Topic: '73 350F carb project

[TDBennett]

Hello SOHC/4 fans,
I recently inherited this 1973 350F, it had sit in my father's garage the past 3 years.  A friend of his mentioned that the bike was being driven regularly up until my father's health wouldn't allow it.  I've taken it to a local shop but the mechanic was hesitant to work on the carbs, claimed he couldn't find parts.  (bah)  Anyway, he said compression was good, and all the electrical checks out, replaced the front brake pads and it seems to run fair, at least until the plugs foul. 
I've only ever rebuilt one other carb and it was on a 1972 VW Beetle.  I'm confident I can do it but would like some guidance before I begin.  I've found a few online sources for parts but I'm always open to great suggestions.  My concern is the condition of the cast part of the carbs around the main jet.  Carb 3 is really pitted and worn and doesn't look like it would hold a good seal on the O ring.  a few of the others are worn as well but not to the extent of carb 3.  I have attached some photos, your input is coveted and much appreciated.
I'm very excited to have this project and look forward to riding again.
Thanks,
Tim

[TDBennett]

here are 2 photos of the 1973 CB350F.  I like it!

[Kevin400F]

While the exterior of the main jet holder is certainly pitted, the bore where the O-ring needs to seal is probably OK.   I've cleaned dozes of CB350F and CB400F carb sets.  From what I've seen so far, you should be fine, and plenty of folks here on the list are more than willing to help.

Keep us posted,

Kevin

[TDBennett]

thanks Kevin.
going to order the kits Monday morning.  got the floats in a jar now, we'll see how they are in the morning.

[hoodellyhoo]

What kind of kits did you buy and what do you plan on doing with them? I ask because in most cases you should be able to reuse all the jets and needles as long as they are clean and not tampered with and just replace the gaskets/orings. I bought a set of Keyster kits and the needle taper was noticeably different from my stock honda one.

[TDBennett]

this is the kit, http://www.oldbikebarn.com/Honda-CB350-F-73-74-Carb-Kits?sc=12&category=52236

I haven't really gone through the jets and needles yet, I plan to clean them and see what is reusable but I know most of the orings were shot.  I have a friend at work that is much more knowledgeable than I, I will defer to his thoughts once he inspects the old parts.  I bought four new kits, if I don't use them all I'll have spares.

I did see the Keyster kits on ebay, but did not purchase.

[Lars]

Agree, I always reuse the brass parts if possible. Sometimes the idle jet is very clogged. Be careful not to make to holes any bigger as you clean them. Let is soak a little in whatever you use in your country, compressed air is good to have. The tiny holes can be cleaned up by useing a hair from a steel brush or similar. I always replace all o-rings and gaskets. I do not think they are included in the kits with the brass. I especially think of the o-rings on the T piece of fuel supply to carb 1 and 2, 3 and 4.

It is a very nice bike!

[flybox1]

re: pic 3.
that brass tube, hiding in the tall post where your main jet goes.  with the hole in the middle.
gotta get it outta there. push it out from the other side when you take your slide and needle out. go easy on it.
its the emulsifier tube.  clean it with a bit of metal polish. has tiny holes along its sides.   clean and open them up with a strand of copper wire.
a new o-ring should seal your main jet just fine there. a little WD40 on it before you slide it into place.

[TDBennett]

thanks gentlemen, I truly appreciate the knowledge. 
what's a good product to soak these parts in?

[flybox1]

carb cleaner can be rough on the rubber bits between carbs.
a good soak in simple green then scrub with carb cleaner always worked for me.

[switchum]

I use chem dip. As log as you don't drop rubber parts or gasket they work quite nice. They last long time, too.


 

[TDBennett]

Got the kits installed, have everything except the o-rings for the adjustment screws.  thought those would have come with the kits.  oh well, will pick those up tomorrow along with some oil and a filter.  What oil are you guys running in your 350F's?

What I may need help with now is getting the getting the carbs synched.  I haven't a clue how to do this.  Guidance is much appreciated.  Oh, and setting the float levels, haven't done this either.

Hopefully I'll be riding this weekend.

Thanks again for the help.
T

[flybox1]

any non-synthetic 10-40w will do.
asking an oil question around here is dangerous.   
seems to start heated debates and frantic consumption of large quantities of popcorn.....

use the SEARCH function and the FAQ's for both bench synching(which only gets you in the ballpark of getting them perfectly tuned) and float adjustment tips/steps. 
tip: set the float heights to 24mms for your 350F, not 21mm's 

[Kevin400F]

Tim, save yourself some time and trouble and use the factory spec of 21mm for the floats.  24mm will cause it to run lean and more than likely it won't pull more than 60mph in high gear.

Been there, done that.

[TDBennett]

OK, got her together and running.  Now she just needs tuned real nice, as soon as I get some gauges.
You all have been very helpful, thanks so much.  I'm fortunate to have found this forum and this community.
Will post some pics and maybe a video once she is tuned real tight.
Thanks again, have a great weekend.
T

[TDBennett]

Have the gauges to synch the carbs but no adapters to fit the 5mm x .80 threads.  Do any of you gents know where to get these adapters or how to manufacture a set?
Thanks.
T

[flybox1]

click on the Assessories link on the left.

http://www.carbtune.com/

[TDBennett]

thanks for the quick reply, flybox, I've found what I needed from an ebay store.
I may have to open my own shop, I should be fairly knowledgeable after this project.
 

[flybox1]

www.motionpro.com also has the permanent (capped) brass ones.

[TDBennett]

synched and running pretty well.  had some blow by to start but after some tuning that has been corrected.
1, 2 and 4 seem to still be a little rich while 3 seems lean but I can't get it worked out.  Input welcome, please.

I think after the fall riding season I'll give the valves and timing and all that a going through.  The mechanic that couldn't find parts for the carb claimed that he checked all this before and all was in order but I think I can probably get her tuned a little better.  I don't know how much I trust his work.

Everything else is working like a champ.  Clutch cable broke while riding Sunday but I've got it working (rigged) until I pick up replacement.  So much fun to be riding again, I've put a couple hundred miles in since Saturday morning.

Thanks again for all the great input, guys.
T

[flybox1]

I think after the fall riding season I'll give the valves and timing and all that a going through. 

why wait?    riding is so much more fun on a dialed-in singing Four!
even if you're new to the process, it'll take you an hour +/- for each.
THEN, dial in your carbs, and enjoy riding until mother nature forces the garage door to close.

[TDBennett]

running very nice, had long ride this morning before college football started.  plenty of get up and go, 75 with some throttle left.

I do get a little lag at about 3500 rpm sometimes, any ideas.  but when revved above 4000 rpm it responds just fine.

Also, the air intake boots on carbs 2 & 3 keep slipping back and nearly coming off.  1 & 4 stay on just fine.  is there a trick to make these stay put or should I track down new parts?

thanks.
T