Engine shake during RPM drop

[rtrofimovich]

Hey all! Started riding the Buell and have been enjoying it a lot! One thing I noticed was when I'm riding and I pull in the clutch to coast, the engine/bike sort of shakes as the engine drops in RPMs. Was wondering if this is normal Buell behavior or something I should investigate. Thanks!

 

[TPEHAK]

You have to investigate how to use clutch and throttle properly. During engaging the clutch you have to twist throttle a little to not let engine to drop RPM to smooth clutch engaging and to prevent jerking.

 

[njloco]

Play no attention to the above response that is, if you can even understand what he wrote !

Model, year, mods, type of tires, how old, how's the wear, balanced, in other words, give us as much info as possible ? This is what the guys will ask to help diagnose.

 

[Chicknstripn]

I think teabag is trying to discribe rev matching while ENGINE braking.
That doesn’t apply when pulling in the clutch and coasting.

Does the engine behavior change when the shaking occurs? Or does the engine sound and act normal?

Could be your primary chain isn’t adjusted properly or your wheel bearings are shot.
I’d start with inspecting those two items.

Good luck

 

[rtrofimovich]

2008 xb12s. The tires are good, it's not the actual ride quality that shakes. It's like I can feel the engine shaking a bit as the rpms fall after pulling in the clutch. It's not like a violent shake or anything just like a thumping shudder as it comes down to idle. And thanks for the heads up on that guy lol been riding for 16 years pretty sure it's not my technique

 

[rtrofimovich]

No the bike rev matches just fine on down shifts. This only occurs if I'm cruising then pull in the clutch to coast. As the engine speed drops, there is a bit of shudder but it doesn't behave weird or misfire or anything. No fault codes neither

 

[rchuff]

It's normal. You will get a little shake from the v- twin on decel with clutch pulled in. It's because you have no load on motor. It will usually do it at a certain rpm as the rpm drops. When you feel it look at where your RPMS are at and take note each time and you will see.

 

[Silverrider]

I understand you have been riding for a longtime, Great, But how long on a Buell ? if I may ask with all do respect.

 

[rtrofimovich]

Okay, thanks! I figured it was normal but thought I'd ask!

 

[Silverrider]

What have your other bikes been ?

 

[rtrofimovich]

Of course! On the XB, only a few days. But I've been on other V-twins (smaller displacement - 649, 821, 1098) that I never noticed that on before. 1203 cc V-twin is definitely a lot different and a lot more piston to move so I'm not surprised that it has that slight shuddering characteristic. Most of my riding experience comes from 599 cc I-4 bikes though.

 

[Silverrider]

Yea, Ducs & 599 cc I-4 are different 1203 cc V-twin for sure.

 

[rchuff]

It all has to do with balanced and not so balanced crackshafts.

 

[Chicknstripn]

Sounds like you’re expirencing the same thing I did when I went from a 2003 Honda VFR to a 2007 Buell back in 2007! At the time my brother was an HD mechanic and parts rep. I would call him, when I first got the bike, and ask him if certain neuances I was feeling with the Buell V-twin were normal. I was especially concerned with the transmission, going from a Honda to a Buell redefines Japanese engineering.

To get back on track, sounds like your engine/bike is perfectly normal.

Bearing in mind how much the bike does shake and rattle it’s a good idea to periodically check all the fasteners and bolts you possibly can. Parts have been know to rattle themselves to freedom!

 

[rtrofimovich]

Bearing in mind how much the bike does shake and rattle it’s a good idea to periodically check all the fasteners and bolts you possibly can. Parts have been know to rattle themselves to freedom!

Yeah I was surprised to see how many times loctite is mentioned in the service manual compared to my zx6r service manual lol but yeah I'll keep an eye on things, thanks!

 

[mmcn49]

Had vibrations, not really a shake, on my new 07. Map tunes, smoothing out the lean dip a bit, correctly doing a TPS reset and setting the idle just under 1000 smoothed things out considerably. It only vibrates around idle now and just a little.

 

[rtrofimovich]

Mine doesn't seem to have any odd vibrations while cruising, its actually really smooth. Pretty sure the engine shake during rpm drop is due to the single-pin crank shaft design and like rchuff said, it not being very well balanced.

 

[leakyrat]

Hey rtrofimovich, I noticed the exact same thing. Engine runs great, upshifting and downshifting are smooth. Just if I pull the clutch in to coast or slow down. Kind of a 1 second shudder that I can feel mostly in my head. Maybe the vibrations are going up my arms. And my bike's only the xb9 so smaller cylinders and less vibration I would think. I replaced the primary tensioner and primary fluid, seemed to reduce it a bit but not much. Just another quirk.

 

[rtrofimovich]

Yeah I think it's not so much engine/piston size as it is the single-pin crank design. It's naturally sort of "off-balance" so a little shaking would seem normal. As long as it's not shaking while cruising I got no worries

 

[herwawan]

I do have a similar feeling, when I release the clutch and the RPM drops around 2k - the whole bike vibrates more right at it, not much before, not much after. I mainly notice it because my rear mirrors are a bit loose and they shake like it's a earthquake with all the shaky noises that go with it.

I simply assumed it's part of it, anyways that thing is vibrating all the time - a little bit more or a little bit less won't make much change.