Topic: CB350f Performance Questions

[Deltarider]

Delta: did you also know it was the only Honda that Sochiro actually bought for himself? After he stepped down as head of Honda in 1973 he rode it to work on the production lines (he liked to work alongside his employees, wearing the white coveralls with everyone else!).

There is a fellow here in Colorado who has a custom bike shop: he is a Japanese immigrant (1984) who worked at Honda when he was in High School (equivalent) on the production lines, and worked many times next to the aged Sochiro. His name is Axel (fitting for his shop?), and he said Sochiro was 'just a normal guy like everyone else, loved to work on engines'. And, he was still riding his 350F to work when Axel knew him!

Great story. Those white overalls (and gloves I believe) and the overall cleanliness on the workfloor have always impressed visitors from abroad. BTW, I hope the Japanese immigrant in Colorado knows about this forum. We dearly miss a member that knows how to read and write Japanese. Could be usefull the more since he even worked there at Honda.

[crazypj]

Friend of mine used to run a dyno,( he was drag racing a CB750, years before Kawaski Z1 came out)
Would dyno anything, 350F is only about 27bhp at the wheel, 350 twin about 32~33, consistent over multiple bikes and multiple runs.
He was telling me that even CB750 could get down into the high 20's when no servicing was being done and they were really worn (although he did say it was quite impressive that they ran at all,  )

[Deltarider]

350F is only about 27bhp at the wheel, 350 twin about 32~33, consistent over multiple bikes and multiple runs.

And that's why the 350Four was never sold in great numbers in Europe, in spite of it's beautiful designed engine.

[crazypj]

The price was also against it, why have less performance and lower power for more money

[andrewk]

Any 350F runs best at 9-10k RPM, anything lower and you're not riding it right.


Tom

Couldn't agree more.  These little fours are a total hoot all wound up too.  I saw a guy in my town ride his 350f all summer, never heard it hit 5k.  Poor bastard doesn't know what he's missing.   Wring 'em out, they love it!

[HondaMan]

Friend of mine used to run a dyno,( he was drag racing a CB750, years before Kawaski Z1 came out)
Would dyno anything, 350F is only about 27bhp at the wheel, 350 twin about 32~33, consistent over multiple bikes and multiple runs.
He was telling me that even CB750 could get down into the high 20's when no servicing was being done and they were really worn (although he did say it was quite impressive that they ran at all,  )

I completely believe that HP figure for the Baby Four, and my own CL350 would kick their butts, if testing one another. But when parked side-by-side at the local Steak-n-Shake, my twin was TOTALLY outclassed!

I have seen many 750s in real worn shape like you describe, too. One in particular: with the tranny in Neutral and the throttle wide open, it would not smoke, but would not reach 7k RPM, either. It felt like a 350 to ride, had 8 leaking valves with real loose guides, 70-80 PSI compression, and points burned so badly they had half their thickness gone. But, it started first kick (it was a chopper, electric start gone, tiny battery) and purred at idle as nice as could be, and was ridden almost daily until a car hit it. The bike got rebuilt, the engine bored 2 steps to .5mm, valve job & guides, and the next time it was burning the rubber off the 5.00 x 16" Harley rear tire.

SOHC4 bikes are tough!

Some day I hope to own a CB250F, too! All 17 BHP of it.

[crazypj]

LOL, I remember various 550 & 750's like that, customers wouldn't believe they were worn out.
 I do remember telling one guy with 750 to be REAL careful as it was now much quicker than it had been since he bought it.
Called shop about 35~40 mins later for us to pick up bike.
I was thinking some kind of engine problem, asked where he was and he said emergency room, busted arm, should have listened as he'd crashed it 
Surprisingly, this happened quite often, people had bikes 'fixed up' and tried to ride exactly the same as when things were way out of spec (running on 2~3 cylinders, etc)
 It did get the shop a lot of work, 'everyone'  just knew their friends were BS'ing, until 'it' happened to them 
Pretty sure you have similar experiences 

[HondaMan]

LOL, I remember various 550 & 750's like that, customers wouldn't believe they were worn out.
 I do remember telling one guy with 750 to be REAL careful as it was now much quicker than it had been since he bought it.
Called shop about 35~40 mins later for us to pick up bike.
I was thinking some kind of engine problem, asked where he was and he said emergency room, busted arm, should have listened as he'd crashed it 
Surprisingly, this happened quite often, people had bikes 'fixed up' and tried to ride exactly the same as when things were way out of spec (running on 2~3 cylinders, etc)
 It did get the shop a lot of work, 'everyone'  just knew their friends were BS'ing, until 'it' happened to them 
Pretty sure you have similar experiences 

Oh, boy, do I !

