Author Topic: 350f issues  (Read 4819 times)

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Offline nk140

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350f issues
« on: June 28, 2011, 12:06:07 PM »
I rebuilt a non-running 350f over the winter/spring.  I got the bike running before I tore into it to replace leaky gaskets.  I now have a problem with trying to get the thing running again.  I replaced the points and condensers.  I also gaped the points.  With a lot of difficulty I can get the bike started.  It only runs on the 2-3 cylinders and will only stay running if I keep the throttle open.  What could cause this and what are the some possible fixes?  Timing?

Offline fmctm1sw

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Re: 350f issues
« Reply #1 on: June 28, 2011, 12:27:39 PM »
Was there spark on 1-4?  Make sure you connected the points the right way for 1-4.
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1973 CB350F
1973 CB350G
1975 CB550K
1983 GL650I
1973 CB750K3 (http://forums.sohc4.net/index.php?topic=92888.0)
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Offline nk140

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Re: 350f issues
« Reply #2 on: June 28, 2011, 12:55:55 PM »
Was there spark on 1-4?  Make sure you connected the points the right way for 1-4.
Wouldn't the bike at least run on 2-3 though?

Offline camelman

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Re: 350f issues
« Reply #3 on: June 28, 2011, 01:34:11 PM »
Yes, it will do 55 with only two cylinders. It does not idle well like that though. Timing can definitely decrease power on these bikes. Even just two degrees retarded will heavily affect power.
1972 350f rider: sold
1972 350f/466f cafe: for sale
1977 CB400f cafe:sold
1975 CB400f rider: sold
1970 CB750 K0 complete bike: sold
2005 Triumph Sprint ST 1050 rider

We've got to cut it off... and then come down on rockets.  (quoted from: seven minutes of terror)

Offline nk140

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Re: 350f issues
« Reply #4 on: June 28, 2011, 03:03:03 PM »
I know I am getting voltage at both points.  Is there anyway to check the timing without a timing light?  The running only at wide open throttle confuses me.  When I back off the throttle it will die almost immediately.

Offline camelman

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Re: 350f issues
« Reply #5 on: June 28, 2011, 04:22:04 PM »
That kinda sounds like timing to me.

Why do you say it is only running on two cylinders?  Are they the only ones getting hot?  Have you checked if the other cylinders are firing their plugs?  I'm starting to wonder if you installed your ignition completely wrong or possibly have your timing chain off some teeth. Check that timing first, and make sure you are timed to the F for both sets of points.
1972 350f rider: sold
1972 350f/466f cafe: for sale
1977 CB400f cafe:sold
1975 CB400f rider: sold
1970 CB750 K0 complete bike: sold
2005 Triumph Sprint ST 1050 rider

We've got to cut it off... and then come down on rockets.  (quoted from: seven minutes of terror)

Offline nk140

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Re: 350f issues
« Reply #6 on: June 28, 2011, 04:40:06 PM »
Yeah the 2-3 are the only ones getting hot.  I haven't checked to see if the other plugs are firing.  How would I do that?  I know both points start to open up on the corresponding F marks.

If I figure out it is not my ignition timing.  I can pull the head cover and check to see if the timing chain is on correctly when aligned with the T mark on the timing plate.

Offline camelman

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Re: 350f issues
« Reply #7 on: June 28, 2011, 04:48:51 PM »
Pull the plugs and hook them up to the wires. Rest the end of the plug against the block and turn the engine over with the ignition on. If they fire, then they are likely good. If they don't fire, then pull a known good plug and repeat the test. If they fire with known good plugs, then replace the bad plugs and try to start the engine. If known good plugs do not fire, then report back with your results.
1972 350f rider: sold
1972 350f/466f cafe: for sale
1977 CB400f cafe:sold
1975 CB400f rider: sold
1970 CB750 K0 complete bike: sold
2005 Triumph Sprint ST 1050 rider

We've got to cut it off... and then come down on rockets.  (quoted from: seven minutes of terror)

Offline nk140

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Re: 350f issues
« Reply #8 on: June 28, 2011, 04:58:41 PM »
Pull the plugs and hook them up to the wires. Rest the end of the plug against the block and turn the engine over with the ignition on. If they fire, then they are likely good. If they don't fire, then pull a known good plug and repeat the test. If they fire with known good plugs, then replace the bad plugs and try to start the engine. If known good plugs do not fire, then report back with your results.

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Offline 333

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Re: 350f issues
« Reply #9 on: June 28, 2011, 06:29:08 PM »
If you had it totally apart, I'd also adjust the valves.
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Offline nk140

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Re: 350f issues
« Reply #10 on: June 28, 2011, 06:31:41 PM »
Well I have spark at the 1 and 4 plugs.  The plugs look dry and feel dry.  I did adjust the valves when I put everything back together.  I adjusted the timing at the points and the bike starts very quickly and almost wants to idle but will sputter and die.

