Can you swap a 96' CB750 motor in an 82' cb650sc

If it's broken or just needs tweaked

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juntjoo
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Can you swap a 96' CB750 motor in an 82' cb650sc

Postby juntjoo » Thu Aug 09, 2018 12:54 pm

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.
82" cb650 Nighthawk

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Folsoml
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Re: Can you swap a 96' CB750 motor in an 82' cb650sc

Postby Folsoml » Thu Aug 09, 2018 3:50 pm

If you can weld, you can make anything fit. I'm not saying it won't bolt right in, I just have no experience with such things.
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My Current Bikes: 2005 HD FLHTCUI Electra Glide Ultra Classic, 2007 Yamaha Vino,

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Volker_P
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Re: Can you swap a 96' CB750 motor in an 82' cb650sc

Postby Volker_P » Tue Aug 14, 2018 2:05 am

juntjoo wrote:Mechanic went back into bike to tighten engine block bolts to stop a leak.

If you want to have a tight engine, you have to clean surfaces carefully before reinstall and follow the stepwise torque schemes with a small enough torque bolt. Try tightening bolts at a CB650 head cover or head to stop a leak from outside will usually just scrap some threads and require some more helicoils.

Is this again the Harley guys you reported in viewtopic.php?f=3&t=14692 ?
Anyway my impression is something really bad is going one there. For whatever reason.

Basically one could make everything fit (and I bet it would not just be done with the engine) but this effort makes no sense if you just want to have a bike that runs. Moreover, if you would these guys let try that, you quite certainly will end up with a scrap frame, too.

Sorry but from my point of view you either find someone that really has some idea of old CB's, learn doing it in a proper way yourself or better forget about old bikes as quick as possible.
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

juntjoo
Posts: 288
Joined: Fri Nov 10, 2017 6:19 pm

Re: Can you swap a 96' CB750 motor in an 82' cb650sc

Postby juntjoo » Tue Aug 14, 2018 9:54 am

Volker_P wrote:
juntjoo wrote:Mechanic went back into bike to tighten engine block bolts to stop a leak.

If you want to have a tight engine, you have to clean surfaces carefully before reinstall and follow the stepwise torque schemes with a small enough torque bolt. Try tightening bolts at a CB650 head cover or head to stop a leak from outside will usually just scrap some threads and require some more helicoils.

Is this again the Harley guys you reported in viewtopic.php?f=3&t=14692 ?
Anyway my impression is something really bad is going one there. For whatever reason.

Basically one could make everything fit (and I bet it would not just be done with the engine) but this effort makes no sense if you just want to have a bike that runs. Moreover, if you would these guys let try that, you quite certainly will end up with a scrap frame, too.

Sorry but from my point of view you either find someone that really has some idea of old CB's, learn doing it in a proper way yourself or better forget about old bikes as quick as possible.


You're right. Yes, same guys. I've already brought it to another mechanic a couple towns away who specialize in old bikes.
82" cb650 Nighthawk

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Volker_P
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Re: Can you swap a 96' CB750 motor in an 82' cb650sc

Postby Volker_P » Thu Aug 16, 2018 3:46 am

Good idea.
Now someone at the Harley shop lost a bet. :wink:
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues


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