Author Topic: Senior project for high school - 78 CB750K  (Read 172846 times)

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Offline calj737

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Re: Senior project for high school - 78 CB750K
« Reply #1075 on: April 24, 2015, 03:43:37 AM »
Yup, that's right. The Pamco was not the issue. Earlier in the diagnosis, we had jumped to the conclusion that the trigger was bad and I said that Ron and Logan were 1:1MM for receiving a DOA. I take it back now, as the BLK/WHT wire (hmmm, someone suggested that pretty early on  ::) ) was the issue all along.

Not wanting to kick a man and his boy while they're forehead smacking, I felt compelled to reiterate my (dare I say,"our") collective esteem for this F/S bike building duo. Hence, my prior post.

Perhaps a thread-map to guide us all along?
'74 550 Build http://forums.sohc4.net/index.php?topic=126401.0
'73 500 Build http://forums.sohc4.net/index.php?topic=132935.0

"Of all tyrannies, a tyranny sincerely exercised for the good of it's victim may be the most oppressive. It may be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated, but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience." - C.S. Lewis

Offline madmtnmotors

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Re: Senior project for high school - 78 CB750K
« Reply #1076 on: April 24, 2015, 03:49:59 AM »
Oh yeah, they have definitely accomplished quite a task here.  8)

I figured once the ignition got sorted it would fire right up. Good call on making sure the triggers get reconnected properly. I've wired mined backwards more than once...

and the engine would not cooperate!  :o
TAMTF...


Wilbur



Projects:
"Evolution": http://forums.sohc4.net/index.php?topic=100352.0
"P.O. Debacle": http://forums.sohc4.net/index.php/topic,126692.msg1441661.html#msg1441661
F2/F3 O-rings: http://forums.sohc4.net/index.php?topic=113672.msg1300721#msg1300721
Cam Tower Studs: https://www.mcmaster.com/#93210a017/=t19sgp
Clean up that nasty harness: http://forums.sohc4.net/index.php?topic=137351.msg1549191#msg1549191
http://forums.sohc4.net/index.php/topic,148188.msg1688494.html#msg1688494
http://forums.sohc4.net/index.php/topic,139544.msg1579364.html#msg1579364
                                          
Charging system diagnosis: http://forums.sohc4.net/index.php?topic=1012.msg8345#msg8345
Get the manuals: http://manuals.sohc4.net/cb750k/
The Dragon: http://forums.sohc4.net/index.php?topic=45183.msg1571675#msg1571675
Headlight Switch: http://forums.sohc4.net/index.php?topic=113986.msg1283236#msg1283236
Branden's leak free top end thread: http://forums.sohc4.net/index.php?topic=107040.0
Engine Lifting Made Easy: http://forums.sohc4.net/index.php/topic,58210.msg1684742.html#msg1684742
                                      http://forums.sohc4.net/index.php/topic,100352.msg1675840.html#msg1675840
Static and Dynamic Timing: http://www.hondachopper.com/garage/carb_info/timing/timing1.html
Airbox Gasket Replacement: http://forums.sohc4.net/index.php/topic,114485.msg1290000.html#msg1290000
"Café" : http://forums.sohc4.net/index.php/topic,84697.msg953814.html#msg953814
PD Carb Choke Linkage: http://forums.sohc4.net/index.php/topic,100352.msg1669248.html#msg1669248
                                    http://forums.sohc4.net/index.php/topic,110931.msg1248354.html#msg1248354
                                    http://forums.sohc4.net/index.php/topic,48858.msg515204.html#msg515204
Follow up on your damn posts: http://forums.sohc4.net/index.php/topic,144305.msg1791605.html#msg1791605
Taiwanese Cam Chain Tensioners:  http://forums.sohc4.net/index.php/topic,155043.msg1774841.html#msg1774841
Gumtwo Seat Cover: http://forums.sohc4.net/index.php/topic,164440.msg1897366.html#msg1897366
Primary Drive: http://forums.sohc4.net/index.php/topic,166063.msg1919278.html#msg1919278
Tank Latch: http://forums.sohc4.net/index.php/topic,165975.msg1919495.html#msg1919495
Shorten your forks: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-shorten-forks-td4042465.html DO NOT CUT THE SPRINGS!
Clutch How To: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-change-and-adjust-a-clutch-SOHC-td4040391.html
Late model K7/K8/F2/F3 front sprocket cover removal: http://forums.sohc4.net/index.php/topic,178428.msg2072279.html#msg2072279
630 to 530 conversion: http://forums.sohc4.net/index.php/topic,180710.msg2094423.html#msg2094423

