Vibration/revving high after downshifting to first and releasing clutch

[februarysnake]

I don't know the best way to describe this in the proper terms so I'll just explain what's going on by giving an example. When I downshift to first gear as I'm approaching a red light, and the light turns green before I've come to a full stop, my bike starts vibrating and revving extremely high (4000RPM or more) as soon as I release the clutch again to keep moving (but before I've had a chance to shift up to second). I've tried different variations of what's going on with my throttle, including keeping a little throttle, no throttle, or giving it a lot of throttle- same problem every time. The bike also loses power and won't go as quickly as it normally does in first gear. This makes low-speed turns and intersections a complete nightmare for me as a new rider and I definitely get some alarmed looks from drivers.

What's recently been done: Carbs have been thoroughly cleaned by my mechanic several times, with new floats put in and adjusted, engine head was replaced and valves were cleaned so they slide up and down more easily. Rejetted after we put in new air filters. Clutch was adjusted with the adjustment below the carbs and the clutch cable was adjusted. I do know that my clutch is worn out, so we have ordered a clutch kit but haven't put it in yet (could this be the problem even though all other shifting is great?). Oil has just been changed. My bike shifts really well otherwise, and if I come to a complete stop, I don't have the problem with the high revving when I start moving in first gear.

My instinct tells me that the engine valves are coming down too slowly, despite that we just cleaned and lubricated them. Could this be right?

Help. Thanks so much everyone.

 

[willem]

it sounds more like a clutch issue to me. First gear is pretty harsh on the clutch, especially when shifting down to it.

I would replace the clutch plates and see if it still happens. How did you diagnose the clutch being worn out btw?

 

[16VGTIDave]

Interim solution: Stop trying to use first gear. I only use first for getting moving from a stop. If the bike is moving, second gear is fine. If the traffic light turns green as you arrive, quickly up shift to second and carry on. If you have to put your foot down and stop, then first gear is appropriate.

p.s. 4000 rpm isn't high, 9000 is. Rev up that little 400, or sell it and buy a massive v-twin that chugs around town and explodes around 6000 rpm!

 

[februarysnake]

it sounds more like a clutch issue to me. First gear is pretty harsh on the clutch, especially when shifting down to it.

I would replace the clutch plates and see if it still happens. How did you diagnose the clutch being worn out btw?

Thanks for the help. Replacing the clutch plates this week and I will report back. Clutch is definitely a problem...I rode today and had trouble shifting a few times, plus I could not get the bike into neutral. God I hope the transmission isn't messed up. It's the only part that I haven't had problems with yet but I'm sure its just a total mess under there judging by the condition of the rest of the bike.

My mechanic diagnosed the clutch being worn out. From what I understand, even after he adjusted the clutch below, he also had to have the cable adjustment all the way out (with most of the threads showing). Shifting was a disaster when I first got the bike (sticky as hell, sometimes just would not shift up, very dangerous), and sometimes when I would pull the clutch all the way in, the bike would still move forward slowly because power was still going to the transmission. It also wouldn't idle at all, but I'm not sure if that's related. It sort of felt like the bike was always in gear. Since my mechanic made the adjustments, shifting and idling has been good, but he did warn me that it is adjusted to accommodate the worn out clutch. Found a clutch kit on ebay for $50. He's not even charging me for labor anymore because he feels so bad for me hahah.

 

[februarysnake]

Interim solution: Stop trying to use first gear. I only use first for getting moving from a stop. If the bike is moving, second gear is fine. If the traffic light turns green as you arrive, quickly up shift to second and carry on. If you have to put your foot down and stop, then first gear is appropriate.

p.s. 4000 rpm isn't high, 9000 is. Rev up that little 400, or sell it and buy a massive v-twin that chugs around town and explodes around 6000 rpm!

Thanks, I will definitely give that a try!