Decell popping - Kawasaki KLR 650 Forum
2008+ KLR650 Wrenching & Mod Questions For repair, maintaining or modifying discussions related to the newly updated 2008 and beyond, Generation 2 KLR650 Motorcycle.

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post #1 of 15 Old 05-06-2015, 06:06 AM Thread Starter
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Decell popping

2011 KLR650 with 11,200 miles, and all stock. No other modifications.

I've been experiencing some popping under deceleration, and closing of throttle. The exhaust seems louder as well. When running, the normal sound of the pistons firing seem louder, and more pronounced. Otherwise it starts good, and runs good. This just started on my last couple of rides.

I have run about 200 miles since I pulled it out of winter hibernation. When I prepped it for the winter, the tank was filled, and treated with Stabil, the carburetor run dry, and kept in my basement shop for winter. I've gassed up twice since then. Both times at a busy local station, so I don't think it's due to bad gas.

Any idea's on what to look for?

Ageing Gracefully



2017 Yamaha XT250
1990 Honda NX250 (Green/White)
2011 Kawasaki KLR 650 (Orange & White )

My KLR Page..http://www.powers31.info/2011_KLR650.htm

Mod's to KLR:
Power socket, L.E.D. Battery Indicator, Camera bag holder
Custom Saddlebag frames .
Louder horns, Firstgear Onyx tail bag.
Custom Aluminum Skid Plate.
Cut down seat with Custom pad.
Go Pro Camera mount.
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post #2 of 15 Old 05-06-2015, 08:14 AM
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Check for an air leak in the exhaust system. I had what sounds like the same symptoms and discovered that one of the nuts on the exhaust header had come off. I replaced it and everything went back to normal.
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post #3 of 15 Old 05-06-2015, 08:38 AM
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+1. Exhaust leak at head. Had a similar issue a few years ago on a trip. Ended up having to reform the gasket. Now carry a spare with me.

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post #4 of 15 Old 05-06-2015, 08:37 PM Thread Starter
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Exhaust

Thanks guys! That's what it was. A missing nut.
Is that something I'll have to keep an eye on, or is it just another instance of Kawasaki not tightening things?

Ageing Gracefully



2017 Yamaha XT250
1990 Honda NX250 (Green/White)
2011 Kawasaki KLR 650 (Orange & White )

My KLR Page..http://www.powers31.info/2011_KLR650.htm

Mod's to KLR:
Power socket, L.E.D. Battery Indicator, Camera bag holder
Custom Saddlebag frames .
Louder horns, Firstgear Onyx tail bag.
Custom Aluminum Skid Plate.
Cut down seat with Custom pad.
Go Pro Camera mount.
Doo-Hicky
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post #5 of 15 Old 05-07-2015, 07:58 AM
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I don't know the statistics of how often an exhaust header nut comes off. All I know is my experience. The nut came off at about 4,000 miles. I've put on a little over 11,000 miles since I put a new nut on and made sure the second nut was tightened appropriately. I check the nuts every so often and haven't observed any loosening.

When I initially went over the bike to make sure all the nuts were tightened appropriately, I did not check the exhaust header nuts.
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post #6 of 15 Old 05-07-2015, 12:21 PM
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The air injection system will cause this on decell some bikes more than others depending on several factors. A lean condition or very rich can cause this also.
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post #7 of 15 Old 05-07-2015, 08:32 PM Thread Starter
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Header nuts

Quote:
Originally Posted by tjduexjr View Post
I don't know the statistics of how often an exhaust header nut comes off. All I know is my experience. The nut came off at about 4,000 miles. I've put on a little over 11,000 miles since I put a new nut on and made sure the second nut was tightened appropriately. I check the nuts every so often and haven't observed any loosening.

When I initially went over the bike to make sure all the nuts were tightened appropriately, I did not check the exhaust header nuts.
I did check all my fasteners.. (nuts.. he said with a smirk! ) when I got my bike but, I too, overlooked the header. Who thinks to look up under the bottom of faring?

I asked the mechanic, at the dealer where I got my nut, if there was a torque for it. ( I know it's supposed to be 15 ft lbs) He said they just "snug" them up. Nothing about torque. ( Maybe that's why some come off? )
I guess you can't tighten them much beyond the limit of the cap nut.

Ageing Gracefully



2017 Yamaha XT250
1990 Honda NX250 (Green/White)
2011 Kawasaki KLR 650 (Orange & White )

My KLR Page..http://www.powers31.info/2011_KLR650.htm

Mod's to KLR:
Power socket, L.E.D. Battery Indicator, Camera bag holder
Custom Saddlebag frames .
Louder horns, Firstgear Onyx tail bag.
Custom Aluminum Skid Plate.
Cut down seat with Custom pad.
Go Pro Camera mount.
Doo-Hicky
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post #8 of 15 Old 05-07-2015, 09:06 PM
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Quote:
Originally Posted by tjduexjr View Post
Check for an air leak in the exhaust system. I had what sounds like the same symptoms and discovered that one of the nuts on the exhaust header had come off. I replaced it and everything went back to normal.

Same here.

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post #9 of 15 Old 05-07-2015, 09:42 PM
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larry31-

The exhaust gasket is a hollowish copper crush gasket. The initial torque deforms the gasket and all is snug. With a bit of time, heat, and vibration the gasket deforms a smidgen more and the torque falls off a bit. A bit more vibration and heat and the nut backs off.

It's one of those nuts that needs a second tightening, which is advisable at the first oil change. I have it as an oil change thing. Change the oil, adjust the balancer, check the tightness of those nuts, inspect the calipers for free movement, top off the chain oiler, etc.

Tom

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post #10 of 15 Old 05-08-2015, 03:08 PM Thread Starter
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Exhaust nuts

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Originally Posted by Tom Schmitz View Post
larry31-

The exhaust gasket is a hollowish copper crush gasket. The initial torque deforms the gasket and all is snug. With a bit of time, heat, and vibration the gasket deforms a smidgen more and the torque falls off a bit. A bit more vibration and heat and the nut backs off.

It's one of those nuts that needs a second tightening, which is advisable at the first oil change. I have it as an oil change thing. Change the oil, adjust the balancer, check the tightness of those nuts, inspect the calipers for free movement, top off the chain oiler, etc.

Tom

Tom
With 11,000 plus on my bike, it sounds like i'm lucky this didn't happen a long time ago. What are the chances of this loosening again in , say, 3,000 miles?
These are cap nuts, so they can't be tightened beyond a certain point.

Ageing Gracefully



2017 Yamaha XT250
1990 Honda NX250 (Green/White)
2011 Kawasaki KLR 650 (Orange & White )

My KLR Page..http://www.powers31.info/2011_KLR650.htm

Mod's to KLR:
Power socket, L.E.D. Battery Indicator, Camera bag holder
Custom Saddlebag frames .
Louder horns, Firstgear Onyx tail bag.
Custom Aluminum Skid Plate.
Cut down seat with Custom pad.
Go Pro Camera mount.
Doo-Hicky
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