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Author Topic: Engine Missing While at Cruising Speed (1981 Honda CB650C)  (Read 37399 times)

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Offline grcamna2

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #75 on: January 22, 2012, 12:44:09 PM »
ARE there any sohc4 members close to F16Viper68 who can give him some "Team encouragement"...? a local to his stomping grounds who can go over and have a look together with him and build him up w/ a fresh supply of ;)   gumption ?? Let him know guys  :P.

Any sohc4 members in(or close to) Tallahassee ?
« Last Edit: January 22, 2012, 12:53:30 PM by grcamna2 »
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Offline F16Viper68

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #76 on: January 22, 2012, 01:12:03 PM »
Quote from: grcamna2 on January 22, 2012, 12:44:09 PM
ARE there any sohc4 members close to F16Viper68 who can give him some "Team encouragement"...? a local to his stomping grounds who can go over and have a look together with him and build him up w/ a fresh supply of ;)   gumption ?? Let him know guys  :P.

Any sohc4 members in(or close to) Tallahassee ?

That are maybe looking for a parts bike?   >:(  Just kidding.  I'll get there but today has been very annoying to the say the least.

I just got it running and idling correctly and was setting up to sync the carbs when I noticed #4 is no longer firing.  It has plenty of spark but there's no RPM delta when I remove the plug wire.  The plug is fine, it sparks when removed from the cylinder. 

Despite a really good cleaning I'm assuming something in carb #4 is plugged again. 

Man, now I know why they invented fuel injection.  I can just see some engineer long ago, in a garage throwing wrenches, realizing there has to be a better way to deliver fuel.

Time to start drinking.

Dave...
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Offline F16Viper68

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #77 on: January 22, 2012, 01:13:50 PM »
This thing is looking really appealing today.

http://www.triumphmotorcycles.com/motorcycles/range/classics/thruxton

Dave...
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72500john

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #78 on: January 22, 2012, 04:58:47 PM »
i feel your pain. when i got my bike the top fork bridge was fractured. got another and it fractured on the first ride.(50 bucks down the tube). got another of flee bay(double ouch 100 bucks more) just to find out spacers where supposed to be installed between the splits in it..no more fractures. have beer or your beverage of choice..go fishn or some thing..basically walk away from it for a few days. if all else fails you can dump the bike in my driveway and i will give it a good home!!(just kidding!)
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Offline F16Viper68

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #79 on: January 22, 2012, 06:38:44 PM »
While I was trying to figure out why #4 wasn't firing I noticed fuel was leaking from the fuel tubes that connect the #3 and #4 carb.  So either way, the rack needed to come out...for the 100th time.  I guess the o-rings didn't like being messed with when I slightly separated the carbs to install the t-fittings. 

I took the #4 carb apart as far as it could go, ensured everything was clear, new o-rings, and re-assembled.



I also separated #1 and replaced those o-rings before it started leaking too.

Put it all back together, got the bike running, and everything is firing again.

I tried to sync the carbs but I'm struggling with the #3 carb adjustment.  The Motion-Pro tool I have works great for #1 and #4 but the #3 carb adjustment is blocked by the frame.  I bent the tool a bit to get it on the nut but the screwdriver won't engage.  It's always something.



I did get the advancer completely disassembled, cleaned and lubed and reset the timing.

I also put in new, standard range sparkplugs. 

Dave...
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Offline grcamna2

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #80 on: January 22, 2012, 06:45:07 PM »
Good work  ;).
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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 F16Viper68

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #81 on: January 22, 2012, 07:04:23 PM »
Quote from: grcamna2 on January 22, 2012, 06:45:07 PM
Good work  ;).

Thanks!  I'm not sure how I'm going to get #3 adjusted but I'll figure something out.

Dave...

