Author Topic: 1973 CB350F - First full resto (Read 9551 times)

Dnor72 · « **on:** December 21, 2016, 08:04:13 AM »

A little history on the bike:
This was my dad's first motorcycle. He bought it slightly used from a neighbor in 1974 and rode it until 1982, at which point he put it aside and moved on to other bikes. It was pretty much forgotten. Last summer I came across it in the corner of his garage and asked him if I could have it. He had made some attempts over the years to bring it back to life, but never got very far. A week later he helped me load it into a van and off I went.

My goal is to get it running, evaluate where it's at, strip it down and bring it back. It will look stock, but I will make improvements where I can. I've worked on cars and bikes before, but I've never done a full restoration. I want to do as much as I can myself.

SIDENOTE: I am mostly done with this project and just wanted to contribute to the forum as I used it extensively over the course of this project, plus it's nice to get some feedback.

I actually started this project in June of 2015.

Here it is as I found it in his garage:

Got it to my garage and took a few more pictures:

Okay, ready to go:

Dnor72 · « **Reply #1 on:** December 21, 2016, 08:17:16 AM »

First things first, the engine is seized. About a week of rocking her back-and-forth with acetone/ATF in the cylinders she finally came free with a "blurp" of liquid gushing out.

Another issue, it was left with a tank full of fuel for the last thirty years. It's a mess in there.

The carbs were apart when I got it, so those will need to be refurbed.

Dnor72 · « **Reply #2 on:** December 21, 2016, 09:14:14 AM »

Finished rebuilding the carbs, new o-rings, cleaned the brass in a bucket of carb dip, scrubbed and sprayed with carb cleaner, cleaned all the passages. Looking okay.

The tank on the other hand, wow. In the end it just took time. Sheetrock screws worked to a point, acetone, prep-n-etch and a lot of shaking the tank and I ended up with this:

Dnor72 · « **Reply #3 on:** December 21, 2016, 09:41:04 AM »

I put in a new battery, reinstalled the carbs, rebuilt the petcock, new plugs, oil change, oil/air filter and tried to get her started. All the lights worked, winkers, brakes, even the old Stanley headlight. The starter worked and the engine turned over, but no dice. A fart here and there, but that's it. Tried a little starter fluid, but nothing. Fuel isn't the main issue as the plugs are soaked and the spark is good. I checked the compression and I don't remember what the numbers are, but they were low and all over the place. Time to remove the head and see what lurks underneath.

auro · « **Reply #4 on:** December 21, 2016, 10:38:04 AM »

keep going - quite promising!

SOHC4 Cafe Racer Fan · « **Reply #5 on:** December 21, 2016, 11:41:00 AM »

Nice project. Looking forward to seeing this come together.

Dnor72 · « **Reply #6 on:** December 21, 2016, 11:43:02 AM »

Thanks auro. More to come.

I filled the combustion chambers with some Marvel Mystery Oil to see if they would hold it. Nope. Cylinder 2 drained fast. I did some mild lapping to see if I could get it to seal better, but to no avail. Looks like this is going to the machine shop for some seat grinding.

Combustion chambers

Valves

Cleaned up and ready to head to the machine shop.

Ordered some new valve seals and checked the valves and guides with a dial gauge, seemed okay. I will have the guys at the machine shop double check. On to the cylinders and pistons.

Dnor72 · « **Reply #7 on:** December 21, 2016, 12:04:52 PM »

Cylinders

Bores

There's some light pitting and they are definitely glazed. The pistons and rings are completely seized together and smooth. By touch only you can barely tell that there are rings on the piston at all. Better bundle this up with the head to drop off at the machine shop for boring.

New cruzinimage +0.5mm (47.5mm) pistons, rings, clips and pins.

Dnor72 · « **Reply #8 on:** December 21, 2016, 12:14:55 PM »

Fast forward two months and look what we've got here.

Also picked up a Mac 4-into-1 exhaust.

