Author Topic: Yet another CB550 Engine Rebuild (Read 9904 times)

clarkbar · « **on:** June 14, 2009, 07:59:56 PM »

Back in February I purchased a 1974 CB550K with a head gasket leak. No problem... tear the engine down and get it re-sealed by spring. Well, she still leaks... a lot. So I've purchased a "spare" engine for $100 and began tearing into it. It has 18,000 original miles on it. My plan is to take my time rebuilding this engine to get it right. NO LEAKS and a little more power than a stock 550.

Ideally I would like to purchase one of those CB500 605cc big bore kits, get the head ported/polished and drop a 650 cam in it. However, money is an issue. I've read in some circles that "there's no replacement for displacement" and to get a bore done but in others they say the top end is where to focus on these engines. I have ZERO experience in machining these engines so Boring and Porting would be outsourced... unless you guys convince me otherwise Mr. Rieck's services look pretty stellar. (I do have a dremel and bits!)

I'm also down to where I could split the case if I so desired. Does anybody have a recommendation either way on that one? I'm a bit hesitant as I've never been that far down before but I would love to give it a proper cleaning. The oil that drained out of this thing was not pretty.

I've looked at post after post of engine rebuilds and I guess I'm just looking for a bit of guidance on this one as it's my first time. Photo's below.

Had to bend the studs to get them out... still one in there that I can't budge! Any tips?

I got in a fist fight with the oil filter retaining bolt...

Pretty sure this engine housed a family of birds at one time.

marksman · « **Reply #1 on:** June 14, 2009, 08:22:02 PM »

if you weld a new nut or bolt to the oil filter bolt you can probably get it out.

clarkbar · « **Reply #2 on:** June 14, 2009, 08:32:05 PM »

That's what the PO did... I put a wrench on the "welded" nut and it split right off. So I took the dremel to it and cut the head off. Ah well, I have an extra filter housing so I wasn't too concerned with giving this one a black eye.

Flying J · « **Reply #3 on:** June 14, 2009, 09:30:15 PM »

Ill be watching this one. I just got my newly acquired 550 running and it has a head leak. So any pointers to keep it from leaking when i do the rebuild will be appreciated.

clarkbar · « **Reply #4 on:** June 15, 2009, 05:18:52 AM »

One thing that may make my splitting the case decision a bit easier... Will I need a new cam chain/sprocket when using the 650 cam? If not, I think I'm just going to call it good and rebuild the top end.

Also, are there any other seals down this far that are notorious for leaking? I want this thing bone dry when I run it! I don't want people to know me by the trail of oil.

cleveland · « **Reply #5 on:** June 15, 2009, 06:47:56 PM »

The only two types of people that split the case are the ones who want to for the fun of it, and those that didn't ask first.

Mine leaks too. I have a spare engine with no leaks and an engine rebuild kit. I'm still on the fence as to which way I am going.

clarkjh · « **Reply #6 on:** June 15, 2009, 07:01:45 PM »

I had the leak on my 550, I had the head and jugs machined flat, (after breaking a ring and having to go 1st oversize). No leaks now, (at least from the head gasket), and the CCs and compression are a little higher.

James

clarkbar · « **Reply #7 on:** June 15, 2009, 08:09:58 PM »

Well as of right now I plan to go oversize, mill true surfaces and go with some heavy duty studs...

I'm just not familiar with the lower engine casing and if there are seals I should be replacing while I'm down this far. It would be fun to tear into it for learning purposes though, which I may end up doing since I have time... I can't seem to leave anything in one piece for too long

clarkjh · « **Reply #8 on:** June 16, 2009, 02:58:34 AM »

I also noticed when I had my case split, the main chain had worn a spot on the main oil line to the filter. And if you haven't had the bike since new, it is nice to know the condition of the rod and mains.

James

clarkbar · « **Reply #9 on:** June 16, 2009, 10:48:42 AM »

Thanks for the info. James!

After digging around a bit more I think I'm going to take this build in the direction StrongPerf has taken his... Gentleman's Express style. Does anybody out there have a set of 750K pistons within spec. for sale?? *feelers*

bwaller · « **Reply #10 on:** June 16, 2009, 02:50:08 PM »

No offence but it would have been wise to ask about studs before you ruined yours. HD studs for these engines are as rare as hens teeth. Unless you get extremely lucky and find a set, or can get a set made, you'll be looking for a used set of stockers to put back in there. Even guys racing them with very high compression are using stock studs, there just wasn't as big an issue with the 500/550's compared to the 750.

