Author Topic: CB550K3 Project - Brat (Read 8587 times)

shads · « **on:** November 02, 2017, 01:18:42 AM »

Ive been looking for a CB to rebuild for a while now. Recently came across an old 1977 CB550K3 which seemed a good candidate, although the price was a bit more than I would have liked (Australia has a pretty big mark up on everything unfortunately....!). These bike are few and far between in Oz so decide to go for it.

Im pretty much a noob when it comes to bikes but reasonably OK with mechanical stuff, so this should be an interesting journey.

I think the bike has been sat for quite sometime but seems to be a relatively solid base to start from. Number 1 exhaust was removed a while ago but everything else seem to be there. The plan is a full strip down and rebuild.

shads · « **Reply #1 on:** November 02, 2017, 01:36:41 AM »

So most of it has been pulled apart. Im slowly figuring out which bits do what. My main concern right now is the condition of the engine as im not sure its been particularly well looked after - lots of chewed screws on the cases, messy black sealing compound around some of the covers and two different size spark plugs (1 & 4 are standard 5/8's and 2 & 3 are a little bigger, maybe 11/16's?). The oil seemed very thick and there was a couple of small flakes of metal in the bottom of the sump pan. Not sure if that's normal or not. As its been sat for a while, there were a load of leaves and crap in the spark plug holes.

Bought a gauge and did a compression test on cylinders 1 & 4 today and was getting around 120 psi. Then messed around with the valve gaps and set them to sizes in the manual and I now cant seem to get much more than 100 psi on either

. Don't have the right socket for the plugs in 2 & 3 so haven't done those yet.

How do I figure out if the engine should be rebuilt? I think i could probably have a go at the top end but dont want to go near the bottom end. I got a quote the other day for a full rebuild, including vapour cleaning, painting, etc, and that came back at $5000 so not too keen to have to fork out that much...!

shads · « **Reply #2 on:** December 09, 2017, 10:26:13 PM »

Progress has been made! The engine has been pulled and has gone out for rebuild. The bike is now down to just a frame and ive started de-tabbing and chopping the rear end ready for the new seat hoop.

The front forks are not in the best condition so they are also being sent out to be re-chromed.

Also pulled the forks apart the other day. I'll be replacing all the seals and corroded bolts. Is it worth looking at new springs, given the bike has been sat for years? Ive measured the length but they seem to be longer than the manual says.....?

shads · « **Reply #3 on:** December 09, 2017, 10:37:25 PM »

Started cleaning the fuel tank today. After shaking the tank it was pretty clear there was a lot of debris inside. I assumed this would be rust but it I think it might just be gummed up old fuel. Its not metallic and smells really bad. Here's about a 1/3rd of what came out.

After pouring boiling water with detergent in a few times, the metal seems to be coming up pretty decent, but there's still a lot of gunk coming out so needs a few more rinses out. Do I need look into lining the tank? I was thinking of POR15 or Red Kote, but seeing how the metal is after cleaning im not sure.

Before

After

calj737 · « **Reply #4 on:** December 10, 2017, 03:19:44 AM »

The stock fork springs pretty much suck, so replacing those with fresh progressives, or single rates based upon your weight with emulators will be a vast improvement. Follow that with quality rear shocks (again based upon your weight) and you’ll have a very tidy handling bike.

A gentle soak with some household vinegar will clean your fuel tank up. Don’t leave it too long lest you destroy the metal. Follow with a phosphorus rinse and you’ll be clean and ready to roll.

There’s a member, Elan, who sells an oil pump rebuild kit (the internal O-rings are NLA separately) and it’s something you should do whilst rebuilding, especially given the prior history of the motor and black goo mentioned.

shads · « **Reply #5 on:** January 20, 2018, 11:19:49 PM »

De-tabbing and welding now complete and dropped off the frame and other bits for powder coating last week! Lots of scrubbing and cleaning done and pretty much everything is in bits now. I guess this means the pulling apart is done and its beginning of the putting back together!

Took the wheels to the local motorcycle shop to get them to take the tyres off so thought id get them to remove the wheel bearings and retainers whilst they had them. Got the wheels back and they'd just used a punch and hammer to turn the retainers to smash them out and ruined them in the process - nice job guys.

Recently got the swing arm bushing out too - I initially tried to cut them with a hacksaw and then collapse them from the front side, but this really wasn't working as only tiny little bits would chip off each time I hit them. Ended up baking the swingarm in the oven for 30 mins then hitting the bushings from behind with a long rod. They came out really easily that way with no damage to the inside. I did destroy the handle of my long screw driver in the process however

The inside of the petrol tank is looking really good now - took the best part of a week to get clean. Turned out there was about 1/2 inch of solidified gas in the bottom which I had to slowly dissolve away with many, many rinses of boiling water and detergent. Eventually got most of it out but there's still a few black stains on the inside so its currently got a load of kerosene in it to see if that can shift it. Don't think im going to bother with a tank lining as all the petrol varnish seems to have protected the metal quite well! An over night soak in metal rescue and then a good spray of WD40 has stopped any flash rusting.

My swing arm collar also looks to be quite worn with some very noticeable flats spots on either end. Measured it and appears to be under the wearable limit so thats another item added to the ever growing shopping list.

JoeCooley · « **Reply #6 on:** January 21, 2018, 12:35:59 AM »

Nice start to the build. I'm excited to see how this one goes. 👍😎

Marissa · « **Reply #7 on:** January 21, 2018, 06:26:26 PM »

Keep up the good work!

shads · « **Reply #8 on:** January 25, 2018, 03:47:26 PM »

Hey all, shameless plug that im selling a few bits off the bike I dont need on ebay. There a few other bits too, let me know if you need anything in particular, I would much prefer they go to someone who can use them rather than sitting in my garage...

