Topic: Dad's 1978 Honda CB550k

[joegeis]

hey all, wanted to give a quick update. Weather has been nice and the bike has been running pretty well. Needs a little ether to start when its chilly, but otherwise runs and rides. I've been enjoying just putting some miles on it so far this spring, but the bike is definitely not yet "finished" (if these bikes ever are). I'm still trying to procure an air cleaner cover / tool tray, the idle still walks a bit, and I've really noticed that the thing is leaking oil. After my 70 mile ride today, the oil pan, kickstand and portions of the bottom of the pipes were slick with oil. It isn't leaking while parked (in fact no drops under the bike all winter), but when running I can definitely see oil seeping from a few places. I think for now, I'll just keep riding it, and maybe towards the end of the season I'll start planning a tear down and rebuild (which I'm definitely anxious about doing!).

Hope everyone is enjoying spring and getting miles on their bikes!

[newday777]

Check between the fins behind the the exhaust header and downward. Might be the rubber pucks in the head covering cyl head bolts leaking.

[joegeis]

Check between the fins behind the the exhaust header and downward. Might be the rubber pucks in the head covering cyl head bolts leaking.

The fins on the front of the head, under the exhaust manifold were definitely covered in oil. I'm not sure what you mean by rubber pucks though.

[newday777]

Check between the fins behind the the exhaust header and downward. Might be the rubber pucks in the head covering cyl head bolts leaking.

The fins on the front of the head, under the exhaust manifold were definitely covered in oil. I'm not sure what you mean by rubber pucks though.

#14

https://www.southsoundhonda.com/--xpartsstream#/Honda_Powersports/CB550KA_(78)_550_FOUR_K%2c_JPN%2c_VIN%23_CB550K-2100001_TO_CB550K-2122082/CYLINDER_HEAD/0f12de96-474a-4fbe-a2ee-8ba2cda5f653/332fe051-e75f-419c-8695-482efb8d6689/y

[denward17]

Here is a picture of my '76 CB550 head, see the 6 holes, flat rubber seals should go there after head is torqued down.

[RAFster122s]

Also note, the ones from the dealer and similar sources have been too thin causing leaks...  Parts n more varies ones which are the correct thickness.

[joegeis]

great, thanks. I'll keep you guys posted.

[lazyMlazyK]

Well, I hit my first challenge today. I goofed something up with the choke mechanism on the carbs (PD 46A). I was trying to gently separate the carb bodies far enough to replace the fuel tube, and while trying to wiggle it back together, something in the springs and gears shifted. My problem is that everything still LOOKS the same! I could see that potentially the light spring is looser. Perhaps it unwound a bit. However, the choke actuator is not really working at all now. Here are some photos and a video of me pulling the choke to the limit of how far it will go. You can see the choke flaps barely move, and that there is a difference between carbs 1&2 vs 3&4. Can anyone tell how to fix what I've botched up? VIDEO

How did you figure out how to fix your issue?  I'm currently going through a set of PD46A carbs, and I'm not sure how that spring setup is supposed to look between carbs 2 and 3. I'd like to separate all the carbs in order to replace the o-rings on the fuel tubes - thats the ONLY reason I'm separating these carbs.

[joegeis]

Honestly, I just kept tinkering with it, and trying to reference photos/manuals. I didn't take pictures of the springs specifically before disassembly, so I had to use other photos that I took with the springs not the focal point. I recommend taking really good pictures before taking it apart!

[joegeis]

Ok, so some time has gone by and not much has happened with the bike. I never quite got it running right. It was hard to start and didn't idle well. I didn't ride it often because I was worried I wouldn't be able to get it started or that it was going to die on me, so it sat parked most of last year while I rode my modern Triumph Street Triple everywhere.

However, the bug has once again bit. I've been racing the Street Triple, which is great fun, but feel less inclined to ride it on the streets now (the irony of the name isn't lost on me). I would much prefer to get the CB running really well, and making some cosmetic modifications to really make it my own and give me more desire to daily it. Of course, everything I do to "Dad's bike" will be reversable. I've ordered a whole slew of parts to rebuild the top end. I'm leaking oil pretty badly, and since I'm in there, I'm going to do everything - hone cylinders, lap valves, replace all seals, replace rings, etc. I hope this will fix my idle stability. Additionally, I'm having the fork lowers powder coated black to match the wheels, replacing the crush washers to fix the oil leaking from the bottom of the forks (fork seals were done last time). I'm also replacing the turn signals and fork ears and putting on superbike bars and bar end mirrors.

