High Revving GPz750?

Very good work so far Nick...
Making several massive changes could have you running around in circles before you know it. :blink:

VALVE CLEARANCES must be within spec, and better if thier close to eachother.

Try setting the fuel level in the carbs first, it takes the most patience. Get them all in spec. Hi or low spec dont matter much, all the same height is most important.

If you have stock airbox and filter/exhaust, then the stock jetting will work perfectly. There is another issue.

The springs that go on the airbox to carb boots are ABSOLUTELY necessary to attain proper input volumes for CV carb venturis'. With frame movement and time and vibration, these will allow air seepage at different intervals creating all sorts of mysterious problems, TRUST ME. they are there for good reason.

To test your current state of sync: get the engine idling off choke.
Drop the idle via the main idle control knob down to where the bike is practically stalling, then leave it there a couple minutes. If your sync is bad, one or more of your header pipes will go cool, as those cylinders will not be reqieving enough charge from the carbs to continue firing correctly.
If this is the case, then a sync is necessary, and the carbs will not function better than 75% efficency below max advance, until a proper vacuum sync is performed.

Hanging idle is 90% air leak, 8% advancer unit not properly maintained, 1% sync, 1% wierd shite. But all need to be attended to.

Sorry for the novel. :laugh:

Patton is the PhotoChopKing! :lol:

GL!

Thanks for the info. and support. I'm going to order the airbox springs and replace my ratty air filter. I have a question about the carb setup -

All of my butterflies on the Mikuni BS34s are set a little open at rest. Is this correct? I ask because if I set the main idle aduster in the middle of the threads, it doesn't touch the the piece that the thottle cable connects to. Hope that makes sense.
Nick

Question about valve adjustment?

All my exhaust valves are within spec. Intake #2,3,4 are off. Should I shim all of the valves to a common value of say .10mm ?

Thanks
Nick

I pulled the carbs and set the fuel height to spec on all 4 carbs. Cleaned again and put replacement 110 main jets from the rebuild kit. I left the metered pilot jets and the needle jets as is. I put the carb rack back on and on start, it races to 6K and stays there. Man this is frustrating. I've tried it with the tank on and running from a satellite tank as well.

- Valves are all within spec
- Compression tests all within spec.
- Electrical/coils check out.
- Carb holders are sealed
- Carbs are fully seated.
- stock airbox with airbox holders fully sealed.
- vac lines are all connected.
- mixture screws are 2 turns out from seated per manual.

I'm running out of things to try. help.
Nick

The only thing worse than this hanging idle problem is that I appear to have a bad starter clutch that I have to fix, because I can't start the bike to troubleshoot the idle problem!

nicksorg wrote:

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Is all the EPA stuff shown in the upper part of photo still fitted?

If so, there may be an air leak.

Would disable the EPA stuff by connecting a tube between the valve cover intakes and plugging all vac nipples (except vac nipple serving petcock).

Plug or tape over now unused hole in airbox.

If bike idles properly, shelve the EPA stuff.

Good Fortune!

I'd be ditching the EPA BS and get new carb mounts at this point.

This would require new pod filters, some jets, vacuum nipples.

Nice to see another 82 Gpz getting back on the road. Main thing is don't rush and it will come together. I understand you may be chasing what's left of your riding season on the east coast but I too have been in this chase and lost many times.

Good luck.

Thanks. You're right about the riding season. oh well.

I started her today on choke. She fired right up and dropped to normal idle when I took the choke off. I had it idling for a few minutes. When I blipped the throttle, it would come back, although with a little hesitation. The air filter on this bike hasn't been right from day 1 so I ordered one for it. My plan today is to take care of the starter clutch. I'm also going to check the carbs one more time and maybe replace the pilot jets and seal up the caps on them a little better. I also have new needles left from the rebuild kit that I'll drop in. Once I fix the starter clutch, I'll drop the new air fileter in and see if anything has changed. Then I'll try your EPA suggestions.
Thanks
Nick

Be carful of a bunch of major changes at once. You will start causing more issues than fixing.

What other needles do you have?

At this point it sounds like you may be getting there with the air leaks. But without seeing these carb boots hard to say how long they will last. At least they had the stock parts helping them support the carbs.

Good point. I pulled the carb holders and inspected them. They looked good. I reinstalled them with sealer.

You're advice about multiple changes is a sound one. A this point I'm going to wait and see if the correct air filter makes any difference. If not, I'll consider next steps, including replacing the airbox holders and adding the springs that hold them onto the rear of the carbs.
Thanks
Nick

nicksorg wrote:

Thanks. You're right about the riding season. oh well.

I started her today on choke. She fired right up and dropped to normal idle when I took the choke off. Nick

Again, this is a tell tale sign you have a very lean running condition. The raw fuel supplied by the choke circut is temporary "Band-Aid" rich condition which is allowing the engine to idle correctly for a short period of time. Is the carbs' mixture screws "de-plugged" and clear of debris ?

Going back to the carb sync procedure, #3 carb is not adjustable, all the others have to be set to match it. The one you think is for #3 & #4 is just for #4. Ill stay out of the other, youve got plenty of helpers already