Sent from my Tandy TRS-80!

Offline Restoration Fan

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Re: Senior project for high school - 78 CB750K
« Reply #1077 on: April 24, 2015, 03:53:16 AM »
Yes, we returned the wires to the proper place.

Wilbur,
Cal's referring back to where he said earlier that Logan and I were 1:1,000,000 because it's so rare to get a faulty PAMCO.  Now that we have determined that the PAMCO isn't the problem, he's saying that we are still that 1:1,000,000 because of all the trouble we go through/cause, etc.  :D
Ron

Stella - Logan's Senior Project    78 750K http://forums.sohc4.net/index.php?topic=141761.0

Logan's Reward - CB500 and CB550 Cafes    http://forums.sohc4.net/index.php/topic,147787.0.html

Offline madmtnmotors

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Re: Senior project for high school - 78 CB750K
« Reply #1078 on: April 24, 2015, 04:00:01 AM »
Good luck with the carbs. I absolutely detest working on carburetors, especially these multi-carb setups! Although I have gotten pretty good at it, I still don't like it!  ;)
TAMTF...


Wilbur



Projects:
"Evolution": http://forums.sohc4.net/index.php?topic=100352.0
"P.O. Debacle": http://forums.sohc4.net/index.php/topic,126692.msg1441661.html#msg1441661
F2/F3 O-rings: http://forums.sohc4.net/index.php?topic=113672.msg1300721#msg1300721
Cam Tower Studs: https://www.mcmaster.com/#93210a017/=t19sgp
Clean up that nasty harness: http://forums.sohc4.net/index.php?topic=137351.msg1549191#msg1549191
http://forums.sohc4.net/index.php/topic,148188.msg1688494.html#msg1688494
http://forums.sohc4.net/index.php/topic,139544.msg1579364.html#msg1579364
                                          
Charging system diagnosis: http://forums.sohc4.net/index.php?topic=1012.msg8345#msg8345
Get the manuals: http://manuals.sohc4.net/cb750k/
The Dragon: http://forums.sohc4.net/index.php?topic=45183.msg1571675#msg1571675
Headlight Switch: http://forums.sohc4.net/index.php?topic=113986.msg1283236#msg1283236
Branden's leak free top end thread: http://forums.sohc4.net/index.php?topic=107040.0
Engine Lifting Made Easy: http://forums.sohc4.net/index.php/topic,58210.msg1684742.html#msg1684742
                                      http://forums.sohc4.net/index.php/topic,100352.msg1675840.html#msg1675840
Static and Dynamic Timing: http://www.hondachopper.com/garage/carb_info/timing/timing1.html
Airbox Gasket Replacement: http://forums.sohc4.net/index.php/topic,114485.msg1290000.html#msg1290000
"Café" : http://forums.sohc4.net/index.php/topic,84697.msg953814.html#msg953814
PD Carb Choke Linkage: http://forums.sohc4.net/index.php/topic,100352.msg1669248.html#msg1669248
                                    http://forums.sohc4.net/index.php/topic,110931.msg1248354.html#msg1248354
                                    http://forums.sohc4.net/index.php/topic,48858.msg515204.html#msg515204
Follow up on your damn posts: http://forums.sohc4.net/index.php/topic,144305.msg1791605.html#msg1791605
Taiwanese Cam Chain Tensioners:  http://forums.sohc4.net/index.php/topic,155043.msg1774841.html#msg1774841
Gumtwo Seat Cover: http://forums.sohc4.net/index.php/topic,164440.msg1897366.html#msg1897366
Primary Drive: http://forums.sohc4.net/index.php/topic,166063.msg1919278.html#msg1919278
Tank Latch: http://forums.sohc4.net/index.php/topic,165975.msg1919495.html#msg1919495
Shorten your forks: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-shorten-forks-td4042465.html DO NOT CUT THE SPRINGS!
Clutch How To: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-change-and-adjust-a-clutch-SOHC-td4040391.html
Late model K7/K8/F2/F3 front sprocket cover removal: http://forums.sohc4.net/index.php/topic,178428.msg2072279.html#msg2072279
630 to 530 conversion: http://forums.sohc4.net/index.php/topic,180710.msg2094423.html#msg2094423