I'm sure I'll have a hundred more questions, and will come back with more photos soon.

Oh, and if you are interested, I posted a couple session from my track day on the Street Triple

Edit - did a compression test, with the engine warm and throttle wide open:
#1 - 140 psi
#2 - 135 psi
#3 - 125 psi
#4 - 145 psi

I put a teaspoon of Marvel Mystery Oil in number 3 and ran the test again, and it jumped to 150. I'm planning to do rings, hone cylinders and lap valves anyways, but just wanted to see how the compression was looking and if there were any significant outliers between the cylinders.

I'll post again soon regarding the top end rebuild. Parts should start arriving this week.

[joegeis]

Okay, so I pulled the forks to fix the oil leak from the bottom. As I was disassembling I realized I only have one "Oil Lock Piece 51432-371-003" (pictured below). I didn't notice this a couple years ago when I rebuilt the forks the first time. The one only came out with a lot of banging, so I imagine I never saw it last time. I don't know if this may have contributed to my oil leak, or if it was simply that I didn't replace the crush washers on the bottom. Either way, I cannot find a replacement anywhere. Does anyone happen to have one in storage they would sell me, or should I just reassemble with one missing? My understanding is that these are there to help buffer the forks from bottoming out.

[grcamna2]

Okay, so I pulled the forks to fix the oil leak from the bottom. As I was disassembling I realized I only have one "Oil Lock Piece 51432-371-003" (pictured below). I didn't notice this a couple years ago when I rebuilt the forks the first time. The one only came out with a lot of banging, so I imagine I never saw it last time. I don't know if this may have contributed to my oil leak, or if it was simply that I didn't replace the crush washers on the bottom. Either way, I cannot find a replacement anywhere. Does anyone happen to have one in storage they would sell me, or should I just reassemble with one missing? My understanding is that these are there to help buffer the forks from bottoming out.

Joe, I wouldn't ride w/o that part.
Have you called a good parts counter person in a reputable Honda dealer ?
They can do a 'Honda dealer nationwide search' using the part # and find you one that way.

[joegeis]

Are you talking about companies like Partzilla? I have a local motorcycle dealership, which sells a variety of Japanese brands, with their own shop, but its no official Honda dealer like you would see for cars.

[grcamna2]

Are you talking about companies like Partzilla? I have a local motorcycle dealership, which sells a variety of Japanese brands, with their own shop, but its no official Honda dealer like you would see for cars.

Joe, check-out South Sound Honda(up near Seattle)and speak with Damian or Dex in parts and have a pen and paper handy when you call;it will help them alot if you look-up the part number for the part you're looking for ahead of time and tell them using the pt.#.  360-357-9633   10am-6PM Tues-Thurs.PST
The have an online site accessed by: hondabike.com,or if you prefer Partzilla.com

[joegeis]

Thanks, I sent them an email with the part number. I've already checked Partzilla and many other similar sites and eBay to no avail. We'll see if they are able to come back with anything.

Worst case scenario, I'll have to buy a whole fork set on eBay to salvage this part from, I suppose

[newday777]

Okay, so I pulled the forks to fix the oil leak from the bottom. As I was disassembling I realized I only have one "Oil Lock Piece 51432-371-003" (pictured below). I didn't notice this a couple years ago when I rebuilt the forks the first time. The one only came out with a lot of banging, so I imagine I never saw it last time. I don't know if this may have contributed to my oil leak, or if it was simply that I didn't replace the crush washers on the bottom. Either way, I cannot find a replacement anywhere. Does anyone happen to have one in storage they would sell me, or should I just reassemble with one missing? My understanding is that these are there to help buffer the forks from bottoming out.

Looks like David Silver has 2 available

https://www.davidsilverspares.com/parts/by-part-number/partnumber_37771/

[joegeis]

Okay, so I pulled the forks to fix the oil leak from the bottom. As I was disassembling I realized I only have one "Oil Lock Piece 51432-371-003" (pictured below). I didn't notice this a couple years ago when I rebuilt the forks the first time. The one only came out with a lot of banging, so I imagine I never saw it last time. I don't know if this may have contributed to my oil leak, or if it was simply that I didn't replace the crush washers on the bottom. Either way, I cannot find a replacement anywhere. Does anyone happen to have one in storage they would sell me, or should I just reassemble with one missing? My understanding is that these are there to help buffer the forks from bottoming out.

Looks like David Silver has 2 available

https://www.davidsilverspares.com/parts/by-part-number/partnumber_37771/

Woo, thank you! I just purchased one.

