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Discussion Starter · #1 ·
Hey everyone,

I'm sure you guys get these questions alot, so if there's a thread of a FAQ or something I missed, feel free to direct me there.

I'm in the planning phases of building an early 70's cl350 that a friend gave me. the bike is in pieces, and has sat that way for many years. He said that he tore it apart after the bike started smoking and lost compression.

This will be my first bike, and my first time rebuilding anything larger than a golf-cart engine. I've been watching alot of youtube videos, have downloaded the original service manual documents, and ordered a Clymers manual. It seems like a daunting task, but i'm in no real hurry to ride. I really would like to learn how to do this.

So with all of that being said, how far should I go with this? Should I go all the way to the bottom end of the engine? For a first time rider/builder, is it worth upgrading pistons/cam shaft? If so, are there pre-selected parts that are proven to work well together?

I appreciate any advice you guys are willing to share.
 

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Well... "started smoking and lost compression" sure looks like you'll need a ring job at the very least.
Most likely you will need to bore the cylinders to the next oversize pistons and rings.
Are the pistons and rings original size?
While there I would check the valves and guides also.
Your cams may be worn and need replacement as well.

Engine aside, how far you want to rebuild this bike is depending on you. Do you want to make it mechanically sound and ride it or did you want to restore it to stock or....?

I haven't worked on the 350 bikes before but I believe oversize pistons are readily available

https://www.ebay.com/itm/68-73-HONDA-CL350-0-5mm-OVERSIZE-PISTONS-SET-2PISTONS-INCLUDE-10-CB350KPS-1/162215405366?hash=item25c4caa736:g:0n8AAOSwAuZX5gbw&vxp=mtrb
 

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^^^agree, and I can add these thoughts. It's great to see you have interest in doing the work yourself - many join here and are intimidated by not having ever worked on bikes before, and paying someone else to do the work is not just a lot more expensive but can often lead to problems because there are few (if any) local shops today who actually have real experience with vintage Hondas. I think you'll find that it isn't as difficult as it seems once you get into it, and there are plenty of people here who can offer advice and info when you have questions, as well as a copy of the factory shop manual (FSM). That said, if you can cancel the order for the Clymer manual, do so and save your money - they are very often wrong and can mislead, and are better used as a doorstop or height adjustment for your computer monitor. In the case of something that old and that has apparently has gone through a major failure (possible piston damage based on POs description), it would be wise to plan a complete overhaul. the top end is the more challenging aspect of the engine, the bottom end is far simpler with only a few things to be cautious about related to proper assembly. As for upgrading internal parts for better performance, perhaps you should stick to stock parts for your first rebuild as aftermarket parts can often present complications and require additional modifications for compatibility than you'd be expecting in your first run through it all.
 

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Discussion Starter · #4 ·
Thanks for the info, 76TWIN,

As far as I know everything on the bike is original. I won't know for sure until tearing into it. My end goal is to have a brat-style bike, that's as stripped down as possible, that I can ride into work 20-30 miles on nice days.
 

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Discussion Starter · #6 ·
Thanks Ancientdad. I'd be lying if i weren't a little bit intimidated, but also excited. I've been watching the Saturdays Wrench series on youtube (again) and the episode where he's at Jeff Busche's garage talking about tolerances, and wear patterns are slightly terrifying. the thought of tearing the engine down, cleaning it up, replacing parts, and then reassembling it only to have missed something small would really suck. Then again, maybe it's not as difficult or as catastrophic as that.
 

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Look around in the forum for a FSM download and simply pay close attention to (and take lots of pictures of) everything during disassembly, then know that if you have questions about things during re-assembly there will be people here who can help. Many of us have either worked at the dealerships during the years these bikes were current or have done lots of work on them as a second life or hobby, and all have gone through most anything you will encounter. And, take some of what you see in videos on the internet with a bit of the "grain of salt" mentality... there are many out there who show how they do things that would make an experienced Honda tech cringe at their methodology. Remember that anyone can post to YouTube... and using a chisel to remove cam bearings before other parts have been disassembled in proper order is a bit like the stories of shadetree mechanics that you've probably heard
 

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Buy lots of zip lock bags and label them for your parts. Keep everything organized and you will be fine.
These old bike engines are relatively easy to work on.
 
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I always strip an unfamiliar engine down to the bare crankcases. Only way the clean out all the trash accumulated over the years.
 

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As someone who has been doing the same with a cb160 and started from an experience level of pretty much 0 (a couple tire/oil changes and a semi successful brake disc/pad replacement on a mazda), I'll share what has helped me.

Read and watch as many videos as you can, and take your time. Don't force things on these bikes, I've found they tend to break when you do. If you get frustrated take a step back and think about it, there's usually a reason things won't come apart/go back together.

There's a lot of really helpful guides on this site, sometimes you have to go looking for them but they are there.

Also if you put together a spreadsheet with parts you need, how much they cost and where to get them cheapest you avoid surprises and save money on parts
 

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Where are you located?

I would say this is a parts engine, or you can rebuild it, but I would settle for nothing less than full as mike in ID suggested.

The past 3 or 4 bikes I've picked up have been recently rebuilt by their previous owners, and all have needed to be redone. You can certainly do it yourself, but I would recommend you try and find someone to help you... or don't be surprised if you end up needing to do it over.
 

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Discussion Starter · #18 ·
I'm in the midwest. I definitely want to give it a go rebuilding it. I'm not really in a rush to get it running, so I'm ok taking it slow to make sure I understand what's going on, having it machined by a professional, etc.
 

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Were there any videos or articles that you found were musts to watch/read?
I don't know about the the 350s but any build threads in the project logs section or anywhere else that go through item by item are hugely useful.

There's a website called dansmc . com and it goes through all the areas of a motorcycle. It's not at all specific to honda twins but if you don't understand how any of the bits of a motorcycle work it's a good resource. He also tells you the by the book way to do it and the way that will work in practice.

I find that there's often a YouTube video for problems you run into, in particular there's a guy called dawino6260 that has a bunch of old honda videos. Quite a character though, don't watch his videos around kids.
 

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Welcome to the forum.

The mid west is a pretty big chunk of land, it's up to you, but if you were to disclose your location someone on the forum may know something about your area that could help you in the build...people, places, parts etc.

If the bike is original, in nice condition and proper running order then it is at it's peak value. If you chop it up the resale value won't cover the cost of an engine rebuild. The classifieds are filled, at least where I am, with "cafe racers, brats and bobbers" that started as nice twins. They sit for sale until the listing expires while the nice originals are snapped up almost immediately. The bike "building" craze of the last 10 years has chewed up and spat out a lot of quality vintage bikes and the thinning herd of originals continue to climb in price.

If the bike is to be restored to original then it is worthwhile to have the engine/transmission thoroughly gone over. If your going to chop the bike then honing the cylinders and throwing in some new rings may get you going.
 
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