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Discussion Starter · #1 ·
In 2015 I was given a '71 CB350K3 by a friend in New Mexico. It had likely been in his shed for 15 years or so. I brought it back to my home in Texas and filled the cylinders with Marvel Mystery Oil and the lower end with ATF. It sat like that until early 2016 when I decided to remove and rebuild the carburetors so that I could see if the engine would start and run (I already new that it was not frozen and had reasonable compression). Since we live in New Mexico about half the year the bike rested in Texas unit fall of 2017 when returned. I flushed all of MMO and ATF out and refilled with Castrol 20w40 Motorcycle oil and reinstalled the carbs. I made a temporary fuel tank, charged up a new battery and after fixing a few wiring issues turned on the key and pressed the starter button. Somewhat to my amazement after a few seconds of cranking the old beast fired up. Over the next few weeks I fiddled with the carbs and replaced the points and condenser and reset the timing. I ran the bike once or twice a week to continue to evaluate the the engine condition. I could not ride it because the tires were shot, the brakes were tight (rusted) and I already thrown away the old seat foam. After observing the engine continuing to smoke from the left cylinder I decided I would pull the engine to check to the top end and make the needed repairs. I am posting a few pictures today and will have more in days to come.

The bike loaded for the trip to Texas with my daughter on board.
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Pretty sad looking
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Beginning the teardown...

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Wow - talk about patina, look at the one-sided fade on that tank! If it were mine I'd keep it that way for a while... :D nice find, looks pretty complete and original. Very cool. You'll find lots of help here for the engine rebuild if you need it
 

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Discussion Starter · #3 ·
I most likely will ride it with the tank as is, at least for test purposes. I do intend to paint the tank, side covers and fork covers in Honda Candy Ruby Red or something close. It was pretty complete but with the usual rust in many places. Unfortunately the silencers are rusted through so the are being replaced. I have already completed the engine work with help from this community. Here are some more photos.

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Discussion Starter · #4 ·
Here are few more pictures taken during the teardown.

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A lot of the rust in this area is form battery leakage.

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Only a little over 10K miles


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The engine is out!


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Down to the frame
 

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Discussion Starter · #5 ·
Enough of the rusty old parts and the teardown phase. I had the frame, footrest mount, center and side stand, chain guard, swing arm and rear footrest and silencer brackets powder coated. Other black parts were stripped or media blasted and painted gloss black or semi-gloss with acrylic enamel. I polished the hubs, brake plates and fork bottoms. Also Evaporusted the rims and fenders and then and the relaced the wheel with new spokes. Here is the current state of the frame reassembly.

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Discussion Starter · #7 ·
Blasting and powder for all parts mentioned was $300 in Weatherford, Tx.

Just FYI the handlebars are CB400F style from EMGO since the originals were bent. I believe that I will like the the lower rise.
 

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Discussion Starter · #8 ·
Here are a couple of photos of the completed engine rebuild. The rebuild included cylinder hone, new standard rings (the cylinders were spec diameter and taper), valve and seat grind, new valve cotters, mild port cleanup, combustion chamber polish, new cam chain rollers, cylinder and head clean and blast, new EBC clutch plates, new Barnett clutch springs, polish alternator and oil filter covers, polish cam chain tensioner, clean and paint side covers, cam box, cam box cover, all gaskets, seals and o-rings.

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Discussion Starter · #9 ·
Project Update

Overdue update on the project. We returned to Texas in late September and I got back to work on the '71 350. The pictures show the current status of project. I have been road testing the bike in the current condition before I begin to disassemble it to take of the paint work. It is running quite well except for small exhaust leaks where the head pipes join the mufflers. As you can see the mufflers are not original but are Road Hawk (EMGO) megaphones from Dime City Cycles. Anyone have any suggestions for what I might use to seal up the leaks?

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Discussion Starter · #10 ·
Update on the exhaust system leak. I found some correct exhaust seals on Amazon > CALTRIC Exhaust Muffler Gasket Fits HONDA 18392-MK4-000, 18391-383-670, 18391-317-010. Perfect fit and the exhaust is now sealed!
 

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I know it's not for everyone, but I love the way the old tank paint looks with that fresh and clean bike. It it were me, I might clear coat it and call it a day. Just my $.02. Awesome work on it.
 

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It's interesting that your wheel hubs are the earlier '68-'69 pattern. I've seen them stock on some early '70 models (I suppose Honda was using up stock), but never on anything later than that.
 

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How did you polish the hubs and stuff? They look amazing. I'd like to do the same thing to my 400F.
 

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Discussion Starter · #15 · (Edited)
"I know it's not for everyone, but I love the way the old tank paint looks with that fresh and clean bike. It it were me, I might clear coat it and call it a day. Just my $.02. Awesome work on it."



You're the second one to make that suggestion and it is an interesting idea. If the tank were to remain the only painted part it would probably work. However, I have new (repro) side covers and the spring covers are also new. My plan to is to go with a bright red (like Porsche Guards Red) for all of the painted parts and no stripes on the tank. I am also going to use an EMGO metal headlight in black. Let me know what you think when I post pictures after painting is complete. Thanks for the compliment.
 

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I love red, and I'm sure it will look good - but the stripes are an iconic part of the CB350 look from that era. Too bad you couldn't find a way to get them back on the tank, like one of these
 

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Discussion Starter · #18 ·
It's interesting that your wheel hubs are the earlier '68-'69 pattern. I've seen them stock on some early '70 models (I suppose Honda was using up stock), but never on anything later than that.
I had not realized the hubs were the older style. This bike has some other oddities. The seat on it was a rear hinge seat also not from a K3 and the rear brake lever was not correct. Judging from other evidence, like bent handle bars, bent turn signals and headlight brackets the bike had hit the ground (or other solid objects) more than once. The rims are what came with the bike but the spokes are new. While re-lacing the wheel I cleaned up the rims inside and out but if you close you can see blemishes on them.
 

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Perhaps it had major damage and someone changed to an older frame sometime ago? Seat mounts come with the frame and unless done professionally, if changed they would probably look like it
 

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Discussion Starter · #20 ·
How did you polish the hubs and stuff? They look amazing. I'd like to do the same thing to my 400F.
All of the parts that I polished were removed from the bike for polishing. I did the hubs while the spokes were out during the re-lacing process. I used a bench mounted drill press with buffing wheels from this kit from Harbor Freight > https://www.harborfreight.com/14-piece-aluminum-polishing-kit-98707.html Because there was serious oxidation on most of the aluminum parts I had use 320 to 1500 grit emery paper before buffing. I did not count the time it required for buffing but I estimate it was 10 -12 hours all together. As I mentioned somewhere in the thread I am using 400F handlebars and really like the way they feel and look.
 
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