Dnor72 · « **Reply #9 on:** December 21, 2016, 12:31:11 PM »

While I have the top end apart, I figure I may as well clean it up and paint it. After extensive degreasing, cleaning and sanding I used VHT Universal Aluminum. This is how it looks on the breather cover, compared to the original color on the upper engine case. Pretty close.

Bake at 200 degrees.

Looking good.

Dnor72 · « **Reply #10 on:** December 21, 2016, 12:44:17 PM »

I installed the rings and checked the end gap by partially pushing the piston/rings into the bore and using a feeler gauge. All good. Okay, let's get this top end back together. New OEM lower gasket, OEM oil galley pucks, o-rings and the pistons installed.

I used some ring compressors from a chainsaw engine rebuild kit. It has some little "blocks" to keep the pistons steady as you lower the jugs.

2 and 3 in.

Here I used some tongue depressor-like hobby sticks to steady the jugs while installing. A few whacks with a rubber mallet and it's on. Replaced both plastic cam chain tensioner blades.

Dnor72 · « **Reply #11 on:** December 21, 2016, 02:30:57 PM »

The head dropped on very easily, OEM gasket, cam installed and lined up no problems, breather cover on, breather connected and tappet clearance checked.

I also installed some 5.0 OHM Dyna Coils, NGK wires and boots.

I put the carbs back on, added some fuel and gave her a go.

Not running well, but running for the first time since 1982! Not content with that result I did some tuning. Carbs off, new jets from Jetsrus, adjusted the floats and checked the fuel level using the clear tube method and a bench sync. Checked the timing and did a vacuum sync.

This is where we landed.

I'm thinking that's pretty good.

SOHC4 Cafe Racer Fan · « **Reply #12 on:** December 21, 2016, 03:08:02 PM »

Great job on the motor refresh. Just curious, after going to all that work rebuilding and prettying up that motor, why not clean and paint or powdercoat the frame, too, while it was out??

Dnor72 · « **Reply #13 on:** December 21, 2016, 03:16:24 PM »

Quote from: CB750 Cafe Racer Fan on December 21, 2016, 03:08:02 PM

Great job on the motor refresh. Just curious, after going to all that work rebuilding and prettying up that motor, why not clean and paint or powdercoat the frame, too, while it was out??

Next step is stripping it down to do just that.

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markreimer · « **Reply #14 on:** December 22, 2016, 09:47:46 AM »

Looooove it! I'm doing a top end rebuild on my 350F next week. Sat since '78. I was lucky to have ok compression and no seized motor so I ran it maybe 5,000km this summer, but it's smoking blue like crazy. Rings are stuck and glazed I'm thinking. Didn't know you could get those Pistons, great score! I'll bookmark this for reference...

Question - these engines are notorious for leaking post-rebuild around cylinder 1. Did you do anything extra to ensure no leaks?

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calj737 · « **Reply #15 on:** December 22, 2016, 09:58:18 AM »

Very nice. I think the tank originally had a liner in it in addition to the varnished gas. The "remnants" would have been dislodged with the chemical soak. Its nice you got it to bare metal after all that.

I sure hope your Pops appreciates what you're doing as its a top class refurbish

Dnor72 · « **Reply #16 on:** December 22, 2016, 10:47:11 AM »

Quote from: markreimer on December 22, 2016, 09:47:46 AM

Looooove it! I'm doing a top end rebuild on my 350F next week. Sat since '78. I was lucky to have ok compression and no seized motor so I ran it maybe 5,000km this summer, but it's smoking blue like crazy. Rings are stuck and glazed I'm thinking. Didn't know you could get those Pistons, great score! I'll bookmark this for reference...

Question - these engines are notorious for leaking post-rebuild around cylinder 1. Did you do anything extra to ensure no leaks?

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I can't wait to get some miles in. I didn't do anything special to cylinder one outside of using an OEM gasket and replacing the little rubber bits. We'll see what happens. Cruzinimage on eBay has at least two overbore sizes for the 350F. Reasonably priced and complete with pins and clips. I haven't run this bike much so I can't say if they're any good, but we really don't have too many choices.