Sent from my Tandy TRS-80!

Offline calj737

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Re: Senior project for high school - 78 CB750K
« Reply #1079 on: April 24, 2015, 04:08:52 AM »
... he's saying that we are still that 1:1,000,000 because of all the work we've done, and done so well.
Fixed that for you, Ron  :D
'74 550 Build http://forums.sohc4.net/index.php?topic=126401.0
'73 500 Build http://forums.sohc4.net/index.php?topic=132935.0

"Of all tyrannies, a tyranny sincerely exercised for the good of it's victim may be the most oppressive. It may be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated, but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience." - C.S. Lewis

Offline Bill/BentON Racing

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Re: Senior project for high school - 78 CB750K
« Reply #1080 on: April 25, 2015, 11:57:41 AM »
Well, Ron left @ 9 last night, progress was made! Carbs had issues. Ignition was also discussed. Stella might run today.......Bill  ;D
BentON Racing Website
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Over 35 years of experience working on vintage motorcycles, with a speciality in Honda SOHC/4 with a focus on the CB750 and other models as well from 1966 - 1985.
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See our latest build 'Captain Marvel' CLICK HERE

Offline Restoration Fan

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Re: Senior project for high school - 78 CB750K
« Reply #1081 on: April 25, 2015, 12:07:13 PM »
Well, we got her to fire one time but that's it.  There's still something at issue with the carbs.

Here's a video of her first fire.  Notice that Logan kept the starter in the whole time and I had to make a cutting motion for him to stop.  I told him, "something sounds wrong" and we watched the video.  I said, "hear that sound?".  He goes, "Yeah, that's just the starter.  Should I have let off of it?"  I look at him and say, "Do you keep turning the key after your Jeep starts?"  :o

Other than that, we haven't gotten her to fire...she just turns over and over and over but isn't firing. 

We confirmed that we have spark on all 4 cylinders but something appears to not be right.

Ron

Stella - Logan's Senior Project    78 750K http://forums.sohc4.net/index.php?topic=141761.0

Logan's Reward - CB500 and CB550 Cafes    http://forums.sohc4.net/index.php/topic,147787.0.html

Offline Stev-o

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Re: Senior project for high school - 78 CB750K
« Reply #1082 on: April 25, 2015, 12:24:42 PM »
Looks to have an abnormal amount of black smoke [rich].
Did you have full choke when firing?
'74 "Big Bang" Honda 750K [836].....'76 Honda 550F.....K3 Park Racer!......and a Bomber!............plus plus plus.........

Offline Restoration Fan

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Re: Senior project for high school - 78 CB750K
« Reply #1083 on: April 25, 2015, 12:27:05 PM »
Looks to have an abnormal amount of black smoke [rich].
Did you have full choke when firing?

