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Author Topic: 1980 CB650 Engine swap  (Read 421 times)

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Offline Tdinova

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1980 CB650 Engine swap
« on: October 09, 2018, 05:40:53 pm »
My son has a 1980 CB650 and it needs an engine. It has mechanical carbs, would the CV carb engine bolt on my frame?
What year engines will work on his bike?

Thanks in advance

Blair
Blair
Nova Scotia, Canada

Offline Tdinova

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Re: 1980 CB650 Engine swap
« Reply #1 on: October 09, 2018, 05:51:14 pm »
I just done a search on this site.. It looks like only a 79 or 80 will work. But I did read that my head will work on a 81 or 82.  Is this true?
Blair
Nova Scotia, Canada

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Re: 1980 CB650 Engine swap
« Reply #2 on: October 09, 2018, 07:25:48 pm »
I got a brand new late head, i would sell.
 I think the heads interchange if you have the right carbs..
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Offline calj737

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Re: 1980 CB650 Engine swap
« Reply #3 on: October 10, 2018, 03:43:42 am »
I just done a search on this site.. It looks like only a 79 or 80 will work. But I did read that my head will work on a 81 or 82.  Is this true?
It would help to know what bike you have to offer compatibility advice.
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Offline kslrr

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1980 CB650 Engine swap
« Reply #4 on: October 10, 2018, 04:12:58 am »
I have an ‘81 engine and a set of engine cases.  The original engine case is cracked due to a thrown chain which also bent the shifting shaft.  If your up for a rebuild........

Edit: it should fit in the frame.  Currently there’s a ‘79 engine in my ‘81 bike.


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« Last Edit: October 10, 2018, 04:14:56 am by kslrr »
Now  1972 CB350FX (experimental v2.0)
        1981 CB650c Custom with '79 engine (wifes)
        1981 CB650 engine
        2004 HD XL883C Custom
        1977 Yamaha XS750D (in progress)
Then 1972 CL175
        1964 Yamaha YGS-1T
No ride is a Bad ride

Offline Scott S

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Re: 1980 CB650 Engine swap
« Reply #5 on: October 10, 2018, 08:08:08 am »
 The manifolds for the carbs are cast into the heads. That's pretty much the only difference in the SOHC4 CB650's.
 If you have a  good bottom end and good head/carbs, just make one good engine.
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'71 CT70
'14 Triumph Scrambler

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Offline Tdinova

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Re: 1980 CB650 Engine swap
« Reply #6 on: October 10, 2018, 12:02:54 pm »
I just done a search on this site.. It looks like only a 79 or 80 will work. But I did read that my head will work on a 81 or 82.  Is this true?
It would help to know what bike you have to offer compatibility advice.
Sorry 1980 cb650

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« Last Edit: October 10, 2018, 12:05:44 pm by Tdinova »
Blair
Nova Scotia, Canada

Offline Tdinova

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Re: 1980 CB650 Engine swap
« Reply #7 on: October 10, 2018, 12:07:26 pm »
I should have added that I live in Nova Scotia Canada

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Blair
Nova Scotia, Canada

Offline CBGhia

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Re: 1980 CB650 Engine swap
« Reply #8 on: October 10, 2018, 12:09:53 pm »
Ok, so you can get an 81 or 82 engine and use the head and carbs from your bike.

Or you can get an 81 or 82 engine and use the carbs from that bike.

Or you can just get a 79 or 80 engine.
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if you dont trial spin the camshaft in the head and cover you are a novice,with no natural mechanical appitude,destined for destruction.
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Offline Tdinova

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Re: 1980 CB650 Engine swap
« Reply #9 on: October 10, 2018, 02:25:03 pm »
I just done a compression test

Dry test throttle wide open
1  110
2  110
3  100
4  100

I added oil to each cyl. Throttle still wide open.

1   130
2   130
3   125
4   120

Are the number too low to have good performance. The bike has 35000km


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Blair
Nova Scotia, Canada

Offline Scott S

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Re: 1980 CB650 Engine swap
« Reply #10 on: October 10, 2018, 04:09:17 pm »
 Those seem OK to me.
'73 CB500/550
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'14 Triumph Scrambler

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Offline DaveBarbier

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Re: 1980 CB650 Engine swap
« Reply #11 on: October 11, 2018, 04:49:44 am »
All 650 SOHC motors will fit in any 650/550/500 frame but the carbs may interfere with the tank/petcock. The 79&80 head spigots are spaced differently than the 81&82 head spigots. Two later years got CV carbs where the two earlier got PD mechanical slide carbs. The heads can swap between all 650’s.

