Author Topic: Can you swap a 96' CB750 motor in an 82' cb650sc  (Read 1502 times)

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Offline juntjoo

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Can you swap a 96' CB750 motor in an 82' cb650sc
« on: August 09, 2018, 10:51:07 AM »
Mechanic went back into bike to tighten engine block bolts to stop a leak, then suddenly the engine is knocking. They're telling me that that is how it sometimes happens. Idk. They were screwing me from the get go and at this point I can't tell fact from fiction. Anyway, they're offering to replace the engine and cover the labor. So far only finding iffy replacements with a lot of miles and then a good looking low mileage 92' CB750. So I'm wondering if it's possible to swap this engine in and if so how much difficult it would be.
-Ben

82 Nighthawk 650..

1982 Honda Nighthawk...

I HAVE A 1982 HONDA NIGHTHAWK FFS! j/k. It's my only bike, my first and last.

Offline Bankerdanny

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Re: Can you swap a 96' CB750 motor in an 82' cb650sc
« Reply #1 on: August 09, 2018, 11:51:30 AM »
Possible? Sure, pretty much anything is possible. Feasible, I doubt it. The DOHC engines are taller
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Current: '76 CB750F. Previous:  '75 CB550F, 2007 Yamaha Vino 125 Scooter, '75 Harley FXE Superglide, '77 GL1000, '77 CB550k, '68 Suzuki K10 80, '68 Yamaha YR2, '69 BMW R69S, '71 Honda SL175, '02 Royal Enfield Bullet 500, '89 Yamaha FJ1200

Offline Scott S

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Re: Can you swap a 96' CB750 motor in an 82' cb650sc
« Reply #2 on: August 09, 2018, 01:27:37 PM »
 Just keep the Nighthawk. They're great bikes, great engines, and not bad looking.
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Offline Duke McDukiedook

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Re: Can you swap a 96' CB750 motor in an 82' cb650sc
« Reply #3 on: August 09, 2018, 02:13:59 PM »
And do not take another bike into that mechanic ever again.
"Well, Mr. Carpetbagger. We got somethin' in this territory called the Missouri boat ride."   Josey Wales

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Offline juntjoo

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Re: Can you swap a 96' CB750 motor in an 82' cb650sc
« Reply #4 on: August 09, 2018, 02:27:04 PM »
Yeah, never again. They tried not to take responsibility for the cylinder block gasket leak, saying that they only touched the head. So I said 'I gave you a whole gasket rebuild kit, (to supposedly fix a valve), the block was loose, where's the new gasket you didn't use?' at first they said they threw it away. I threatened to take them to court, suddenly the story changed and he decided he would fix the leak but then back stepped saying he couldn't guarantee there wouldn't be problems with the pistons just from changing the gasket, if he even had to do more than tighten the bolts. Low and behold I get a call, "good news we got the leak fixed, bad news is the engine is (suddenly) knocking". I wouldn't be surprised if in total they purposely messed up my valve then purposely messed up my piston cuz I called them out for being the crooks they are. How does the previously fine running engine block suddenly start knocking cuz they went in to tighten block bolts? But now he's offering to replace the motor and cover the labor. What's that mean? He's got half a heart? Eh.... I'm just gonna pick it up and part it out. I bet you the original car mechanic who looked at it and thought I just over tightened the adjustment nut was right, and all the bike needed was a proper adjustment. Then I ran into these a-holes. Maybe I'll have someone take it apart inspect everything get some proof they messed it up(I think the valve and other mechanic as witness it wasn't nicked like that is enough) and sue him for all of it.
-Ben

82 Nighthawk 650..

1982 Honda Nighthawk...

I HAVE A 1982 HONDA NIGHTHAWK FFS! j/k. It's my only bike, my first and last.

Offline scunny

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Re: Can you swap a 96' CB750 motor in an 82' cb650sc
« Reply #5 on: August 09, 2018, 09:40:45 PM »
I wouldn't let them put the air in a kids tricycle tyres, let alone do an engine swap.
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Offline Gurp

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Re: Can you swap a 96' CB750 motor in an 82' cb650sc
« Reply #6 on: August 10, 2018, 04:20:53 AM »
I would just tell them you are taking them for small claims court for the cost of a complete rebuild at a reputable shop. Doesnt matter if you are or aren't. Just let them stew on it.
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Offline dave500

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Re: Can you swap a 96' CB750 motor in an 82' cb650sc
« Reply #7 on: August 11, 2018, 12:22:13 AM »
you wont be getting a 96 motor into that bike full stop!its not like a car swap you've got the drive chain alighnment and carbies etc to squeeze in,get an exhaust system on it etc,it wont happen.

