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A strange one

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modelman
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Location: Yorkshire, UK
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A strange one

Post by modelman » Tue Jul 17, 2018 12:33 pm

Not too sure what section to post this, but here goes.
Complete strip down & re-build, first-kick, instant start, so not far out!!
Only rode around the block a couple of times, when it starts acting-up, a mis-fire, pulled the plugs, VERY sooty, then no spark, then intermittent spark, it already has new HT leads, new plug caps, so I fitted NEW plugs, started, ran fine for another couple of laps!!
Same misfire & sooted plugs!!
Stripped the carb (again) all looked good, but I can't identify the jet sizes as the numbers are too lightly stamped.
Float-level at 26.5mm
Air-jet perfect & set at 1/1/8 turn-out. Tickover nice & smooth, but colour-tune indicates a rich burn, & air-screw won't reduce it, hence sooted plugs??
Timing bang-on & set with light & at correct gap.
Here's an interesting one, when running (& mis-firing) if I pull off & hold the plug-cap away from the plug, a large spark jumps the gap & it instantly picks up & starts running perfect, put it back on & it mis-fires!!
I have tried another twin ( Suzuki ) coil, the same happens, so I guess its not the coil.

The only thing I haven't tried is the condenser, could it be that, should I re-new??

Do you think I should buy a carb- jet set?
Then at least i'd KNOW the carb is good!!
Good compression, no smoke, but I should add that it starts first kick but with NO choke.

Or have I missed something obvious??
GSX1400 Red/silver
GSX1400 Blue
GS1000G
Brockhouse Corgi
CB77
CA77
T140
BSA 250

I DO have to grow old, I DO NOT have to grow up.

rrietman
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Posts: 561
Joined: Mon Oct 13, 2008 6:45 pm
Location: bellingham wa.

Post by rrietman » Tue Jul 17, 2018 7:31 pm

carb slides backwards? there is a right and left.
Good luck
Randy

modelman
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Posts: 222
Joined: Wed Jun 24, 2015 2:27 am
Location: Yorkshire, UK
Contact:

Post by modelman » Wed Jul 18, 2018 1:17 am

Sorry, I forgot to mention, CA77 Dream, single carb.
GSX1400 Red/silver
GSX1400 Blue
GS1000G
Brockhouse Corgi
CB77
CA77
T140
BSA 250

I DO have to grow old, I DO NOT have to grow up.

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G-Man
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Joined: Wed Mar 25, 2009 5:17 pm
Location: Derby, UK
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Post by G-Man » Wed Jul 18, 2018 5:33 am

Have you tried dropping the needle?

Is it a genuine Honda needle or a kit part?

Needle jet may be worn.

Correct inlet spacer with the strange notch in it?

G
modelman wrote:Sorry, I forgot to mention, CA77 Dream, single carb.
'60 C77 '60 C72 '62 C72 Dream '63 CL72
'61 CB72 '64 CB77 '65 CB160
'66 Matchless 350 '67 CL77
'67 S90 '77 CB400F

modelman
honda305.com Member
Posts: 222
Joined: Wed Jun 24, 2015 2:27 am
Location: Yorkshire, UK
Contact:

Post by modelman » Wed Jul 18, 2018 11:28 am

G-Man wrote:Have you tried dropping the needle?

Is it a genuine Honda needle or a kit part?

Needle jet may be worn.

Correct inlet spacer with the strange notch in it?

G
modelman wrote:Sorry, I forgot to mention, CA77 Dream, single carb.
1- Don't know as no markings, ordered new kit.

2- Don't know, ordered new kit.

3- I'll have to take it off again to identify, its a brown 'Bakelite' thing with O ring recess, whats with the 'strange notch' then??
GSX1400 Red/silver
GSX1400 Blue
GS1000G
Brockhouse Corgi
CB77
CA77
T140
BSA 250

I DO have to grow old, I DO NOT have to grow up.

rrietman
honda305.com Member
Posts: 561
Joined: Mon Oct 13, 2008 6:45 pm
Location: bellingham wa.

Post by rrietman » Wed Jul 18, 2018 1:16 pm

I have had success in your situation by progressively lowering the float level until you can get a correct fuel mixture (if all the jets are correct). I don't know why, but it works.
good luck
Randy

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G-Man
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Joined: Wed Mar 25, 2009 5:17 pm
Location: Derby, UK
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Post by G-Man » Thu Jul 19, 2018 2:27 pm

Modelman

I try and clean & reuse all the old jets & needles as the kit ones often give problems.

If you look at the flange side of your carb there is a cutout on the bottom edge. The correct spacer as a cutout to match it.

G

modelman wrote:
G-Man wrote:Have you tried dropping the needle?

Is it a genuine Honda needle or a kit part?

Needle jet may be worn.

Correct inlet spacer with the strange notch in it?

G
modelman wrote:Sorry, I forgot to mention, CA77 Dream, single carb.
1- Don't know as no markings, ordered new kit.

2- Don't know, ordered new kit.

3- I'll have to take it off again to identify, its a brown 'Bakelite' thing with O ring recess, whats with the 'strange notch' then??
'60 C77 '60 C72 '62 C72 Dream '63 CL72
'61 CB72 '64 CB77 '65 CB160
'66 Matchless 350 '67 CL77
'67 S90 '77 CB400F

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