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Discussion Starter · #1 ·
Is there any point to cramming the whole transmission from a 650 into a 500? Is it even doable? I know that the 650 primary gear and clutch is needed for the common RPM dropping upgrade, but since I happen to have all the gears, I was hoping there would be a benefit to using them.
 

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It is do-able, but not simple as it requires engine disassembly and careful machining of the inner cases so that the 650 gears will clear the casting, certain individual gears need to be ground down and some alterations to the main/lay shafts

Ofapar did it on his CX as detailed here



http://ofapars-.webs.com/gearboxtransplant.htm



If you are just looking to lose rpm, then fit the 650 clutch and primary, and use an 18" rear wheel. this will drop your rpm by about 550-600 revs in top
 

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Discussion Starter · #3 ·
Good to know, thanks for the link and the answer!
 

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After reading the attached link, I think I'd better chime in. For Dan Wagners Salt Flats CX500 I installed a GL650 trans by simply hand carving the case area above the two "deepest" gears (using a burr in my die grinder), and leaving out the cast steel shield (over the gears). I made no modifications to the gears or shafts, and used the GL500 clutch package with the same washers as GL650, but without the added spacer (the 650 bearing has it built into the side of the input shaft bearing).



Perhaps the euro stuff is different? ....doesn't seem likely. All I know is that the bike works fine and is only turning 9500 RPM at 127.2 MPH.



Good enough.



JimL
 

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Discussion Starter · #5 ·
Good to hear your input Jim, do you think there would be a need for machining beyond what you described with the 650 clutch package? I cannot imagine it would be, but it is always nice to be certain.
 

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I`d also like to know how a 650 `box fits into the 500 case with just the milling to allow for 5th gear being made, because as you can clearly see form the two pics, the 650 case (bottom pic) has a cast-in recess to allow for 2nd gear clearance. Without making provision for that during the swap, the 650 pinnion fouls the 500 casing.........











Perhaps JimL made clearance for the pinnion by running the bike at 9500 RPM at 127.2 MPH!
 

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For what it's worth, the 500 Turbo does not have that recess for 2nd gear. Otherwise, the transmissions for the 650 and Turbo 500 seem to be very similar (5th gear is shorter on the Turbo).

Could the case material on the 650 be thicker there, necessitating the recess?
 

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I do not know who it was or When it was, but about 5 years ago someone put just the 5th gear set out of a 650 trans into their 500 trans. took a grinder like Jiml and cleaned out just enough material in the case to give 2mm (~1/8") clearance.



Took like 6 or 7 trial fits to get it far enough and shaped right. but doable.



Reported it worked fine. don't know anything else about it.
 

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Discussion Starter · #9 ·
I certainly would not mind having only a taller 5th gear "overdrive," especially if that seems to be the only real way to avoid the extra machining work. The whole transmission would be nice to easily swap however
 

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Is there any point to cramming the whole transmission from a 650 into a 500? Is it even doable? I know that the 650 primary gear and clutch is needed for the common RPM dropping upgrade, but since I happen to have all the gears, I was hoping there would be a benefit to using them.
 

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If all the ratios are the same... what is the advantage of doing the swap?? from what i have read, the 500's trans is very durable. I know that the 650's clutch ratioes bring the RPM down thru the range... just wondered thanks! Good Riding Mike
 

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Let me know how this goes, Zach. It's a long-term possibility I'm considering.



R
 

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I certainly would not mind having only a taller 5th gear "overdrive," especially if that seems to be the only real way to avoid the extra machining work. The whole transmission would be nice to easily swap however


As I understand it, the 5th gear requires machining too. but I don't Know if that is right.



FYI, the 650's have a different primary AND different 1st-5th gear ratio's.

500 5th is 0.931 (27/29)

650 5th is 0.839 (31/26)



Looks like one gear in the 650 5th gear set is a bit larger then the 500's.
 