One in particular still makes me laugh. A rider (July 1972) brought in a K2 and said he wanted to "kick his Kawasaki and BMW buddies into a corner". He didn't have $$ for a big-bore or such, but "he had heard about a Honda Man who worked at this shop". I was behind the Part Counter as they took in his bike, just listening. I decided to take it on as my "personal project", as it was a K2 much like my own, a 3/72 build, IIRC. So, it had the 1-row final drive bearing, a great start.

I pulled out the emulsifier tubes and drilled them, jetted it up 5 to 115 mains and dropped the needles a notch so he wouldn't suffer too-rich sparkplugs all the time (this causes an undesirable low-end hesitation, which shows up below...). Then I set the idle air screws to about 1-1/16 turns, cut off 1/2 turn of the spark advancer springs, got some ND X24ES-U plugs (not easy to get in those days) and new points and condensors. I set the valve lash to all .004" and made sure the cam chain was snug. Then I set the static advance up 3 degrees, which put it just past the end of the full advance marks at 3000 RPM, and installed a 17-tooth countersprocket, Diamond XDL chain in place of the RK chain, and pulled out the final baffles, drilled 4 (or maybe 5, don't remember for sure) 1/2" holes in the last chamber of the muffler, and reinstalled the final baffles. It was a little throatier, but not too much so unless you knew the bike.  I also ended up setting the floats in the carbs to 24mm after a test ride, as it wanted to fall off power at about 110 MPH because the fuel wasn't draining fast enough. So, I drilled the airbox (as shown in my book) and put the bowl vents into the box to pull a little vacuum at speed and help deepen those bowls "up high". This let it pass 120 MPH easily.

The owner came back the next week and I rolled it out and started it up. He looked a little crestfallen when it just sat there and idled happily. I guess he thought it was supposed to be "lumpy" or something? He paid his bill and started up to ride off. When he got out in front of the shop, in 1st gear at about 2 MPH, he ripped open the throttle, which almost stalled the engine for a second and he started to fall forward. Then the fuel caught up and the front wheel lifted about a foot, which matched the opening in his mouth, as far as I could see when he zipped off.

The following weekend, he was back with 3 other 750 owners. They ALL wanted the same thing done to theirs: apparently he had gone back to Blandinsville that Saturday night and took all comers, the Z1, the Blue Streak, and even the R90S we had sold to one of his buddies. That Sunday found him on Main Street in Peoria, cleaning other clocks. After that weekend, I was waist-deep in 750 bikes for the whole rest of that year!

[HondanutRider]

...and you have to go and say all this in a topic about the "CB350F Performance"

LOL, I remember various 550 & 750's like that, customers wouldn't believe they were worn out.
 I do remember telling one guy with 750 to be REAL careful as it was now much quicker than it had been since he bought it.
Called shop about 35~40 mins later for us to pick up bike.
I was thinking some kind of engine problem, asked where he was and he said emergency room, busted arm, should have listened as he'd crashed it 
Surprisingly, this happened quite often, people had bikes 'fixed up' and tried to ride exactly the same as when things were way out of spec (running on 2~3 cylinders, etc)
 It did get the shop a lot of work, 'everyone'  just knew their friends were BS'ing, until 'it' happened to them 
Pretty sure you have similar experiences 

Oh, boy, do I !

One in particular still makes me laugh. A rider (July 1972) brought in a K2 and said he wanted to "kick his Kawasaki and BMW buddies into a corner". He didn't have $$ for a big-bore or such, but "he had heard about a Honda Man who worked at this shop". I was behind the Part Counter as they took in his bike, just listening. I decided to take it on as my "personal project", as it was a K2 much like my own, a 3/72 build, IIRC. So, it had the 1-row final drive bearing, a great start.

I pulled out the emulsifier tubes and drilled them, jetted it up 5 to 115 mains and dropped the needles a notch so he wouldn't suffer too-rich sparkplugs all the time (this causes an undesirable low-end hesitation, which shows up below...). Then I set the idle air screws to about 1-1/16 turns, cut off 1/2 turn of the spark advancer springs, got some ND X24ES-U plugs (not easy to get in those days) and new points and condensors. I set the valve lash to all .004" and made sure the cam chain was snug. Then I set the static advance up 3 degrees, which put it just past the end of the full advance marks at 3000 RPM, and installed a 17-tooth countersprocket, Diamond XDL chain in place of the RK chain, and pulled out the final baffles, drilled 4 (or maybe 5, don't remember for sure) 1/2" holes in the last chamber of the muffler, and reinstalled the final baffles. It was a little throatier, but not too much so unless you knew the bike.  I also ended up setting the floats in the carbs to 24mm after a test ride, as it wanted to fall off power at about 110 MPH because the fuel wasn't draining fast enough. So, I drilled the airbox (as shown in my book) and put the bowl vents into the box to pull a little vacuum at speed and help deepen those bowls "up high". This let it pass 120 MPH easily.

