Bucking Z900? | GTAMotorcycle.com

Bucking Z900?

Fr0stByte24

Well-known member
I've noticed something a bit unusual happening with my Z900 this season. Doesn't matter what gear or speed I'm going, when I hold the throttle at 4,000 RPM the bike will lurch back and forth. RPM from 1 to 3.5k and 5k + is fine, smooth in all gears. The bucking/lurching back and forth is controllable and not violent, but does not feel normal and in low gears when I need to be smooth really messes with me. The tachometer looks like it can't decide if the digital meter wants to be at 4 or 4.5, 4 or 4.5 as it keeps going back and forth.

The bike has 4,200 KMs on it. Never experienced this before with any other bikes I've had.
 

r3r3r3

Well-known member
Any chance its the same gas from last fall? Might be worth checking out your air filter/intake as well.
 

TK4

Well-known member
Take it somewhere with a dyno and exhaust sniffer.
It may simply be a case of TMDT (that machine does that) and now that you have more seat time you simply hadn't noticed before.
When the CBR250Rs came out they had a really nasty mid-range lean spot for emissions testing.
 
It's called surging. It feels like the engine hunting for the right RPM and can't seem to find it and settle down. Its caused by the extremely lean fuel settings required to meet emissions requirements. It wasn't unusual the BMW R1100/ R1150 series motorcycles. My own R1150RS ran fine, but lots of folks had bikes that didn't. The surging was minimized by ensuring the two throttle bodies were in sync. In other works the throttle openings from the cables were exactly the same. As I am not familliar with a Z900 I am not sure if the throttle bodies require syncing?
 

boyoboy

Well-known member
agree w other posts - surging/bucking due to lean condition. I remember reading a magazine test on the Z900 and they spoke of this condition.

ecu flash should be available - and not emissions legal. So don't ask your local dealer. Some performance / race shops will do the work though-and some shops will do it by mail. ~ $300, good value for the money? I think so imo.
 

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