Author Topic: 1973 CB350F "Modest Original" build  (Read 101597 times)

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Offline iiAtlas

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Re: 1973 CB350F "Modest Original" build
« Reply #475 on: December 07, 2016, 11:32:26 AM »
Atlas,
How did it run before the work? Did you change anything inside the points cover,cam chain/valve adj. ?

It didn't run!  Managed to make it work without removing carbs (mixture screw, carb cleaner) but was only running on one cylinder and only still only revving to 5k.  Then moved on to adjust static timing, set points gap, cam chain tensioner, and valve lash.  Same behavior.  Then decided it was a must to remove carbs so did that, rebuilt twice and now still same behavior!

Offline grcamna2

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Re: 1973 CB350F "Modest Original" build
« Reply #476 on: December 07, 2016, 11:45:00 AM »
Well,if it was me I would remove the points plate and take ea. pair of points and clean the contacts(I use light wet/dry 800 grit sandpaper folded in half in small strips myself)if they are still in 'ok to use condition'. BUT! before that:
I would remove the points cover and run the bike as-is first,run the engine same as you did in the last video and keep an eye on the points to see if you have any excess sparking('arcing') coming off them.
75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
  I love the small ones too !
Do your BEST...nobody can take that away from you.

Offline iiAtlas

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Re: 1973 CB350F "Modest Original" build
« Reply #477 on: December 07, 2016, 11:46:12 AM »
Well,if it was me I would remove the points plate and take ea. pair of points and clean the contacts(I use light wet/dry 800 grit sandpaper folded in half in small strips myself)if they are still in 'ok to use condition'. BUT! before that:
I would remove the points cover and run the bike as-is first,run the engine same as you did in the last video and keep an eye on the points to see if you have any excess sparking('arcing') coming off them.

Thanks grcamna, I will do just that!  Also thinking it could be the mechanical advance?

Offline grcamna2

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Re: 1973 CB350F "Modest Original" build
« Reply #478 on: December 07, 2016, 11:54:33 AM »
Well,if it was me I would remove the points plate and take ea. pair of points and clean the contacts(I use light wet/dry 800 grit sandpaper folded in half in small strips myself)if they are still in 'ok to use condition'. BUT! before that:
I would remove the points cover and run the bike as-is first,run the engine same as you did in the last video and keep an eye on the points to see if you have any excess sparking('arcing') coming off them.

Thanks grcamna, I will do just that!  Also thinking it could be the mechanical advance?

The condensers don't age well and will make the points 'arc' and that cooks the points pretty fast,that's my guess at this point.. and that can kill any spark going to the plugs to fire the fuel mixture which can look very rich.
75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
  I love the small ones too !
Do your BEST...nobody can take that away from you.

Offline iiAtlas

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Re: 1973 CB350F "Modest Original" build
« Reply #479 on: December 07, 2016, 11:55:55 AM »
Well,if it was me I would remove the points plate and take ea. pair of points and clean the contacts(I use light wet/dry 800 grit sandpaper folded in half in small strips myself)if they are still in 'ok to use condition'. BUT! before that:
I would remove the points cover and run the bike as-is first,run the engine same as you did in the last video and keep an eye on the points to see if you have any excess sparking('arcing') coming off them.

Thanks grcamna, I will do just that!  Also thinking it could be the mechanical advance?

The condensers don't age well and will make the points 'arc' and that cooks the points pretty fast,that's my guess at this point.. and that can kill any spark going to the plugs to fire the fuel mixture which can look very rich.

Neat! Luckily that is one thing I can do without removing the exhaust...

Offline RAFster122s

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Re: 1973 CB350F "Modest Original" build
« Reply #480 on: December 07, 2016, 12:12:48 PM »
Stay away from the cheap chinese Daichi points and condensors...truely crappy product.
A new set of condensors is a wise part replacement if you have not changed them, or if you used the Daichi parts.  Get a good quality condensor, Tec, NippoDenso, etc
David- back in the desert SW!

Offline grcamna2

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Re: 1973 CB350F "Modest Original" build
« Reply #481 on: December 07, 2016, 01:37:39 PM »
What was the result of checking the points Atlas ?
75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
  I love the small ones too !
Do your BEST...nobody can take that away from you.

Offline MoMo

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Re: 1973 CB350F "Modest Original" build
« Reply #482 on: December 07, 2016, 02:07:20 PM »
Air screws control idle so most likely not applicable to your problem.  Floats level should not affect high end either.  From your description I was fairly certain air filters were the culprit..Is the spark advance working correctly?...Larry

Offline iiAtlas

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Re: 1973 CB350F "Modest Original" build
« Reply #483 on: December 07, 2016, 04:08:04 PM »
Stay away from the cheap chinese Daichi points and condensors...truely crappy product.
A new set of condensors is a wise part replacement if you have not changed them, or if you used the Daichi parts.  Get a good quality condensor, Tec, NippoDenso, etc

Thank you for the warning!

What was the result of checking the points Atlas ?

Air screws control idle so most likely not applicable to your problem.  Floats level should not affect high end either.  From your description I was fairly certain air filters were the culprit..Is the spark advance working correctly?...Larry

No worries MoMo, I am sure the old girl is happy to be breathing more freely now.  As for the points..


