Author Topic: "Mile High" CB350 Four project (Read 32710 times)

Denver_Larry · « **on:** November 07, 2015, 04:10:03 PM »

So I've got myself something new to keep me busy! I've been trying to find a small bore Honda four to get my hands dirty with for a little while, and finally found this little guy for $500 locally. Tear down will take a little while, but I'm going to try and bite off small chunks at a time and see about completely rebirthing this into a tidy cafe bike. It hasn't run for about a decade so I have my work cut out for me I think, but I plan on tearing it down to the cases so I should be able to uncover any hidden issues.

Here is the day I brought it home:

Couldn't resist tearing into it that night and cleaning it up a bit:

Denver_Larry · « **Reply #1 on:** November 07, 2015, 04:15:05 PM »

So I picked it up about a month ago, but finally had a chance to give the tank some attention.

After splitting the tank in half:

After a few hours of bead blasting, sanding, and banging dents out:

A bit more stripping to do, but it's getting there. Then to find a badass welder..

2strokeTrush · « **Reply #2 on:** November 08, 2015, 05:46:45 PM »

Cool!

timbo750 · « **Reply #3 on:** November 09, 2015, 12:11:12 AM »

I am curious to know how you split the tank and also how tricky it is to weld back together ensuring it is sealed properly.

calj737 · « **Reply #4 on:** November 09, 2015, 04:04:13 AM »

It is very tricky to weld it back together, not so much to prevent pinhole leaks, but to prevent warping the metal. Pressure test after welding insures you've got it welded up, but it will take a very competent welder about 8 hours to seal it without warpage. He will spend more time off the heat, than on if he pays attention.

I've knocked heaps of dents out of tanks, and often though about splitting them as you did then re-welding. So I got a spare tank and did just that. I will never split another unless I'm modifying it; its not worth the welding time.

Denver_Larry · « **Reply #5 on:** November 09, 2015, 08:23:12 PM »

I'm a little nervous every about the welders bill to tack this thing back together, but if it ends up being too much I figure I can just pick up another tank. The other benefit of this is inherently I AM ending up with a subtly modified tank by virtue of no longer having the pinch weld. I like the clean custom tank look, and it's something that won't get noticed right away...

Cal, did you weld it back up yourself? TIG or otherwise?

Denver_Larry · « **Reply #6 on:** November 09, 2015, 08:26:01 PM »

To answer your question timbo, I spent some considerable time with an angle grinder removing the pinch weld entirely. Followed with a file for clean up.

calj737 · « **Reply #7 on:** November 10, 2015, 04:19:13 AM »

I did. TIG. Took over 8 hours to do it without warping. Tack here, move a foot, tack, move a foot, tack, and so on. If you rush, you'll warp the shell. I don't have sheet metal working tools, so shrinking and pie cuts are way beyond me. But clamp, tack, repeat I can do.

I will never split the shell again unless I am modifying the damn thing

Instead, I've rilled holes in the bottom and used PDR tools to push dents out, then hammer smooth. Welding up a 1/2" hole with sheet metal and a TIG followed by an air grinder makes short work of it all.

WhyNot2 · « **Reply #8 on:** November 13, 2015, 04:44:33 AM »

Wow....purdy aggressive on that tank there...................

SOHC4 Cafe Racer Fan · « **Reply #9 on:** November 13, 2015, 07:08:53 AM »

Good luck mating that tank back together. That will require some skill and patience.

Denver_Larry · « **Reply #10 on:** November 13, 2015, 12:38:02 PM »

Thanks, the plan is just to get it tacked together in a dozen spots or so, and then bring it to someone who has some actual welding chops..

dbbrian350F · « **Reply #11 on:** November 13, 2015, 10:09:25 PM »

Thanks for sharing this. Now I know what my 350 tank would look like on the inside. The metal sure is in nice shape on yours.

two40 · « **Reply #12 on:** November 16, 2015, 06:58:47 PM »

Like yourself, I tend to go too far with stripping things in order to restore them but often that's the only way to do things properly!

Denver_Larry · « **Reply #13 on:** November 16, 2015, 09:16:53 PM »

No problem. I'm hoping to get the cleanup work finished this week and get it tacked up. I think the effort will be worth it in the end.