Yes, we had it on full choke. 
Ron

Stella - Logan's Senior Project    78 750K http://forums.sohc4.net/index.php?topic=141761.0

Logan's Reward - CB500 and CB550 Cafes    http://forums.sohc4.net/index.php/topic,147787.0.html

Offline Stev-o

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Re: Senior project for high school - 78 CB750K
« Reply #1084 on: April 25, 2015, 12:36:10 PM »
Looks to have an abnormal amount of black smoke [rich].
Did you have full choke when firing?

Yes, we had it on full choke. 

Ok. Reduce to half choke once fired.   My K7 was a finicky starter, try this procedure:

1. Fuel, choke, kill and ignition on
2. 2 twists of throttle [accel will squirt gas into carb]
3. Push starter button with no throttle 'til she fires [4 seconds MAX]
4. Repeat steps 2&3 as required

'74 "Big Bang" Honda 750K [836].....'76 Honda 550F.....K3 Park Racer!......and a Bomber!............plus plus plus.........

Offline madmtnmotors

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Re: Senior project for high school - 78 CB750K
« Reply #1085 on: April 25, 2015, 12:41:13 PM »
I'm with Stev-o here. Lay off the full throttle twists while starting. Two twists before starting. Let the choke work its magic. If full choke seems too much then gradually reduce the amount of choke while trying to start.

And definitely let off the start button!  ;)
TAMTF...


Wilbur



Projects:
"Evolution": http://forums.sohc4.net/index.php?topic=100352.0
"P.O. Debacle": http://forums.sohc4.net/index.php/topic,126692.msg1441661.html#msg1441661
F2/F3 O-rings: http://forums.sohc4.net/index.php?topic=113672.msg1300721#msg1300721
Cam Tower Studs: https://www.mcmaster.com/#93210a017/=t19sgp
Clean up that nasty harness: http://forums.sohc4.net/index.php?topic=137351.msg1549191#msg1549191
http://forums.sohc4.net/index.php/topic,148188.msg1688494.html#msg1688494
http://forums.sohc4.net/index.php/topic,139544.msg1579364.html#msg1579364
                                          
Charging system diagnosis: http://forums.sohc4.net/index.php?topic=1012.msg8345#msg8345
Get the manuals: http://manuals.sohc4.net/cb750k/
The Dragon: http://forums.sohc4.net/index.php?topic=45183.msg1571675#msg1571675
Headlight Switch: http://forums.sohc4.net/index.php?topic=113986.msg1283236#msg1283236
Branden's leak free top end thread: http://forums.sohc4.net/index.php?topic=107040.0
Engine Lifting Made Easy: http://forums.sohc4.net/index.php/topic,58210.msg1684742.html#msg1684742
                                      http://forums.sohc4.net/index.php/topic,100352.msg1675840.html#msg1675840
Static and Dynamic Timing: http://www.hondachopper.com/garage/carb_info/timing/timing1.html
Airbox Gasket Replacement: http://forums.sohc4.net/index.php/topic,114485.msg1290000.html#msg1290000
"Café" : http://forums.sohc4.net/index.php/topic,84697.msg953814.html#msg953814
PD Carb Choke Linkage: http://forums.sohc4.net/index.php/topic,100352.msg1669248.html#msg1669248
                                    http://forums.sohc4.net/index.php/topic,110931.msg1248354.html#msg1248354
                                    http://forums.sohc4.net/index.php/topic,48858.msg515204.html#msg515204
Follow up on your damn posts: http://forums.sohc4.net/index.php/topic,144305.msg1791605.html#msg1791605
Taiwanese Cam Chain Tensioners:  http://forums.sohc4.net/index.php/topic,155043.msg1774841.html#msg1774841
Gumtwo Seat Cover: http://forums.sohc4.net/index.php/topic,164440.msg1897366.html#msg1897366
Primary Drive: http://forums.sohc4.net/index.php/topic,166063.msg1919278.html#msg1919278
Tank Latch: http://forums.sohc4.net/index.php/topic,165975.msg1919495.html#msg1919495
Shorten your forks: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-shorten-forks-td4042465.html DO NOT CUT THE SPRINGS!
Clutch How To: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-change-and-adjust-a-clutch-SOHC-td4040391.html
Late model K7/K8/F2/F3 front sprocket cover removal: http://forums.sohc4.net/index.php/topic,178428.msg2072279.html#msg2072279
630 to 530 conversion: http://forums.sohc4.net/index.php/topic,180710.msg2094423.html#msg2094423

Sent from my Tandy TRS-80!

