650 on a 500 frame

5527 Views 92 Replies 12 Participants Last post by SirFoxx, Jan 17, 2022

SirFoxx

Discussion Starter · Jan 11, 2022

Hey--

Just wanted to start a general discussion about the thoughts, or personal experience of a cx/gl650 engine swapped onto a 500 frame. I've got a cx500 standard that I rip around every now and then, and I think the extra power from the 650 would be nice!

I've talked to murray about it several times, and I know he loves the extra power the 650 has to offer, even with the slightly longer gears.

What got me going on wanting to do this is, I picked up two GL650 engines from an estate sale for $100. One has the end of the camshaft snapped off, where the water impeller goes, and the other is complete. I need to stick my endoscope into the complete engine and see how the cylinders are, make sure the complete one is in decent shape and not blown up from lack of oil. Makes me curious why the PO was trying to take apart the other motor, and how hard he was prying at the impeller to break the cam.

I've been trying to get a 2nd starter as neither engine has one so I can also crank them over and listen for anything funny, but it seems they are becoming hard to come by and rather expensive. I'd use the one off my cx500, but I'd rather not drop the engine just to borrow a starter...

(if anyone has one they'd sell to me cheap I'd really appreciate it~)\

I think I have everything mentally written down that I am going to need / do for the swap:

Rae-San ignition, timing jumper to aggressive
12v coils
murray mid-pipes
rejet murray carbs
modify cx500 engine hangar
gl650 radiator + efan wiring
swap output shafts
inspect cam chain, replace mechanical seal while swapping output shaft
Swap over HD clutch springs?

I don't think I'm missing anything..but I probably am. If the cam chain tensioner isnt stretched to the max, I am going to leave it. No reason to change good parts. Same with the stator.

Only thing I have ordered right now is the 650 radiator, mainly because it was in great shape, came with the efan and the shroud for $70 shipped!

I may make a build thread once I get this project going. The hardest part will be modifying the engine hangar, but theres a video on youtube doing it, and its pretty easy if you have a welder (which i do lol).

See less See more

61 - 80 of 93 Posts

Randall-in-Mpls

· #61 · Jan 14, 2022

I haven't tried them on the 650, but I suspect HD takeoffs might be a good replacement.

jlbutler81

· #62 · Jan 14, 2022

Randall-in-Mpls said:
I haven't tried them on the 650, but I suspect HD takeoffs might be a good replacement.

Most harley's being over 1200cc, are you saying one muffler for both cylinders?

Randall-in-Mpls

· #63 · Jan 14, 2022

Usually a pair. Older Dynas are a good choice, but getting harder to find.
Used with the stock h-box, too free-breathing isn't a concern. Might need re-jetting with the mid-pipes.

SirFoxx

Discussion Starter · #64 · Jan 14, 2022

Randall-in-Mpls said:
Usually a pair. Older Dynas are a good choice, but getting harder to find.
Used with the stock h-box, too free-breathing isn't a concern. Might need re-jetting with the mid-pipes.

what pipes does murray recommend with his carbs?

also, thoughts on this? I mainly need the headers, though the bigger mufflers would be nice. My concern is that it appears that the baffles are rotted out of these..

1983 83 Honda GL650I GL650 650 Silverwing Interstate Exhaust | eBay

also, how restrictive are the 650 mufflers? reason i ask is, I had an '86 vf500f, and when I swapped the stock mufflers out for aftermarket ones designed for the bike, it gained a quite noticeable bump in power.

Fafnir

· #65 · Jan 14, 2022

Surprised not to see SidecarBob in this thread. He put a 500 in a GL650 He might have some insights.

SirFoxx

Discussion Starter · #66 · Jan 14, 2022

Fafnir said:
Surprised not to see SidecarBob in this thread. He put a 500 in a GL650 He might have some insights.

im trying to do the opposite lol. im putting a 650 in a 500 frame.

Fafnir

· #67 · Jan 14, 2022

SirFoxx said:
im trying to do the opposite lol. im putting a 650 in a 500 frame.

It would seem that one could inform the other.

nolimitz

· #68 · Jan 15, 2022

Fafnir said:
It would seem that one could inform the other.

apples, oranges, bananas. Cx/GL/turbo. This thread is all over the place

SirFoxx

Discussion Starter · #69 · Jan 15, 2022

nolimitz said:
apples, oranges, bananas. Cx/GL/turbo. This thread is all over the place

meh. its in the general discussion for a reason. ive gotten a bunch of useful info already.

nolimitz

· #70 · Jan 15, 2022

SirFoxx said:
meh. its in the general discussion for a reason. ive gotten a bunch of useful info already.

I'm it is still a bit varied/confusing

Randall-in-Mpls

· #71 · Jan 15, 2022

SirFoxx said:
im trying to do the opposite lol. im putting a 650 in a 500 frame.

