Topic: 75' CB550 and my first rebuild in 25 years

[2ceebees]

Glad we could help each other out goldarrow!  Guess what I scored?  SOHC CB650 cam and tach drive!  Thanks to Spike. 

[goldarrow]

Very nice.  Double check the lobes sizes against your stock 550 cam.  Tach drive should be different than the stock one also.  350 forks may be too small for 550, not sure.  Do research before you decide to buy them. 

[2ceebees]

Just talked to a guy in that has a really nice set of CB750A forks I'm getting in for the 550.  Says that bike has the same caliper setup.  Apparently they are a bit shorter than the non-automatic 750 front end and should fit the 550 nicely.   I was working up a set with gnarlycharlie4u but I decided to go a different way.  He's a top notch guy though and was good to work with. 

[goldarrow]

Just talked to a guy in AZ that has a really nice set of CB750A forks I'm ordering in for the 550.  Says that bike has the same caliper setup.  Apparently they are a bit shorter than the non-automatic 750 front end and should fit the 550 nicely.

i have read many build threads that people use gsxr frontend set.  inverted forks and dual discs setup and all, looks nice and better performance than older system.  so, if your bike needs set of new front end, i say go that route instead.  here's an example of squirely's built, very nice looking cafe style build.

http://forums.sohc4.net/index.php?topic=34836.0

oh and get project build thread going

[2ceebees]

No pics yet but I wire wheeled a buncha rust off the front rim.  Also screwed up the bearing retainer in the process making me feel like a noob.  Gotta find another one to replace it. 

[2ceebees]

I began engine teardown tonight.  Would like some extra eyes on this.  I'm seriously considering sending out the head for valve and porting work.  Any suggestions?

Also, how bad does this cam lobe look? 

Thanks in advance..

[2ceebees]

Looking for experienced opinions on the lobe damage

[goldarrow]

Hard to tell in the picture how badly the lobes are pitted, can you feel it with your finger nail? I would be more concern that the top end might have been starved of oil or lack of proper maintenance.  So, while the engine is out, check the oil jets to make sure those holes are clear.  Also check your rocker arms for pitting. 

[2ceebees]

Hard to tell in the picture how badly the lobes are pitted, can you feel it with your finger nail? I would be more concern that the top end might have been starved of oil or lack of proper maintenance.  So, while the engine is out, check the oil jets to make sure those holes are clear.  Also check your rocker arms for pitting.

Yeah, you can feel it a bit.  There was oil everywhere I expected in the top end and otherwise it looked good but I'm not 100% sure.  This pic is the lobe over #1 cylinder.  I also bought a 650 cam that has minor pitting on the very same lobe so I'm not sure if I got hosed on that deal.  I was wondering if it's common over that cylinder?.  The rocker arm has minor pitting as well although less than on the lobe.  I'll try to post a pic of the 650 cam lobe and the rocker arms tonight.

Any thoughts on the head work?

Thanks!

[Fritz]

Any thoughts on the head work?

Your head looks fine to me. Depends on where you want to go. With a 650 cam, I think you need to grind the head a tiny bit to make place for the larger lobes.
In general, the 500/550 heads suffer from
a) Valve guide wear, so you might want to have the guides measured and mabye replaced
b) restictive ports

You could consider having the ports taken care of. That would really make a difference but you would have to think about different carbs or at least re-jetting...
If you do not want to go that far, you should at least take out the valves and inspect the guides for wear (the Honda shop manual shows the numbers). A valve leak test and possibly lapping the valves and seats should follow. Valve guide seals should be part of the gasket kit.

Please post pictures of your rocker arms.

[RAFster122s]

550 heads can also wear eccentrically at the ends of the cam in the head. This cam wear of course in the head and it is brought on by oil issues. Bad cases can lead to siezure and the cam chain can eat into top cover.

[2ceebees]

550 heads can also wear eccentrically at the ends of the cam in the head. This cam wear of course in the head and it is brought on by oil issues.

I think this is what happened. 

Here are pics of lobes, rocker arms etc.   The third pic shows 550(R10) vs. the 650(R9) cam lobes.  Pretty sure I'm going with the 650 although it's not perfect. 

Still looking for recommendations for a machine shop that does these heads right.  My understanding is that there isn't much extra material in the valve seats so you have to be careful when doing a valve job. 

[dave500]

those "R" numbers dont denote which cam it is,they are the blank forging numbers or something,ive seen r9/10/12 on 500 and 550 cams.

[2ceebees]

those "R" numbers dont denote which cam it is,they are the blank forging numbers or something,ive seen r9/10/12 on 500 and 550 cams.

Gotcha, didn't know that.   It's how I figured I could tell them apart.  I can't really tell the difference otherwise.