Offline Retro Rocket

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Re: Senior project for high school - 78 CB750K
« Reply #1086 on: April 25, 2015, 03:39:09 PM »
I'm with Stev-o here. Lay off the full throttle twists while starting. Two twists before starting. Let the choke work its magic. If full choke seems too much then gradually reduce the amount of choke while trying to start.

And definitely let off the start button!  ;)

Agreed, you must learn to feather the throttle and "read"  the engine when starting a cold blooded engine, large twists of the throttle and choke will just flood it.... ;)  Almost there.....
750 K2 1000cc
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750 Bitsa 900cc
If You can't fix it with a hammer, You've got an electrical problem.

Offline Restoration Fan

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Re: Senior project for high school - 78 CB750K
« Reply #1087 on: April 25, 2015, 04:53:41 PM »
Major milestone. 

While we still have issues, at least we now have a runner! *happy dance*

The issue was the choke.  Pulling the choke to full closed position is really only closing the choke about 80 - 85% of the way.  It appears that the edge of one of the butterfly valves is binding against the side of the carb body and stopping it from going when you do it via the choke cable.  If you remove the carb face plate, it removes the binding and the cable will allow all 4 to close via the cable.  So we need to take the carb rack back off and figure out what's going on. 

But if you manually close the choke the rest of the way (we removed the air box to see what was going on inside the carbs), she starts up every time.

We're getting oil pressure at about 60 - 65 PSI according to our oil gauge, but our oil light isn't going off on the idiot lights.  So we need to sort out what's going on with that one.

Final issue:  only pipes 3 and 4 are getting hot.  One and two are completely cool so I don't think they're firing.  We double & triple checked the wires and I know we are still getting spark (I tested) but it appears there's an issue with the carbs on those 2 cylinders not sending in enough (or too much) gas.

Also, Bill texted me these 2 cool pics of a great guy I met yesterday named Charlie.  While I was there working on our carbs, Charlie was working on finishing up cleaning the inside of the tank on his 1970 K0.  There's a cool story behind the bike in that Charlie bought the bike in really bad shape.  It had been his buddy Mike's bike who had died years ago and Charlie went looking for the bike about 2 years ago and bought it from Mike's sister.  After a lot of help from Bill, the 2 of them have restored the bike to absolute showroom condition.  It's a GORGEOUS bike and I'm really happy for Charlie because Mike's sister is coming to town next week and he has been wanting her to see the bike.  Really cool personal connection to the bike for Charlie and he's a cool guy so I couldn't be happier for him.


« Last Edit: April 25, 2015, 05:09:49 PM by Restoration Fan »
Ron

Stella - Logan's Senior Project    78 750K http://forums.sohc4.net/index.php?topic=141761.0

Logan's Reward - CB500 and CB550 Cafes    http://forums.sohc4.net/index.php/topic,147787.0.html

Offline vfourfreak

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Re: Senior project for high school - 78 CB750K
« Reply #1088 on: April 25, 2015, 05:17:18 PM »
Great news lads !!! Huge progress. I think the non firing of 1 and 2 cyls has to be fuel supply problems, can you open the drain screws on those two carbs and verify there is fuel present ?

Kev

Offline madmtnmotors

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Re: Senior project for high school - 78 CB750K
« Reply #1089 on: April 25, 2015, 05:46:35 PM »
Right on! I've had the same issue with the choke plates binding. Best bet is to loosen the choke plate screws, set the choke to "full on" (almost have to in order to tighten the screws) and tighten them back down. Check the operation of the choke and watch for any more binding. It doesn't take much, these are not "direct driven" by the linkage, they are only spring driven.

