9SX motor shudder on higher rpms

Enemy Zero · Jul 30, 2013

I just want to get some info if this is normal or not. I've had no experience with these or Harley motors in the past.

the issue I've been having is when the bike is in higher rpms around the 85+ mph range there's a very rhythmic shudder. Trying to explain it visually it goes something like this:

("-"= smooth; "^"=light vibration) -----^^-----^^----^^-----
kinda like that. I wanted to know if this is common for this motor or if this is something to worry about. 75mph and under its smooth and wonderful. If I go over that and its in higher rpms for any amount of time, this is what it does.

any help/info is appreciated

go cytocis · Jul 30, 2013

You mention it as occurring both at "higher rpms" and at "85mph +".

Do you have a sense of if it's related to engine speed or road speed? The answer to that question is critical to determining if it's an imbalance in the wheel or engine.

My XB12 sometimes develops a bit of what could be described as a shudder at 4000 rpm, depending on how warm the engine is, the tension on the primary chain, and the lube level in the primary case. I find that excessive slack in the primary chain can cause a vibe that resonates throughout the bike.

Theycallmecrash · Jul 30, 2013

("-"= smooth; "^"=light vibration) -----^^-----^^----^^-----

My imagination fuse must be blown. [confused]

Shudder? Is that the right word to describe what you feel? Or are we talking "vibration" or engine performance? Need a better description of what you are feeling, not just when it happens.

Enemy Zero · Jul 30, 2013

I have only really noticed it above a certain speed so I'm not sure what rpm range its exactly happening at. I'm sure if I left it in fourth and wrung it out it would do the same thing. The tires were replaced recently and everything was balanced at that time so I'm pretty confident its not the tires. The only way I could describe it is it shudders as if the motor is humming along just fine, then the pistons go really fast, almost slipping out of rhythm then go right back to ok. This continues in a very rhythmic fashion unless I bring the speed/motor speed back down. It doesn't seem to be doing anything detrimental as in no loss of power or anything going wrong it just kinda goes in and out like a sine wave.

unfortunately I just went through a medical procedure this past Friday and can't ride until I'm cleared by the doctor or I'd leave right now and be back with the exact rpm range for you all.

go cytocis · Jul 30, 2013

I'm sure if I left it in fourth and wrung it out it would do the same thing.... This continues in a very rhythmic fashion unless I bring the speed/motor speed back down.

Assuming you dont have a broken motor mount, I'd recommend checking your primary drive chain slack is properly adjusted first. I'll bet you find it's loose and the cause of your 'shudder'.

Theycallmecrash · Jul 30, 2013

Check your exhaust mounts, check your front muffler support bushings, pull them out and visually make sure they are good, any tiny play there allows the exhaust to vibrate. Chased an issue there for ever and it caused a lot of damage before the forum helped me figure it out.
Anther possibility is primary chain out of adjustment can vibrate slap around through it seemingly out of rhythm or balance.

Enemy Zero · Jul 30, 2013

Thanks for the info. I'll check both of these out. I'm in the process of changing out my Jardine for a buell race exhaust so I may find it loose in the process. I'll definitely have to check the primary chain. Don't want anything going wrong in there.

9SX motor shudder on higher rpms

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