CB350K3 Revival
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  1. #1
    Junior Member 68Ford's Avatar
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    CB350K3 Revival

    Hello all,

    This project is already mostly wrapped up, however I am coming back now to put together a project log with lots of pictures and more explanation. I'll make a post or two as I have time. Hope you enjoy coming along for the ride!

    A little background first. This bike belonged to a neighbor just across the road from my family. It is a 1971 CB350K3, and he bought it new in 1972. He rode it for a few years, but put it away after he had put around 9,000 miles on it. During this time the bike picked up a few scratches, and appears to have been dropped onto the right side at some point (The brake lever is slightly bent, and the end of the right handgrip is chewed up). It must have just been tipped over and not laid down at speed because there is really no other damage. He also managed to blow out one of the original mufflers, so for a long time after the bike rode about with one original muffler and one replacement he picked up from somewhere. As far as we know (the PO's memory is a little fuzzy on this) there was no mechanical reason the bike was parked.

    After it sat for many years one of the PO's sons decided he wanted to get it going again, so he did a bit of work to it and then started riding around. He put about 1,800 more miles on the bike, but at some point during this is stopped firing on the right cylinder. They played with it a little bit, but never managed to figure out why it wasn't running right, and so the bike was parked once more. This was in 1990.

    Fast forward to the summer of 2019 and the bike has now been sitting in a little partially enclosed structure for nearly 30 years. It was protected from the sun, but only somewhat protected from rain and snow during this whole period. I should have taken a picture or two of how it was stored, but I never did. I do however have pictures of the bike encrusted in dust from storage, and I'll attach those to this post. Honestly it's a miracle the bike is as nice as it is looking back on how it was stored. I can't believe the seat survived having no protection from mice. A testament to how well these were made in the first place I guess.

    Anyway back to the story. The PO is tired of watching the bike sit and rot away, so he asks if I'd like to take it and work out some kind of deal if I could get it running (if anyway is interested I ended up giving him a logsplitter in exchange for the bike). Obviously I said yes, and so the next day my dad and I walked over and dug it out of the shed. The tires (still the factory originals ) held air, and the bike was in neutral, so I pushed it over to our garage and began a short inspection. Those of you with a good eye will notice something right away; the ignition switch can't be seen in the pictures, and the horn is just hanging there. I'll talk about that later.

    Anyway, after a few pictures my sister and I (she wanted a mechanical project to work on, so she helped with the bike) pulled the spark plugs, dripped some oil in the cylinders, made sure there was oil in the crankcase, and I gently tried the kick starter. The engine turned over! This was our first major hurdle, a locked up engine would have been a different and much more involved project. As it was we stood a chance of getting the thing running without a rebuild. We screwed the spark plugs back in to keep the cylinders closed up, and then we hosed the thing down to get rid of as much dust as we could. After the bath, we started to disassemble the bike, and that first day ended with the bike sitting there minus a tank, seat, and airbox covers.
    CB350K3 Revival-img_20190526_140217.jpgCB350K3 Revival-img_20190526_140226.jpgCB350K3 Revival-img_20190526_143916.jpg
    Last edited by 68Ford; 08-20-2019 at 06:12 AM. Reason: Spelling
    BabyBiker and Archangel like this.
    First Car: 1968 Mustang
    First Bike: 1971 CB350K3

  2. #2
    Senior Member ancientdad's Avatar
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    It's a nice survivor. Little things like the amount of fade on the top of the tank, or the bright red color of the redline area, mean the bike didn't spend nearly as much time out in the sun over the decades as many did. Looking forward to more pictures as you catch up to the present
    Tom

    Ride along at the drag strip - https://www.youtube.com/watch?v=20jFPazXlvU



    running points... because I'm too old for mysteries that begin with pushing

  3. #3
    Member BabyBiker's Avatar
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    What an amazingly well preserved beauty. The fact that the tires and seat are as well preserved as they are as a true testament to how well it was stored. I am very intrigued to see how this turns out in your upcoming post as the 1971 model year is less documented on then the K4 and later generations.


    Sent from my iPhone using Tapatalk
    1971 CB350 K3 (Cafe Rebuild In Progress)
    2014 CRF250L (SOLD: to fund above)

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  5. #4
    Senior Member Pops's Avatar
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    Nice bike...but I wanna know what's under the cover next to it!
    Butch
    72 SL350 Basket Case

    Age and treachery will always overcome youth and enthusiasm

  6. #5
    Junior Member 68Ford's Avatar
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    Quote Originally Posted by ancientdad View Post
    It's a nice survivor. Little things like the amount of fade on the top of the tank, or the bright red color of the redline area, mean the bike didn't spend nearly as much time out in the sun over the decades as many did. Looking forward to more pictures as you catch up to the present
    The PO did make sure the bike was out of the sun for all the time that it sat, that's for sure. Protection from anything else though... not so much.

