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Breva 1100 strange sounds

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Doppelgaenger:
So lately I've been noticing a strange sound while riding the Breva. I've only noticed it when the bike is properly hot, say hot like I just rode stoplight to stoplight for 10 minutes, and it seems to happen just over 4000 rpm when i roll on the throttle HARD. It doesn't make the noise when I roll on slowly.

The sound could be described as the sound of maybe throwing a handfull of rice into a pan or the sound a few times, or the sound of sand hitting your windscreen in your car or gravel hitting the body as you pull away. It seems to be coming from the left cylinder head, but this is subjective and therefore suspect. It isn't a constant noise, it just comes off and on when doing a full power roll-on from 4k.

Valves were adjusted less than 200 miles ago at MI in seattle and both CARC and gearbox oil were changed less than 100 miles ago.

Any ideas?

balvenie:
             The engine could be pinging. Heard it called pre-ignition. Have you been using a lower grade of fuel lately? Try looking those expressions up to start with.

Vasco DG:
Unlikely pre-ignition. More likely detonation. My guess is it's a tuning problem. What's the bike's maintenance history?

Pete

boatdetective:

--- Quote from: Vasco DG on February 21, 2015, 05:08:39 AM ---Unlikely pre-ignition. More likely detonation. My guess is it's a tuning problem. What's the bike's maintenance history?

Pete

--- End quote ---

Yup.  Be aware that this is a degenerative condition and can cause severe damage to your piston and cylinder.  This will be at it's worst with the engine laboring during acceleration (for example- in the old days, lumbering Winnebagos trying to climb up mountains in the summertime would blow their big blocks due to detonation).

As noted, fuel grade/condition can be a factor as higher octane retards ignition. However, I would tend to suspect that other factors could be at play. The most common are overly lean fueling and advanced timing. Obstructions in the fuel system can be caused by old ethanol gas that has gone through "phase separation". It only takes a tiny speck to partially block the flow.

Pull the spark plugs and have a look. They should have a brown deposit if everything is normal. If they look sandblasted, this will tell you there's an issue. If there is aluminum debris on them, it's too late. Look down in the hole with a scope or a flexible head flashlight. This will let you look at the surface of the piston crown. It should have a thin black coating of carbon. If it looks like the coating is sand blasted off and the crown is pitted- that is bad.

Do NOT  ride the bike until you dope this out. Detonation can be seriously bad ju-ju

Doppelgaenger:
Thanks for the replies guys, this is bad, but potentially easier to fix than something that is worn out. I've only noticed it a few times so far so this isn't something that has been going on for a while.

The maintenance history is known to me only with what I've done to it, and I've described it all. The bike just rolled over 15k miles. The fuel tank did get taken off when I took it to Moto International for the valve adjust. At that time I looked at the right side spark plug when it was off and everything looked fine on it. The plugs have about 1000 miles on them. The previous spark plugs had some buildup on them.

I get gas from a station that sees very heavy traffic, it's one of the cheaper stations in town because it's on reservation land and right next to the I-5. They supposedly can get ethanol free fuel, but I always fill up with premium. It's possible I could have made a mistake and put in regular, but I think it's unlikely. I ride the bike almost daily, shouldn't phase separation happen only when the bike has sat for a long period?

I'm experiencing no power loss or abnormal feel from the bike when this happens. Just noise.

I'll pull the plugs and report back with what I see and maybe some pictures.

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