I can notice the occasional spark at idle, under acceleration, and under deceleration.  You can see a few in the video above, and a few more below.

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In this video I tried to capture the mechanical advance action.  I couldn't see much but maybe you all with a keener eye can sniff something out.  I was attempting to avoid removing the points plate and having to redo the timing at least until tomorrow AM, so this will have to do for now.

How much spark is too much?  Is this an indication of bad points? Condensor? etc?  Would be curios to know as I have know ballpark for this.  Cool to see!



Also note the plugs indicating a very rich condition and wet with excess fuel.  These are after a "plug chop" at 5.5k rpms.

I found new OEM points on 4into1..

http://4into1.com/genuine-honda-points-left-30204-286-004-cb350-cb360/
http://4into1.com/genuine-honda-points-right-30203-286-004-cb350-cb360/

But nothing yet on an OEM quality condenser.  A lead on that would be great!

You guys are the best!

Offline grcamna2

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Re: 1973 CB350F "Modest Original" build
« Reply #484 on: December 07, 2016, 04:48:34 PM »
Hi Atlas,
You would do best to replace both condensers w/ new ones that have less than 5yrs. shelf life;I spoke w/ HondaMan about this and he said when the condensers sit for a while w/o running the bike they degrade and shouldn't be trusted.While you're replacing them I would carefully inspect the coil cases for any cracks where wax is leaking from them(when you set the static timing don't leave the key on for more than 30 seconds;a self powered continuity tester w/ it's own batteries is best)and hopefully your coils are still good.The points are probably badly burnt beyond cleaning.
I had another thought on the plugs being SO rich;make sure you don't still have any brass parts in the carbs. that isn't oem Honda stock.The aftermarket carb. kits are notorious for supplying new emulsion tubes/needle jets and new slide needles.. I would make sure to remove them if they aren't stock as they will usually mess-up your jetting.
75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
  I love the small ones too !
Do your BEST...nobody can take that away from you.

Offline MoMo

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Re: 1973 CB350F "Modest Original" build
« Reply #485 on: December 07, 2016, 05:33:43 PM »

Atlas,  my question about the spark advance made a bit clearer,  does the advance work with a timing light attached? It could be rusted.

Offline iiAtlas

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Re: 1973 CB350F "Modest Original" build
« Reply #486 on: December 08, 2016, 06:31:41 AM »
Hi Atlas,
You would do best to replace both condensers w/ new ones that have less than 5yrs. shelf life;I spoke w/ HondaMan about this and he said when the condensers sit for a while w/o running the bike they degrade and shouldn't be trusted.While you're replacing them I would carefully inspect the coil cases for any cracks where wax is leaking from them(when you set the static timing don't leave the key on for more than 30 seconds;a self powered continuity tester w/ it's own batteries is best)and hopefully your coils are still good.The points are probably badly burnt beyond cleaning.
I had another thought on the plugs being SO rich;make sure you don't still have any brass parts in the carbs. that isn't oem Honda stock.The aftermarket carb. kits are notorious for supplying new emulsion tubes/needle jets and new slide needles.. I would make sure to remove them if they aren't stock as they will usually mess-up your jetting.

Interesting about the condensers going bad from sitting.  I will look for a high quality set but so far it's been difficult!  Points I have found OEM.  Expensive at $22 per point but worth it to go Honda I am sure.  One of my least favorite things about this bike is the gas cross feed tube on the bottom of the tank.  Your only option should you need to remove it (coils, condensers, etc) is to spill gas EVERYWHERE!!

Does the sparking you see from the previous videos indicate bad points?

Atlas,  my question about the spark advance made a bit clearer,  does the advance work with a timing light attached? It could be rusted.

We've only played with the static timing so haven't checked with a gun yet, but I will do that next!  It does look somewhat rusty back there.  Hard to see, could just be oil buildup.  Only way to know is to take that plate off or use the timing gun.  Thanks Larry.

Another thing I forgot to mention last night.  BOTH float bowls are leaking out the seam.





This to me indicates either a bad seal (though it is a new o-ring) or improper float height.  Something important to note is that before when the bike would not rev past 5.5k the float bowls were not leaking.  So I am keen to say this is not THE source of the problem, though I would still like to fix it!  No gas out the overflow tubes so either they too are clogged (I just cleaned them thoroughly..) or something else is happening.

Anyways as always I really appreciate you all chiming in here and helping me get this bike back on the road!

Offline 540nova

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1973 CB350F "Modest Original" build
« Reply #487 on: December 08, 2016, 07:37:53 AM »
Motion Pro makes a quick disconnect for your fuel balance tube. Eliminates fuel mess when you have to remove the tank. Highly recommended.


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« Last Edit: December 08, 2016, 07:39:36 AM by 540nova »

Offline iiAtlas

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Re: 1973 CB350F "Modest Original" build
« Reply #488 on: December 08, 2016, 07:42:15 AM »
Motion Pro makes a quick disconnect for your fuel balance tube. Eliminates fuel mess when you have to remove the tank. Highly recommended.


