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Discussion Starter · #1 ·
Over the last couple of days I've noticed a heavy knock comming from the drive train. It is intermittent when comming on or off power and sometimes happens quite severely when changing gear. It was at it's worst in the cold of this morning. The return journey seemed to be pretty clunk free for the first five miles. It generally gets worse as he journey progresses and sounds like it's comming from the RH side. I've noticed a small quantity of oil on the road where I park, so I'll top it up tomorrow and report back. My oil can is 30 miles away in another house.
 

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First thing I'd take a look at is the drive shaft where the rubber boot covers over. Try pulling that back and see if you can peek at the u-joint area. There may be some extra free play there that needs attention.
 

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I've recently experienced a similar problem with my bike.

I'm sorry that I can't help with a cure for your problem, as I've got more that 1 bike and all I've done so far is park it and ride another one.

What I do want to let you know is that when you put it on the centre stand in gear, there is a certain amount of movement there.

I initially thought I had a problem there, but after trying 4 other bikes, they all had the same amount of movement.
 

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I'd make sure that "oil leak" you see isn't really your drive train fluid leaking out there at the r/h side of the rear wheel ??



If so you may have your answer to the noise.



Just saying
 

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Thinking the U-joints on these bikes are FAIRLY bullet-proof, the noise you are describing sure SOUNDS like what a U-joint would sound like. IMHO
 

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Here are the fische for both the shaft and the final drive. Any of the bearings in the shaft might be going south. There should be a little bit of free play, but not very much.





 

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Check your final drive oil level. With bike on center stand it should be to the level of the filler hole. If you are losing final drive oil it means you have a bad seal in the unit. The final drives are really robust and a failure is rare other than the large bearing and seal (#21 and #25)



That being said a clunk could be lots of other things. Check for any loose fasteners on the bike.
 

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Discussion Starter · #10 ·
Thanks guys. I rode the bike today for 60 miles and found I could stop the clunk by using the clutch and front brake to slow down and avoid going down through the gears or the rear brake.



The bike is fine on harsh accelleration and gear changes.



What I really nead is a plan of action. Even if I took the drive apart, I'm not sure I'd recognise the problem if I saw it.

I'm pressed for time at the moment so I'll probably have to take it to the local bike shop for a look.
 

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Another thing you could check would be the swing arm bushings.

Put the bike on the center stand and see if you can move the back wheel/swing arm side to side, look for play where the swing arm attaches to the frame. It may not hurt to have someone steady the bike while you check.
 

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The three causes I've had to fix for this was



1:Change a drive shaft(Got a decent one off Ebay) and

2:Much more involved full engine strip and re-build a decent gearbox as some of the dogs and gears were shot.

3:Crapped out drive box.Again got a decent one off Ebay but Ebay is hit-and-miss.The drive boxes can be re-built but didn't fancy it.



My 10 penn'th.
 

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Discussion Starter · #13 ·
I've just pried back the gater between the shaft tube and gear box. I put the box into 1st and turned the back wheel. The outside of the tyre moves about 2" and the drive shaft turns about 20 to 30 degrees. Does this mean game over?
 

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There's always some play but that does seem excessive.



If I put mine in 1st and then put my finger across from the Rear shocker to the metal side rim and move mine back and forth there's about a 2 inch movement one one of my CX500s.

The problem now is determining where the play is e.g in the engine or outside.





Just thinking out loud here.If you grab the UJ or can lock it some how with the bike NOT in gear,then move the rear wheel and the play is still there we can make an educated guess that the play is outside the engine which is good.It's easier to replace a drive box and or drive shaft than take out and strip the engine.I think you can see how I'm trying to diagnose it?

If you know a really trusted Motorcycle mechanic he may be able to help.Although I do all my own spannering/wrenching when faced with some thing I'm not sure of my Motorcycle MOT bloke is my ,"Go-To" guy.What he doesn't know isn't worth knowing and he builds Customs/Choppers and Trikes.



Also if you have a Wilkinsons Supermarket(Or Asda) go and get a gallon of 15w40 made for diesel car oil or even the cheapest 20w50 car oil and change it.It may not cure it but make it bearable but I think there is some service work to be done.
 

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Discussion Starter · #15 ·
Having pulled back the gator, I can see that 99% of the play is from the gear box. The output shaft has 30 degrees of play!.



However, if your bike also has 2" of play on the outside of the rear wheel in first then maybe that's not the issue. I'm not sure how I'd lock the UJ at the moment.
 

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I've never seen the innards of the U joint, so without having a visual, I'm not sure if this would work, but maybe taking a long, stout screwdriver and sticking it through the joint so the tip of the screwdriver rests on the ground, then step on the top of it to hold if firm to the ground while you wiggle things about.
 

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I looked into this issue on my CX-650C and called it excessive drive-train backlash. I found that the final drive, drive line, U-joint, and final drive shaft are very heavy duty for the engine horse power and they were all tight. The backlash was in the transmission assembly. There is slack caused by space between the syncro dogs. It is what it is, does not appear to be a wear issue. My bike has very low miles but I did replace the starter clutch rollers while the case was open. The Tork screws were loose, stripped out and the flywheel was junk so the tear down was not a waste of time. It now starts right up every time and still has what I think is more play going from power off to power on than I expected. My CX experience 1s limited to this 650, so I can't compare it to another CX.
 
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