Sorry to be the bearer of bad news.

clarkjh · « **Reply #11 on:** June 16, 2009, 03:23:53 PM »

I have the stock studs in mine with no problems. I just removed them and chased the treads, tightened right up.

James

clarkbar · « **Reply #12 on:** June 16, 2009, 05:44:58 PM »

Quote from: bwaller on June 16, 2009, 02:50:08 PM

No offence but it would have been wise to ask about studs before you ruined yours. HD studs for these engines are as rare as hens teeth. Unless you get extremely lucky and find a set, or can get a set made, you'll be looking for a used set of stockers to put back in there. Even guys racing them with very high compression are using stock studs, there just wasn't as big an issue with the 500/550's compared to the 750.

Sorry to be the bearer of bad news.

No offense taken! I'm new to all of this so it would be a dis-service to take offense

However, I am not concerned about ruining the studs... I want this thing bone dry and I see replacing the studs an improvement. I work for a mobile hydraulic manufacturer and we have hardened stud kits for our valves. These studs take 43 foot pounds of torque and over 3,500 PSI year after year for snow plow trucks... If anything, I'll thread some of those bad boys up!

Actually, if I do get that to work I wouldn't mind threading some up for others...

DsKing416 · « **Reply #13 on:** June 25, 2009, 09:50:50 PM »

You can order those studs and many other aftermarket parts from Cyclexchange.net. Check out their ignition system too. They make the best.

Nice work. I just tore open my cb550f engine 2 hours ago I'm looking for high compression pistons. Any help would be great.

clarkbar · « **Reply #14 on:** July 01, 2009, 07:29:41 PM »

Well I have the studs taken care of... purchased from McMaster Carr. I've also received a set of 750 pistons. As of right now I'm trying to find a competent machine shop to take care of business. What I plan to have done:

-Bore the 550 liners from 58.5mm to 61mm to accept standard 750 pistons
-Machine valve pockets in the 750 pistons to accept stock valve clearances in the 550 head
-Order custom head gasket from Cometic.com??

Are there any glaring holes I'm missing here?? I know Paulages did the whole 650 hybrid thing but I just plan to use the 550 top-end. I still need to read up on how to machine the 750 pistons as well... what a learning process.

Please, if anybody has any advise it's most welcome!

DsKing416 · « **Reply #15 on:** July 03, 2009, 08:24:08 PM »

You are coming along quick. I'm also in the same process. If you drop off the jugs, sleeves, pistons, and head at a GOOD(!!!!!!!) machine shop (some specialize in motorcycles) they will do all the conversions for you.

clarkbar · « **Reply #16 on:** July 06, 2009, 04:52:47 PM »

Well, I've acquired a few more parts over the weekend... a 650 head and cam. So this will be a 550 with 750 pistons and a 650 head and cam... *if it all works together*... I've yet to mock it all up as I'm awaiting the arrival of parts.

My main issue is that I cannot find a machinist to do my 750 pistons. It seems that every single person I talk to about my project has the same reaction... "Why are you putting all this time and money into a 550? Save your money and just buy a newer bigger bike"

bwaller · « **Reply #17 on:** July 06, 2009, 05:59:14 PM »

If you plan to follow Gordon Jennings 750 piston modification, keep in mind a 650 head won't be a good choice. Those mods were for use with a stock smaller 500/550 combustion chamber, the 650's is much larger. One thing I don't know is whether a "410" higher compression 750 piston would fill enough of that bigger 650 chamber to bump the CR to reasonable. That might be interesting and Paulages might know.

More homework dude.

Tretnine · « **Reply #18 on:** July 10, 2009, 07:17:51 AM »

what kind of performance increases do you get off a good overbore on a 550? I'm interested in the overall HP increase and the HP and torque that make it to the rear wheel. Also, how much are you getting out of the 650 overhead?

clarkbar · « **Reply #19 on:** July 10, 2009, 08:44:52 AM »

Quote from: Tretnine on July 10, 2009, 07:17:51 AM

what kind of performance increases do you get off a good overbore on a 550? I'm interested in the overall HP increase and the HP and torque that make it to the rear wheel. Also, how much are you getting out of the 650 overhead?

Well what I'm doing is similar to Paulages build here: http://forums.sohc4.net/index.php?topic=40414.0
He has performance updates in his post.

However, I do not plan to take it down to the crank... as stated above, I have A LOT of homework to do yet

Slowly but surely, I'll be on the road by next spring

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Author Topic: Yet another CB550 Engine Rebuild (Read 9904 times)

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