Topic: 350F Gearing

[The Mayor]

I'm looking at replacing my crusty old chain, and was reading around some on the web and came across a bit about the 350F being "overgeared" and that "losing a tooth" would close the gap on it's 0-60 time somewhat significantly...
Have any of you messed with the 350's stock gearing? Good/bad results? Realizing that I'd be losing some top-end speed (not like I'm driving this thing on long distance highway trips anyhow) what could be done/recommended to make my old 350F a little zippier around town?

[socalenduro]

im looking to do the same thing, some say that you might not actually loose top end speed as the bike has a hard time pushing 5th gear anyway..... i know i cant get mine to redline in 5th.
im going to drop a tooth in the front shortly

[wdhewson]

Hi:  Let me know how this turns out as I am re-doing a 1971 CB350F right now.  Both sprockets seem to have minimal wear on the teeth, but the chain seems a big "long". 

I generally like tall gearing because of long riding with tailwinds in my area.  Coming home I can always drop into 4th.  Don

[The Mayor]

What's involved in this process? (sorry, newbie!) I can't redline in 5th either, and think the extra low-end torque would be very welcome.
Where do I find a front sprocket that accomplishes this? And how's that affect the chain and rear that I need to replace?

[333]

First, chain and sprockets NEED to be changed together.  They all wear at the same rate.  If you do one and not the other, you'll be swapping it out in about 10% of it's normal life.  Second, only go down one tooth on the countershaft.  I'm not sure what's on the market these days, one may be the most you can get.  Going smaller on the countershaft (front) sprocket give the engine more advantage over the rear sprocket.

These bikes top out around 85 with stock gearing(if you can pull redline).  Mine is stock, and on a cool day (these air cooled bikes like it in the 50s), and on level ground, I can tuck and pull redline, without having to go "Rollie Free". *




* See Dukiedook's avatar

[Jarhead12]

So you cb350f tops out at 85 at 5th redline? That doesnt seem like stock gearing. Mine seems to says its going 75mph at 8000rpm..... or is my speedo screwed up hahah

[HondanutRider]

I believe on the 350 Four if you hit red-line in 5th you will be pulling just over 100mph.  Reaching that level seems to be a bit of a stretch on these bikes - you need a tailwind or downhill, with a full tuck.  Dropping down to 4th, red-line is much more feasible to reach.

However, just tonight, on level road with some crosswind, I was able to easily pull an indicated 80mph on my 350F.  Mind you, that "easy" was a still a lengthy build-up compared to a simple rush on bigger bikes.   But, there was still some forward momentum building before the roll-off.

[Gordon]

These bikes top out around 85 with stock gearing(if you can pull redline). 

While this may be true for your particular bike, it's not true for all stock 350F's.  I've owned a stock 350F that would do an indicated 105 (probably more like 95 or 100 in reality), and Heffay's stock 350F will do over 100, too. 

[Jarhead12]

Yeah mine seems to go pretty good and i'm sure it will do over 90 and maybe hit a hundred. What tires do you use that have a good speed rating?

[Gordon]

Yeah mine seems to go pretty good and i'm sure it will do over 90 and maybe hit a hundred. What tires do you use that have a good speed rating?

I think you'd be hard-pressed to find a tire that couldn't handle the speed that a 350F can muster. 

[HondanutRider]

Yeah mine seems to go pretty good and i'm sure it will do over 90 and maybe hit a hundred. What tires do you use that have a good speed rating?

Good speed rating?  Heck, on a light bike like these, a quick side gust is liable to blow you over if you're not alert at those speeds - so speed ratings are your least concern.  (And I agree, most tires can handle the mustard of a 350F. )

[Gordon]

Good speed rating?  Heck, on a light bike like these, a quick side gust is liable to blow you over if you're not alert at those speeds

You ain't kiddin!  The few times I had my 350 up to the ton the front end would start to float off the ground.

[Jarhead12]

haha ok i was just checkin. Has anyone ever turbo-ed one of these bikes?

[333]

Okay, I don't want to get into an argument here, but both Cycle magazine and Cycle Guide did tests on this bike when they first came out.  Both put the top speed at around 85, although Cycle Guide specs the speedo off by about 10%.  Specifically, they said that "At a true 63 MPH, the speedometer is reading 70".

So you guys can beat your chests and say "mine goes faster", but...

