84 GPz750 bogs and dies once hot

You need to check all the basics (spark/fuel/compression/timing) 

You have not mentioned compression, if it is low then the next step is checking the valve lash. Its all in the FSM which you can download from here.

Injected wrote:

You need to check all the basics (spark/fuel/compression/timing) 

You have not mentioned compression, if it is low then the next step is checking the valve lash. It’s all in the FSM which you can download from here.

Those are all on my list. I’m just baffled that for months while finishing things up I’ve been starting it and letting it run a minute or two 3-4 times a week and have had no issues with snappy throttle or what I have now. Then I think it’s ready to run, put all the body panels back, and now it’s not happy. 

I did a compression test last summer and got 115, 120, 120, and 135 from 1 to 4. 

wrote:

wrote:

You need to check all the basics (spark/fuel/compression/timing) 

You have not mentioned compression, if it is low then the next step is checking the valve lash. It’s all in the FSM which you can download from here.

Those are all on my list. I’m just baffled that for months while finishing things up I’ve been starting it and letting it run a minute or two 3-4 times a week and have had no issues with snappy throttle or what I have now. Then I think it’s ready to run, put all the body panels back, and now it’s not happy. 

I did a compression test last summer and got 115, 120, 120, and 135 from 1 to 4. 
 

If your valve lash is correct those numbers are low for healthy combustion, check the FSM for the spec. If you have black damp plugs your just not burning the fuel charge completely. May not be a carb issue after all.
 

Hey guys, I haven’t had enough time to recheck compression or pull the head off but this morning I took a few minutes to fire it up. It didn’t want to initially start but threw it on the battery charger, pulled the choke, and got it running. Still didn’t seem to be running well and absolutely didn’t want to rev. Messed with the pilot screws, going from 2.5 turns out up to 3.5 turns out then down to 2 and nothing seemed to make a difference.

I then decided I was going to pull the carbs again to make sure my pilot jets were free and clear and I pulled the intake rubbers off and decided to see how it ran without them hooked up. Fired up right away and it was much happier. Had no problem revving up. Covered each carb with a plastic scraper and it would start to die down covering each individual carb which I was expecting. 

Without checking the valve shims and lash I can’t know if those things are contributing but does what happened today point to it being fat and the restriction of the airbox is further fattening it up? This is with stock pilot jets and 112.5 mains.

Dan

Does sound like the airbox is choking it, how does it run with the airbox hooked up but the filter removed ? (how old is the filter ?)

Quick check in. When I pulled the carbs off last week I pulled the fuel bowls off and noticed the float needle valve sprung ends had varying levels of motion and that the floats had wildly different heights. I had recorded the levels I has set them at last spring so I am not sure if parts wore out or I did something incorrectly. Anyways, I purchased all new float needle valve assembly's and set float heights to 22.4mm. Some were 5-6mm low resting on the new float needle valves so had to bent the tang quite a bit to get them there. 

Wondering if I never had the bogging issues while the bike was up on the rear wheel stand due to the change in the fuel angle within the bowls artificially shutting the valves before the level rose too high. Once down on the ground on both wheels, the level would be higher and maybe that's why pulling the intake rubbers off caused it to run better?

Able to take it for a quick trip down the road and back, less than half a mile but the only issue I'm having now is just off idle there is a slight hiccup still but with slightly more throttle it clears up and runs great. Just did that this morning before heading into work so I'll need to look into it further as I have a chance.

Here she is in all of her current lack of beauty.
 

I’m not sure if this should be a new post in a different section or not. Put in 8 heat range plugs this morning and fired it up. Idles okay but if I hold the throttle around 1500-2000rpm for a few seconds and let off it almost dies. Also tried to take it down the street after it was warm and as I let off the clutch it will die as well unless I give it a ton of throttle. I heard a faint tick sound from the top end every 20 or so seconds, it wasn’t cyclic so I decided I was going to pull the valve cover off and check my valve clearances. Here is what I measured.
 

When turning the crank with a socket, the bike in neutral, and the spark plugs out I had some concerns that I wanted opinions on. There were areas in the crank rotation that were very tight and then it would free up and the cam chain would have slack. I took a video and I’ll throw it in here as well. Let me know what you think. Maybe it’s nothing, or just another thing that’s on my list to repair.

If you read the FSM it tells you not to rotate the engine without cam cover on.

The KZ750 fours Kawasaki service manual I have does not mention that. I'm not sure I understand how one would check the clearance without this off unless you're saying to install the cover when rotating the motor over then remove it and repeat this process?

The “tight-loose-tight” is usually an indication of piston to valve contact. Did you tension the chain after removing the cover before rotating?

Wookie58 wrote:

The “tight-loose-tight” is usually an indication of piston to valve contact. Did you tension the chain after removing the cover before rotating?

No @Wookie58, I did not. I pulled the cover and started measuring with a feeler gauge right away. Did I skip a step? 

I did note that the most "tight" feeling area of the rotation was while #2 intake and #4 exhaust valves were being depressed.
 

When the cam moves over the top of one of the lobe tips, it will tend to thrust forward, and cause that tight then loose cam chain situation,  It's perfectly normal.

Regarding not turning over the engine without the cam cover on, that's news to me.  I've done it hundreds of times.