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Online Jerry Rxman Griffin aka MuthaF'er

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #82 on: January 22, 2012, 09:31:44 PM »
Perhaps #3 is the ONE that the others get adjusted to?? I don't do 650's but I do believe the 750's have one carb that doesn't adjust that the others adjust to. Someone correct me if I'm wrong.
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Offline scunny

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #83 on: January 23, 2012, 03:15:45 AM »
it's the number 2 carb that is the baseline.
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Offline faux fiddy

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #84 on: January 23, 2012, 03:49:45 AM »
Sorry I missed the first four pages. Engine missing at speed..  Is this a bike on a trailer like the other thread?

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Offline F16Viper68

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #85 on: January 23, 2012, 05:58:05 AM »
Quote from: fiddy of industry on January 23, 2012, 03:49:45 AM
Sorry I missed the first four pages. Engine missing at speed..  Is this a bike on a trailer like the other thread?



It's not on a trailer but it may be going missing soon.   8)

Dave...
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Offline grcamna2

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #86 on: January 23, 2012, 08:26:47 AM »
That bike above with the engine that's "missing" looks a lot like a good old nice CB450 twin  ;) and it's a very decent looking rolling chassis :) !

fiddy...does she belong to you ??
« Last Edit: January 23, 2012, 01:16:00 PM by grcamna2 »
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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 grasscutter

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #87 on: January 23, 2012, 11:42:38 AM »
Team encouragement!

Does me drinking a beer while I read this thread, count??  If so, I'm in full 'encouragement mode'!

Yes #2 is the baseline.  It is the one that has the accelerator pump.

Glad you went back through the carbs.  I slight dab (i mean SLIGHT) of oil on the o-rings will allow you to disassemble hem a few times without them getting twisted, pinched, etc.

Good to see you doing more than a bench sync.

Did you figure out the # 4 firing issue?  (didn't see that mentioned yet)  Would be nice to eliminate spark issues if possible.
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Offline Hush

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #88 on: January 23, 2012, 01:49:15 PM »
Um I have to report you to the admins now Viper cos you swore! quote "I'll buy a H ;D ley"
Just image how nice this bike is going to go with all that extra work you have done.
My 79 650 was a PITA and I redid everything in a year of total frustraition, the pay off was 3 years of pure bliss and no problem riding....do it once, do it right. ;)
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Offline Grabcon

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #89 on: January 23, 2012, 05:48:13 PM »
F16Viper68, I have read this whole string and I think I caught everthing, but just on the chance that I did not, here are a couple of more thoughts. This is from a CB900F experience recently. Very similar carbs and ignition.

Ignition First. See the first attached link. Providing that all ignition parts are good this is a way to provide extra juice to the coils. I did this and what a different, It removed most of the missing at varied RPMs. High RPMs were still not archival.

http://cb750c.com/modules.php?name=Forums&file=viewtopic&t=2740

The second part of the story. Search for Mike Nixon and he was some good books on how to clean and rebuilt the CV carbs. Make sure all needles are on the same clip notch. If these carbs are like the CB900F CVs the primary and secondary jets are interchangeable. OGM why did Honda/KEHIN do this. I found after several time going through the carbs that two of the carbs had the primary and secondary jets swapped around. It is very difficult to see the jet size so a magnify glass is in order.

I know this sounds stupid like why didn't I catch this, because the physically look the same to a non expert. With everything in order there is no miss at any RPM and a lot of power that was not there before. Make sure you complete the carb Sync.

I saw our last set of plug photos and 1 and 3 (from left to right) appears to have less soot on the ring of the plug. Check cylinders 2 & 4 on the jets.

Check to see if all cylinders are firing with a quick hand to the exhaust pipes all obvious should be hot.

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CB750F 1976 - Gone :(
CB550   1978 - Gone & now back
CB900F 1981 - Gone
ST1100 1991 - Gone
ST1100 2000 - Gone
VFR800 2008 - Gone
ST1300 2008 - Gone
BMW F700GS - Wife's
VFR1200X 2016 - Mine

Offline F16Viper68

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #90 on: January 23, 2012, 07:23:20 PM »
Quote from: grasscutter on January 23, 2012, 11:42:38 AM
Team encouragement!