No, it doesn't.

[Gordon]

Okay, I don't want to get into an argument here, but both Cycle magazine and Cycle Guide did tests on this bike when they first came out.  Both put the top speed at around 85, although Cycle Guide specs the speedo off by about 10%.  Specifically, they said that "At a true 63 MPH, the speedometer is reading 70".

So you guys can beat your chests and say "mine goes faster", but...

No, it doesn't.

So you say you don't want to get into an argument, but then proceed to call me a liar.  

You have my permission to believe whatever you want, be it a magazine article or your poor-performing CB350, but I'll continue to go by what I have actually done myself and seen with my own eyes. 

[333]

First off Gordon, is yours bone stock, exhaust and all?  Mine's not.  Stock size tires? (The actual outside diameter is different between same size tires from different manufacturers, much less converting to metric).  Mine's not.  And finally, were you trusting your speedo, or were you clocked with radar?  I was actually doing neither.  I was trusting the magazines.  The guys who were equipped to do relatively scientific tests.

But more importantly, there is a big difference between calling one a liar, and saying someone is wrong.  I'll admit, I was not specific.  I'll correct that right now.

If you think you did the ton on a "bone stock" CB350F-  You're wrong.

[Gordon]

But more importantly, there is a big difference between calling one a liar, and saying someone is wrong.  I'll admit, I was not specific.  I'll correct that right now.

If you think you did the ton on a "bone stock" CB350F-  You're wrong.

Thanks for clarifying the "liar" part, but generally when I say I've done something and somebody tells me I haven't, I consider that being told I'm lying, and I think most other people would, too. 

As for "bone stock", I have to admit it wasn't.  It had the common slip-on 4-2 mufflers that are prevalent on many 350F's, which I don't think would increase the performance at all, and a small windscreen attached to the bars which probably decreased the drag normally caused by the riders upper body and head. 

As for the speedo, I already said I did an "indicated 105, which was probably more like 95 or 100 in reality". 

Heffay's 350 is not bone stock either, but the only differences are the mufflers and handlebars (drag bars IIRC), which would also decrease the drag from stock configuration.  On at least two separate occasions we were riding together at a speed of what the speedometer on my 750 was showing to be 110, and from radar clocking I know my 750 speedo to be off by 10%. 

Perhaps the decrease in drag from the rider's body is all it takes to get the humble 350F up to the ton. 

[333]

Even a small 1/4 fairing is HUGE.  It'll get the wind off of you from the chest down.  Easily can tuck in behind it and get maybe 5 MPH.  4 into 2, certainly enough scavenging affect to notice some power increase.  Not as much as a 4 into 1.  But it was certainly faster than a stock one.  I think your flaw was trusting the speedo.  These early speedo's were notorious for not being accurate.  Most magazine's of the day noted this.

And I never thought you were a liar, Gordon.  I've always known you as an honest prick!

[The Mayor]

Damn! Anyhow, I should be getting new chain and sprockets in today. As well as a hondaman ignition! Best Wednesday I've had in a while! I ended up dropping a tooth on the front, left the back alone. Newb or not, I'll check back in with my findings.

[The Mayor]

Well, part 1 is done. Replaced the stock 17 front with a 16 tooth JT sprocket, and threw on a new DID chain - all for $60.

First off - WOW.

I had no idea how much a new chain thats not completely spent (like the old one was) would make a difference. The smoothness is incredible.
As for the gearing, I'm digging it. Where I felt like I had to rev it a bit before I took off in 1st, it now just goes. I'm racing threw the gears but it's much more spirited around town.
On the highway, you hit 5th fast, but once you get used to it, I still think it's an improvement. I'm running about 6100-6300 @ 60mph, which is nice actually, cause I'm out of my flat spot and able to get more response for maneuvering thru traffic. Since I'll rarely see 75+ I don't see the higher rpms being much off an issue - if anything, I feel like it's more likely to see the redline in 5th where before it was near impossible.

Should be getting the hondaman ignition today

Other thought... I kept my old rear sprocket on - it look serviceable and thought I'd try and save a $. I've read that it might wear out the new chain faster than if I had a new one...
Anything I should look for to see if it's fitting OK with the new chain? And if I were to replace it - would it be worth it to try for an aluminum one to drop weight or would it be a negligible difference?