Knocking upon deceleration ??????????

[Brian McVickers]

Hi,
Mystery of the day needing a diagnosis!

Scenario, cruising at 45-50mpb 3rd or 4th gear, stoplight, roll off throttle and let the bike slow while in gear. Down around 15-20mph I start to hear a knocking that is steady and does not speed up or slow down with rpm. The knocking goes away with acceleration or depressing the clutch.

In addition I can't seem to find Neutral which is normally easy to find.

Other than that the bike accelerates fine and will cruise nicely even up around 75mph+.

Any thoughts?????

Thanks
Brian

 

[Hltoppr]

Try putting a tank of 91 octane in it....then see if you get the same results. Just remember...that rig isn't a high performance machine...which is the beauty of it.

-H-

 

[proto]

OK, I'll offer up some guesses:

So it's not related to engine rpm, but is related to road speed? That points to transmission, or perhaps drive chain.

Take the simple-to-check stuff first:
Does the geometry change when you pull in the clutch? (Does the rear settle a bit?) There might be an alignment issue between the sprockets that lets the chain hit at certain swingarm angles. I suppose it could be a bad link in the chain that's only audible because there's not much other noise under your conditions. But I have seen a chain with a sideways kink due to the installer bashing it with a sledge hammer to set the link pin. (sheesh!)

Those are the easy things I can think of. The hard stuff I can think of involves worn bushings in the transmission, or loose/broken cases. Good luck with that!

 

[Brian McVickers]

I've never put anythin but 91 octane premium in it.

Saturday morning I did a run up near lake Pleasant 175miles with about 50 miles of dirt and 100 miles of highway at 55-75mph and the rest in town traffic of 25-45mph. Then Sunday afternoon I rode down to Casa Grande, 150 miles of pavement, much of it at 55-75mph (on a side note - the wind crossing the desert was CRAZY! I had to adjust my speed to miss or outrun 200 foot tall dust devils a few times and actually pulled off to the side while one crossed the road 100 yards in front of me with buckets an other trash caught up inside it!)

This knocking did not start untill I was about 15 miles from home, after running at highway speeds for over an hour.

Acceleration and maintaining speed is not affected at all and the engine sounds great. It is just this knocking when declerating in gear.

I think a key characteristic of the sound is that it goes away when I press the clutch lever or accelerate. I'm thinking it is gearing/tranmission related more than engine related.

Also, on a possibly related note, I have had an unresponsive start button a few times. I have figured out that wiggling he clutch lever will get it to start but this is random, it normally starts right up. Could there a switch direcevly related to the clutch linking it to the ignition?

Thanks
Brian

 

[UK4X4]

15-20mph in 3rd or 4th- mine would be about to stall and backfiring/poping

Not sure what bike you have but a single likes revs, and not slow engine braking

I stalled my single yesterday in sand and almost went over the bars.

a triple or 4 cylinder does'nt mind engine breaking so much.

 

[panzer]

Check your chain tension.
I recently had a similar experience with "loaner" bike.

 

[Oni]

Maybe your chain has a kink or sticky link in it? Try riding around to get it warm and then lube it with a quality lubricant. Lube should penetrate well overnight, then see if it improves.

Chain may be too loose too and slapping around and hitting chain guide or guard by swingarm pivot.

 

[R_Lefebvre]

I'm also thinking it could be a chain problem, loose, seized, etc.

But, here's one that's a bit out there, have a look at your steering head bearings make sure they are properly tight. I've had a knocking sound before I thought was something in the rear suspension, but turned out to be the steering head bearings.

 

[Brian McVickers]

Thanks everyone,
It is the chain, it was too loose and is still too slack even after maxing out the rear wheel adjustment. Looks like a new chain just made its way to the top of the list!

After reading all the posts I figured checking the chain tension was the easiest to check. On this bike the chain should have 1-1/4" to 1-5/8" of movement. Mine had 3", plenty of room to slap around. Even now after tightening it has a generous 2". I could pull a link out of the chain but the bike would probably appreciate a new chain so I'll use the old one as a spare.

While I was down there adjusting the chain tension I decided to replace the 15t countershaft sprocket with the new 14t sprocket. It is more responsive to throttle input and I can still cruise at 70mph at 5,000 rpm.

Brian

 

[R_Lefebvre]

Chances are your chain is stretched beyond limits, but it's worth measuring, if you've been playing with sprockets.

 

[Brian McVickers]

Any recomendations on a quality brand of chain?

 

[Oni]

http://www.didchain.com/offroad.htm

Be aware if you have a KTM...they usually run chains a little looser than the norm.

If you are replacing the chain...you should replace both sprockets as well. New chain and worn sprockets = chain not lasting very long. Same with old chain and new sprockets. All components should be replaced at the same time if they are worn out.

 

[grahamfitter]

Also, on a possibly related note, I have had an unresponsive start button a few times. I have figured out that wiggling he clutch lever will get it to start but this is random, it normally starts right up. Could there a switch direcevly related to the clutch linking it to the ignition?

Thanks
Brian

Most bikes have a safety interlock microswitch in the clutch lever that needs to be closed to start the engine. Like the side stand engine kill switch, opinions on whether you actually need it vary. At least if it does fail its easy to bypass.

Cheers,
Graham

 

[Brian McVickers]

Thanks Graham,
I figured out that the clutch lever needs to be depressed and pushed down to fully engage the switch. As the clutch lever floats up and down a bit it does not seem to engage the switch near the top of its float area.

Brian

 

[R_Lefebvre]

Most bikes should crank without pulling the clutch if you are in neutral. You neutral switch might not be working properly either.

As for the chain, DID is a good name. I went with an EK myself. Less expensive and supposedly just as good. We'll see...