    Quote Originally Posted by BabyBiker View Post
    What an amazingly well preserved beauty. The fact that the tires and seat are as well preserved as they are as a true testament to how well it was stored. I am very intrigued to see how this turns out in your upcoming post as the 1971 model year is less documented on then the K4 and later generations.

    Sent from my iPhone using Tapatalk
    Wait until you see some of the pictures of how it cleaned up! The funny thing is, it really wasn't stored well at all. I'll have to grab a picture of the little structure it sat in for 30 years. It got it out of the sun, and the PO's son drained the gas, but that's really all they did to it. I still don't know how it survived so well sitting like that for so long.

    Quote Originally Posted by Pops View Post
    Nice bike...but I wanna know what's under the cover next to it!
    Ask and ye shall receive. That's my '68 Mustang hiding under there. You can see the GT hubcap just peeking out from under the cover. It's not a real GT, but I did use real GT parts on it. Here's a few older photos without the cover.

    CB350K3 Revival-mustang_1.jpgCB350K3 Revival-mustang_2.jpgCB350K3 Revival-mustang_3.jpgCB350K3 Revival-mustang_4.jpgCB350K3 Revival-engine_1.jpgCB350K3 Revival-img_1496.jpg
    Last edited by 68Ford; 08-20-2019 at 06:09 AM. Reason: Formatting
    ancientdad likes this.
    First Car: 1968 Mustang
    First Bike: 1971 CB350K3

  7. #6
    Senior Member budlite282's Avatar
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    Nice 'stang, and good looking bike as well.

    I had a 65 'stang, just a little lighter color green.
    "If it ain't raining, I'm riding......"

    Work in process:::::::

  8. #7
    Junior Member 68Ford's Avatar
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    All right, project log part 2 inbound. Probably not any new information in this for the pros, but it might help a newbie.

    One thing I wanted to mention first in this post that I didn't talk about in the last one is the removal of the airbox covers. The center attachment point under the chrome button on the air box pops off fairly easily. The two tabs that go into the frame at the top do not. The rubber grommets that hold the tabs were extremely hard and did not want to let go. I found it was easiest to pop the center first, and then work SLOWLY and CAREFULLY on the upper two. Once you get one of the two upper points out the other comes out pretty easily, but getting the first one can be tough. Working slowly and carefully will get them off eventually without damage.

    The next task after removing the tank, seat, and side covers was to pull the carbs and airboxes. We knew that the carbs would need a rebuild after sitting, and we had no idea whether gas had been left in it or not. The airboxes are pretty easy to remove, one 10mm bolt at the top of the box that threads into the frame, one long stud that goes between both boxes and threads into brass nuts (which double as the center mount for the side covers), and one clamp on the carb boot. The black covers can be removed from the airbox by removing the long stud and releasing a tab at the top of the box. The covers can then be pulled right off. They might be a bit stiff because they fit tightly over the carb boots, but they'll pull right off. Removing the black covers is not necessary to remove the boxes, but you'll want to remove them to inspect the filter anyway, and I found removing the covers made removing the 10mm bolt a bit easier. The last step is to loosen the clamp on the carb boot and then pull the filter out and back and it should come right off the bike. Make sure you either bag and label the 10mm bolt or thread it back into the frame so it's not lost.

    CB350K3 Revival-fuel-air.jpgCB350K3 Revival-airbox.jpg

    After some cleaning, I decided that my stock airboxes were in decent shape, so they went back on as is. I will probably pull them later and replace the element with foam, but they're working fine for now.

    Once the airboxes were off the next step was to remove the carbs. The carbs are held onto the engine by the intake manifolds, just loosen a clamp and give them a yank and they'll pop off. To remove them completely you need to detach the throttle cables and the choke bracket. I found that it was much easier to do both of these things once the carbs were out of the manifolds. To remove the choke bracket, just loosen the bolt that connects to the choke bracket on the left carb. Once the bolt is loose you can just pop the bracket right off the carb. No reason to remove it from the right carb.

    CB350K3 Revival-choke_bracket.jpg

    To remove the throttle cables remove the adjuster bracket with a screw driver and then you can rotate the carb and cable around to allow the cable to slip through the slot in the mounting point on the throttle shaft.

    CB350K3 Revival-throttle_cable_1.jpgCB350K3 Revival-throttle_cable_2.jpg

    Pull the fuel lines off and the carbs will be free! Just be warned, sometimes the fuel nipples can pull out of the carb body along with the fuel line. This isn't a big deal, one of mine did it. I'll talk about how to address this later.

    We did a bit of looking once we had the carbs and tank off. The PO's son had used some kind of tank liner that was still holding up well, so we left that alone. It also looks like he drained the fuel from the tank and carbs before parking it. This was an extremely good idea, our carbs were really pretty clean on the inside because of this. If you are going to store a bike for a long time, DRAIN THE FUEL!!! Not just from the tank, make sure the carbs are dry as well. If you drain everything it will sit happily for years with no damage. If you don't, you'll have a pretty gruesome fuel system clean / rebuild in your future.

