Jump during acceleration

[Blessed1277]

Hopefully someone can have some input on Themis for me before I take it to the shop. While accelerating between 30 and 50 mph while in 2nd gear my bike jumps an it only happening in 2nd gear once I'm passed that 50 mile mark she run good. What could this jump be an what could be causing it. It been happing for about my last two rides. I have a 2009 classic 1700 vulcan


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[OldSchool]

Are you saying that you are holding the bike in 2nd gear until you hit 50 mph ??

[Blessed1277]

No im saying when i hit 2nd gear going toward 50 mph in between that it jumps then catches back right before i 3rd

[Demolition Man]

50mph in second ? At this speed, I'm already in 5th gear ????

It is a CRUISER not a racer.


Cu,
Sven

[Snake Ranch]

Originally Posted by Blessed1277

No im saying when i hit 2nd gear going toward 50 mph in between that it jumps then catches back right before i 3rd

Define "jumps" if you can. I just can't see this thing jumping down the road.

Could the engine be surging, or is it slipping out of gear and back into gear, or maybe the clutch is slipping. A little more description would be helpful.

[cnc]

Does this jump feel like the motor falters and catches again or poping out of gear and back in? Wonder if you are hitting the rev limiter? Try shifting at a lower speed and see what happens.

[gv550]

When applying throttle in second gear only, the bike will jump out of gear then back in, which results in a jerk and loud clunk noise. All other gears are fine, correct?
This is caused by not completely engaging second gear before applying throttle, this wears the edges off the small dogs on the side of the gear and results in a rounded surface and the gear will 'ramp' out of engagement. This will bend and wear the shift fork to the point of not fully engaging the gear and problems become more frequent. Eventually the gear or fork will break and you will not have second gear at all, and of course broken parts could jam up inside the case.
This can happen with any motorcycle, second gear is most common.
The fix is to replace the gear and its mate and the shift fork, complete engine and transmission disassembly is required.

[redjay]

Is your drive belt too loose ?

[Fullcircle]

My GSXR750 would do that, only on the track. Hard acceleration in second it would jump and make a noise. Turned out to be a worn gear and bent shift fork. The life of a track bike.

I would look at the belt tension first as it can also jump. Hope it turns out to be something easy.

[Blessed1277]

Originally Posted by gv550

When applying throttle in second gear only, the bike will jump out of gear then back in, which results in a jerk and loud clunk noise. All other gears are fine, correct?

This is caused by not completely engaging second gear before applying throttle, this wears the edges off the small dogs on the side of the gear and results in a rounded surface and the gear will 'ramp' out of engagement. This will bend and wear the shift fork to the point of not fully engaging the gear and problems become more frequent. Eventually the gear or fork will break and you will not have second gear at all, and of course broken parts could jam up inside the case.

This can happen with any motorcycle, second gear is most common.

The fix is to replace the gear and its mate and the shift fork, complete engine and transmission disassembly is required.

That's is what is happening so j do have to take it to the shop to get it fixed. Thanks for you help


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[Gypsy Dragon]

Originally Posted by Demolition Man

50mph in second ? At this speed, I'm already in 5th gear ????

It is a CRUISER not a racer.


Cu,
Sven

Speak for yourself, mine's a racer. And if the weather holds, it'll be even more of one after the 4th.

[Gypsy Dragon]

Originally Posted by Blessed1277

That's is what is happening so j do have to take it to the shop to get it fixed. Thanks for you help


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If this is the issue, it means opening up the transmission. This is a serious bit of work and can be expensive. If the bike is new enough to be under warranty, I would take it in immediately. It should be covered. If you don't it will get progressively worse. I damaged the 2nd gear dogs on my Vaquero, and by the time I got to it, I couldn't use more than half throttle in second, and couldn't rev past 3500 rpm, or it would jump out of gear. When I did have it opened up, I sent the fully built shafts to RACINRAY and had him under cut all the gears. It shifts smoother, and more solidly than when it was new.