Stuck choke

I just got my bike back from the shop (I'll admit it, I gave up and took it in for a diagnosis for a seemingly unrelated problem). When I brought it home, it took ages to fire up, then after it finally did, with the choke off, the rpms hovered at 4000, where it should be for the choke on. With the choke full on, it shoots up to 6000 rpm. I checked the throttle cable and it's not tugging at all. Thoughts?

It's an 82 GPZ750, stock.

Vacuum leak?

freakinbike wrote: I just got my bike back from the shop (I'll admit it, I gave up and took it in for a diagnosis for a seemingly unrelated problem). When I brought it home, it took ages to fire up, then after it finally did, with the choke off, the rpms hovered at 4000, where it should be for the choke on. With the choke full on, it shoots up to 6000 rpm. I checked the throttle cable and it's not tugging at all. Thoughts?

It's an 82 GPZ750, stock.

I've had the enricher slide fail to seat entirely after use which causes fuel to continue to pour into the intake. Try manually depressing each of the enricher slides. Do any of them move down when pressed upon?

Bill

Back the idle screw off ?

I thought you said the choke is stuck ?

bluej58 wrote: I thought you said the choke is stuck ?

I thought that's what it was at first. Where is the enricher slide? I apologize.

Also, is there a vacuum diagram anywhere?

So I found a broken (ripped?) vacuum line, going from carb 2 to the fuel petcock. Odd thing about this is that the last time this line gave me trouble, it caused the bike to die. Now it's causing the opposite.. I don't get it.

I have another amateur question. How important is the diameter of vacuum lines? Obviously it needs to fit, but if the line is slightly wider/thinner, will there be negative effects?

freakinbike wrote: So I found a broken (ripped?) vacuum line, going from carb 2 to the fuel petcock. Odd thing about this is that the last time this line gave me trouble, it caused the bike to die. Now it's causing the opposite.. I don't get it.
I have another amateur question. How important is the diameter of vacuum lines? Obviously it needs to fit, but if the line is slightly wider/thinner, will there be negative effects?

When there's no vacuum being applied to a vacuum petcock, fuel flow should be disallowed in the ON or RES position. PRI position allows flow with or without vacuum applied.
No vacuum in ON or RES would mimic being out of gas (bike dies).
No vacuum in PRI would mimic air leak (racing idle).

Tubing size should be okay provided the wall-thickness is rigid enough not to collapse against itself when vacuum is applied.

Good Fortune!

I replaced the line and the idle hasn't changed. I played with it between on, pri, and res and it wasn't affected. I suppose I could turn down the idle speed (which screw is that by the way) but warming up the bike will take ages.

freakinbike wrote: I replaced the line and the idle hasn't changed. I played with it between on, pri, and res and it wasn't affected. I suppose I could turn d

Yes, just turn down the throttle stop screw (idle speed) so the bike idles at about 1,000 rpm. When you are warming the engine up from cold use the choke to start the bike then as soon as possible turn it down to about 1,000 rpm. You should not let the bike "idle" at high rpm, especially when warming the engine. Letting a cold engine sit there and run above 1,500 rpm or so is not good for it. Warming the bike up properly should still take only a couple minutes. Ed

Where is the throttle stop screw? I apologize, I haven't done much carb work

You should see a thumbwheel on a shaft sticking out of the back of the carbs. As you turn it the throttle stop is moved and this in turn raises or lowers the idle speed. Ed