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Discussion Starter · #1 ·
Howdy all, new member here. I have a 1978 CX500 that I really like. But the stator went out and since it was a box of parts when I got it I am not sure what else might be wrong with it. I am looking at a good running complete motor from a 1981 and was wondering if that would be an easy swap. I have changed out motors before but I won't touch it if it does not just bolt in and hook up. I don't want to get into fabricating anything or moving motor mounts and such. Thanks for any info!!!
 

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This would be a direct swap,,no modifications needed, as long as you are sure both are CDI bikes. If the rear covers are the same the engines are the same.
 

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1978 CX has a manual camchain adjuster - the later ones were auto adjust . Early engine is CDI ignition , later models were not. It is possible to put the early case on to later engine , just block the cam adjust hole other wise it will leak.

Basically it is a plug and play swap but unless identical rear case then it may be necessary to swap rear cases. The engine mounts are identical so not as daunting as some engine swaps I could mention . Carbs , exhausts etc. are the same so there should be no need to fabricate anything.
 

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It's a direct swap, the only real differences I know of between the 78-81 is that the 78 has different rims, the rear is 2" bigger, and the 81 has a vacuum operated petcock, and is the 1st year they used it. Also the forks of the 81 are air/hydraulic, whereas the 78-80 aren't. Then in 82 they went to an improved TI ignition system, and a better stator. I wouldn't be suprised if there are other differences, but I don't think there was anything else major or that would make things not bolt up.



The 81's forks have a larger outer diameter than the 80, not sure if the 78-80 are the exact same or what, but I have an 80 and 81, so I'm quite familiar with those 2, andhave reserched some of them.
 

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1978 CX has a manual camchain adjuster - the later ones were auto adjust . Early engine is CDI ignition , later models were not. It is possible to put the early case on to later engine , just block the cam adjust hole other wise it will leak.

Basically it is a plug and play swap but unless identical rear case then it may be necessary to swap rear cases. The engine mounts are identical so not as daunting as some engine swaps I could mention . Carbs , exhausts etc. are the same so there should be no need to fabricate anything
The carbs are slightly different, the 81 is vacuum, so I don't know if they'll work that way without getting an 81 tank and petcock, because the petcocks nut is different and not compatible, therear case should be the same, other than the fact that the 81 has the cam chain adjusting nut on it. CDI was used 78-81 on the CX, all GL's, 82 CX, and all 650's use the TI ignition.



Th 78 was supposed to be brought in so they could make it have a cam chain adjuster, if it's been done, there will be 3 punch marks by the engine's VIN number
 

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1978 CX has a manual camchain adjuster - the later ones were auto adjust . Early engine is CDI ignition , later models were not. It is possible to put the early case on to later engine , just block the cam adjust hole other wise it will leak.

Basically it is a plug and play swap but unless identical rear case then it may be necessary to swap rear cases. The engine mounts are identical so not as daunting as some engine swaps I could mention . Carbs , exhausts etc. are the same so there should be no need to fabricate anything
I do not believe any of that is relevant. The auto cam chain tensioner was added to the 650s in '83. The '81 GL had TI igntition, but I think the CX waited for '82.
 

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If I were you I would just save the money and not buy the other motor since they are almost identical and put the money towards the motor thats in it now get a new stator, mechanical seal and do the cam chain and have a great motor. But that is just my opinion cause you might have to end up doing the same on the other motor you are thinking about getting.Wlecome to the forum.
 

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Discussion Starter · #8 ·
Wow, posted my question, went to work, came back and I can't believe all the info here already. Thanks all. I have the guy selling the motor taking a look at it to make sure the electronics are OK, other than that the price with shipping is about the same as what it would cost me for the parts to fix this one. I figure the labor in swapping has got to be easier than a partial re-build, plus I'll have a 2nd motor to mess with if needed. So to me it seems to be the better deal, if it really is a good motor of course. Any other thoughts are appreciated, but you guys have been great already.
 

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I swapped an '82transistorized engineblock into my '81 cdi bike its close enough... used my old rear case and fashioned a new vent off of the inspection cover waiting to put it in tomorrow I hope finally but all should be good



anything is possible with this forum
 

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To make more clear what has been said in some of the previous posts, and referring to US bikes, if the '81 engine is from a CX it is a direct swap into your CDI bike. If it is from a GL500 or GL500I it will have the transistorized ignition (usually called TI or TIA)and require the the rear cover and insides exchanged. Have you considered the aftermarket Ignitec ignition retrofit? Folks find that upgrade cost effective, simple, and almost 100% successful. I'm sure it increases the value of the bike as well.
 

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If you can get the engine for a good price (to me that would be anything under maybe $200) it would be worth it just for the peace of mind knowing you have plenty of spare parts now. When I first got my bike I only had it a few weeks before the cam chain tensioner broke, and I did end up fixing it with new parts but I also looked around and found a spare engine to replace the broken one. I was able to fix the original one slowly while still being able to ride. If you think about the number of usable spare parts you have in an extra engine it's easily worth at least a few hundred dollars.
 

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Discussion Starter · #14 ·
Yes it is a CX500 motor. I was of the same mind on spare parts and peace of mind and such. I am still waiting for the seller to tell me if the stator is good though. If that's shot, I will be in the same boat. I have not heard of that aftermarket retrofit, if I get the bike going again I'll have to look into it. Thanks.....
 

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1978 CX has a manual camchain adjuster - the later ones were auto adjust . Early engine is CDI ignition , later models were not. It is possible to put the early case on to later engine , just block the cam adjust hole other wise it will leak.

Basically it is a plug and play swap but unless identical rear case then it may be necessary to swap rear cases. The engine mounts are identical so not as daunting as some engine swaps I could mention . Carbs , exhausts etc. are the same so there should be no need to fabricate anything.




I do not believe any of that is relevant. The auto cam chain tensioner was added to the 650s in '83. The '81 GL had TI igntition, but I think the CX waited for '82.


I believe that in the U.K. the T.I. 500's did have the auto cam tensioner,,I am not positive of that though.
 

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Discussion Starter · #18 ·
Sorry all, forgot to update. I got the motor and it went in with no issues at all. It was an easy swap with no mods needed. The motor seems to run great too, but I think I still have some electrical problems. I lose power to the right cylinder at high rpm's. Did this with the old motor too. I have a spare set of coils, wires with caps, new plugs and have tried swapping them all out with the spares as well as swapping from side to side and I still get the right side cut out. I pulled the carbs and went through them and they seem fine. I am leaning toward the CDI now and have one coming in a few days. Hopefully that is it, but if you have any other suggestions pleeeeze let me know. Otherwise I just wanted to confirm that the 81 to 78 engine swap was an easy to do thing with no mods whatsoever. Thanks for the help all......



P.S. - If you could post a link or specific manufacturer info to that ignition upgrade kit I'd appreciate it. It'll save me searching the web and not being sure I found the right one. Lots of junk out there any more.
 

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Discussion Starter · #19 ·
Well, the bike is still running but still has some issues. Any CX500 carb experts out there? I think I have a carb issue but want to make sure before I start spending more cash on this thing. I am thinking of getting another set of carbs due to some issues I saw with mine. Figure it'd be better than re-building mine, same as the motor. The 81 CX has a vacuum petcock system so I am thinking i'd need to stay with 80 or earlier carbs. What I got is that high rev cut out issue, on the right cylinder. When I stripped the carbs I found an air tube glued into the float bowl as some kind of bubba fix for an unknown carb issue. But if I can fix mine easy enough that would be better too. So I am fishing for a carb expert to pick his/her brain. Any thoughts?
 
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