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Discussion Starter · #1 ·
I am planning on purchasing a Cb350 very soon (once I can find one) and want to get some ideas on what I can to do bump up the motor. What are some mods that will increase my power the most? Any suggestions or comments are welcome. Basically I want to have a quick little 350 but dont know what to do with these old motors. Thanks

· Registered
1,217 Posts
Cheap overbore kits are available on ebay; expensive kits are available from Todd Henning Racing

A set of Dyna coils and good wires are a must (use NGK plugs ONLY-Champions or Bosch plugs are poop), electronic ignition upgrades are out there, but as far as I know they are REALLY pricey (like $500). Get some Mikuni VM carbs (Sudco supplies 'em and will even set them up for you If you wanna go as far as cam (Megacycle – parts store item only) and headwork, check Todd Henning Racing for that as well...again, expensive but its the best stuff out there…

350s have a tendency to grind down their cam chain tensioners over time. Both stock replacement and trick ones are out there.

Clymer manuals used to have a repair manual in print that had a hop up section for 350s. Check Amazon or ‘da bay.

Honda go sideways!

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The thing to remember with the Honda 350 is that it is a 350. It will never be fast in the sense of any modern bike 500 or bigger. Don't get me wrong here I currently have 3 of them, but am not under any delusions about what they will do. If you are not going to be racing then I would look at making sure you have a really good running basically stock motor. On the track a few HP can make the difference. On the street, ridability and reliability are key. My current race motor would be great in a street bike, which is where it is going to go when I build a better race motor. The only thing it has that I would not do for a street motor is the ported head. I will be using that on my next race motor and replace it with a stocker.
1. Fresh bore or at least rings
2. Check the valves do a valve job if needed
3. Check the cam chain tensioner, replace rollers and slippers as needed
4. Check the cam lobes and rockers replace as needed. Note a type 1 cam has more lift if you can find one.
5. keep the stock carbs and replace the air filters with freer flowing ones
6. exhaust system. get rid of the mufflers for sure and hopefully the headpipes too.

The stock points won't float until after 12000 rpm. Keep them gapped and adjusted and they will be fine. As long as they are in good shape, the stock coils are fine. Check your plug caps. Stck carbs are fine and easy to use because of the soft throttle return spring. Bigger carbs won't help much since a stock motor can't flow much more air than the stock carbs can deliver. Mikunis will only give you more on top end usually at the sacrifice of mid-range and bottom end. Fine for a race bike, not much use on the street.
Now, take all the money you saved on your motor and spend it on tires ( I like the Avons or Bridgestone BT-45), suspension (get some decent shocks, replace your fork seals and oil, put tapered roller bearings in the steering head) and wheels ( I laced up WM3 dirt bike rims from e-bay to stock hubs using the original spokes). Do a search on here about brake (JohnnyB on here is the man and has the answers).

Remember it is only a 350 and will never be fast, but it can be way cool and handle really well.

Good luck,

Vintage racing - old guys on old bikes
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