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7 Posts
Discussion Starter · #1 · (Edited)
Hey all,

I bought my first bike, a '70 CB350 a few weeks ago. Having next to no experience with engine-driven mechanics, and having never ridden, I figured it'd be a great adventure. So far, it has been, but it's just beginning; this bike, while running, still has a ways to go. I figured I'd make this thread to document that whole process, as well to ask for help without clogging up other forums.

Off the top of my head, here's the history of the bike: It was bought around 2009 by a mechanic who worked on it on and off for ten years, who then sold it to the guy I bought it from. The guy I bought it from learned on it, but was too short to comfortably ride it. He had a shop redo the wiring after he dropped it, and also swapped the gauges (for cheap gauges that read km/h, for some reason). He said his mechanic "friend" was never able to get it running right. Because of the dubious history of the bike, I don't want to take any chances and trust the work of others if anything seems off, so, if/when anything happens, I'm going to default to treating that part like a rebuild rather than a realignment/tune up.

When I bought the bike, here's the known problems:
  • It backfired a lot, both idling and while riding.
  • Was severely underpowered compared to a casually-ridden SR400 (i'd struggle to catch up to them when riding in residential neighborhoods, even; slow acceleration).
  • It will "sputter" and lurch forward at times, especially at the top end of 1st gear
  • Bike ran extremely lean (wouldn't run at all with the choke anywhere but open, idle mixture screw turned 4-6 full turns from bottomed out).

I figured a good place to start would be by pulling the carbs and rebuilding them, which I did, and it runs better (and actually ran with the choke closed). However, it's still finicky with the adjustments, and this morning, after putting in a recharged and reconditioned battery, I noticed the exhaust on the right side was cold; I'm thinking(/hoping) the timing is off on the right cylinder and it's not firing properly. It would certainly explain most of the issues I've been experiencing.

Here's my current to-do list:

[X] Rebuild carbs

[X] Recondition battery

[X] Compression test

[X] Check timing and points (maybe just swap points as a pre

[ ] Swap speedometer and tach

[ ] Attach back L turn signal

[ ] Tighten chain to spec

[ ] Tighten shift and kickstart lever

[X] Tighten clamp around R exhaust

[ ] Remove front fender

[ ] Swap turn signals for small LED

[ ] New fuel filter

[ ] New air filter

[ ] Locking gas cap

[ ] Front wheel lock/antitheft measures

[ ] New seat

If anyone has any suggestions or speculation, I'm more than open to hearing them. I'm not as concerned with being right about things as I am with having my bike run better than it did the day it came off the assembly line.

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7 Posts
Discussion Starter · #2 ·
Worked on the bike today. Compression test yielded 145(ish) on the left and 155(ish) on the right. Went ahead and checked the timing and found something peculiar: it looked like the points were set to fire off of the "T" instead of the "F" marks on the stator coil; and even those were off. I corrected this, slapped everything back together, reset the carb adjustments, and got her running again, this time much smoother. Before I could really take her for much of a ride, though, I noticed she was sputtering and losing power going up a small hill; after parking and taking a look, I noticed I'd forgotten to put the right spark plug boot on and had the petcock set to "off", so I fixed those, but still had to walk her home with a low battery, which is now on the charger. I'll take her for a ride tomorrow and see how she does.

Also figured out that the clamp I have on my R exhaust pipe sticks out just enough to get bumped when I kickstart the bike; all I had to do was turn it 45° down so it'd be out of the way.
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