    At this point the intake manifolds were removed to check them from pliability and cracks. They were actually in good shape, so they went right back on. If you have any doubts, replace them. They can cause some weird / tough to diagnose vacuum and lean running issues. To end the day we stuffed a clean shop rag in each intake manifold to keep junk out of the cylinders. This is a good idea to keep things protected, but don't forget they're there when you reassemble!
    First Car: 1968 Mustang
    First Bike: 1971 CB350K3

  9. #8
    Senior Member Pops's Avatar
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    Great write up! I'm in the process of "refreshing" a friend's CB350 and went thru the carb removal and rebuild process just last week. Yes, it can be a real pain to remove and replace the plastic side covers without damaging the tabs. I've always tried to remember to squirt some silicone spray or WD40 on the mounting grommets before pulling things apart - it usually helps to make them more compliant. I know it's tempting to purchase cheap carb rebuild kits online, but do your best to clean and reuse all the brass jets that are already in the carbs. They're almost always better quality, and it's less expensive to simply buy the gaskets you need to reassemble the carbs. My carbs were in pretty good shape and came very clean after a day's soak in Simple Green, followed by spraying thru all the ports with aerosol carb cleaner and compressed air. I even managed to get the corroded chrome caps pretty presentable using some 0000 steel wool followed by chrome polish.
    CB350K3 Revival-img_0566.jpg CB350K3 Revival-img_0567.jpg
    Butch
    72 SL350 Basket Case

    Age and treachery will always overcome youth and enthusiasm

  10. #9
    Junior Member 68Ford's Avatar
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    Alright, short entry today.

    With the carbs off I packed them up and sent them off with my sister and dad to get rebuilt. Between the various configurations the Mustang has been in and all the small engines we have around, I have rebuilt my fair share of carbs, so I was happy to hand these off. My dad rebuilt one carb with my sister, and then let her rebuild the other on her own. They reused all the original brass parts, tested the slides, and did a bench sync. I had warned them about the felt washers on the throttle shaft before they soaked the carbs, so we were able to avoid drying them out and causing a vacuum leak. I don't have many details on the rebuild process because I did not participate, but one tip I have for people new to carbs is to pick up a cleaning kit for paint guns. They have lots of little wires and bore brushes that are perfect for the tiny passages in a carburetor. Soaking in carb cleaner and blowing out with compressed air is good, but you don't always get everything out that way.

    While they were working on that my task was to start cleaning up the bike and some of the parts we took off. First I just wiped everything down with soapy water to get rid of years of dust and grease. The next step for the seat was to use a vinyl cleaner on the seat. I used an old cut-up T-shirt to apply the cleaner. I did this a few times to make the seat shine and make the soften up a bit. The cleaner was followed up with several applications of a vinyl conditioner / protector, also using an old T-shirt. Pretty straightforward, but it really helped the seat. We also got lucky that the seat pan was not rusted out.

    To clean up the side covers and the tank I started with some rubbing compound just working slowly and really rubbing it in. After the rubbing compound I can back with polish and did the same as the rubbing compound, working slowly and really rubbing in in. I finished it all off with a coat of wax and then came back and hit the chrome trim and badges with a cleaner wax. I think it all came out pretty well. It's the best I can do without having a real buffer, and there is no way we were going to lose the original paint because it's just too nice.

    CB350K3 Revival-cleaned_cover.jpgCB350K3 Revival-img_20190527_150922_1560699283473.jpg
    Archangel likes this.
    First Car: 1968 Mustang
    First Bike: 1971 CB350K3

  11. #10
    Junior Member 68Ford's Avatar
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    Quote Originally Posted by Pops View Post
    Great write up! I'm in the process of "refreshing" a friend's CB350 and went thru the carb removal and rebuild process just last week. Yes, it can be a real pain to remove and replace the plastic side covers without damaging the tabs. I've always tried to remember to squirt some silicone spray or WD40 on the mounting grommets before pulling things apart - it usually helps to make them more compliant. I know it's tempting to purchase cheap carb rebuild kits online, but do your best to clean and reuse all the brass jets that are already in the carbs. They're almost always better quality, and it's less expensive to simply buy the gaskets you need to reassemble the carbs. My carbs were in pretty good shape and came very clean after a day's soak in Simple Green, followed by spraying thru all the ports with aerosol carb cleaner and compressed air. I even managed to get the corroded chrome caps pretty presentable using some 0000 steel wool followed by chrome polish.
    Click image for larger version. 

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    Thanks Pops, I appreciate it. Hopefully it can help someone one day. You got those carbs looking great! Our came out really nice as well. I was really surprised how well my dad and sister got the chrome caps to clean up despite all the dust and pitting.
    Archangel likes this.
    First Car: 1968 Mustang
    First Bike: 1971 CB350K3

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