Offline MikeSimon

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Re: Can you swap a 96' CB750 motor in an 82' cb650sc
« Reply #8 on: August 11, 2018, 05:48:04 PM »
I am not really sure what you are talking about. In the subject line you talk about a 96 CB750, in the post it is a 92 CB750, although it wouldn't make much difference as they are both RC38 engines. Unfortunately, your CB650 is probably just one year too old as it is a SOHC and the motor is quite a bit different. 83 would probably be less of an issue. For someone with some skill, however, it would still be possible. just not a simple swap.
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1974 CB350F -218 orig miles, sold
1976 CB750K - in restoration

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Plus Kawasakis, BMws & Ducatis

Offline SOHC4 Cafe Racer Fan

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Re: Can you swap a 96' CB750 motor in an 82' cb650sc
« Reply #9 on: August 12, 2018, 12:29:40 PM »
you wont be getting a 96 motor into that bike full stop!its not like a car swap you've got the drive chain alighnment and carbies etc to squeeze in,get an exhaust system on it etc,it wont happen.

That and IF YOU COULD, you'd fold the frame with the torque of a 96 CBR motor.
1975 CB550K1 "Blue" Stockish Restomod (http://forums.sohc4.net/index.php?topic=135005.0)
1975 CB550F1 frame/CB650 engine hybrid "The Hot Mess" (http://forums.sohc4.net/index.php/topic,150220.0.html)
2008 Triumph Thruxton (http://forums.sohc4.net/index.php/topic,190956.0.html)
2014 MV Agusta Brutale Dragster 800
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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)

Sold/Emeritus
1973 CB750K2 "Bionic Mongrel" (http://forums.sohc4.net/index.php?topic=132734.0) - Sold
1977 CB750K7 "Nine Lives" Restomod (http://forums.sohc4.net/index.php?topic=50490.0) - Sold
2005 RVT1000RR RC51-SP2 "El Diablo" - Sold
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Offline MikeSimon

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Re: Can you swap a 96' CB750 motor in an 82' cb650sc
« Reply #10 on: August 13, 2018, 06:21:47 AM »

That and IF YOU COULD, you'd fold the frame with the torque of a 96 CBR motor.

Who is talking about a CBR?
1973 CB350F -sold
1974 CB350F -218 orig miles, sold
1976 CB750K - in restoration

Other Hondas:
3 x CBX
CB1100R
GB500
Plus Kawasakis, BMws & Ducatis

Offline Duke McDukiedook

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Re: Can you swap a 96' CB750 motor in an 82' cb650sc
« Reply #11 on: August 13, 2018, 10:54:00 AM »
Looks like fan was.
"Well, Mr. Carpetbagger. We got somethin' in this territory called the Missouri boat ride."   Josey Wales

"It's Baltimore, gentlemen. The gods will not save you." Ervin Burrell

CB750 K3 crat | (2) 1986 VFR750F

Offline Bankerdanny

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Re: Can you swap a 96' CB750 motor in an 82' cb650sc
« Reply #12 on: August 14, 2018, 08:12:15 AM »
Looks like fan was.

No, I don't think so. Honda had reintroduced the Nighthawk 750 by that time.
"The problem with quotes on the Internet is that you never know if they're true" - Abraham Lincoln

Current: '76 CB750F. Previous:  '75 CB550F, 2007 Yamaha Vino 125 Scooter, '75 Harley FXE Superglide, '77 GL1000, '77 CB550k, '68 Suzuki K10 80, '68 Yamaha YR2, '69 BMW R69S, '71 Honda SL175, '02 Royal Enfield Bullet 500, '89 Yamaha FJ1200

Offline SOHC4 Cafe Racer Fan

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Re: Can you swap a 96' CB750 motor in an 82' cb650sc
« Reply #13 on: August 14, 2018, 08:22:00 AM »
Looks like fan was.

No, I don't think so. Honda had reintroduced the Nighthawk 750 by that time.

You are right.  I was thinking the OP was talking about a 1996 and my brain went to CBR900.  You guys are totally correct that, in 1996, Honda had the CB750 Nighthawk. 
1975 CB550K1 "Blue" Stockish Restomod (http://forums.sohc4.net/index.php?topic=135005.0)
1975 CB550F1 frame/CB650 engine hybrid "The Hot Mess" (http://forums.sohc4.net/index.php/topic,150220.0.html)
2008 Triumph Thruxton (http://forums.sohc4.net/index.php/topic,190956.0.html)
2014 MV Agusta Brutale Dragster 800
2015 Yamaha FZ-09 (http://forums.sohc4.net/index.php/topic,186861.0.html)

"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)

Sold/Emeritus
1973 CB750K2 "Bionic Mongrel" (http://forums.sohc4.net/index.php?topic=132734.0) - Sold
1977 CB750K7 "Nine Lives" Restomod (http://forums.sohc4.net/index.php?topic=50490.0) - Sold
2005 RVT1000RR RC51-SP2 "El Diablo" - Sold
2016+ Triumph Thruxton 1200 R (http://forums.sohc4.net/index.php/topic,170198.0.html) - Sold