[grcamna2]

Okay, so I pulled the forks to fix the oil leak from the bottom. As I was disassembling I realized I only have one "Oil Lock Piece 51432-371-003" (pictured below). I didn't notice this a couple years ago when I rebuilt the forks the first time. The one only came out with a lot of banging, so I imagine I never saw it last time. I don't know if this may have contributed to my oil leak, or if it was simply that I didn't replace the crush washers on the bottom. Either way, I cannot find a replacement anywhere. Does anyone happen to have one in storage they would sell me, or should I just reassemble with one missing? My understanding is that these are there to help buffer the forks from bottoming out.

Looks like David Silver has 2 available

https://www.davidsilverspares.com/parts/by-part-number/partnumber_37771/

I just checked,someone must have just bought one;only one left.

[newday777]

Okay, so I pulled the forks to fix the oil leak from the bottom. As I was disassembling I realized I only have one "Oil Lock Piece 51432-371-003" (pictured below). I didn't notice this a couple years ago when I rebuilt the forks the first time. The one only came out with a lot of banging, so I imagine I never saw it last time. I don't know if this may have contributed to my oil leak, or if it was simply that I didn't replace the crush washers on the bottom. Either way, I cannot find a replacement anywhere. Does anyone happen to have one in storage they would sell me, or should I just reassemble with one missing? My understanding is that these are there to help buffer the forks from bottoming out.

Looks like David Silver has 2 available

https://www.davidsilverspares.com/parts/by-part-number/partnumber_37771/

I just checked,someone must have just bought one;only one left.

Joe did it

[Stev-o]

Edit - did a compression test, with the engine warm and throttle wide open:
#1 - 140 psi
#2 - 135 psi
#3 - 125 psi
#4 - 145 psi

I put a teaspoon of Marvel Mystery Oil in number 3 and ran the test again, and it jumped to 150. I'm planning to do rings, hone cylinders and lap valves anyways, but just wanted to see how the compression was looking and if there were any significant outliers between the cylinders.

With comp numbers like that, I would not pull the motor apart hone, and re-ring, should not be necessary.

You most likely have carb and/or head issues that are not making it run reliable. 

[seanbarney41]

+1

[joegeis]

I'm trying to get the head off now, but it is so stuck! The bottom gasket has come loose, but the head is still holding strong. I removed the 12 acorn nuts, two 10mm bolts at the front and rear, and the top bolt holding the cam chain tensioner to the head. I believe that is all the bolts. I've sprayed with PB Blaster, given a little persuasion with my dead blow mallet and its just not budging. I'm afraid to try and wedge or pry anything in there so I don't mar up the mating surface. The alignment pins between the head and the cam cover (not sure what the correct name is for that) were really corroded and very difficult to remove, so I assume its the same problem here.

Besides continuing what I'm doing, does anyone have any suggestions??


UPDATE! - I got the head off. It just needed a little heat and bit more percussive persuasion. Nothing broke, luckily. Here are a few more photos:

[BenelliSEI]

Well done! Heating the end dowels usually does it.

[HondaMan]

Your pistons look great: I STRONGLY recommend leaving those alone. If not, they will not ever seal well again until you rebore with larger pistons. Do NOT just "hone and replace the rings" as the bike WILL forever burn oil afterward. This is a trait of the 500/550 engine.

There are 3 leaking intake valves, though: you might want to pull them out and clean them on a wire wheel, then re-lap their seats and faces together. Might as well do all 8? This is contributing strongly to your poor idling situation.

PM me your address. You will need 2 O-rings for the oil passages through the head gasket that do not come in any gasket kit, because modern head gaskets are 0.2mm thicker than OEM ones were, and the oil port O-rings in your gasket set (all of them) will be too thin, resulting in oil leaks on both outer sides of the head when it goes back together. I'll send you some.

[joegeis]

Hey Mark, I'm the same guy that just sent you my cylinders    In for a penny, in for a pound. At this point, we'll bore oversized and make this thing rock solid for another 40 years. I'll be doing the valve job, porting the head and cleaning up the intake manifold over the next week or two.

Meanwhile, I'm waiting on that rare fork part to arrive so I can get the front end put back together. I also bought some superbike bars, new grips and mirrors too that will be going on while I wait to finish the engine rebuild.

Oh, and I did find a NOS petcock, so I can finally replace whatever it is that is on my bike now that doesn't include an internal sock filter, so I can eliminate my inline fuel filter too.

Once I start cleaning up the valves and head, I'll post more photos.