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Holy crap that is AWESOME!  I am so ordering one of those...it is awful frantically rushing to plug those hoses while fuel sprays everywhere...

https://www.amazon.com/Motion-Pro-System-Disconnect-Coupling/dp/B000WJ8XGC

Offline 540nova

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Re: 1973 CB350F "Modest Original" build
« Reply #489 on: December 08, 2016, 07:47:24 AM »
Available in black or white


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Offline iiAtlas

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Re: 1973 CB350F "Modest Original" build
« Reply #490 on: December 08, 2016, 07:48:13 AM »
Available in black or white


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Black please  ;)

Offline MoMo

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Re: 1973 CB350F "Modest Original" build
« Reply #491 on: December 08, 2016, 07:51:55 AM »
Trick is to clamp the hose , pull it off the other side and quickly put your finger over the other outlet.  Served me well for many years but that shut-off looks to be the cats pajamas.  Put a timing light on while it is running to eliminate the advance..  Best of luck and keep up the good work Atlas

Offline iiAtlas

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Re: 1973 CB350F "Modest Original" build
« Reply #492 on: December 08, 2016, 12:58:39 PM »
Trick is to clamp the hose , pull it off the other side and quickly put your finger over the other outlet.  Served me well for many years but that shut-off looks to be the cats pajamas.  Put a timing light on while it is running to eliminate the advance..  Best of luck and keep up the good work Atlas

Hah!  Good trick Larry.  I will try that.  I figure the quick disconnect is a good safety feature for the current owner should he ever need to remove the tank over a hot engine  :)

Offline grcamna2

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Re: 1973 CB350F "Modest Original" build
« Reply #493 on: December 08, 2016, 01:30:17 PM »
Trick is to clamp the hose , pull it off the other side and quickly put your finger over the other outlet.  Served me well for many years but that shut-off looks to be the cats pajamas.  Put a timing light on while it is running to eliminate the advance..  Best of luck and keep up the good work Atlas

Hah!  Good trick Larry.  I will try that.  I figure the quick disconnect is a good safety feature for the current owner should he ever need to remove the tank over a hot engine  :)

I couldn't agree more,it's a real PITA over a hot engine..  :o
75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
  I love the small ones too !
Do your BEST...nobody can take that away from you.

Offline iiAtlas

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Re: 1973 CB350F "Modest Original" build
« Reply #494 on: December 09, 2016, 07:02:08 AM »
Plan of attack is as follows..luckily none should involve removing that damn exhaust!

First, I will try to touch up the points with sandpaper or a fine file. I know filing points is typically a no-go but since these are considered shot I figured I would give it a try.  If they show any sign of improvement I will know this was the source of my problem and replace.  Then I will re-gap them and redo the static timing, then check the timing and full advance timing with my timing gun.  If there is any sign of improvement here I will know I'm on the right track and will replace condenser, and OEM points.

If none of that solves the problem or it looks like the mechanical advance is at fault, I'd consider switching this bike over to a Pamco electronic ignition: http://www.cb450ignition.com/Index350.htm.  What are all of your thoughts on that?  My thinking is an issue with the mechanical advance will be hard to replace.  To note, the cost of OEM points and high quality condenser are just about the same as the Pamco unit.  Seeing as I am also handing the bike back to a man who will not be checking and setting the timing every 3k miles or whatever the service interval is this could further be a good option.

Offline MoMo

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Re: 1973 CB350F "Modest Original" build
« Reply #495 on: December 09, 2016, 08:27:53 AM »
Atlas, sounds like a plan, especially if the owner is mechanically challenged electronic seems the ways to go. On the other hand though,  If the spark advance is seized it can be repaired by soaking it in the rust dissolver of your choice then smooth sanding the surfaces with fine grit wet/dry.  I've done it several times

Offline iiAtlas

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Re: 1973 CB350F "Modest Original" build
« Reply #496 on: December 09, 2016, 08:30:47 AM »
Atlas, sounds like a plan, especially if the owner is mechanically challenged electronic seems the ways to go. On the other hand though,  If the spark advance is seized it can be repaired by soaking it in the rust dissolver of your choice then smooth sanding the surfaces with fine grit wet/dry.  I've done it several times

Interesting, I didn't realize it was such a serviceable unit.  I suppose the parts cleaner would be a good tool for this job!  Springs would be one-n-done though, would need replaced if they are not operating properly.  I figure these could be hard to source...how likely are they to go?

The electronic ignition could pay dividends for the not mechanically inclined owner.  I don't want to go that route until I can track this down to ignition though!

Thanks for the input Larry.

Offline MoMo

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Re: 1973 CB350F "Modest Original" build
« Reply #497 on: December 09, 2016, 08:32:56 AM »
I reused the springs.  Also, the cam lobe I believe is directional so take note of where the lobe points to

Offline iiAtlas

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Re: 1973 CB350F "Modest Original" build
« Reply #498 on: December 09, 2016, 08:34:00 AM »
I reused the springs.  Also, the cam lobe I believe is directional so take note of where the lobe points to

Will take lots of pictures as always!

Offline MoMo

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