Offline nk140

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Re: 350f issues
« Reply #11 on: June 28, 2011, 06:41:00 PM »
Also it will only run on full choke.  If I move the lever to open the carbs the bike will die

bigedd

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Re: 350f issues
« Reply #12 on: June 28, 2011, 06:44:25 PM »
you may have already checked this but make sure both of your coils are getting a hot wire, i had that prob with my 350f. neither one was hot so i just hooked a jumper off the batt (temperately) and it fired right up

Offline nk140

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Re: 350f issues
« Reply #13 on: June 28, 2011, 06:50:09 PM »
you may have already checked this but make sure both of your coils are getting a hot wire, i had that prob with my 350f. neither one was hot so i just hooked a jumper off the batt (temperately) and it fired right up
I am getting spark at all plugs, so the coils are getting power.

Offline hondamatteo

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Re: 350f issues
« Reply #14 on: June 28, 2011, 07:25:17 PM »
If its only running with the choke then it sounds like you might have a fuel delivery problem. What has been done to the carbs? Petcock screen clean and inline fuel filter good?
'74 CB350F

Offline nk140

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Re: 350f issues
« Reply #15 on: June 28, 2011, 07:27:56 PM »
If its only running with the choke then it sounds like you might have a fuel delivery problem. What has been done to the carbs? Petcock screen clean and inline fuel filter good?

I totally disassembled the carbs and cleaned them up.  I did clean the petcock screen.  I can see fuel in the inline fuel filter.

Offline hondamatteo

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Re: 350f issues
« Reply #16 on: June 28, 2011, 07:46:05 PM »
If its only running with the choke then it sounds like you might have a fuel delivery problem. What has been done to the carbs? Petcock screen clean and inline fuel filter good?

I totally disassembled the carbs and cleaned them up.  I did clean the petcock screen.  I can see fuel in the inline fuel filter.

And you cleaned the emulsifier tubes under the main jet as well?
'74 CB350F

Offline nk140

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Re: 350f issues
« Reply #17 on: June 28, 2011, 08:00:32 PM »
If its only running with the choke then it sounds like you might have a fuel delivery problem. What has been done to the carbs? Petcock screen clean and inline fuel filter good?

I totally disassembled the carbs and cleaned them up.  I did clean the petcock screen.  I can see fuel in the inline fuel filter.

And you cleaned the emulsifier tubes under the main jet as well?

yeah I clean those as well.  Maybe I need to take the carbs off and double check everything.

Offline hondamatteo

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Re: 350f issues
« Reply #18 on: June 28, 2011, 08:08:26 PM »
ya I would try and run it again and if plugs 1 and 4 are still dry then you for sure arent getting fuel. They would be noticeably wet if you had fuel but no spark.
'74 CB350F

Offline hondamatteo

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Re: 350f issues
« Reply #19 on: June 28, 2011, 08:12:37 PM »
also double check your needles arent stuck closed in carbs 1 and 4 and crack open the float bowl drain screw to see if there is fuel inside. You can tap on the bowl with a soft hammer or screw driver handle to help free a stuck needle.
'74 CB350F

Offline camelman

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Re: 350f issues
« Reply #20 on: June 28, 2011, 08:17:18 PM »
Stuck needles might just be the culprit. Try tapping on the carbs with the plastic handle of a screwdriver before dismantling them again. It might just fix the problem.
1972 350f rider: sold
1972 350f/466f cafe: for sale
1977 CB400f cafe:sold
1975 CB400f rider: sold
1970 CB750 K0 complete bike: sold
2005 Triumph Sprint ST 1050 rider

We've got to cut it off... and then come down on rockets.  (quoted from: seven minutes of terror)

Offline nk140

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Re: 350f issues
« Reply #21 on: June 29, 2011, 04:44:14 AM »
I will give the carbs a tap tonight.  If that doesnt' fix it I will take the carbs off.

Offline 333

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Re: 350f issues
« Reply #22 on: June 29, 2011, 05:26:30 AM »
While you're in the area, check the intake boots between the carbs and the head.
Go metric, every inch of the way!

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Offline nk140

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Re: 350f issues
« Reply #23 on: June 29, 2011, 05:37:03 AM »
While you're in the area, check the intake boots between the carbs and the head.

What am I looking for on the boots?

Offline flybox1

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Re: 350f issues
« Reply #24 on: June 29, 2011, 07:55:21 AM »
What am I looking for on the boots?
clamps not tight/bad seal/old cracked rubber = air leak
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