Indicators

Wiring Harness

Air Filter Chamber Comp.

Electric Plate

Helmet Seat Lock

shads · « **Reply #9 on:** January 28, 2018, 01:45:56 AM »

With the frame and engine out there's not too much for me do at moment other than polishing various aluminium bits. Also waiting on a couple of big (and way more expensive than I planned for) deliveries of parts for rebuild of the wheels, forks and a few other bits. Getting parts sent all the way to oz sucks!

Been doing some research on the next steps and inspecting parts and noticed theres a fair bit of wear on the inside of the rear hub and the collar spacer also came out with quite bent tabs, which I assume is the cause of the wear. Ive ordered a new collar so no issues with that, but is the wear on the hub going to be an issue?

On the plus side my final drive looks to be nearly brand new. Hardly any wear on the inside face compared to other pictures ive seen on the web!

shads · « **Reply #10 on:** February 28, 2018, 12:18:46 AM »

The frame and various parts are back from powder coating! Pretty amazing how good they look!

Polishing is also coming along nicely, although very very slowly

Ive put hours and hours into it so far, and really only got the wheel hubs done...

Also got a report back from the engine builder - he's pulled it apart and inspected everything and said it looks really solid inside. He even said its one of the better engines he's pulled apart (he specialises in old CB's, so has seen many over the years). The only significant issue was rust in the cylinders from being sat for so long, so the head has gone out for a rebore. The engine is now fully stripped, bead blasted and ready for paint!

calj737 · « **Reply #11 on:** February 28, 2018, 03:28:54 AM »

Quote from: shads on February 28, 2018, 12:18:46 AM

The only significant issue was rust in the cylinders from being sat for so long, so the head has gone out for a rebore.

When the cylinders are being bored, have them also mill the deck flat, flat. Same for the head. Small deviations in the flatness of the surface effect the seal and encourage oil leaks.

shads · « **Reply #12 on:** March 10, 2018, 10:15:31 PM »

Cylinders (!) after being bored and head milled flat

shads · « **Reply #13 on:** March 10, 2018, 10:18:04 PM »

Engine painted and polished and ready to go back together!

shads · « **Reply #14 on:** March 10, 2018, 10:28:57 PM »

Wheel polishing final complete and rebuilt using the guide I found on SOHC, much appreciated! Wasn't too difficult one you get your head around the pattern layout.

calj737 · « **Reply #15 on:** March 11, 2018, 04:30:17 AM »

Looks good. Did they also mill the cylinder block flat? You don't what to only do the head as both sides want to be truly flat.

shads · « **Reply #16 on:** March 21, 2018, 12:30:46 AM »

Quote from: calj737 on March 11, 2018, 04:30:17 AM

Looks good. Did they also mill the cylinder block flat? You don't what to only do the head as both sides want to be truly flat.

I asked my engine builder about this and he said he inspected the cylinder and is happy with how it is. He mentioned that most of the seal is formed against the steel wall of the cylinder anyway so the rest doesn't matter than much - seems plausible to me, does that sound right??

shads · « **Reply #17 on:** March 21, 2018, 12:39:51 AM »

This beauty arrived in the post today! My swing arm woes should now be over! Just need to decide on whether I use the bronze ebay bushings or OEM fibre ones now...

Tyres also came today, what an exciting day, went with the Metzeler Sportec Klassic in 3.25 x 19 and 4.00 x 18.

calj737 · « **Reply #18 on:** March 21, 2018, 04:05:27 AM »

Quote from: shads on March 21, 2018, 12:30:46 AM

Quote from: calj737 on March 11, 2018, 04:30:17 AM
Looks good. Did they also mill the cylinder block flat? You don't what to only do the head as both sides want to be truly flat.

I asked my engine builder about this and he said he inspected the cylinder and is happy with how it is. He mentioned that most of the seal is formed against the steel wall of the cylinder anyway so the rest doesn't matter than much - seems plausible to me, does that sound right??

I know many machinists that would disagree with him on the importance of the head and deck being milked. Thousands of heat cycles warp those surfaces over time and that can creat leaks and poor sealing for oil and combustion blow-by. Fingers crossed yours is fine.

slikwilli420 · « **Reply #19 on:** March 21, 2018, 06:08:21 AM »

For the small sum of money it costs to get it flat, I would go for it. Why go 99% of the way? Especially since everything is apart now. Pulling it all apart later to fix a leak will result in even more money spent. This is one surefire way to prevent leaks at the top end. There is also high pressure oil feeding the top end, so it more than just the sleeves that need to seal.

shads · « **Reply #20 on:** March 21, 2018, 09:46:53 PM »

Too late! She's all back together!!

Im sure it'll be ok, the guy specialists in CB engines and has been rebuilding them for decades, so I trust his judgement. I think his work speaks for itself!

shads · « **Reply #21 on:** April 06, 2018, 01:18:49 AM »

Engine is home and back in the frame. I followed SohRon's guide by laying the engine on its side and slipping the frame over. The process was surprisingly easy. Took all of 30 minutes and no scratches! Now the actual rebuild can begin

shads · « **Reply #22 on:** May 20, 2018, 02:37:19 PM »

Roller bearings on and triple tree installed. Swingarm bushings pressed in also.

shads · « **Reply #23 on:** May 20, 2018, 02:40:01 PM »

Forks legs all polished up and rebuilt. The inner legs were hard chromed so they're good as new and fit well.

shads · « **Reply #24 on:** May 20, 2018, 02:42:42 PM »

Pulled the starter motor apart and it was pretty messy so just ordered a rebuild kit. Think I need to extend the starter cable to get it to where my box will be but the cable is soldered in so not sure how to deal with that yet.

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Author Topic: CB550K3 Project - Brat (Read 8587 times)