Progress!
TAMTF...


Wilbur



Projects:
"Evolution": http://forums.sohc4.net/index.php?topic=100352.0
"P.O. Debacle": http://forums.sohc4.net/index.php/topic,126692.msg1441661.html#msg1441661
F2/F3 O-rings: http://forums.sohc4.net/index.php?topic=113672.msg1300721#msg1300721
Cam Tower Studs: https://www.mcmaster.com/#93210a017/=t19sgp
Clean up that nasty harness: http://forums.sohc4.net/index.php?topic=137351.msg1549191#msg1549191
http://forums.sohc4.net/index.php/topic,148188.msg1688494.html#msg1688494
http://forums.sohc4.net/index.php/topic,139544.msg1579364.html#msg1579364
                                          
Charging system diagnosis: http://forums.sohc4.net/index.php?topic=1012.msg8345#msg8345
Get the manuals: http://manuals.sohc4.net/cb750k/
The Dragon: http://forums.sohc4.net/index.php?topic=45183.msg1571675#msg1571675
Headlight Switch: http://forums.sohc4.net/index.php?topic=113986.msg1283236#msg1283236
Branden's leak free top end thread: http://forums.sohc4.net/index.php?topic=107040.0
Engine Lifting Made Easy: http://forums.sohc4.net/index.php/topic,58210.msg1684742.html#msg1684742
                                      http://forums.sohc4.net/index.php/topic,100352.msg1675840.html#msg1675840
Static and Dynamic Timing: http://www.hondachopper.com/garage/carb_info/timing/timing1.html
Airbox Gasket Replacement: http://forums.sohc4.net/index.php/topic,114485.msg1290000.html#msg1290000
"Café" : http://forums.sohc4.net/index.php/topic,84697.msg953814.html#msg953814
PD Carb Choke Linkage: http://forums.sohc4.net/index.php/topic,100352.msg1669248.html#msg1669248
                                    http://forums.sohc4.net/index.php/topic,110931.msg1248354.html#msg1248354
                                    http://forums.sohc4.net/index.php/topic,48858.msg515204.html#msg515204
Follow up on your damn posts: http://forums.sohc4.net/index.php/topic,144305.msg1791605.html#msg1791605
Taiwanese Cam Chain Tensioners:  http://forums.sohc4.net/index.php/topic,155043.msg1774841.html#msg1774841
Gumtwo Seat Cover: http://forums.sohc4.net/index.php/topic,164440.msg1897366.html#msg1897366
Primary Drive: http://forums.sohc4.net/index.php/topic,166063.msg1919278.html#msg1919278
Tank Latch: http://forums.sohc4.net/index.php/topic,165975.msg1919495.html#msg1919495
Shorten your forks: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-shorten-forks-td4042465.html DO NOT CUT THE SPRINGS!
Clutch How To: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-change-and-adjust-a-clutch-SOHC-td4040391.html
Late model K7/K8/F2/F3 front sprocket cover removal: http://forums.sohc4.net/index.php/topic,178428.msg2072279.html#msg2072279
630 to 530 conversion: http://forums.sohc4.net/index.php/topic,180710.msg2094423.html#msg2094423

Sent from my Tandy TRS-80!