Does me drinking a beer while I read this thread, count??  If so, I'm in full 'encouragement mode'!

Yes #2 is the baseline.  It is the one that has the accelerator pump.

Glad you went back through the carbs.  I slight dab (i mean SLIGHT) of oil on the o-rings will allow you to disassemble hem a few times without them getting twisted, pinched, etc.

Good to see you doing more than a bench sync.

Did you figure out the # 4 firing issue?  (didn't see that mentioned yet)  Would be nice to eliminate spark issues if possible.

The #4 cylinder is now firing.  I'm assuming something was amiss with the carb but honestly I can't figure out what.  I cleaned, checked, prodded, blew out with compressors, air, etc.  Nothing I hadn't done earlier.  There are times feel like I'm chasing a ghost.  A ghost that I'm going to beat with hose...

After everything was put back together...again...I was able to verify all cylinders were firing.  I know this because if a cylinder if not firing, the sync gauge slams to the top for the offending cylinder.  This is actually how I figured out #4 wasn't firing.  Plus I confirmed a drop in RPM's if the wire is removed from the sparkplug.

Dave...

« Last Edit: January 23, 2012, 07:32:08 PM by F16Viper68 »
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Offline F16Viper68

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #91 on: January 23, 2012, 07:31:37 PM »
Quote from: Hush on January 23, 2012, 01:49:15 PM
Um I have to report you to the admins now Viper cos you swore! quote "I'll buy a H ;D ley"
Just image how nice this bike is going to go with all that extra work you have done.
My 79 650 was a PITA and I redid everything in a year of total frustraition, the pay off was 3 years of pure bliss and no problem riding....do it once, do it right. ;)

Someday I'll own a HD but it's going to be new.  :)

Dave...
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Offline F16Viper68

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #92 on: January 23, 2012, 07:40:50 PM »
Quote from: Grabcon on January 23, 2012, 05:48:13 PM
F16Viper68, I have read this whole string and I think I caught everthing, but just on the chance that I did not, here are a couple of more thoughts. This is from a CB900F experience recently. Very similar carbs and ignition.

Ignition First. See the first attached link. Providing that all ignition parts are good this is a way to provide extra juice to the coils. I did this and what a different, It removed most of the missing at varied RPMs. High RPMs were still not archival.

http://cb750c.com/modules.php?name=Forums&file=viewtopic&t=2740

The second part of the story. Search for Mike Nixon and he was some good books on how to clean and rebuilt the CV carbs. Make sure all needles are on the same clip notch. If these carbs are like the CB900F CVs the primary and secondary jets are interchangeable. OGM why did Honda/KEHIN do this. I found after several time going through the carbs that two of the carbs had the primary and secondary jets swapped around. It is very difficult to see the jet size so a magnify glass is in order.

I know this sounds stupid like why didn't I catch this, because the physically look the same to a non expert. With everything in order there is no miss at any RPM and a lot of power that was not there before. Make sure you complete the carb Sync.

I saw our last set of plug photos and 1 and 3 (from left to right) appears to have less soot on the ring of the plug. Check cylinders 2 & 4 on the jets.

Check to see if all cylinders are firing with a quick hand to the exhaust pipes all obvious should be hot.

Thanks for reading through this entire train wreck.  :)

The link requires registration.  Is that for the GM HEI upgrade?

I'm not sure what you mean by "clip notch"?  Maybe my carbs are different.  Luckily I don't have to worry about secondary jets since these CV carbs don't have them.  Dodged that bullet.  Although I really wish the idle jets were removable.   >:(

Once I figure out how out how to adjust #3 I'll be sure to complete the sync and adjust the idle mixtures.

I know it was running lean which is why I backed out the screws to 3.5 turns vs. 2.5 turns (seem to run better). 
 
Thanks for the link to Mike Nixon's site.  http://www.motorcycleproject.com/ Looks interesting! 

Dave...

