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CX Customization and Modifications
Started by NightBiker07 at 03-03-2010 11:32 PM. Topic has 12 replies.
  
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 03-03-2010, 11:32 PM
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NightBiker07
 
Joined on 04-20-2009
Toledo, OH
Posts 506
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CX 500 transmission swap/modification Q's
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The tranny on my bike likes to do some wierd crap. sometimes it will slip in between gears after i finish shifting, or fall back down a gear right after i shift it. it has gotten progressively worse, and since a whole tranny (shift drum, forks, gears etc) can be had cheap, and since the motor is out, i am going to change it out.
will all year's CX500 trannies fit?
Since i will have it that far apart, i have heard that gears are swappable (namely 4th and 5th) to drop the RPM a bit at cruising speeds.
are there any threads specific to these changes? i have dug around, and havent found what i am looking for.
80 CX 500
2000 CR 250 DIRT BIKE!!!!!!!!!!
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03-04-2010, 12:02 AM
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Blindstitch
Joined on 03-14-2009
Greenfield Wisconsin
Posts 9,863
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Re: CX 500 transmission swap/modification Q's
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All Cx500 and Gl500 trannys should swap.
1979 CX500 Supertanker
ATGATT makes riding a bike like a sled easier.
Quick Reference
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03-04-2010, 7:01 AM
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NoXi
Joined on 08-04-2008
UND
Posts 308
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Re: CX 500 transmission swap/modification Q's
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my bike does the same weird crap, no fun. i've got a gl transmission im going to swap it with. make sure you check everything on the shift mechanism as well
82 gl 500 silverwing (dizzy)
82 gl 500 interstate (the brown streak)
81 susuki gs550 (suzy (chopper))
99 R6 chop project (ace of speed)
Tell me the location and velocity of every particle in the universe and ill tell you your future
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03-04-2010, 9:22 AM
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Panther
Joined on 05-09-2006
Las Vegas, NV
Posts 1,264
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Re: CX 500 transmission swap/modification Q's
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It is possible to put the 4th and 5th gear from a CX/GL650 transmission into it, but you have to grind some clearance into the case for 5th gear to fit.
Peace & Light
>^..^<
..........
'83 GL650swi "My Little Grey Lady"
'82 GL500swi parts bike
'78 DT175
'86 LS650 Milady's bike
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03-05-2010, 6:24 PM
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JimL1581
Joined on 04-19-2009
Posts 176
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Re: CX 500 transmission swap/modification Q's
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I just put a complete GL650 trans into the 500 block. You need to carve clearance above the input shaft 5th gear. This area is pretty far back in the case, just beyond the connecting rod window in the block. You will be "thinning" the area of the case below the rear crankshaft throw, but only by about 1/8" of an inch or so.
The 500 output drive shaft coupler fits the 650 counter shaft, and the 500 clutch fits the 650 input shaft (that's what I'm using in one engine). 650 gears are considerably wider than 500 gears, but room is saved between them.....which could be an issue with a partial modification. I do not know that for certain....I'm just using the whole unit.
The step up for 5th gear ratio is significant. I counted teeth and did the math myself, when I found all the manuals wrong. GL500 5th gear is 29 tooth over 27 tooth (.931:1) and GL650 5th is 31 tooth over 26 tooth (.838:1). That is 16% overdrive in the 650 trans, which explains why the ports and valves are so small in the 650 heads!
Good luck on your project.
JimL
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03-07-2010, 9:05 AM
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LRCXed
Joined on 05-15-2008
Sacramento, California
Posts 1,670
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Re: CX 500 transmission swap/modification Q's
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Jim, have you ridden your bike yet after the tranny swap? How much did it improve the RPM's?
If your going to do something, do it right, don't do it half as@*d.
78 CX500 Std, 79 CX500 project, 80 CX500C, 83 GL650I
http://globalcxglvtwins.hostingdelivered.com/
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03-07-2010, 8:51 PM
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JimL1581
Joined on 04-19-2009
Posts 176
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This is another Salt Flats bike for a friend (for Modified Partial Streamlined-Pushrod Gas 500cc class). With the 500 primary drive, 650 trans, and stock 18" rear tire size (still shaft drive), the bike will be geared for 126.8 MPH @ 9500 RPM. This bike will make peak power at 10,000 RPM, equivalent to 133.5 MPH if it can actually pull it.
Keep in mind, the bike will look similar to the bike I ran last year, which with a near stock engine had top speed measured 124.9 and still accelerting (mile exit speed was about 126-127)..
To figure your RPM at any speed (in 5th gear using 650 trans and 500 primary ratio) multiply your current RPM by 90% (close enough). For example, if you're cruising at 5000 RPM on your stock 500, the 650 trans will give 4500 RPM at the same speed.
Interesting stuff.
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03-08-2010, 8:36 PM
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NightBiker07
Joined on 04-20-2009
Toledo, OH
Posts 506
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Re: CX 500 transmission swap/modification Q's
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So do you access the tranny from the front of the motor or the rear? the pictures in the manual arent very clear as to the orientation of the motor upon their disassembly.
80 CX 500
2000 CR 250 DIRT BIKE!!!!!!!!!!
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03-08-2010, 9:13 PM
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LRCXed
Joined on 05-15-2008
Sacramento, California
Posts 1,670
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Re: CX 500 transmission swap/modification Q's
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You'll need to take both ends of the motor off to get the tranny out.
If your going to do something, do it right, don't do it half as@*d.
78 CX500 Std, 79 CX500 project, 80 CX500C, 83 GL650I
http://globalcxglvtwins.hostingdelivered.com/
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03-08-2010, 9:18 PM
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Blindstitch
Joined on 03-14-2009
Greenfield Wisconsin
Posts 9,863
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Re: CX 500 transmission swap/modification Q's
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03-08-2010, 9:28 PM
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LRCXed
Joined on 05-15-2008
Sacramento, California
Posts 1,670
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Re: CX 500 transmission swap/modification Q's
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If you try to pull the transmission out without pulling the back case off the hook that is attached to the shifter that rotates the shifter drum will stay against the drum and not let the transmission slide out of the case.
That shifting hook needs to be lifted up to let the transmission slide out of the main case.
If your going to do something, do it right, don't do it half as@*d.
78 CX500 Std, 79 CX500 project, 80 CX500C, 83 GL650I
http://globalcxglvtwins.hostingdelivered.com/
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03-08-2010, 10:59 PM
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NightBiker07
Joined on 04-20-2009
Toledo, OH
Posts 506
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Re: CX 500 transmission swap/modification Q's
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So in other words, inspecting the Cam chain/tensioner will be pretty easy while this is torn apart. Because its shifting like shit, i have no problem raring both ends off, as i want to personally inspect everything involved......
So, the transmission pulls out the Front of the motor, correct?
80 CX 500
2000 CR 250 DIRT BIKE!!!!!!!!!!
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03-09-2010, 3:22 PM
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LRCXed
Joined on 05-15-2008
Sacramento, California
Posts 1,670
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Re: CX 500 transmission swap/modification Q's
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Yes. Out through the front.
If your going to do something, do it right, don't do it half as@*d.
78 CX500 Std, 79 CX500 project, 80 CX500C, 83 GL650I
http://globalcxglvtwins.hostingdelivered.com/
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