Denver_Larry · « **Reply #14 on:** February 01, 2016, 10:21:57 PM »

A bit of an update. Got the tank dropped off to get welded back up last week, hoping to have it come back soon...

Knocked off of work a bit early today and finally got some play time in the garage. First things first I built myself a stand to get the project up to a decent height.

Since I had already started tearing down the motor a few days ago, pulling it from the frame went pretty quick.

And I spent my first real money on the bike this week...Cognitomoto is cooking one of these up for me:

sbeckman7 · « **Reply #15 on:** February 02, 2016, 12:02:23 AM »

Good to see another 350F getting the treatment! You paid 5x as much for yours as I did, but yours looks to be at least 5x better than mine as a starting point

Denver_Larry · « **Reply #16 on:** February 26, 2016, 09:32:15 PM »

A bit more tear down work completed over the last few days. Pistons are off, oil pump off, and the clutch assembly and shift linkage are all gonzo. May split the cases this weekend finally.

Found out what may have been the main cause of the complete disaster area that is the left side of the motor underneath the sprocket cover. The oil pump o-ring is supposed to be a complete circle right?

After a closer look at the pistons, one of them has a 25 marking on the skirt. Does this mean it's oversize? I thought the +.25 piston had 25 stamped in the crown?

And lastly, you all think these pistons are still serviceable (assuming the bores are still in spec)?

Also tried my hand at polishing the case covers. I think I'll be deferring to a shop to complete the job since getting this relatively easy part done took HOURS! Lol

sbeckman7 · « **Reply #17 on:** February 27, 2016, 12:45:08 AM »

Looking good so far, keep it up.

calj737 · « **Reply #18 on:** February 27, 2016, 03:28:34 AM »

Quote from: Denver_Larry on February 26, 2016, 09:32:15 PM

The oil pump o-ring is supposed to be a complete circle right?

Yes, else it would be a "C"-ring.

Denver_Larry · « **Reply #19 on:** February 27, 2016, 02:31:16 PM »

Quote from: calj737 on February 27, 2016, 03:28:34 AM

Quote from: Denver_Larry on February 26, 2016, 09:32:15 PM
The oil pump o-ring is supposed to be a complete circle right?
Yes, else it would be a "C"-ring.

Sarcasm was implied

Denver_Larry · « **Reply #20 on:** February 27, 2016, 03:19:23 PM »

Alright, need help! Splitting the cases and something seems hung up around the tensioner and I can't get the thing apart. Cases have broken free of each other but I can go no further!

calj737 · « **Reply #21 on:** February 27, 2016, 07:13:35 PM »

Quote from: Denver_Larry on February 27, 2016, 02:31:16 PM

Quote from: calj737 on February 27, 2016, 03:28:34 AM
Quote from: Denver_Larry on February 26, 2016, 09:32:15 PM
The oil pump o-ring is supposed to be a complete circle right?
Yes, else it would be a "C"-ring.

Sarcasm was implied

Ditto.

Denver_Larry · « **Reply #22 on:** March 12, 2016, 04:43:17 PM »

Finally realized that I needed to pull the main shaft..

An update: After struggling with woefully inadequate internal ring pliers and failing, I ordered up a new Wiha one and had the main shaft bearings out in seconds! Nothing beats having the right tool..

Also, decided to go ahead and order up som CI .50 over pistons/rings etc. They got here in incredible time! One problem though: one of the Pistons is a little nicked up...

It is just about enough to catch your nail on and I don't really want to slip it down (what will be) a newly bored and honed cylinder. You all think I can get away with remedying the situation with a some careful work with a fine hobby file and 800-1200 grit paper? Or should I hassle CI about getting a replacement?

neevo · « **Reply #23 on:** March 12, 2016, 07:24:39 PM »

I would get a replacement.

Denver_Larry · « **Reply #24 on:** March 13, 2016, 09:22:21 PM »

Contacted CI and they are replacing the damaged piston no problem. Refreshing to see a company standing by their product without a hassle!

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Author Topic: "Mile High" CB350 Four project (Read 32710 times)