Bob was working with GL and Eurosport frames. They're close enough to identical that the engine was almost a direct bolt-on.
I believe it was Gerard who recently put a GL650 engine into his GL500. Here again, there was no CX500 frame involved, so it was almost a direct replacement.
It's the single- vs triple-spine frame that necessitates all the adaptation.

jlbutler81

· #72 · Jan 15, 2022

Those mufflers look very unrestricted lol

Randall-in-Mpls said:
Bob was working with GL and Eurosport frames. They're close enough to identical that the engine was almost a direct bolt-on.
I believe it was Gerard who recently put a GL650 engine into his GL500. Here again, there was no CX500 frame involved, so it was almost a direct replacement.
It's the single- vs triple-spine frame that necessitates all the adaptation.

And I'm doing a CX650c into a Turbo 500 frame; both triple backbone frames, I feel it's the easier situation to be in.

@Randall-in-Mpls The only thing off the top of my head for @SirFoxx to worry about is the carb body issue; where the 650 carbs need the space the 500 frame takes up, the 500 carbs being spaced to the outside of that. And the radiator return area is different on the 500 from 650. Was there more?

@nolimitz I'm probably a catalyst in your confusion since I started in on the turbo stuff with my 650 into a turbo 500 frame. Probably should have stayed out of it. But like he said, general discussion lol

Randall-in-Mpls

· #73 · Jan 15, 2022

jlbutler81 said:
And I'm doing a CX650c into a Turbo 500 frame;

You're in new territory, there.

Randall-in-Mpls

· #74 · Jan 15, 2022

jlbutler81 said:
@Randall-in-Mpls The only thing off the top of my head for @SirFoxx to worry about is the carb body issue; where the 650 carbs need the space the 500 frame takes up, the 500 carbs being spaced to the outside of that.

According to the respective FSMs, both the GL650 and '78 CX500 use 35mm carbs. My first attempt will be to mount a pair from a '78 CX. I think it was Charles who said the CX500 stock isolators can work on the 650 engine. Maybe I'll need to adjust the brackets and transfer pipes a little. I think that would be easier than straightening and spacing the 650 carbs. It might be easier still to 3D print custom intakes, assuming the ASA I'd use could take the heat.

And the radiator return area is different on the 500 from 650. Was there more?

I'm tempted to use the CX500 radiator with a GL1200 cooling fan (the one with the flat motor) that I have on hand. That would mean less modification to the engine hanger. I'll need to mock that up before deciding.

ChopperCharles

· #75 · Jan 15, 2022

So, the CX500 carbs can be used with fresh, new, pliable insulators. It's a tight fit every time and every time you risk cross-threading the M6 bolts that secure the plenums to the heads. Worse, if you use the new reproduction intakes, the stress from the connection will eventually pop the rubber bit off of the aluminum bit, leaving you in the lurch. (Duct tape will get you home).

Ideally, you'd want to separate the CX500 carbs and extend the brackets, crossover pipes, and linkages. The brackets are easy, just cut and weld (they're steel). The crossover tubes are also easy; Any machinist can make those for you. Hell I could make those on my hobby lathe. Make them out of brass so you can drill and tap the hole for the "T" for the fuel line, and then solder it up. The linkages between the two carbs is where you'll have to get creative.

Also, if you're doing all that, it might be a better idea to make custom brackets and crossovers to mount the 650 carb bodies in such a manner. I don't know if the linkages will be easier or harder, I haven't held a set of 650 carbs in my hands in at least a decade. But going from eBay pictures, the CX500 will need the throttle shaft elongated (easy to do, as it's steel, cut and weld), as well as the choke finger. (Piece of flat steel welded to the end should do it). For the 650 carbs, it looks like the linkages are more or less separate, and you could unbolt the stock linkage and make an adapter. Not sure about the choke, but it looks like swapping in a CX500 choke for the right side carb should work, and then you can extend the linkage as needed.

Charles.

See less See more

Reactions: 1

Sidecar Bob

· #76 · Jan 15, 2022

Randall-in-Mpls said:
Bob was working with GL and Eurosport frames. They're close enough to identical that the engine was almost a direct bolt-on.

Which is exactly why I didn't post in this thread sooner.
BTW: I was among the first on the forums to put a 650 engine (actually from a CX650E) into a GL500. At the time there was very little knowledge about what was required and there was even some speculation that it might not fit or the frame and drivetrain might not be strong enough. I had to us the 650 carbs & intake runners because the 500 ones wouldn't line up with the 650 and the 650 airbox because the boots between airbox and carbs are completely different but it turned out that the biggest issues were that I would have to modify the GL500's rad's mounting lugs beyond what I considered reasonable to make it fit the 650 hangers (I went back and bought the 650 rad) and that I had to put the 500 engine's final shaft into the 650 so that it would mate with the GL500's u-joint (the GL650 uses the same final shaft as the GL500 so this is only necessary if you have a CX650E or CX650C engine).
And about a year later the camchain broke and I ended up putting the 500 engine &c back into it.