Offline DaveBarbier

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Re: 1980 CB650 Engine swap
« Reply #12 on: October 11, 2018, 04:55:22 am »
Is this bike missing an engine or are the compression numbers from the engine it has and you felt that it’s low and needs work?

As said above, those numbers look good. If that’s the only thing you we’re worried about I would just do the 3k mile service and run it.

Offline Tdinova

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Re: 1980 CB650 Engine swap
« Reply #13 on: October 11, 2018, 10:06:16 am »
Those r my numbers.  I done it last evening. The bike acts like it hits a wall just after the throttle leaves idle. It doesn't do it all the time which really bugs me. Then when I get it up to 5th idling along the bike almost surges.

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Blair
Nova Scotia, Canada

Offline CBGhia

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Re: 1980 CB650 Engine swap
« Reply #14 on: October 11, 2018, 11:45:59 am »
That sounds like carb issues.  Maybe ignition, but sounds more like carb.   Have you pulled them apart and done a good rebuild?  It also has an accelerator pump that you may want to look at. 

Are you running the stock air filter?
CB550 Cafe, GL1000
if you dont trial spin the camshaft in the head and cover you are a novice,with no natural mechanical appitude,destined for destruction.
"The cleaner the dipstick, the closer to God." -Rev. Horton Heat
“Faster, Faster, until the thrill of speed overcomes the fear of death.”  - Hunter S. Thompson

Offline Tdinova

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Re: 1980 CB650 Engine swap
« Reply #15 on: October 12, 2018, 05:05:43 pm »
Yes stock filter. I took the carbs off yesterday and done another cleaning.  She fired tight up as usual. Idle is super smooth.. but   its raining here so tomorrow I'm going for a spin if the rain stops. I took the connections apart and they all look good. I even done an ohm rest on the plug caps and they are all round 5k

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Blair
Nova Scotia, Canada

Offline cb650

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Re: 1980 CB650 Engine swap
« Reply #16 on: October 13, 2018, 04:48:04 am »
check the ignition advance and the distance of the pickups.
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Offline Tdinova

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Re: 1980 CB650 Engine swap
« Reply #17 on: October 14, 2018, 11:37:15 am »
Here we go with my findings.
Gas cap had no difference.
-Torn carbs off again and untra sounds each one individually.
- rechecked all gaps on carbs. Acl pump good. One other measurement on top 8 to 10mm. Good
- checked all connections. All good
- measured ohms on pulse and caps    all good
- checked timer advanced readj pulser gaps
 I did not check the valves as I done them 4 to 5 times over the past year or so.

Fired right up . Smooth idle. Went for a drive and I think it is fixed. I will not finalize until I get 4 to 5 days of smooth operation. Chilly today 8c
All seemed good but did some adj to pulsers

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« Last Edit: October 15, 2018, 12:56:45 pm by Tdinova »
Blair
Nova Scotia, Canada

Offline Tdinova

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Re: 1980 CB650 Engine swap
« Reply #18 on: October 15, 2018, 04:52:28 pm »
Went for a small drive after work today.. It seems to be cured.... Rain tomorrow but I'll try another day. I should say but I think the pulser generators were out a little bit.
Blair
Nova Scotia, Canada

Offline Tdinova

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Re: 1980 CB650 Engine swap
« Reply #19 on: October 16, 2018, 12:50:36 pm »
Day 3 n the books. Seems cured

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Blair
Nova Scotia, Canada

Offline Scott S

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Re: 1980 CB650 Engine swap
« Reply #20 on: October 16, 2018, 03:38:50 pm »
 Very nice. So, you think it was the adjustment on the pulsers?
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'71 CT70
'14 Triumph Scrambler

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Offline Tdinova

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Re: 1980 CB650 Engine swap
« Reply #21 on: October 17, 2018, 01:54:45 pm »
Day 4 is done... absolutely fixed.

Yes the only thing I can say is ' I adjusted the pulsers'.

Recap . When taking off the bike would make a big dive and stall most times other times I had to rev and rev to 2 to 3k and ride the clutch.

It now idles at 1100rpms let out the clutch and speed up... like a normal bike

Last report...

nite

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« Last Edit: October 18, 2018, 04:29:11 pm by Tdinova »
Blair
Nova Scotia, Canada

 

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