spark knockin....

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Mar 2, 2011 | 04:04 PM

cuda67bnl

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From: GA.

spark knockin....

My bike seems to be spark knockin like hell. I usually ride with the radio wide open, so I don't hear much most of the time. I've heard it knock a few times before when I should down shift a gear, but nothing like it's doing now. Yesterday I rode without the radio on, and that's when I noticed how bad it is. I had filled up at a station I don't normally frequent, so I thought it might be bad gas. I put some octane boost in the tank, but it made no difference.

Today I siphoned out about 4 gallons, then went and filled up at one of my normal stations. It's still knocking like hell. When I had it dynoed last year, the tuner told me that my TPS was acting up, and kept jumping off 5%. I haven't had a chance to call him to discuss this yet.

Is it possible for the TPS to act up enough to cause the bike to spark knock? Or are they even related? What else might cause this suddenly? I'm pretty certain it hasn't been doing this every since the dyno tune. I'm slow every once in awhile, but there's no way in hell I haven't been paying that much attention.......

Mar 2, 2011 | 04:07 PM

Beemervet

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From: Ohio

It could be a number of things, but one thing for sure...........
do not ride it anymore until it is fixed. That is not just an annoying sound, it is the sound of your motor destroying itself.

Mar 2, 2011 | 07:47 PM

cuda67bnl

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From: GA.

Anybody??

Mar 2, 2011 | 08:04 PM

1931jamesw

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Cuda, Im not sure about the TPS issue. My first thought was the timing needs to be backed off. Whats your compression at? Did you end up shimming your rockers?

Mar 2, 2011 | 08:41 PM

onaride63

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From: in the wind

If I was sure it wasn't pre detonation ping, I would probably do a leak down test and check the rings and valves. Do you have adjustable pushrods ? maybe one needs adjusted. Just my .02 $ Are you carbed or injected ? injector goin bad ?

Mar 2, 2011 | 08:48 PM

cmhfguy

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From: Ontario, Canada

This isn't the answer you are looking for, but just so you will understand what is happening, it is not "spark knock".. it is not caused by the spark or spark plugs. It is pre detonation where the fuel and air mixture is igniting a bit early because of the pressure and temperature in the cylinder. Octane usuaslly prevents that, but not enough spark advance can also cause that spontaneous ignition. It is actually exactly how diesel engines work. They have no spark plugs and ignite based on pressure and temperature in the cylinder. Ignition too soon can cause major damage and as a previous responder noted, you don't want to ride without getting it dealt with.

Mar 2, 2011 | 09:21 PM

cuda67bnl

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From: GA.

Quote:

Originally Posted by 1931jamesw

Cuda, Im not sure about the TPS issue. My first thought was the timing needs to be backed off. Whats your compression at? Did you end up shimming your rockers?

Haven't checked the compression since the build. It was 185 or so then, iirc. I don't think it's changed as the bike runs too good. Never did shim the rockers either.

Quote:

Originally Posted by onaride63

It's a fairly new build. I may check tomorrow for the hell of it, but I know it's not rings or valve related. I did adjust the pushrods again today chasing valve train noise that's always bugged me. It's injected.

Quote:

Originally Posted by cmhfguy

I know exactly what is happening. Spark knock is the redneck term for detonation, and has been used longer than I've been alive. I had the right term, but thanks for the explanation anyway.

I'm gonna replace the TPS since it needed it anyways, and call my tuner in the morning. I'll tweak my map if the sensor doesn't help, and get it back to the tuner.