Offline AintNoEasyWay

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Re: Senior project for high school - 78 CB750K
« Reply #1090 on: April 25, 2015, 06:12:22 PM »
Aww yeaaaa!!   8)

Offline SOHC4 Cafe Racer Fan

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Re: Senior project for high school - 78 CB750K
« Reply #1091 on: April 25, 2015, 09:57:17 PM »
Congratulations on firing the bike.  Sounds like you may have some fuel issues with 1 & 2.
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1975 CB550F1 frame/CB650 engine hybrid "The Hot Mess" (http://forums.sohc4.net/index.php/topic,150220.0.html)
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"There are some things nobody needs in this world, and a bright-red, hunch-back, warp-speed 900cc cafe racer is one of them — but I want one anyway, and on some days I actually believe I need one.... Being shot out of a cannon will always be better than being squeezed out of a tube. That is why God made fast motorcycles, Bubba." Hunter S. Thompson, Song of the Sausage Creature, Cycle World, March 1995.  (http://www.latexnet.org/~csmith/sausage.html and https://magazine.cycleworld.com/article/1995/3/1/song-of-the-sausage-creature)

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Offline knottedknickers

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Re: Senior project for high school - 78 CB750K
« Reply #1092 on: April 25, 2015, 11:20:00 PM »
Brings a big smile to my face. 8) Way to persevere, guys! If it was up to me, Logan would get an A+2!
CB750 K6 http://forums.sohc4.net/index.php?topic=141388.0

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Offline evanphi

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Re: Senior project for high school - 78 CB750K
« Reply #1093 on: April 26, 2015, 02:13:47 AM »
Congrats!
--Evan

1975 CB750K "Rhonda"
Delkevic Stainless 4-1 Header, Cone Engineering 18" Quiet Core Reverse Cone, K&N Filter in Drilled Airbox
K5 Crankcase/Frame, K4 Head and Cylinders, K1 Carbs (42;120;1 Turn)

She's a mix-matched (former) basket case, but she's mine.

CB750 Shop Manual (all years), searchable text PDF
Calculating the correct input circumference for digital speedometers connected to the original speedometer drive

Offline martin_uk

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Re: Senior project for high school - 78 CB750K
« Reply #1094 on: April 26, 2015, 02:50:45 AM »
Well done guys.

Its worth running first without the air cleaner, so you can visually check the accelerator jets and choke operation.

I had a problem with a twisted choke linkage, which prevented full closure and fast idle.

Not sure if I might have caused when fitting carbs, as need to make sure linkage is out of way of strap.

2015_0411eng0008 by nitram2010, on Flickr

The linkage has to swivel to get this to fully operate.

Fast idle should be about 3k rpm


Off

2015_0418eng0013 by nitram2010, on Flickr

Full on
2015_0418eng0015 by nitram2010, on Flickr

I found best starting was choke full on and leave throttle alone and let the fast idle mechanism do its job.

Did you sort out the mixture screws washer and O rings OK?

Mine runs well 1.5 turns out from fully in.

Did you remove slow jets to clean them and passage ?

2015_0407eng0007 by nitram2010, on Flickr

Apologies if I have coved points already mentioned in your posts.

Great work and not far to go. ;D

CB750F1, CB750K8,  Triumph Street Triple R, AJS 350, Triumph 3TA

Offline Restoration Fan

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Re: Senior project for high school - 78 CB750K
« Reply #1095 on: April 28, 2015, 05:48:33 PM »
Well, tomorrow is the big day!  Logan presents at 4:40 tomorrow afternoon and we have decided not to take the bike up there.  Not because it isn't ready but because we think it would be almost impossible to control the amount of time needed to walk the judges out to the bike and back.  It turns out that you get penalized more for going overtime than it would be helped by taking the bike up there.  So instead, he's going to include the following short video into his PowerPoint presentation tomorrow so that he can better control the time.