15 years later I found myself putting a GL500 engine into what had started life as a CX650E. I had replaced the original rear end with a GL500 swingarm & driveshaft, CX500 final drive & wheel and a brake with CX and GL500 parts when I first got the 650 (& installed a 500 final shaft in the original 650 engine) and the rad and electric fan are neither stock or in the original location so that wasn't an issue. I think spent more time on cleaning & painting things than I did actually taking one engine out and putting the other one in. You can read about it here

www.cx500forum.com

Eccles: The Never Ending Build (retroactive to 2006)

It looks like I finished messing with Eccles just in time. Mr.H's biggest problem is that the combination of a GL1000 engine (& transmission) and a GL1100 final drive results in gearing that is a little higher in 1st than the stock combination is in 2nd (great on 2 wheels but too high with a...

www.cx500forum.com

www.cx500forum.com

See less See more

ChopperCharles

· #77 · Jan 16, 2022

Sidecar Bob said:
Which is exactly why I didn't post in this thread sooner.
BTW: I was among the first on the forums to put a 650 engine (actually from a CX650E) into a GL500. At the time there was very little knowledge about what was required and there was even some speculation that it might not fit or the frame and drivetrain might not be strong enough. I had to us the 650 carbs & intake runners because the 500 ones wouldn't line up with the 650 and the 650 airbox because the boots between airbox and carbs are completely different but it turned out that the biggest issues were that I would have to modify the GL500's rad's mounting lugs beyond what I considered reasonable to make it fit the 650 hangers (I went back and bought the 650 rad) and that I had to put the 500 engine's final shaft into the 650 so that it would mate with the GL500's u-joint (the GL650 uses the same final shaft as the GL500 so this is only necessary if you have a CX650E or CX650C engine).
And about a year later the camchain broke and I ended up putting the 500 engine &c back into it.

15 years later I found myself putting a GL500 engine into what had started life as a CX650E. I had replaced the original rear end with a GL500 swingarm & driveshaft, CX500 final drive & wheel and a brake with CX and GL500 parts when I first got the 650 (& installed a 500 final shaft in the original 650 engine) and the rad and electric fan are neither stock or in the original location so that wasn't an issue. I think spent more time on cleaning & painting things than I did actually taking one engine out and putting the other one in. You can read about it here

Eccles: The Never Ending Build (retroactive to 2006)

It looks like I finished messing with Eccles just in time. Mr.H's biggest problem is that the combination of a GL1000 engine (& transmission) and a GL1100 final drive results in gearing that is a little higher in 1st than the stock combination is in 2nd (great on 2 wheels but too high with a...

www.cx500forum.com

I did the 650 swap into an 82 cx500 way back in 2004. I used the stock cx radiator and a cbr electric fan on a modified hanger bracket. Cx carbs and stock air box.

Pretty sure I had to swap the output shaft too.

Charles.

murrayf

· #78 · Jan 16, 2022

the bottle breather on the 650 as i was told in a honda class (there is a service bulletin about it have seen it ) was to relieve extra crankcase pressue
caused by our higher speeds and more prolonged distance riding
the higher crank case pressure would force oil by the weaker oil control rings (due to increased piston rock) and cause oil consumption and oil
building up to quickly in the breather catch can so we fitted the kit to twin the vents to all the gl650s and cx650e we sold in canada

that was my understanding of it

murrayf

· #79 · Jan 16, 2022

Randall-in-Mpls said:
According to the respective FSMs, both the GL650 and '78 CX500 use 35mm carbs. My first attempt will be to mount a pair from a '78 CX. I think it was Charles who said the CX500 stock isolators can work on the 650 engine. Maybe I'll need to adjust the brackets and transfer pipes a little. I think that would be easier than straightening and spacing the 650 carbs. It might be easier still to 3D print custom intakes, assuming the ASA I'd use could take the heat.

I'm tempted to use the CX500 radiator with a GL1200 cooling fan (the one with the flat motor) that I have on hand. That would mean less modification to the engine hanger. I'll need to mock that up before deciding.

the bad part of that is you don't get the honda OEM rad fan switch IMO the best way of controlling the fan all else is fiddly and does not work as well or as long as the direct control switch in the 650 rad or the gl 4 cylinder direct contact controller that is designed to handle the full amperage draw of the fan for years and years

Reactions: 1

Sidecar Bob

· #80 · Jan 16, 2022

Randall-in-Mpls said:
According to the respective FSMs, both the GL650 and '78 CX500 use 35mm carbs. My first attempt will be to mount a pair from a '78 CX. I think it was Charles who said the CX500 stock isolators can work on the 650 engine. Maybe I'll need to adjust the brackets and transfer pipes a little. I think that would be easier than straightening and spacing the 650 carbs. It might be easier still to 3D print custom intakes, assuming the ASA I'd use could take the heat.

I don't think that will work very well. I know the GL500 runners & carbs won't line up with the 650 engine (& vise versa) so I doubt the CX500 ones will work either.
You might be better to use the 650 carbs and print something to mate them with the bike's airbox.

61 - 80 of 93 Posts

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.