Topic: 1973 CB350F top speed?

[Vfrman]

Hi, new guy here with a 1973 CB 350 F purchased less than a week ago from a retired Honda mechanic in Arkansas. It’s in great shape, all original except for the four to one. I’ve been writing it around and have noticed that Top speed is about *65 to 70 mph, and it seems to be stuttering a bit at times under full throttle, But not consistently. The hour or so I’ve ridden it in last few days is prob the most its been run in a year or so.

*I weigh ~235…am I the limiting factor? :'(

[willbird]

I have not messed with a 350F but across all of the SOHC IMHO the fuel line routing needs to be correct in order for them to get enough fuel to properly run WOT. Some successfully run inline filters but overall they often fail miserably. I'd check the petcock screen and look for "stuff" in the float bowls.


Bill

[newday777]

Welcome aboard the forum Vfrman
I haven't been on a 350F WOT since the mid 1970s but even at your weight you should be closer to 90 mph, so you have something amiss. Dirty carbs or as Bill says fuel flow issues. 

[willbird]

Welcome aboard the forum Vfrman
I haven't been on a 350F WOT since the 70s but even at your weight you should be closer to 90 mph, so you have something amiss. Dirty carbs or as Bill says fuel flow issues.

I have struggled with my bike with fuel cap venting too. I used a fore into one cap, took it apart once and reduced the amount of what looks like cotton wadded over a small hole inside, that is easy enough to diagnose though because issues vanish if you open and close the fuel cap. Mine acts up the worst when nearly full of fuel.

[Nurse Julie]

To be honest, I've found the 350 fours are pretty gutless and woolly to ride but you should get more than 70mph, down hill with the wind behind you.

[Vfrman]

Thanks to all / guess I have some fuel issues to run down.

[carnivorous chicken]

I'm 215 or so, and usually don't push my 350Fs past about 80, but there is still some room to the red line. I'd check fuel delivery, but also the standard 3k-mile tune up, spark advance, and compression.

[Tracksnblades1]

Make sure it’s getting fuel…

Then ride it like a CR125R two stroke….

Report back…😏

[ADW]

Hi, new guy here with a 1973 CB 350 F purchased less than a week ago from a retired Honda mechanic in Arkansas. It’s in great shape, all original except for the four to one. I’ve been writing it around and have noticed that Top speed is about *65 to 70 mph, and it seems to be stuttering a bit at times under full throttle, But not consistently. The hour or so I’ve ridden it in last few days is prob the most its been run in a year or so.

*I weigh ~235…am I the limiting factor? :'(

Nope. I'm at 235 and my '72 will pull 75mph all day long. Long upgrades and headwinds notwithstanding, but you should definitely get enough power to do 75 easily. Don't be afraid to rev it...it's gotta spin to make the power, I've ridden mine at 8200 rpm for extended periods many a time. It's a Honda! The 350 has damn near a gallon of oil in it so it's got plenty of cooling.

[Tim2005]

As above, it ought to top out around 90 and do 75 easily. Has it been stood up a long while? Maybe it just needs a service (the stuttering at full throttle suggests a problem exists, that should not happen) , or even the rings have stuck in their grooves and it has lost some compression. Also, you mention a 4 into 1, often the carbs need rejetting for them to get it running correctly

[scottly]

 Don't be afraid to rev it...it's gotta spin to make the power, I've ridden mine at 8200 rpm for extended periods many a time.

1+ The baby Hondas need to rev! The start of the red-line "wedge" on the tach is the maximum continuous RPM, and the end of the wedge is the maximum short term RPM.

[kslrr]

About 40 years ago, on the 405 in Southern California, I ducted down putting my helmet into the notch of the Cafe' style fearing and opened her up.  100mph at 10Krpm.  Maintained that speed for 5 minutes or so weaving in and out of traffic.  It was a blast.

[Vfrman]

Thanks for all the intel guys / I appreciate it. Looks like I have some things to check out.

[Tracksnblades1]

Thanks for all the intel guys / I appreciate it. Looks like I have some things to check out.

Check adjust, recheck adjust, check readjust, the points and timing until it’s spot on before going waist deep into the carbs..
Bad condensers and misadjusted points, can cause cut outs, misfires, and the high rpm stuttering you posted..

The 3000 mile checkup was a good starting point advise…it would be good while you’re there to verify the bowls are all full..

I got volunteered to help with my son’s buddies 836 carburetor woes. It turned out just to be points and timing only..It was a back brake only chopper..After a test ride, I’ll never ride it again.. I thought I was never going to get it stopped after a redlined  1-2..

[grcamna2]

Thanks for all the intel guys / I appreciate it. Looks like I have some things to check out.

