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Author Topic: 72 CB750 almost back on the road  (Read 3980 times)

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Offline BenelliSEI

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Re: 72 CB750 almost back on the road
« Reply #25 on: April 14, 2021, 06:08:59 pm »
Really nice work! And well written story too. Much appreciated and congrats!
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Offline Casor

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Re: 72 CB750 almost back on the road
« Reply #26 on: April 14, 2021, 06:10:56 pm »
Thank you!
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1966 Ducati 250 Monza project, 1971 BMW R75, 1972 Honda CB750, 1972 Norton 750 Commando, 1974 Ducati 750 Sport,  1974 Laverda SF2, 1975 BMW R90S, 1975 Honda 250 XL, 1975 Honda CB400F, 1983 BMW R100S, 1986 Ducati Mike Hailwood Replica Mille, 1994 Bimota DB2, 1995 Ducati 916, 2005 BMW R1200 GS, 2005 MV Agusta F4 1000 Ago, 2016 Triumph Thruxton R

Offline Casor

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Re: 72 CB750 almost back on the road
« Reply #27 on: April 14, 2021, 06:12:14 pm »
Thanks for the comments, I thought I did install the stock Honda pads.  Going to take it all apart and see what I can see.  Apparently this is a common problem.  The bike sounds like a freight train!!
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1966 Ducati 250 Monza project, 1971 BMW R75, 1972 Honda CB750, 1972 Norton 750 Commando, 1974 Ducati 750 Sport,  1974 Laverda SF2, 1975 BMW R90S, 1975 Honda 250 XL, 1975 Honda CB400F, 1983 BMW R100S, 1986 Ducati Mike Hailwood Replica Mille, 1994 Bimota DB2, 1995 Ducati 916, 2005 BMW R1200 GS, 2005 MV Agusta F4 1000 Ago, 2016 Triumph Thruxton R

Offline andy750

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Re: 72 CB750 almost back on the road
« Reply #28 on: April 14, 2021, 06:46:13 pm »
Quote from: Casor on April 14, 2021, 06:12:14 pm
Thanks for the comments, I thought I did install the stock Honda pads.  Going to take it all apart and see what I can see.  Apparently this is a common problem.  The bike sounds like a freight train!!

Very well written Restoration notes thank you. I use some Corning high temp silicone on the back of the brake pads and this usually works from May - November with no squeaking at all. When it does come back simply reapply after cleaning and you are good to go. 
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Current bikes
1. CB750K4: Long distance bike, 17 countries and counting...2001 - Trans-USA-Mexico, 2003 - European Tour, 2004 - SOHC Easy Rider Trip , 2008 - Adirondack Tour 2-up , 2013 - Tail of the Dragon Tour , 2017: 836 kit install and bottom end rebuild. And rebirth: http://forums.sohc4.net/index.php/topic,173213.msg2029836.html#msg2029836
2. CB750/810cc K2  - road racer with JMR worked head 71 hp
3. Yamaha Tenere T700 2022

Where did you go on your bike today? - http://forums.sohc4.net/index.php?topic=45183.2350

Offline Casor

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Re: 72 CB750 almost back on the road
« Reply #29 on: April 14, 2021, 06:55:11 pm »
I have started writing up all the bikes that I have done significant work to or have had for a long time.  Some of them I have gone back and written up because you forget.  While I have receipts etc, these really don't tell the story that well.

Re the silicone - is that the wet tube stuff?
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1966 Ducati 250 Monza project, 1971 BMW R75, 1972 Honda CB750, 1972 Norton 750 Commando, 1974 Ducati 750 Sport,  1974 Laverda SF2, 1975 BMW R90S, 1975 Honda 250 XL, 1975 Honda CB400F, 1983 BMW R100S, 1986 Ducati Mike Hailwood Replica Mille, 1994 Bimota DB2, 1995 Ducati 916, 2005 BMW R1200 GS, 2005 MV Agusta F4 1000 Ago, 2016 Triumph Thruxton R

Offline andy750

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Re: 72 CB750 almost back on the road
« Reply #30 on: April 15, 2021, 05:30:07 am »



Sent from my iPhone using Tapatalk
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Current bikes
1. CB750K4: Long distance bike, 17 countries and counting...2001 - Trans-USA-Mexico, 2003 - European Tour, 2004 - SOHC Easy Rider Trip , 2008 - Adirondack Tour 2-up , 2013 - Tail of the Dragon Tour , 2017: 836 kit install and bottom end rebuild. And rebirth: http://forums.sohc4.net/index.php/topic,173213.msg2029836.html#msg2029836
2. CB750/810cc K2  - road racer with JMR worked head 71 hp
3. Yamaha Tenere T700 2022

Where did you go on your bike today? - http://forums.sohc4.net/index.php?topic=45183.2350

Offline MauiK3

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Re: 72 CB750 almost back on the road
« Reply #31 on: April 15, 2021, 08:32:52 am »
Very nice bike!
I note that the previous owner must have assembled the jewels on the side cover with the wings facing rearward. They are easy to swap so they face forward. It's a common mistake.
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1973 CB 750 K3
10/72 build Z1 Kawasaki

Offline Casor

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Re: 72 CB750 almost back on the road
« Reply #32 on: April 15, 2021, 08:39:35 am »
Thanks for pointing out that disturbance in the force!  I will definitely fix that.  I know that the tank was repainted before I got the bike so the sides must have been also...
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1966 Ducati 250 Monza project, 1971 BMW R75, 1972 Honda CB750, 1972 Norton 750 Commando, 1974 Ducati 750 Sport,  1974 Laverda SF2, 1975 BMW R90S, 1975 Honda 250 XL, 1975 Honda CB400F, 1983 BMW R100S, 1986 Ducati Mike Hailwood Replica Mille, 1994 Bimota DB2, 1995 Ducati 916, 2005 BMW R1200 GS, 2005 MV Agusta F4 1000 Ago, 2016 Triumph Thruxton R

