« previous next »
Pages: [1]   Go Down

Author Topic: #2 not firing....steps to take  (Read 1349 times)

0 Members and 1 Guest are viewing this topic.

Offline flybox1

  • My wife thinks I'm a
  • Really Old Timer ...
  • *******
  • Posts: 14,301
#2 not firing....steps to take
« on: May 24, 2014, 07:20:24 PM »
#2 doesn't get hot. Just warm from the others. I  can grab the header when all others are scalding hot.  I just finished this rebuild.  Hone, re-ring, valves lapped.  Everything was tight and within spec as noted in Hondamans book. 

#2 Plug sparks when held against the head, and Plug caps are all new, but #2 read @ 5.24
Swapped 2/3 coil wires.  #2 still doesn't get hot.
I meticulously cleaned my carbs, but will verify cleanliness and choke butterfly operation in the morning...

What else should I check.  Thanks.
Logged
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline goldarrow

  • one day, i'll be an
  • Old Timer
  • ******
  • Posts: 3,361
#2 not firing....steps to take
« Reply #1 on: May 24, 2014, 08:49:18 PM »
Check the pilot jet again, try new spark plug.  I had new plug that was bad before.  Check plug wire is good, not internally broken. That's all I could think of right now
Logged
Life Is Full Of Challenges - And My Backyard Is Full Of SOHC4's

CB550 K0
CB750 K0, K2, K23 JDM, K45, K5
And the little ones z50r, xr50r, st90


750k5 http://forums.sohc4.net/index.php?topic=114817.0

Offline Jimsun

  • Hot Shot
  • ***
  • Posts: 325
Re: #2 not firing....steps to take
« Reply #2 on: May 24, 2014, 08:54:35 PM »
I had similar issue with my cb550. The culprit for me was my emulsion tube being clogged. After i cleaned them, cyl 2 header is as hot as the others.
Logged
74 cb550

Offline flybox1

  • My wife thinks I'm a
  • Really Old Timer ...
  • *******
  • Posts: 14,301
Re: #2 not firing....steps to take
« Reply #3 on: May 24, 2014, 09:07:38 PM »
I will pull my carbs to verify, but I disassembled and cleaned them for winter storage, and recently put them all back together.  They were still spotless and shiny.
Clean filtered gas, too.
Logged
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline goldarrow

  • one day, i'll be an
  • Old Timer
  • ******
  • Posts: 3,361
Re: #2 not firing....steps to take
« Reply #4 on: May 24, 2014, 09:14:36 PM »
On a 750, just drop the bowls and see the jets
Logged
Life Is Full Of Challenges - And My Backyard Is Full Of SOHC4's

CB550 K0
CB750 K0, K2, K23 JDM, K45, K5
And the little ones z50r, xr50r, st90


750k5 http://forums.sohc4.net/index.php?topic=114817.0

Offline ekpent

  • Really Old Timer ...
  • *******
  • Posts: 13,512
  • To many bikes-but lookin' for more
Re: #2 not firing....steps to take
« Reply #5 on: May 25, 2014, 05:20:03 AM »
A bad plug can still get spark when just laid on the head but may not work correctly under full compression.
Logged

Offline Vinhead1957

  • Expert
  • ****
  • Posts: 1,196
Re: #2 not firing....steps to take
« Reply #6 on: May 25, 2014, 06:17:57 AM »
+1 on ekpent
Logged

Offline flybox1

  • My wife thinks I'm a
  • Really Old Timer ...
  • *******
  • Posts: 14,301
Re: #2 not firing....steps to take
« Reply #7 on: May 25, 2014, 06:42:18 AM »
Ok. I'll try this first, but I gotta wait till the neighborhood wakes up ::)
Logged
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline Stev-o

  • Ain't no
  • Really Old Timer ...
  • *******
  • Posts: 34,324
  • Central Texas
Re: #2 not firing....steps to take
« Reply #8 on: May 25, 2014, 08:31:10 AM »
Quote from: Vinhead1957 on May 25, 2014, 06:17:57 AM
+1 on ekpent

+1....time to wake up the neighbors
Logged
'74 "Big Bang" Honda 750K [836].....'76 Honda 550F.....K3 Park Racer!......and a Bomber!............plus plus plus.........

Offline flybox1

  • My wife thinks I'm a
  • Really Old Timer ...
  • *******
  • Posts: 14,301
Re: #2 not firing....steps to take
« Reply #9 on: May 25, 2014, 09:45:40 AM »
#2 still cold with new plugs.   :-\  Carbs coming off for a re-check
Other ideas welcome and appreciated.....
Logged
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline Tetter

  • Full Member
  • *
  • Posts: 78
  • CB500F Café - CB750F K6
Re: #2 not firing....steps to take
« Reply #10 on: May 25, 2014, 10:09:59 AM »
As mentioned above... pilot jet.
I had the exact same issue after my rebuild.  :o


Logged

Offline flybox1

  • My wife thinks I'm a
  • Really Old Timer ...
  • *******
  • Posts: 14,301
Re: #2 not firing....steps to take
« Reply #11 on: May 25, 2014, 10:30:39 AM »
Hope that's it. Meticulously going thru mine...again  ::) ;D
Logged
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline TwoTired

  • Really Old Timer ...
  • *******
  • Posts: 21,805
Re: #2 not firing....steps to take
« Reply #12 on: May 25, 2014, 10:50:15 AM »
Sometimes the float valves stick, starving the bowl for fuel.  Check the drain screw for #2.  Tap on the bowl to see if mechanical shock will dislodge the float/valve.

