Topic: 1973 CB350F "Freakshow Build" completed! Stay tuned for updates...

[Artfrombama]

I run the idle speed up until it will stay running then adjust the idle mixture screws.
Screw the idle mixture screws (the one you're pointing to) in until the engine loads up, then back out 1/2 turn.

As you go you'll have to twist the idle speed down, then adjust the mixture some more... Keep doing this until you have the idle speed where you want it.

For most Hondas, I think the "default" setting on the idle mixture screw is 1 turn out from lightly bottomed. That's where I start anyway.

[Sporkfly]

Awesome job Tim! Do we get a video of its "maiden voyage" too?

[mattcb350f]

Well done Tim!  

..I was gonna second Art's recommendation but you already figured it out I see.

My carbs always do that after a rebuild too.

..and now to second Arts other comment, turn in the idle speed screw to get the idle rpm up to where it runs on its own and then adjust the mixture.

These engines take a while to warm up and run right so get the engine warm too.

I have to leave the choke on at least partially for a few minutes before my 350 will run smooth on its own.

 Matt.

[Tim in Ohio]

Thanks guys.  I am sure I will be able to figure this out when I get home, but I take the comments to mean that the "idle speed screw" and the "idle mixture adjusting screw" are two different screws. 
Do I need to adjust the "idle speed screw" for each individual carb? or is there just one? 

[mattcb350f]

Thanks guys.  I am sure I will be able to figure this out when I get home, but I take the comments to mean that the "idle speed screw" and the "idle mixture adjusting screw" are two different screws. 
Do I need to adjust the "idle speed screw" for each individual carb? or is there just one? 

On the RIGHT side of the carb rack, between carbs 3 & 4 is a great big screw that adjusts the idle speed. Shouldn't be hard to find.

Stock speed is about 1200 rpm, but for starters, put it around 1500 till you get the mixture set then bring it down.

 Matt.

[TwoTired]

The carb sync makes all slides open the same amount in the bore at idle.
The main idle knob moves all the slides at once to set the idle speed.

The pilot screws on each carb or (Idle Air bleed screws) fine tune the mixture when the carbs are at idle setting.

If your bike is stock, (air filter and exhaust) then the factory setting of 1 and 1/2 turns out from lightly seated is the correct setting.  This setting allows the idle mixture to be rich enough that opening the throttle up to 1/2 total travel will result in smooth acceleration under load.
If the air filter and/or exhaust have been changed, then the factory setting may require alteration.

The farther the pilot screws are turned out, the leaner will be the idle mixture, and the less responsive the throttle will be to demand for acceleration.  Sudden throttle application will result is a wheeze, where the engine doesn't get enough fuel to pick up until the throttle position is reduced.
Mark your throttle and note the half way point of total travel.  If you engine doesn't respond smoothly to one half throttle travel under load, then turn the pilot screws in 1/8 turn at a time and check the throttle response again, repeat as necessary.

The stock bike will be best at 1 1/2 turns.  But, if it's not stock, you have to find the correct setting to correspond to the changes.

Cheers,

[Tim in Ohio]

Guys thanks for your help.  I got the idle set, and the air mixture screws set at the default 1.5 turns out.  I am still awaiting the Morgan carbtune but it was running so well I couldn't resist a short test run.  I took some video of the start of the maiden voyage.  It ran great.  Is the carb synching mainly for optimal performance... I guess I am asking, is there any risk of causing engine damage if I ride it around a little before I get a chance to synch those carbs? 

[mystic_1]

OMG!! Don't do that!! You'll destroy the.... nah, just kidding   carb sync mainly ensures smooth idle and low-throttle performance.  Won't hurt anything to ride it if you're in the ballpark.  Did you do a bench sync

cheers
mystic_1

[Tim in Ohio]

  Mystic...  You had my heart skip a beat there for a minute... good one.
Yes,  I did a rough bench synch.  I took it for a 17 mile spin...  including a short stretch on the highway.  I didn't want to flog it too hard.  I have heard that after an engine re-build one should follow the break-in procedures in the owners manual just like it was a new bike.  I did get it up to 70 mph for a short stretch without straining it too much.  It felt like a noticeable improvement over how she ran before the build! 

[scunny]

pat yourself on the back Tim. from scared noobie to seasoned wrench in one easy lesson.

[Tim in Ohio]

  Thanks Scunny.  I couldn't have done it with out you.  It is a great feeling of accomplishment.   

Noobs:  Go for it.  You can do this, with the help of these guys on this board.  Heck, I even know a thing or two now and may chip in a bit of input on YOUR build.

