High RPM when shifting

I have a 650 xj and whenever I'm running over 3000 rpm and shift gears it takes a long time for the motor to drop the rpm's. If I shift over 3000 rpm it sounds like I'm trying to speed shift the bike.
And it will only do this if the bike is warmed up. If its still cold it shifts just fine and the rpm's drop normally.
I have rebuilt and reset the carbs and it ran just fine. But then today I was out for a ride and all of a sudden it started to do it again.
I have checked and rechecked for vacuum leaks and cannot find any. I have replaced all of the caps on the vacuum outlets and I have removed the vacuum line going to the gas tank. I replace the pitcock with a standard one so it is now a gravity flow only. I have also replaced the throttle cable.
Has anyone ever had something like this happened? What could be causing it.
Could this be happening because of a bad diaphragm in the carb?

 

Many factors can contribute to it.

When you rebuilt your carbs did you take them to Church?
http://xjbikes.com/forums/threads/in-the-church-of-clean.14692/

I believe you when you said you did not find any vacuum leaks.

After cleaning your carbs and reinstalling it is highly recommended to do a wet set of fuel levels, Colortune and then a running synch. The later being something that could be causing what you described.

 

Sounds like the mixture screws are set wrong.
Refer to the manual for the correct amount of turns out and start there.

 

How did you synch your carbs? 4 vacuum gauge is my preferred way , your synch maybe off , and when you did carbs have you replaced shaft seals? it is possible if you did the butterfly plate could be off ever so slightly.

 

Another thing to check, could the throttle cable be hanging up?

Per others above, sounds like you are running lean - either a vacuum leak, mixture setting, or needing a synch. Once I synched my carbs on an otherwise good running bike (valves, carbs, etc in spec), mine returned to idle much quicker after revving. Before synching properly, it would "hang" momentarily at about 2.5- 3k rpm.

FYI - I replaced my vacuum caps with some from the local auto store just because the originals were a bit hard. When the engine was hot, the new ones softened and gave me problems, even with clamps they would be loose when hot, and one even broke in half. (and I didn't buy the cheap vinyl ones, but rubber ones.) After I replaced with the old, beefy originals and had no more problems. They get pretty hot back there, XJ4ever sells OEM style if you need replacements.

 

check throttle adjustment and cable routing make sure end of cable is in the cup. what do you have your idle set at? and did you set it when bike is warmed up well like after a 10 to 20 mile ride?

 

When rebuilt the carbs I replaced the seals on the throttle shaft. When I synch the carbs I used a four vacuum gauge. When I rebuilt the carbs I found that two of the carbs air/fuel mix screws were screwed all the way in. I then reset all of them to spec.
I'm not sure where the vacuum cabs came from because I already had them in the toolbox. So I will change them again and see what happens.

Would a bad rubber diaphragm in the carb be doing this?

Also, I have found that when I try and set the idle that my idle screw is backed out so it is not making contact with the carbs. I didn't think anything about this because the idle on the bike is just fine.

 

look at the diaphrams in the light and see if you have any holes they can be patched .
Idle knob is located at back of carbs between 2 and 3 carbs.
is the metal end of throttle cable sitting in the cup on the carbs?
if your idle knob is not touching the carb lever your throttle cable may be to short remove it and see if the shaft from idle adjuster makes contact then.
there is an adjuster on the throttle cable at the throttle grip to make the cable longer. or your throttle grip is sticking remove it clean handle bar lube the slot for the cable use graphite on the throttle tube and bar. when was the last time you lubed the throttle cable? there is a cheep tool to do this or use a plastic bag and gravity

mixture screws there is a tiny o ring held in place by a washer and spring you should replace the tiny o rings and possibly the washers if they are cruddy .xj4ever is the ONLY place I know of that sells the correct size o ring.

have you adjusted the mixture screws when you did the sync or just set them to 2-1/2 turns out from soft bottom ?

 

1. No. A hole in a slide diaphram would prevent the slides from lifting properly, resulting in bogging.
2. Pull the carbs and look at the position of the throttle plates. With the idle screw not contacing the throttle linkage, the throttle plates should be fully closed, and not flow enough fuel to idle. Mthinks you have a lingkag prolem that could be due to impoper assembly, or throttle plate misalignment.

 

Check the throttle cable length first, as XJ550H suggested.
Is it the original? If not, who is the manufacturer? There are sveral who sell the same cable no matter which XJ it's being sold for, and that results in having the wrong cable length.

 

compare every thing on your carbs to the photos in this thread
OWWW, My Eyes!

 

your cable length choices
HCP2691 OEM original THROTTLE CABLE, with black curved metal tube, and adjuster nut, at the throttle end of the cable, for all XJ650 Maxim and XJ650 Midnight Maxim models. Wire length = 42".

HCP2649 Aftermarket THROTTLE CABLE, with curved metal tube, adjuster nut, and thumb-wheel on the throttle end of the cable, for all XJ650 Maxim and XJ650 Midnight Maxim models. Wire length = 41-1/2".

OEM original THROTTLE CABLE, with black curved metal tube, and adjuster nut, at the throttle end of the cable, for all XJ650 Euro models and XJ650RJ Seca models. Wire length = 37-1/4".

Aftermarket THROTTLE CABLE, with curved metal tube, adjuster nut, and thumb-wheel on the throttle end of the cable, for all XJ650 Euro models and XJ650RJ Seca models. Wire length = 37-1/4".

 

one of these
the throttle cable is the same when it's in the garage, at a red light or stop sign but no high idle.
there could be a vacuum leak at the petcock

that would be really lean, more like 3 to 3.25

 

Does the bike also idle around 3k after it warms up? This happened to me once after pulling and replacing the exhausts. Was driving me nuts. It ended up being an exhaust leak. I'd forgot to tighten the nuts on the #4 exhaust collar. Luckily I found the problem right as I was getting ready to pull the carbs.

 

I’m wondering if those might be part of my problem. Would you happen to have, (or can take a photo) or how far your exhaust clamps are seated? I feel like mine might be father out, but that was as snug as they fit when installing.

 

I reset the air/fuel mixtures and rerouted my throttle cable and got some good results. I will check the exhaust at the head and make sure they are tight.