Or remove the carbs...
Logged
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline jamesb

  • Expert
  • ****
  • Posts: 1,167
Re: #2 not firing....steps to take
« Reply #13 on: May 25, 2014, 11:52:10 AM »
Mine was just doing that but on #1. I changed plugs wires  he ked everything then finally dropped the bowl on that carb to see I there was a problem and low and behold it must have been because it hasn't had any problems since. So I'm thinking it washed some debris out of there
Logged
I've done a lot of things in my life that I'm not proud of...and the things I AM proud of, "are disgusting"

Offline fire113

  • Expert
  • ****
  • Posts: 1,011
Re: #2 not firing....steps to take
« Reply #14 on: May 25, 2014, 12:16:07 PM »
...check the vacuum screw at carb #2

Logged
Honda CB750 K0 & K0 & K1 & K1 & K2 & K2 & K6

Offline flybox1

  • My wife thinks I'm a
  • Really Old Timer ...
  • *******
  • Posts: 14,301
Re: #2 not firing....steps to take
« Reply #15 on: May 25, 2014, 12:20:36 PM »
Ok. Still not firing on #2
Each carb was inspected, broken down and reassembled. 
No blockages in any of the jets.  Passages blown clean. Float heights verified correct.
Carbs back on bike....Bowl drain screw on #2 opened allowing gas to flow.
When tightened, float valve shut off fuel.  Carbs are operating as they should as far as I can tell.

Next option.... :-\
Logged
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline flybox1

  • My wife thinks I'm a
  • Really Old Timer ...
  • *******
  • Posts: 14,301
Re: #2 not firing....steps to take
« Reply #16 on: May 25, 2014, 12:22:25 PM »
Quote from: fire113 on May 25, 2014, 12:16:07 PM
...check the vacuum screw at carb #2
Ok...
Logged
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline flybox1

  • My wife thinks I'm a
  • Really Old Timer ...
  • *******
  • Posts: 14,301
Re: #2 not firing....steps to take
« Reply #17 on: May 25, 2014, 12:28:54 PM »
« Last Edit: May 25, 2014, 12:33:07 PM by flybox1 »
Logged
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline fire113

  • Expert
  • ****
  • Posts: 1,011
Re: #2 not firing....steps to take
« Reply #18 on: May 25, 2014, 12:50:32 PM »
...try a shot of start pilot spray at carb #2 to be sure that something explosive is in cyl. #2 and see if pipe #2 is getting hot. If not do a compression test on cylinder #2.


 
Logged
Honda CB750 K0 & K0 & K1 & K1 & K2 & K2 & K6

Offline TwoTired

  • Really Old Timer ...
  • *******
  • Posts: 21,805
Re: #2 not firing....steps to take
« Reply #19 on: May 25, 2014, 12:52:16 PM »
  Do the plugs get wet after cranking with full choke and the kill switch blocking spark?

Inspect the valve operation through the inspection/adjustment ports, verify they all move full travel.
Compression check.

Fuel/air, compression, spark = must run.
Logged
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline flybox1

  • My wife thinks I'm a
  • Really Old Timer ...
  • *******
  • Posts: 14,301
Re: #2 not firing....steps to take
« Reply #20 on: May 25, 2014, 02:13:58 PM »
Quote from: TwoTired on May 25, 2014, 12:52:16 PM
  Do the plugs get wet after cranking with full choke and the kill switch blocking spark?

Inspect the valve operation through the inspection/adjustment ports, verify they all move full travel.
Compression check.

Fuel/air, compression, spark = must run.
Exactly...so, I pulled the new densos I put in this am, and im pretty damn embarassed ::) but I'll post here and take my lumps.    ;D  I added four 1" screened airbox powerholes and I didn't account for this change.

Holy isht those are lean  :o
After going out 2 turns on my mixture screws, they are just starting to tan. And #2 is warming up.  Certainly not hot like the others, but noticeably warmer after 2-3 min idle.
#42 pilots are on order...
Thanks for the input guys. 
Logged
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline Duanob

  • Bold Timer
  • Old Timer
  • ******
  • Posts: 4,009
  • Gotcha!
Re: #2 not firing....steps to take
« Reply #21 on: May 25, 2014, 07:11:58 PM »
Hey Rob, it wouldn't be a good story without a few bumps along the way ;)

I would throw the ND plugs in the trash and go get some NGKs. I had the same problem earlier this year with 550F. It was  bad plug and it was fairly new.

Also:
Did you recheck your valve tappets? Maybe #2 is too tight? No comp, no fire.

Are you sure you have OEM spec pilots? I had that same problem as well with the F.

I hope you get it on the road soon, but today is a good day to wrench in a nice dry garage.
Logged
"Just because you flush a boatload of money down the toilet, doesn't make the toilet worth more",  My Stepfather the Unknown Poet

1974 CB360T
1976 CB550K2 Resurrected
1976 CB550F2 Barn Find
1979 CX500 VG "HONDA-GUZZI"
2007 Moto Guzzi Breva 750ie
2015 BMW F700GS
Another 1976 CB550K Cafe?

  __o
_- \_<,
(*) /' (*)

Offline disco

  • Hot Shot
  • ***
  • Posts: 571
Re: #2 not firing....steps to take
« Reply #22 on: May 26, 2014, 01:51:54 AM »
+1 to what Fire113 said.....a bit of starting fluid thru the carby will firstly determine whether your problem is fuel or spark. Then tackle the problem once you have narrowed it down.
Logged
1976 CB750 K6 Sapphire Blue
1972 CB750 K2 836 Orange Sunrise
1972 CB750 K2 Candy Red
1972 CB750 K2 Candy Gold'
Pages: [1]   Go Up
« previous next »