The owner came back the next week and I rolled it out and started it up. He looked a little crestfallen when it just sat there and idled happily. I guess he thought it was supposed to be "lumpy" or something? He paid his bill and started up to ride off. When he got out in front of the shop, in 1st gear at about 2 MPH, he ripped open the throttle, which almost stalled the engine for a second and he started to fall forward. Then the fuel caught up and the front wheel lifted about a foot, which matched the opening in his mouth, as far as I could see when he zipped off.

The following weekend, he was back with 3 other 750 owners. They ALL wanted the same thing done to theirs: apparently he had gone back to Blandinsville that Saturday night and took all comers, the Z1, the Blue Streak, and even the R90S we had sold to one of his buddies. That Sunday found him on Main Street in Peoria, cleaning other clocks. After that weekend, I was waist-deep in 750 bikes for the whole rest of that year!

[crazypj]

We can't help it 
Working in a shop gives you all sorts of 'interesting' customer stories 
Fitted new rear tyre for one guy, told him to take it easy first 100 miles or so.
 I didn't know until then that bike could 180 in it's own length AND use workshop wall to stop if you dumped clutch @9,000rpm while slightly leaned over 
We got to do the 'accident repair' as well, plus delivery to home address

[faux fiddy]

It took me over 35 years to finally get one myself. It's a wreck in appearance, but it looks like a gem in the rough to me: next summer it will rise again.

Did you ever find a top triple to pattern one  after?

[s_vandise]

Well I managed to replace the mains with #78's and some minor tweaks to the air mixture -- she happily pulls evenly and climbed up to 87'ish mph which isn't bad considering I'm not a 140lb japanese test rider.

This thing screams! It has such a unique sound that the neighborhood instantly knows it's my 350f putting along main street  Can't really go anywhere without people telling me stories of their 750's and 350 twins back in the day. There really isn't a whole lot I enjoy more than other people appreciating my work and it bringing back memories of their past bikes.

I appreciate the suggestion to use 78's instead of the stocks I was using. It's made a huge difference in performance.

Still have a long way to go in order to make this relic as stunning as it was back in '74!

[farmerobrown]

You folks are really making me get the 'F' fever. Farmer

[flybox1]

Well I managed to replace the mains with #78's and some minor tweaks to the air mixture -- she happily pulls evenly and climbed up to 87'ish mph which isn't bad considering I'm not a 140lb japanese test rider.

This thing screams! It has such a unique sound that the neighborhood instantly knows it's my 350f putting along main street  Can't really go anywhere without people telling me stories of their 750's and 350 twins back in the day. There really isn't a whole lot I enjoy more than other people appreciating my work and it bringing back memories of their past bikes.

I appreciate the suggestion to use 78's instead of the stocks I was using. It's made a huge difference in performance.

Still have a long way to go in order to make this relic as stunning as it was back in '74!

78's made all the difference in mine. 
+ air screw @ 1 turn out and 24mm float height seemed to take care of the richness at idle(stock airbox & 4 into 2's)

[HondaMan]

It took me over 35 years to finally get one myself. It's a wreck in appearance, but it looks like a gem in the rough to me: next summer it will rise again.

Did you ever find a top triple to pattern one  after?

I did, but then the guy with the CNC in his garage quit (where I worked) the next week. It took me almost 2 months to get the (cracked) tree back. I haven't found someone since then that would take it on.

[HondaMan]

We can't help it 
Working in a shop gives you all sorts of 'interesting' customer stories 
Fitted new rear tyre for one guy, told him to take it easy first 100 miles or so.
 I didn't know until then that bike could 180 in it's own length AND use workshop wall to stop if you dumped clutch @9,000rpm while slightly leaned over 
We got to do the 'accident repair' as well, plus delivery to home address

Then there was the guy who traded in his Bonnie for a CB750K0 at the Peoria shop...

We had only a standard 40" wide "people door" at that shop entrance, where we rolled the bikes in and out. This fella, with his almost 30" inseam pushing hard against those square side covers to hold up the bike, asked my mentor Jim to "take him through it", as he only had Brit bikes before (shifter and brake are backward!). So, Jim c-standed the bike for him, got him back on it, and took him through the routine there in the shop foyer. Off the stand and to the sidestand, Jim gave the guy the key and the nervous new owner walked the bike halfway through the door. Then he started the bike, pulled in the clutch, popped it into 2nd (Brits...), gave it Bonnie-like throttle (which became 4000 RPM) and started to let out the in-out box of a K0 clutch. He shot out the door, leaving a black mark on the floor (that was still there 2 years later), then stomped it down to 1st without the clutch (brake?), barely missed the telephone pole at the alley as he also narrowly missed the building across that pavement between us and the back-door neighbor's building while trying to lean it left (high COG?), and wobbled his way to the street. I could only hear him now, but we were laughing so hard I thought we'd cry: then we heard about 5000 RPM and a tire screech, followed by a bogging engine heading up toward Main Street.