Check adjust, recheck adjust, check readjust, the points and timing until it’s spot on before going waist deep into the carbs..
Bad condensers and misadjusted points, can cause cut outs, misfires, and the high rpm stuttering you posted..

The 3000 mile checkup was a good starting point advise…it would be good while you’re there to verify the bowls are all full..

I got volunteered to help with my son’s buddies 836 carburetor woes. It turned out just to be points and timing only..It was a back brake only chopper..After a test ride, I’ll never ride it again.. I thought I was never going to get it stopped after a redlined  1-2..

+1 to points and condensers:make certain the points are OEM stock of very good quality.

[seanbarney41]

 Don't be afraid to rev it...it's gotta spin to make the power, I've ridden mine at 8200 rpm for extended periods many a time.

1+ The baby Hondas need to rev! The start of the red-line "wedge" on the tach is the maximum continuous RPM, and the end of the wedge is the maximum short term RPM.

+2, I have never ridden a 350 four, but I know on the 550's if you short shift 4th to 5th, you won't be able to rev out to the top of fifth, unless you shift back down to 4th and rev it up!

[newday777]

I got volunteered to help with my son’s buddies 836 carburetor woes. It turned out just to be points and timing only..It was a back brake only chopper..After a test ride, I’ll never ride it again.. I thought I was never going to get it stopped after a redlined  1-2..

Like you I have no desire to get on another chopper the rest of my life.....

[HondaMan]

The Baby Four will get to the ton, although you may have to take 4th up to 90 first as the 5th is overgeared a bit.
If the fuel is old, start there: those tiny bores need fresh fuel, for sure.
Look also for the bowl vent lines for the carbs. There should be long, thin hoses on them that reach back up under the seat. Those MUST be there (many were often removed for various reasons) or else the float bowls won't be able to push the fuel up thru the mainjets above about 65 MPH because of the turbulence around the tiny air ports (if the hoses are missing). This is surprisingly important!
Air filter: does it have the whole stock airbox assembly in place, taking in air from behind your butt, under the seal? If that is gone, so is the top speed. It's REALLY important to have this in place on the Baby Fours (350F and 400F).

[scottly]

Since we have so little information, other than the bike won't go faster than 70, I would suggest pulling all 4 spark plugs and inspecting them.

[Vfrman]

3 more pieces of intel re- my top speed stutter:
1- there is a quarter-sized hole at the end of the header right before it connects to muf
2- it pissed fuel all over garage floor 2 nights ago. It was dripping from the #2 carb (from kick starter side), or at least thats where it was condensing into drops & falling. I had firgotten to turn the petcock off after last ride- but still- it shouldnt have done that. I gave it a few taps w brass hammer and it stopped
3- it has an upgraded ignition: no points

Today I will pull & inspect plugs. Yesterday I changed oil to Rotella T4 15w40 and no more slippage on test ride. Unfortunately I couldnt get the bolt off to change the filter. I read on here thats a common problem

[grcamna2]

I think the carbs. need to be removed and opened up to inspect,imo.  if it were my bike,that's the thing I would do first;there may be at least worn float valves.
I would get the carbs sorted,then look at the fuel tank inside,possibly a bit of rust from the tank getting into the carbs?   You can flush that out.

I look forward to see the condition of the spark plugs;remove them and keep them in order according to the cylinders they were removed from.

Is that a Pamco ignition ?

[M 750K6]

Electronic ignition. Is it still using the original advancer mechanism? Might be sticking = retarded ignition and you'll not get full power at higher revs. Can be checked it isn't sticky by removing the ignition plate, can also be cleaned and lubed, while you're there.

Whether it uses Honda’s advancer, or it is done electronically in the replacement ignition unit, it is worth using a strobe light, to check it is advancing. Don't know the curve for a 350, but the manual will contain this info.

[Vfrman]

Electronic ignition. Is it still using the original advancer mechanism? Might be sticking = retarded ignition and you'll not get full power at higher revs. Can be checked it isn't sticky by removing the ignition plate, can also be cleaned and lubed, while you're there.

Whether it uses Honda’s advancer, or it is done electronically in the replacement ignition unit, it is worth using a strobe light, to check it is advancing. Don't know the curve for a 350, but the manual will contain this info.

Hondaman on here says the digital thing a previous owner installed to replace the points may be poorly engineered. Would a strobe light confirm?  I dont have one nor know how to use one

[scottly]

That might be a Pamco ignition, which uses the stock mechanical advance mechanism.
What do the spark plugs look like???

[Vfrman]

That might be a Pamco ignition, which uses the stock mechanical advance mechanism.
What do the spark plugs look like???

Have not had time to check yet. I have the links to the manuals on here, I guess they will tell me proper ones to put back in & gap. Not asking you to look up for me but do u happen to know, and/or is there a better plug than what the manual says?