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[murphy]

I'm hearing a unique sound under certain conditions.

When the motor is under load, say for example going up hill, as I twist the throttle about 1/4 turn I hear a sound like there are stones hitting the fins on the heads.

The sound is not constant, and is not like a knock or ping.

There are a number of staggered dings that I hear with no set pattern.

The bike is running great other than that... it's a 103.

I put gas in it over the weekend that may be suspect as well.

Is this something I should be concerned about.

[sportygordy]

I know you said it sounds like ping and i would be willing to bet it is ping....

[SPIDERMAN]

The conditions you describe this happening under and the sound points to engine detonation (pinging) This is really bad for your engine, so yes you should be very concerned. It could be bad gas. It could be engine timing. It could be bad sparkplugs. Or a combination of all three. Without knowing what's been done to your bike for mods (changing the pipes and breather without tuning can really screw things up) One thing I can tell you to do when this happens is down shift and increase your RPM's. Jerry (GRC) or one of the guys on the site who knows more than me can explain why that helps, all I know is that it does. You need to nail down the source and soon however or you will be doing a top end job on your motor before long.

B B

[grc]

Sounds like a textbook case of detonation.  Some call it spark knock, pinging, etc., but whatever you call it, it's a noise caused by abnormal combustion and resulting pressure spikes.  If this is something new, I would first suspect a load of substandard fuel.  Try filling up with 93 octane Shell and see if the problem goes away.  If the problem persists or seems to be getting worse, I would suspect carbon buildup on the pistons and heads, or perhaps a lean mixture caused by partially clogged fuel injectors.  How is the engine running other than the noise issue?

Jerry

[SPIDERMAN]

Sounds like a textbook case of detonation.  Some call it spark knock, pinging, etc., but whatever you call it, it's a noise caused by abnormal combustion and resulting pressure spikes.  If this is something new, I would first suspect a load of substandard fuel.  Try filling up with 93 octane Shell and see if the problem goes away.  If the problem persists or seems to be getting worse, I would suspect carbon buildup on the pistons and heads, or perhaps a lean mixture caused by partially clogged fuel injectors.  How is the engine running other than the noise issue?

Jerry

Yeah what he said.

I just know it sucks. Jerry can tell you why it sucks 

Good post (as usual) Jerry

B B

[murphy]

Engine runs great...

I put a tank of fuel that had an octane rating of 91 in on Sunday (was the only one available).... I hope this is the problem..

I added some Sunoco 94 after, but it wouldn't be enough to solve it if it is the gas.

If it is detonation, shouldn't it be happening all the time and not just under load?

[iski]

Detonation is worse under load.  I added octane booster out west when mine detonated/pinged last fall.  Lousy 91 (so it said) octane gas was the culprit.  Problem corrected with octane boost.

[Bungy]

I carry a bottle of octane boost w/ me all the time. A lot of small towns out here only have regular (89), especially in Sask.

[Talon]

Pull you plugs, look for green and black spots on the electrodes, that's signs of detonation.

[murphy]

I've run most of the crap gas out and the spikes have almost all disappeared... thanks to everyone for the input!