Problems with torque @ 5-7k rpm

[katana]

Greetings from Lithuania You have a nice site here.

So to the point: I have gs500 '89. Once after 20km ride with passenger, just returned to town and noticed that something is wrong. That is when rpm rise till 5k it starts to roar hollowly and no torque at that point. Rpm rise very slowly. The same in all gears, but in neurtal everything is fine. It seems to be even fine if it stands on center stand with rear wheel not touching ground through all shifts (but I would not count on that for it was tested for short time in garage). Then tried to ride alone and twisted throttle almost till the end when this happens. Usually at 7k rpm it like spits something out and everything back to normal but only for short time, since i have to shift and again I am at those 5-7k dead rpm. Thought it was air filters problem. Tried to clean it with compressed air like it is written in manual, but it did not help. Then today tried to ride without air filter in order to test. But it is even worse then. When I release throttle and rpms fall it detonates or smth like with race exhaust Do not mind that, but before the problem it did not happen.
Oh and when moving from complete stop I have to do it gently, for too much throttle might stall the enginge. Somehow it is more sencitive to that now. I mean when it starts to move and I completely release the cluch, or straight after that.
Hope I have explained enough. You have more exp and skills than I do, so please advice something or guess what could be wrong and should be checked.

[davipu]

it sounds like you have a really lean spot there between 5-7 the first thing to check would be the carb boots, then the air filter to see if it has any gaping holes or isn't seated correctly.  then slides opening too fast.  then rejet.

[My Name Is Dave]

I look for gaping holes on a daily basis. She needs to have morals also, though  

Dave C, class act

[scratch]

Welcome!

I am having difficulty trying to figure out what is wrong. At first, my thoughts are that it might be the clutch slipping. These bikes typically do not have much power below 4000rpm. So, when you say above 5000rpm there is no torque, I think it is the clutch.

When rpm's rise slowly, either the clutch is overloaded, or you are in too high a gear.

Again, if everything is okay in neutral, I think it is a power delivery problem with the clutch. With the bike on the centerstand there is no load on the clutch.

It also sounds like the carburetion is too lean (too much air, not enough fuel).

[katana]

If there would be problems with cluch, then IMHO it would not gain torque again at 7k. Or am I wrong. And as I have mentioned it sound strange. Like it could gain rpm but something is blocking something Of course maybe it is my imagination Anyway thanks for thoughts. I guess first of all is the best to get new air filter. Even if we tested we though air could not flow through it , but if it is ripped somewhere we could just not notice it. Maybe there is to much of air, for after removal of filter it got worse.

[scratch]

Time to check the spark plugs. What do they look like? What color is the left one, and the right one? Is either one just wet? Do they both have spark?

[katana]

Davipu, what did you mean by saying "then slides opening too fast"? Which part is it? Something in carbs from air box side?

[katana]

Finally it is fixed. The reason was one of the needles in carbs. Since it was not original it went out of its place. Because of this spark plugs needed replacement too.
Any way thank you for your help.