 
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Offline scunny

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #93 on: January 23, 2012, 07:54:56 PM »
wooooooooooooooooaaaaaaaaaaaaaaahhhhhh there, back up the train. did you say the idle jet isn't removable ?
how did you clean them then. can't you pull them out. ?????
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past-cb100,ts250,cb500,cb500,gs1000,gs650g.phillips traveller
present-CB 650 retro
            VTR1000F3
           XL250S riverbed rocket
           TS250[sold]
           TS185[sold]
           XL125S[sold]
           MT50 (white)
           MT50 (red)[sold]
           KN250/XS400 project
           XR/XL250 bitsa under construction
           SL100[sold]
           XL250R
           pedal(pub bike) leaks oil
my gallery http://gallery.sohc4.net/members/personal/scunny

Offline F16Viper68

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #94 on: January 23, 2012, 08:06:06 PM »
Quote from: scunny on January 23, 2012, 07:54:56 PM
wooooooooooooooooaaaaaaaaaaaaaaahhhhhh there, back up the train. did you say the idle jet isn't removable ?
how did you clean them then. can't you pull them out. ?????

Lol.  Carb cleaner and compressed air.  I know they are clear. I've forced carb cleaner through them.  They are pressed in and can't be removed without major modifications.  Think drill, extactor, tap/die, etc. 
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Offline scunny

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #95 on: January 23, 2012, 08:09:31 PM »
pity I'm about to go to work now. in the morning I shall play with a set of cv carbs I have, my pd carbs have pressed in jets and are removable, don't see why the cv's would be different. time to experiment. I'll report back.
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past-cb100,ts250,cb500,cb500,gs1000,gs650g.phillips traveller
present-CB 650 retro
            VTR1000F3
           XL250S riverbed rocket
           TS250[sold]
           TS185[sold]
           XL125S[sold]
           MT50 (white)
           MT50 (red)[sold]
           KN250/XS400 project
           XR/XL250 bitsa under construction
           SL100[sold]
           XL250R
           pedal(pub bike) leaks oil
my gallery http://gallery.sohc4.net/members/personal/scunny

Offline Grabcon

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #96 on: January 23, 2012, 09:18:09 PM »
Clip Notch maybe a bad term. It is the notch on the needles that are mounted on the slides. All needle have to have the clip in the same notch on the needles. This requires that you can check the length of each needle to make sure they are the same length. Or pull the needles out of the slides to verify.
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ST1300 2008 - Gone
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Offline cb650

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #97 on: January 24, 2012, 05:28:17 AM »
The CV carbs dont have adjustable needles.  I have seen them shimmed but think that creates other problems.   
Viper do you have the carb vent tube hooked to the airbox?
Unless the jetting is way off the CV's will do a good job compensating.
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Offline F16Viper68

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #98 on: January 24, 2012, 05:36:52 PM »
Quote from: cb650 on January 24, 2012, 05:28:17 AM
The CV carbs dont have adjustable needles.  I have seen them shimmed but think that creates other problems.   
Viper do you have the carb vent tube hooked to the airbox?
Unless the jetting is way off the CV's will do a good job compensating.

Are you talking about the hoses that originate from the t-fittings that go between 1/2 and 3/4 and route back towards the airbox? 

Dave...
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Offline scunny

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Re: Engine Missing While at Cruising Speed (1981 Honda CB650C)
« Reply #99 on: January 24, 2012, 05:50:39 PM »
well my are the VB54A CV carbs with pressed in idles and they come out with a pull. go back in nicely with a little tap.
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past-cb100,ts250,cb500,cb500,gs1000,gs650g.phillips traveller
present-CB 650 retro
            VTR1000F3
           XL250S riverbed rocket
           TS250[sold]
           TS185[sold]
           XL125S[sold]
           MT50 (white)
           MT50 (red)[sold]
           KN250/XS400 project
           XR/XL250 bitsa under construction
           SL100[sold]
           XL250R
           pedal(pub bike) leaks oil
my gallery http://gallery.sohc4.net/members/personal/scunny
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