedo  2240:60  Tach 20:3

[smileswithadimple]

would be interested in this mod, but I have a few questions, hope I'm not hi-jacking the thread, but, will a 500 head bored to 550 still be able to run the 650 cam?  The po bored the motor.  Tia!

[Kevin400F]

Maybe I missed it somewhere in the thread, but in addition to the cam gear difference, keep in mind the 500/550 uses a roller type cam chain, while the 650 uses a Hy-Vo (plate type) cam chain.  Take the old sprockets off your 500/550 cam, and bolt it to the 650 cam.

[Loki]

wow...talk about coming back to life. hey broshi, how bad would the tacho be off if you where to use a 550 tacho with the 650 cam and tach gear, i cant imagine it being off by a huge amount?
oh and kevin its done and done.i figured that one would be a must when doing this change, but thanks for the input im sure it will help someone here.

[NickC]

wow...talk about coming back to life. hey broshi, how bad would the tacho be off if you where to use a 550 tacho with the 650 cam and tach gear, i cant imagine it being off by a huge amount?
oh and kevin its done and done.i figured that one would be a must when doing this change, but thanks for the input im sure it will help someone here.

Mine was off around 3k

[Loki]

but now how did you know it was off that much? is there a way of measuring it?