85 GPz 750 Cafe Project

I had to add some spot welds as I had some seepage. Drain the tank, dry the tank, weld, repeat. Sealed at last, filled her with gas yesterday, took her out front and attempted to start her. No fuel to carb #4. Carbs coming off....again.

Carb #4 had the screen from the needle valve base fall off and block the passage.



...ouchie. Anyone have a Mikuni BS34 for sale? This SOB is possessed.

I scored two sets of Mikuni carbs for $50. BS32s I'll put on the KZ650 motor on the shelf and BS34s. Both appear to be off of a Suzuki. Metal top cap style instead of the plastic cap style. There are some circuitry differences. Anyone know if it will be a problem to add one of these to my bank of GPz750 carb bank? GPz carb on the right.
PS - I had my bass ackwards, this is carb #1.

I'm hearing from the techs on KZ650 this carb will not work with my BS34s with the jet in the air horn.

Making progress again.

I called JB Weld and they tell me the original formula is in fact gasoline resistant contrary to my previous experience. I placed some JB on the break, matched up the base casting and the broken piece and let it dry overnight. Came back the next day and added added as much reinforcement as I could without interfering with the fuel bowl. I let that dry overnight and came back with the POR fuel cell liner and painted that over the top. 96 hours later I'm hoping I can install the float and pin with support on the backside of the upright portion. I'll put a slight taper on the leading edge of the pin. Weds is the assembly day.

After a 5 day diversion to replace a totaled car I'm back in the garage. (No one was hurt) Wet sanded the tank with 800 grit in preparation for shooting paint. Target for that is Saturday I reinstalled the cam cover and did a compression test with the bike ice cold. 145 to 150 lbs on every cylinder so compression isn't my problem. I'll reassemble carbs tomorrow and set the fuel/float levels.

The carb 'fix' failed when I tried to make a float height adjustment even thought I was trying to be oh so careful. Back to grinding on a solution for that. Meanwhile back at the ranch I've sprayed the tank. Amazing to me the colors used come together in a way to produce the result. I'll wet sand and stripe it today, then shoot the final clear tomorrow.

ajsfirehawk wrote: . . . I reinstalled the cam cover and did a compression test with the bike ice cold. 145 to 150 lbs on every cylinder so compression isn't my problem. . . .

Just a memo, if not already done, that now could be a good time to assure valve clearances are within specs.
Because if too tight, the good compression may likely become poor compression at normal operating temps.

Good Fortune!

Have carb issues been resolved so that fuel mixture is reaching the combustion chambers when attempting to start the engine?

At closed throttle and low rpm operation, It's critical that fuel mixture passes into the carb bore through the small orifices located near the pointed tip of the pilot screw.

If the orifices through the carb bore are obstructed, mixture can't enter the bore, which results in no mixture being drawn into the combustion chamber (evidenced by spark plugs staying dry -- not dampened with fuel).

Here's a less cluttered diagram that might be helpful.
Note absence of tiny passageway from the main jet to the pilot jet and absence of plug over the pilot jet.



Good Fortune!

Thanks for the follow up Patton. I did set the valve clearances, all now have .20mm + - .03mm. I took the carbs apart again with your diagrams on the bench. All passages verified clear with brake cleaner. Just this morning I located a new bank of the proper version of BS34 carbs so I can replace the one with the broken float pillar. I'll sort out a permanent fix for that carb after I get this thing running. Headed out the the garage now to set of my make shift paint booth and spray final clear. I striped the tank last night after wet sanding the first two coats of clear.
I should also mention there are two small openings at the base of the brass pilot feed tube and I ran a small wire through each of those as well. Thank you for the support. I'll be on hold for starting the bike until I get the new carb body here and rebuilt.

Striped and final cleared. At last I'm back to where I was 7 months ago. Sealed the pinholes and moved the petcock to the rear.