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Been away awhile....need to clarify something. I did NOT use a CX500 engine in Dan Wagner's CX500 LSR bike. I used a late model GL500 engine (needed the newer style ignition) and the 650 trans (complete) went in with only a small bit of hand carving. I have not tried a GL/CX650 trans into an earlier CX500 case. I'll have to take a look inside the two CX500 engines I just bought, to see what the case difference might be.
 

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I'd need to look to be sure, but I think the CX500 and GL500 cases are identical. The only differences would be in the rear cover and the heads (venting).

R
 

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I'll have to look, in the next month or so, and compare the 650 case to the 500 case. I'm wondering if the 650 case is thicker, in some areas, than the 500 case. As I said, I put that 650 trans in and out several times, during the build process, and (after shaving under the connecting rod area) it slipped right in and bolted down solid with no effort. It spins freely, and we've had no problems or noise.



I don't think I'd run this trans unless your are making a lot of power....it has much wider gears (more drag) and almost too much 5th gear. Just use the 650 primary drive and call it good.
 

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Well, if you were gonna run this trans, Don't do the clutch swap.
 

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Discussion Starter · #18 ·
"I don't think I'd run this trans unless your are making a lot of power....it has much wider gears (more drag) and almost too much 5th gear. Just use the 650 primary drive and call it good."



My friend was also concerned that the 500 engine would be too weak to adequately run the 650 transmission, but I said I thought it would be alright since the power curves max out at redline. Of course, that could have absolutely nothing to do with anything, but that is why I have all of you. When you say making a lot of power, I suppose you mean about 65 horse worth of power? I am hopefully a bit higher than stock with a different exhaust and larger jets. I had anticipated that the drop in RPM's with the 650 transmission and clutch would have been significant, but not detrimental to operation. Was there something I missed with Ofapar's description of the work he did on a 500, as everything seemed to work out quite well. I do have a local machine shop that could do the same work he did, but it would be a touch more expensive
 

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Well, if you were gonna run this trans, Don't do the clutch swap.
That's probably the way I'll be going, since I have a 650 trans on the way, but I haven't yet sourced a 650 clutch.



This project started out as the stripping of a irrecoverably dead engine. Once I had a rebuildable block coming, it became a build up of a ready spare. Now, I'll probably use it to experiment with some of these upgrades. I have the dead lump on which to test fit the 650 trans before I do any real cutting, and I can swap it in and out of the Grub for testing without risking my original engine.



Does anyone know the relative 5th gear ratio differences of the 500 stock setup vs the 650 clutch with the 500 trans, the 500 clutch with the 650 trans, and the 650 clutch with the 650 trans?





Thanks,



R
 

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That's probably the way I'll be going, since I have a 650 trans on the way, but I haven't yet sourced a 650 clutch.



This project started out as the stripping of a irrecoverably dead engine. Once I had a rebuildable block coming, it became a build up of a ready spare. Now, I'll probably use it to experiment with some of these upgrades. I have the dead lump on which to test fit the 650 trans before I do any real cutting, and I can swap it in and out of the Grub for testing without risking my original engine.



Does anyone know the relative 5th gear ratio differences of the 500 stock setup vs the 650 clutch with the 500 trans, the 500 clutch with the 650 trans, and the 650 clutch with the 650 trans?





Thanks,



R


Try this as an Excell file - should have a chart on there for the 500T (pretty close to the 650) with the 500 primary:





Honda CX500/650 Gearing OptionsUse 25.5 inch tire diameter = 80.1 inch circumference = 6.68 feet per revolution = .001264 miles per revolution (791 revs per mile)Gearcx/gl500500T650650T500TwCX primary118.942.7415.882.52.52.517.3212.821.8510.891.711.711.7111.8439.811.428.131.281.281.288.8647.961.156.61.041.041.047.256.450.935.50.870.840.846.02Primary2.242.0552.062.111.7252.24Final3.093.093.093.093.43.09010000010000040.04929043.84587059.16798064.06533077.32248085.61326095.293150105.35190117.60210126.0022



OOPS - That didn't work. Why can't I attach an Excel file?
 
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