Mystery carbs Mikuni 26mm's
Moderator: rztom
Mystery carbs Mikuni 26mm's
Was about to fire up the bike after dealing with timing adjustment but it won't kick over. Prior to kick over, replaced both carb needle seats and needles (fuel was leaking out the drain lines) , tested the carb floats would float - working, set both float levels @ 21mm at 60 degree tilt, set the carb slide dimple in the centre of the carb glass sites & balanced the carb slides with popicycle sticks. Pulled out the plugs - both spark is blue/white and gapped to spec. Put a 5mls of fuel in each pistion and tightened in the spark plugs. Fired up 1st kick and 2nd kick but just died after the fuel was depleted. Kicked the engine over about 6 time throttle wide open - nothing. Ck'd the plug again and both appeared dryish. It appears to me the carbs are the issue. Pulled the carbs apart again and ck'd the main and pilot jets with compressed air - both had flow. Had th carbs cleaned them last year and drained the bowls . Dirty carb channels perhaps?
Re: Mystery carbs
Pull out the pilots and see if they are plugged.
Also, the Popsicle method only sets the sync of the carbs mechanically. It does not consider the different vacuum rates of each cylinder. Unisyn is needed for that.
Choke should be on, no throttle.
Not kicking over means seized. Not firing up when kicked over is a different story.
Also, the Popsicle method only sets the sync of the carbs mechanically. It does not consider the different vacuum rates of each cylinder. Unisyn is needed for that.
Choke should be on, no throttle.
Not kicking over means seized. Not firing up when kicked over is a different story.
Rory
2 1984 RZ350s
1985 RZ350
9 1986-1990 RZ350s
2000 ST2
2005 749
2005 749 with 999 engine
2 1984 RZ350s
1985 RZ350
9 1986-1990 RZ350s
2000 ST2
2005 749
2005 749 with 999 engine
Re: Mystery carbs Mikuni 26mm's
Both pilots are clear - ck'ed with a light. Also ck'd the reeds to see if they were opening - functional. Just one unisyc required?
Re: Mystery carbs Mikuni 26mm's
Yes, you move it from carb to carb, with no filters or boots. You'll need that when it's running. About $80 delivered off e-bay.
Plugs are new?
Do you have gas flow out of the petcock?
Plugs are new?
Do you have gas flow out of the petcock?
Rory
2 1984 RZ350s
1985 RZ350
9 1986-1990 RZ350s
2000 ST2
2005 749
2005 749 with 999 engine
2 1984 RZ350s
1985 RZ350
9 1986-1990 RZ350s
2000 ST2
2005 749
2005 749 with 999 engine
Re: Mystery carbs Mikuni 26mm's
Plugs are new and there is flow fm the tank to the carbs. Unscrewed to the drain screw and had flow. Learnt that I can purchase the unisync from my local Lordco. Will use it once it running again. Perhaps its a vacuum leak near the reed boots that prevents draw into the combustion chambers.
Re: Mystery carbs Mikuni 26mm's
Is the gas all new, or was it mixed with old?
Rory
2 1984 RZ350s
1985 RZ350
9 1986-1990 RZ350s
2000 ST2
2005 749
2005 749 with 999 engine
2 1984 RZ350s
1985 RZ350
9 1986-1990 RZ350s
2000 ST2
2005 749
2005 749 with 999 engine
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- Location: gold coast Australia
Re: Mystery carbs Mikuni 26mm's
is the fuel transfer pipe between the left and right carb installed? (part number 30 in service manual). I found my bike would not start without it. Also check you have float bowls installed on the correct carb. they are different from each other.
yamaha fanatic.
Re: Mystery carbs Mikuni 26mm's
Gas is a mth old when mixed. The transfer pipe is/was connected. What the differentiation between the float bowls (choke vs. non choke carb) - the exterior joining pattern half way up the bowl Graham?
Re: Mystery carbs Mikuni 26mm's
Sounds a bit like swapped float bowls.
Unfortunately they cannot be distinguished from the outer shape, so get the carbs off once again and check if the left one has the choke jet at the bottom of the appropriate passage.
Unfortunately they cannot be distinguished from the outer shape, so get the carbs off once again and check if the left one has the choke jet at the bottom of the appropriate passage.
Bye
Martin
Martin
Re: Mystery carbs Mikuni 26mm's
after many years the inner passages get gummed up, people drill the brass balls out and replace them after. 4.5mm brass balls is what you need, drill 3mm hole and use either a tap and bolt or a self tapper to remove, hammer new ones in after.
80 XT500 Supermoto!
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82 RD350LC decapitation project
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81 RD350LC Resto
82 RD421LC Hybrid
82 RD350LC decapitation project
82 RD250LC JDM '251LC' YPVS
83 RZ350 Resto
84 RZ500 Resto
85 RZ350 F1 Resto
86 RZ350 F2 Resto
86 RZ350 F2 Hybrid
Like Watches? www.PloProf.com & www.DeskDivers.com
Re: Mystery carbs Mikuni 26mm's
I suspect Redman412 is having the same issue as myself. So, pulled out the bowls and photographed them from the bottom. Which is left or right? The only marking I note are the numbers on the top of the bowls. Yes, I'm aware one is brass but that's what was in one set of carbs. I'm wondering if I should just by a new OEM set (assuming they will arrive left/right).
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Re: Mystery carbs Mikuni 26mm's
Now I am confused. The float bowls are what get swapped, not the floats!
Red/White US '84, Spec II pipes, Y-boot w/K&N, Fox Shock, Mikuni carbs?
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Re: Mystery carbs Mikuni 26mm's
Floats are the same. It is the float bowls that are different the left hand bowl has a hole in the pick up tube to recieve fuel when you pull the choke. The righy carb has the tube but it doesn't have a hole in it. Hope this explains it for you. some times it can get blocked. i fould a thin guitar string can clean it out. you should be a ble to suck air through it.
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Last edited by graham heise on Wed Jun 21, 2017 6:40 am, edited 2 times in total.
yamaha fanatic.
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- Location: gold coast Australia
Re: Mystery carbs Mikuni 26mm's
Cheers Graham for info not in the manual. Ck'd all 6 carbs I have in stock only one set had the proper left choke float bowl and it was the set on the bike properly arranged. My next step is to replace the pilot jets with brand spanking new ones after I sonic clean both carbs.