Dnor72 · « **Reply #17 on:** December 22, 2016, 10:51:21 AM »

Quote from: calj737 on December 22, 2016, 09:58:18 AM

Very nice. I think the tank originally had a liner in it in addition to the varnished gas. The "remnants" would have been dislodged with the chemical soak. Its nice you got it to bare metal after all that.

I sure hope your Pops appreciates what you're doing as its a top class refurbish

If that sludge was a liner I wouldn't be surprised, it was nasty. Pops loves what I'm doing. When I was five or six I would ride on the tank with him around our neighborhood. He still rides, but he's got a cruiser these days. Still a Honda though.

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bill440cars · « **Reply #18 on:** December 22, 2016, 02:07:16 PM »

That is so cool, that you are going through the ol' 350. And I'll bet that, when your Dad goes for a ride on that one, he will be in 7th Heaven.

Dnor72 · « **Reply #19 on:** December 23, 2016, 12:11:29 PM »

I'm satisfied with the state of the engine at this point. I'm not going to touch the bottom end. It shifts through the gears fine and if after I'm finished and riding it I find something wrong, well... I'll take the engine out again and have at it. So now to the strip down. Not much to show here. It went from a bike to a frame pretty fast. Lots of bagging and tagging.

Off to the powder coater.

Dnor72 · « **Reply #20 on:** December 23, 2016, 12:26:05 PM »

I had two issues while stripping the bike down.

1. Getting those damned bushes out of the swing arm. Wow. I read a lot of different strategies here on the forum and none of them worked. What did work: I used the expandable side of a blind bearing puller without the weighted handle, I got that on the lip of the bearing as if you were going to use the tool normally, I then inserted a pretty serious metal rod on the opposite side until it contacted the end of the bearing puller. I held the swing arm and a friend smashed on the rod with a large hammer. Less than a dozen strikes later and they were out.

2. My top bridge fork was cracked on both sides.

Off to eBay.

Dnor72 · « **Reply #21 on:** December 23, 2016, 12:47:53 PM »

While the frame is off being coated I'm evaluating what parts I need and what I can refurb. I've got the engine out, and the top end looks great while the bottom end is a visual mess. I sanded it down, degreased and painted with the same VHT Universal Aluminum I used on the top end.

The tach and speedo had rust on the bodies, foggy lenses and grime on the inside, so I took those apart and refinished. I dismantled them with info from the forum using a paint can opener and a scewdriver. Kind of a fiddly pain in the butt. I used a satin black paint for the bodies, polished the chrome bits and cleaned the lenses. I had to drill out the trip meter's reset screw and replaced it. I also found the little rubber bootie that protects the reset on eBay. I replaced the lights with some LEDs from superbrightleds.com. My dampers and faces were good, so I left them as is. UPDATE: I just noticed that CB750Faces.com has the trim rings for the CB350F gauges. If I were to do this again, I would buy those and just Dremel off the old trim rings.

Dnor72 · « **Reply #22 on:** December 23, 2016, 01:05:49 PM »

Other parts I refurbed.

Fork cases. I don't like polished look, I prefer satin. I used sandpaper up to 800 and just spun them so there are some light concentric "scratches" in them. Finished with some aluminum polish by hand and here is one before and after.

Same thing with the hubs. Before:

Dnor72 · « **Reply #23 on:** December 23, 2016, 01:20:49 PM »

The frame is back from the coater and it looks fantastic. Got the freshly painted engine back in the frame and sent the swing arm off to Hondaman for a rebuild.

I can't do to much without the swing arm, so I'm going to tackle the wheels and body work. Got some repro parts on the way: front and rear fenders, rear shocks and a seat.

Dnor72 · « **Reply #24 on:** December 23, 2016, 01:46:43 PM »

I've never laced or trued wheels before, but I'm determined to give at a go. I want to do as much of this myself as possible. So I got a truing stand, some DID wheels from DavidSilverSpares, a spoke kit, a torque wrench for spokes (did not know that existed) and the FAQ on this topic open.

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Author Topic: 1973 CB350F - First full resto (Read 9551 times)