Acceleration doesn't respond to RPMs. Jet problem?

My xj650 is having problems when I pull the throttle more than maybe 15-25%. The engine will increase the RPMs which seem appropriate to the throttle, but the acceleration just stays the same. For example, a quarter turn gives me x amount of acceleration @ 3k RPMs, whereas an almost full turn would also give me x acceleration, but @ 8k RPMs. I remember seeing somewhere about this being a specific jet problem, with different jets corresponding to different levels of throttle use.

I should mention that this was not a problem a week ago when I still had an air leak through 3/4 of my rubber intake boots. Before, I could pull the throttle and my bike would haul ass. The bike would be a pain in the ass to start, but would run beautifully once it was running. That rubber intake boot problem is fixed now, and my bike starts up instantly with just a tap on the electric start button and no choke. I can't find anything on this issue online or in my manual. Any ideas?

 

Sounds more like a slipping clutch to me. Have you checked it?
Does the engine run smooth during acceleration or does it sputter?

 

First off
LOVE your avatar
Second
What are you running
Pods, Exhaust, Jet kit?
My bike has the same(ish) problem.
Above 4k RPMS she has a decent hesitation before throwing me back in the saddle. I've got a little larger jets in (2 sizes, and intentional) but it has the wrong needles in it
Y-15s instead of Y-20s
I am 99% sure thats my problem
Check your jets. Check your needles.
Post your findings
-Chris

 

sounds like you clutch is slipping to me. Rpms should not just jump up when you crack open the throttle while in gear they are a function of the gear you are in and the speed you are currently going.

 

A clutch slip in just a week?
Maybe. I think it would noticeably get worse, and a week just doesnt seem long enough to me to have a CONSIDERABLE slip

 

Yep agree with Maverickbr77 sounds like clutch slip to me. Changed your oil lately? if so check out the link.

http://xjbikes.com/Forums/viewtopic/p=3 ... tml#386749

 

It runs smooth until I pull back the throttle and it revs up really high. I'll look into the slipping clutch.

 

haha yeah, Robo rocks! I'm guessing that's a Megaman character on yours? As for what I'm running, it's just all stock besides cut pipes from the PO. I don't know if the PO rejetted, but things seemed to be ok before this possible clutch slipping. If it is the clutch slipping, I just don't get why this would happen so quickly. I'll look into it though. Thanks everyone.

 

Are you thinking it's the oil or the old plates? I seem to be getting different solutions. My books tell me to adjust the clutch free-play, so I'll try that first when it's light out. I suppose I'll then try replacing the oil before I re-build the whole thing.

 

You'll need to rebuild the original clutch sooner or later. If you continue to run it when it's slipping, you'll just drive up the cost of the rebuild.

I don't have time to type a whole paragraph or two, do a forum search on the subject; original clutches DO "age out" and there's nothing you can do but rebuild it. It's not difficult.

 

Thanks, bigfitz. I understand that it is probably worn out, it's just odd that it would be fine, and then start slipping the next day after I had fixed my air leaks, checked my plugs, and installed new handlebars (maybe a cable problem).

 

A clutch "slips" when the torque being transmitted overcomes the static friction between the plates (Friction being a force, and the radius of the plate being the moment arm = friction torque).

If you engine suddenly outputs more torque (because you improved the fuel mixture, especially when you enrich it), and now that it's running better you are running it harder (higher RPM = more torque until 6000-7000 rpm when you reach peak torque) then you might be overcoming the static friction between your (aged) plates.

Also note that sometimes clutches can be slipping "a little" before you notice them. This will wear them out more quickly, and may warp the plain plates (increasing the cost of replacing the clutch). You might be seeing a combination of both.

Adjusting the free play only helps if you have no slack, and the cable is in effect, "holding the clutch open" a little. If you have the proper slack, adjusting the cable will do nothing to solve your problem.

I can attest to the advice BigFitz gives about clutches. Both of my new-to-me Secas required it. I learned after warping the plain plates on my first one not to even wait on the second one. Replace the clutch and be done with it.

 

As I was hoping, it just turned out that I didn't have any slack on my clutch lever after changing from the stock bars to the lower clubmans. I guess during the swap I pulled on a cable too hard or something. All I did was loosen the adjuster a bit, and now there is no more clutch slipping.

I also had a high idle problem where the engine would sit at around 3000rpms, but I got the bike to idle to around the specified 1050rpms just by adjusting the idle screw (duh ). This also made the bike sound much better all over.

Of course my Maxim needs other things done, but I'm really relieved that the bike runs great after fixing these two small things.

Thanks for your help guys. I'm glad my clutch plates aren't kaput (yet)!

 

Oh, they are. You just don't know it (yet.) But if they're the originals they are "kaput."