Offline Casor

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Re: 72 CB750 almost back on the road
« Reply #33 on: April 19, 2021, 10:44:54 pm »
Dropped a couple cyls on the way home from a 40 mi ride Sunday but then they came back a few miles later.  Appeared that the #3,4 cyls said goodbye for a while as the headers had cooled for those two.  Have not investigated yet but has to be electrical.  Has a new Honda coil pack and plugs which were the only major elec changes made.  Points were checked before disassembly.  Will start poking around this week....
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1966 Ducati 250 Monza project, 1971 BMW R75, 1972 Honda CB750, 1972 Norton 750 Commando, 1974 Ducati 750 Sport,  1974 Laverda SF2, 1975 BMW R90S, 1975 Honda 250 XL, 1975 Honda CB400F, 1983 BMW R100S, 1986 Ducati Mike Hailwood Replica Mille, 1994 Bimota DB2, 1995 Ducati 916, 2005 BMW R1200 GS, 2005 MV Agusta F4 1000 Ago, 2016 Triumph Thruxton R

Offline MauiK3

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Re: 72 CB750 almost back on the road
« Reply #34 on: April 20, 2021, 09:04:13 am »
Did the coils include the plug ends? They have been known to go bad.
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1973 CB 750 K3
10/72 build Z1 Kawasaki

Offline Casor

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Re: 72 CB750 almost back on the road
« Reply #35 on: April 20, 2021, 09:15:21 am »
No, just the four high tension leads.  Having trouble remembering but I think I re-used the caps from the original set.
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1966 Ducati 250 Monza project, 1971 BMW R75, 1972 Honda CB750, 1972 Norton 750 Commando, 1974 Ducati 750 Sport,  1974 Laverda SF2, 1975 BMW R90S, 1975 Honda 250 XL, 1975 Honda CB400F, 1983 BMW R100S, 1986 Ducati Mike Hailwood Replica Mille, 1994 Bimota DB2, 1995 Ducati 916, 2005 BMW R1200 GS, 2005 MV Agusta F4 1000 Ago, 2016 Triumph Thruxton R

Offline MauiK3

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Re: 72 CB750 almost back on the road
« Reply #36 on: April 20, 2021, 02:54:03 pm »
Check resistance in the caps with a digital ohm meter, if above 8k ohms, replace. Yamiya and David silver usually have them . I think 8k home is right, mine were over 10k ohm so I got new ones.
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1973 CB 750 K3
10/72 build Z1 Kawasaki

Offline Casor

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Re: 72 CB750 almost back on the road
« Reply #37 on: April 20, 2021, 03:02:19 pm »
Quote from: MauiK3 on April 20, 2021, 02:54:03 pm
Check resistance in the caps with a digital ohm meter, if above 8k ohms, replace. Yamiya and David silver usually have them . I think 8k home is right, mine were over 10k ohm so I got new ones.

Roger that, thanks much
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1966 Ducati 250 Monza project, 1971 BMW R75, 1972 Honda CB750, 1972 Norton 750 Commando, 1974 Ducati 750 Sport,  1974 Laverda SF2, 1975 BMW R90S, 1975 Honda 250 XL, 1975 Honda CB400F, 1983 BMW R100S, 1986 Ducati Mike Hailwood Replica Mille, 1994 Bimota DB2, 1995 Ducati 916, 2005 BMW R1200 GS, 2005 MV Agusta F4 1000 Ago, 2016 Triumph Thruxton R

Offline Stev-o

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Re: 72 CB750 almost back on the road
« Reply #38 on: August 27, 2021, 02:43:05 pm »
Quote from: Casor on April 20, 2021, 09:15:21 am
No, just the four high tension leads.  Having trouble remembering but I think I re-used the caps from the original set.

Just following up, did you get the 3/4 cyl issue resolved?
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'74 "Big Bang" Honda 750K [836].....'76 Honda 550F.....K3 Park Racer!......and a Bomber!............plus plus plus.........

Offline Casor

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Re: 72 CB750 almost back on the road
« Reply #39 on: August 27, 2021, 04:51:16 pm »
Stev-o
Thanks for asking.  After thinking about it a lot, I elected to replace the SP caps with NGK's.  I wanted to change only one variable at a time, so that is all I have done.

Interestingly, when I pulled the old caps off the plugs, #3 felt very loose.  I could tell that it was not positively locked on the #3 plug - you can just feel it and it didn't come off the plug like the other three did.  I replaced the caps and made absolutely sure that they were all positively seated and locked on each plug.  It must be a casting issue as #3 took quite a push to get it on.  I think that may have been the problem all along.

I just had carpal surgery on my hand which is now ready to go, so I did this two wks ago but have not ridden the bike again to test it all out.

Will advise!
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1966 Ducati 250 Monza project, 1971 BMW R75, 1972 Honda CB750, 1972 Norton 750 Commando, 1974 Ducati 750 Sport,  1974 Laverda SF2, 1975 BMW R90S, 1975 Honda 250 XL, 1975 Honda CB400F, 1983 BMW R100S, 1986 Ducati Mike Hailwood Replica Mille, 1994 Bimota DB2, 1995 Ducati 916, 2005 BMW R1200 GS, 2005 MV Agusta F4 1000 Ago, 2016 Triumph Thruxton R
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