(Note:  I told him to rev the engine a couple of times so the judges could hear that on the video.  So he's not just ignoring the advice you guys gave us!)  ;)

We still have a few issues:
1)  There's a short somewhere.  We were blowing fuses on the main 15A circuit.  Just jiggling the wires around in the bucket and underneath the seat back by the battery box somehow fixed the issue for us to take the video.  But that is something we are going to have to investigate and solve before I'll feel comfortable riding it.
2)  After adjusting and bench synching the carbs on Sunday at Bill's house, #2 cylinder is now firing but #1 cylinder still isn't getting hot on it's exhaust.  I don't know if this will be solved by vacuum synching the carbs or not.
3)  Front brakes are still not bleeding properly.  Bill helped by cleaning out the little small return hole in the master cylinder and replacing our crappy diaphragm.  After doing so, we were seeing fluid come out of the end of the lever.  Indeed, now we can see fluid coming down the Slingshot Cycles stainless steel braided lines (I just like saying/typing that, sorry!  :D) and out the hole if we remove the nipple.  But with the bleeding nipple in (even just barely), it doesn't want to come out at all.  Since I've never bled motorcycle brakes before, I'm not sure if we're doing it properly or not.
4)  Tachometer stopped working.  Since this one's purely mechanical, we removed it from the valve cover today and discovered the braided line inside had broken about 4 inches up.  We removed the broken piece and re-inserted the magnet for the video but I'm going to have to get a new tach cable.
5)  Our oil pressure light still doesn't want to go out.  We're getting around 65 pounds of oil pressure, according to the gauge we attached but the light itself isn't going out.  We got another sensor from Bill this weekend and replaced the one that was in it but we're still seeing the light on.  I guess the next step is to diagnose if the problem is with the wiring of the light itself.

But we took Stella out of the garage today and shot the video in front of the garage.  When it was time to put her back up, Logan offered to help push her back in.  I looked at him and said, "I'm riding her back in."  To which he replied, "You don't have front brakes."  And I said, "I do have rear brakes and I don't plan on getting her going much faster than a walk...but it's time for her to be ridden."

And thus, even though it was only about 40 feet or so, I got to ride Stella briefly today for the first time.  Now it's time to get her buttoned up properly and go take my MSF class so I can ride her out on the road.
« Last Edit: April 28, 2015, 06:05:01 PM by Restoration Fan »
Ron

Stella - Logan's Senior Project    78 750K http://forums.sohc4.net/index.php?topic=141761.0

Logan's Reward - CB500 and CB550 Cafes    http://forums.sohc4.net/index.php/topic,147787.0.html

Offline evanphi

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Re: Senior project for high school - 78 CB750K
« Reply #1096 on: April 28, 2015, 06:03:43 PM »
Good luck tomorrow!
--Evan

1975 CB750K "Rhonda"
Delkevic Stainless 4-1 Header, Cone Engineering 18" Quiet Core Reverse Cone, K&N Filter in Drilled Airbox
K5 Crankcase/Frame, K4 Head and Cylinders, K1 Carbs (42;120;1 Turn)

She's a mix-matched (former) basket case, but she's mine.

CB750 Shop Manual (all years), searchable text PDF
Calculating the correct input circumference for digital speedometers connected to the original speedometer drive

Offline calj737

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Re: Senior project for high school - 78 CB750K
« Reply #1097 on: April 28, 2015, 06:10:53 PM »
 :D

I lament the end is nigh on this journey. Many of us have lived vicariously through you two and to think it may be coming to a close is saddening. But very best of luck tomorrow for Logan! I'm sure you're very proud of him  :)
'74 550 Build http://forums.sohc4.net/index.php?topic=126401.0
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Offline dave the welder

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Re: Senior project for high school - 78 CB750K
« Reply #1098 on: April 28, 2015, 06:47:00 PM »
if Logan worked as hard on his speech as he has on Stella I cannot imagine nothing less than A PLUS  good luck
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Offline Stev-o

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Re: Senior project for high school - 78 CB750K
« Reply #1099 on: April 28, 2015, 07:41:05 PM »
Good luck to Logan, we'll be waiting on a full report. 

BTW - no, a carb sync will not help the #2 non-fire issue.  The bike doesn't sound quite right, like it's only running on 3 cyl.  You sure you have spark on all 4?
'74 "Big Bang" Honda 750K [836].....'76 Honda 550F.....K3 Park Racer!......and a Bomber!............plus plus plus.........