I appreciate the support of everyone who has contributed to this build.  I feel like I have made some new friends who share my passion for these old bikes.  It is a fun club to belong to.

I am not sure... Is this build thread a wrap??  Of course there are more things to do, and more threads to come on this bike...  carb synching... cosmetic work... maybe some mods like morphing it into a "micro touring bike" with the addition of hard saddlebags/panniers and a fairing?   But are these things "post build" items worthy of a separate thread.  Whattaya think guys, is this build done? 

[scunny]

keep it on the same thread, it's all "part of the journey"

[mattcb350f]

keep it on the same thread, it's all "part of the journey"

Yup. Think of this thread as your bikes thread. Keep track of changes and interesting things on here.

Might be time to update the subject line though...

I'm almost sad you're done now                But now I can look at some of the other projects on here.

 Matt.

[hoodellyhoo]

I'm almost sad you're done now                But now I can look at some of the other projects on here.

 Matt.

Me too! I was enjoying those daily updates for quite a while.

Great Job Tim!!!! I totally agree, anyone can do this because that's just how great the folks are on this forum.

[Artfrombama]

Nice work!
Was the journey more fun or the destination? (Referring to the rebuild)

[Tim in Ohio]

Matt, Hoodelly, Art...  You guys have all been a tremendous help.  Thanks.

(Matt-  hehe, I didn't know I could change the neame of the thread... good tip)

No worries mates, it ain't over...  heck naw...  It's just getting started. 

[Tim in Ohio]

BTW-  how do I change the thread title?   

[Tim in Ohio]

Nice work!
Was the journey more fun or the destination? (Referring to the rebuild)

Art it was all fun-  but there were times when I got a little twitchy wanting to get it done before winter set in .  A great experience...  Now that I know it runs like I want it to, I can relax and start making some changes to how it looks, etc.  Hard bags for sure, probably a fairing.  I want to use the bike for my daily 50 mile round trip commute when weather permits.

[mattcb350f]

BTW-  how do I change the thread title?   

If you change the subject line of your very first post, it will show up in the project forum like that. In other words, the first subject line is what the thread is labled for all to see and subsequent replies to the thread will be labled that too.

 Matt.

[kghost]

Well done 

[Spikeybike]

fantastic job my friend     and very timely indeed

i too will miss the daily updates

[dagersh]

Bravo Tim!  Its been a fun and informative read.  Keep it up!

Gersh

[Tim in Ohio]

Hey friends.  I got my Morgan carbtune.  Very pleased with it.  I will create a whole separate thread on the carb synching process and show you guys how the thing performs.  I did some initial fiddling with it...  hoo boy, my carbs were WAY out of synch.  The synching process isn't technically difficult, but a minor adjustment to one carb causes the others to change as a result it is a little more challenging to dial them in than I had thought it would be.  No fault of the tool though... it is great and I am very glad I got it.  Like I said, we will have fun with that later.

One interesting thing that did come to light... when I did get the vaccuum readings on all four carbs to match up relative to one another, the actual nominal reading on the gauges was on the low side of the spec range. The manual says they should all be within 3 cm-hg of one another and that the value should be between 16 and 24 cm-hg. Well, mine were reading at just barely 16 maybe a bit under.  I suspect the airbox isn't as airtight as it should be and thus not allowing strong vaccuum to build.  (I have a replacement one on the way that I got from a member of this forum... I'll give him props after I get it.)
For a couple of reasons, I decided to pull the carbs and do some tweaking before continuing on with the carb synching.  I had not done a float height inspection...  for one.
So that brings me to today's question.  My manual says that the "standard height" for the float level when just touching, but not compressing the valve spring is 21mm.
Mine all measured 24 or 25 mm:


Now, I ask you tech wizards... what are the likely effects of this condition? 
Here is a theory, is it technically sound?:  The airbox is leaky... which would tend to cause a lean mixture all other things being equal.  To compensate, the floats have been adjusted out of spec to provide more fuel.   Net effect, mixture balances out OK... but vaccuum is low.
This is all just me trying to think like a motorcycle.  Am I on the right track or is there a fundamental flaw to my logic?   Should I adjust those floats to 21mm?

[TwoTired]

The float height is NOT measured to the lowest point the floats will swing, but rather the position of float swing as it just closes the float valve.

Cheers,

[MCRider]

The float height is NOT measured to the lowest point the floats will swing, but rather the position of float swing as it just closes the float valve.

Cheers,

He mentioned in his text that was how he was doing it. to the point: "My manual says that the "standard height" for the float level when just touching, but not compressing the valve spring is 21mm."