The next day, the guy was back, wanting his Bonnie back. But, it had sold that same day to someone else, so he was out of luck. He left the 750 there for about a week before someone came and rode it off for him, presumably to his house?

I never did see that red K0 on the streets of Peoria after that...I think the guy probably had to change his shorts when he got home.

[faux fiddy]

It took me over 35 years to finally get one myself. It's a wreck in appearance, but it looks like a gem in the rough to me: next summer it will rise again.

Did you ever find a top triple to pattern one  after?

I did, but then the guy with the CNC in his garage quit (where I worked) the next week. It took me almost 2 months to get the (cracked) tree back. I haven't found someone since then that would take it on.

I've got a friend who might do them but he might want money to do it on a hitache. I was just asking him about what materials would cost, and suggested the 350  is one that gets snapped.  I have a few but the only one not installed is cracked, but he's done several, just did a batch for a guy that rebuilds Suzuki rg's.  I guess he  does more fork swap stuff. I've been wanting ignition parts, maybe he'd do one to get us trade for hondaman ignition parts.....?  I could send a picture of some he's done.  PM if you think about it... Sorry for the threadjacking...

[zeech]

I think people are afraid to wind up on any of the old Hondas. These bikes were build for top end RPM love. Crank it till it explodes (or gives you great power!) My 550 isn't happy unless it's above 7K

[crazypj]

He shot out the door, leaving a black mark on the floor (that was still there 2 years later), then stomped it down to 1st without the clutch (brake?), barely missed the telephone pole at the alley as he also narrowly missed the building across that pavement between us and the back-door neighbor's building while trying to lean it left
The next day, the guy was back, wanting his Bonnie back. But, it had sold that same day to someone else, so he was out of luck. He left the 750 there for about a week before someone came and rode it off for him, presumably to his house?

I guess we could start a thread for 'shop stories'

[s_vandise]

I've actually come across something while adjusting the tappets and such (one cover is rather stuck so excuse the noise). I'm not entirely sure where this knocking is coming from, my best judgment it the upper half of the engine. I'm leaning more to either a rod knock / worn bearing or piston slap. It doesn't get  louder when revved, but a real close listening you can hear it go faster.
I did hone the cylinders and put stock 47mm pistons in, rod bearings didn't show any signs of wear (at the time). I'm hoping to get some feedback as I intended to crack open the engine case again this winter anyway and get the cam chain adjuster working, rebore the cylinders, new valves, etc.

Video:
http://youtu.be/X0y6yqfIt7M

[flybox1]

If your valve lash is correct, and your timing correct, Readjust you cam chain, and then do a vacuum sync. 
The vacuum sync usually shirts much of the noises.

[s_vandise]

I've actually come across something while adjusting the tappets and such (one cover is rather stuck so excuse the noise). I'm not entirely sure where this knocking is coming from, my best judgment it the upper half of the engine. I'm leaning more to either a rod knock / worn bearing or piston slap. It doesn't get  louder when revved, but a real close listening you can hear it go faster.
I did hone the cylinders and put stock 47mm pistons in, rod bearings didn't show any signs of wear (at the time). I'm hoping to get some feedback as I intended to crack open the engine case again this winter anyway and get the cam chain adjuster working, rebore the cylinders, new valves, etc.

Video:
http://youtu.be/X0y6yqfIt7M

If your valve lash is correct, and your timing correct, Readjust you cam chain, and then do a vacuum sync. 
The vacuum sync usually shirts much of the noises.

I can guarantee that the timing is correct and I just adjusted the valve lash for the two (the tappet covers were stuck before). The rattling is gone like it should be -- the knocking still remains. I know the cam chain could be causing the noise, but im beginning to think it's a piston knocking around. I'll play with adjusting the cam chain (the automatic adjuster doesn't work ofcourse) and see if there is any improvement. So far .. none.

[ADW]

I'll comment since I have one of each.....

Spin it up 6000+ is its happy place.

Agreed. Mine seems to get "on the pipe" at about 6500 and pulls like hell (for a 350!) to 10k. You gots to rev these little suckers to get the power out of them, but MAN is it fun! LOVE the sound it makes!