Author Topic: Startup after long layup  (Read 530 times)

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Offline Eengers

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Startup after long layup
« on: June 17, 2022, 09:21:03 AM »
Hello all, new member here looking for a little advice/direction. I recently got a 1976 CB750A from a guy who parked it and lost interest roughly 4 years ago. The bike is complete and in pretty good shape for the age. I got it home and popped the plugs out, squirted some oil in the cylinders, and put them back. Drained the gas and put in fresh, and drained the carbs. The starter button doesn't work so I jumped the solenoid. Bike would start with choke and throttle but wouldn't idle. I didn't really have time to dive in any farther, so I parked the bike and that's where I've left off. As I get more time now I plan on working on it, but wanted to know the "order of operations" when starting one of these up after a long layup. I have several goldwings and usually start with the carbs before going any farther with electrical, brakes, cooling, etc. but didn't know if this is any different being a points/air cooled bike vs a goldwing. Should I consider electronic ignition and new coils/wires? I need to look at timing/points regardless, and inspect the coils closer to look for cracks or other issues. I like to think I can run some fresh fuel and cleaner to clean out the carbs without yanking them, but maybe not. Any advice is appreciated, thanks!
1976 CB750 Hondamatic - Current project
1981 CB650 - Project in pieces
1982 GL1100 - "Daily Driver"
1981 GL1100 - "Cafe Racer" Frankenstein bike
2x - 1979 GL1000 - Projects for later

Offline newday777

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Re: Startup after long layup
« Reply #1 on: June 17, 2022, 09:39:21 AM »
Welcome aboard.
Yes basically the same as the wings. Except cam chain adjustment before valves. Carbs will need a good cleaning.  Check the tank for rust in the bottom with a good flashlight. Do you have a service manual for it yet?
If not there is a download for it.
http://manuals.sohc4.net/cb750a/
Stu
Honda Parts manager in the mid 1970s Nashua Honda
My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
1976 K6 Anteres Red rebuilding project, was originally my brother's that I set up from the crate, it'll breath again soon!
Project 750s, 2 K4, 2 K6, 1 K8
2008 GL1800 my daily ride and cross country runner

Prior bikes....
1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
New CB450 K7 after my friend returned...
New CB750 K5 Planet Blue, demise by ex cousin in law at 9,000 miles...
New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
1983 GL1100A, 1999 GL1500 SE, 1999 GL1500A

Offline Stev-o

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Re: Startup after long layup
« Reply #2 on: June 17, 2022, 01:59:47 PM »
+1...carbs need to be spotless, pull 'em.  It would be good to give it the full "3000 mile tune up", resist the urge to buy cheap aftermarket carb kits, points and condensers. These have been known to give tuning issues.  Dive in!
'74 "Big Bang" Honda 750K [836].....'76 Honda 550F.....K3 Park Racer!......and a Bomber!............plus plus plus.........

Offline BenelliSEI

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Re: Startup after long layup
« Reply #3 on: June 17, 2022, 02:57:24 PM »
Carbs for sure. If it only runs on full choke, idle (slow running) jets will be plugged. You can probably reuse 99% of the carb parts, but if you take the rack apart replace the “0” rings on the fuel tubes that connect the bowls. If you have access to an ultrasonic cleaning tank, get them in there.....

Offline Airborne 82nd

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Re: Startup after long layup
« Reply #4 on: June 17, 2022, 07:24:27 PM »
Yes on the carbs you can yank them now or fart around with them a few days or weeks then yank them. I would not be changing other parts like the points until you prove them to be bad other wise you could be adding a new problem. Not sure about the autos but are your plug wires part of the coils? Caps can be changed but ohm them out first. I did change my wires with the NGK splice kit and new caps. And +1 on the 3K tune up.

Offline Eengers

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Re: Startup after long layup
« Reply #5 on: June 19, 2022, 05:38:16 AM »
Thanks all for the information. I will yank the carbs and stick them in my 10L ultrasonic cleaner, probably not a bad idea as noted. Where does everyone order carb parts from? The coil wires do come out of the coils, I'll ohm everything and look at getting some new caps if I need to.
1976 CB750 Hondamatic - Current project
1981 CB650 - Project in pieces
1982 GL1100 - "Daily Driver"
1981 GL1100 - "Cafe Racer" Frankenstein bike
2x - 1979 GL1000 - Projects for later

Offline newday777

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  • Posts: 5,534
  • Avatar is my 76 K6 in Colorado w/Cody on back 1980
Stu
Honda Parts manager in the mid 1970s Nashua Honda
My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
1976 K6 Anteres Red rebuilding project, was originally my brother's that I set up from the crate, it'll breath again soon!
Project 750s, 2 K4, 2 K6, 1 K8
2008 GL1800 my daily ride and cross country runner

Prior bikes....
1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
New CB450 K7 after my friend returned...
New CB750 K5 Planet Blue, demise by ex cousin in law at 9,000 miles...
New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
1983 GL1100A, 1999 GL1500 SE, 1999 GL1500A

Offline Eengers

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Re: Startup after long layup
« Reply #7 on: September 02, 2022, 04:07:07 AM »
Just to follow up on this one, I pulled, cleaned, and rebuilt the carbs and reinstalled them finally last weekend. To my surprise, it fired right up! It's going to need a tune-up to include oil change, brake service, valve adjustment, points inspection, and I got some new caps for the plugs. A lot of this I will do this weekend I hope. This thing starts pretty weak but once it warms up it runs good.
1976 CB750 Hondamatic - Current project
1981 CB650 - Project in pieces
1982 GL1100 - "Daily Driver"
1981 GL1100 - "Cafe Racer" Frankenstein bike
2x - 1979 GL1000 - Projects for later

Offline newday777

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  • Avatar is my 76 K6 in Colorado w/Cody on back 1980
Re: Startup after long layup
« Reply #8 on: September 02, 2022, 05:14:49 AM »
Good to hear you got it running. What kits did you get?
Is the tank rust free?
Stu
Honda Parts manager in the mid 1970s Nashua Honda
My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
1976 K6 Anteres Red rebuilding project, was originally my brother's that I set up from the crate, it'll breath again soon!
Project 750s, 2 K4, 2 K6, 1 K8
2008 GL1800 my daily ride and cross country runner

Prior bikes....
1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
New CB450 K7 after my friend returned...
New CB750 K5 Planet Blue, demise by ex cousin in law at 9,000 miles...
New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
1983 GL1100A, 1999 GL1500 SE, 1999 GL1500A

Offline Eengers

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Re: Startup after long layup
« Reply #9 on: September 02, 2022, 04:34:02 PM »
Well to be honest all I replaced was the float bowl gaskets and the air mixture screw o rings and that seemed to be enough. The tank does appear to have a little rust in it but I'm running a fuel filter from the tank to the carb. The tank has a large dent in it and I'm debating how to fix it vs replacement.
1976 CB750 Hondamatic - Current project
1981 CB650 - Project in pieces
1982 GL1100 - "Daily Driver"
1981 GL1100 - "Cafe Racer" Frankenstein bike
2x - 1979 GL1000 - Projects for later