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Mystery carbs Mikuni 26mm's

Posted: Mon Jun 19, 2017 12:55 am
by LC Cnd
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

Posted: Mon Jun 19, 2017 1:03 am
by hondaror
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.

Re: Mystery carbs Mikuni 26mm's

Posted: Mon Jun 19, 2017 1:38 am
by LC Cnd
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

Posted: Mon Jun 19, 2017 1:43 am
by hondaror
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?

Re: Mystery carbs Mikuni 26mm's

Posted: Mon Jun 19, 2017 1:58 am
by LC Cnd
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

Posted: Mon Jun 19, 2017 3:35 am
by hondaror
Is the gas all new, or was it mixed with old?

Re: Mystery carbs Mikuni 26mm's

Posted: Mon Jun 19, 2017 6:00 am
by graham heise
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.

Re: Mystery carbs Mikuni 26mm's

Posted: Tue Jun 20, 2017 12:58 am
by LC Cnd
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

Posted: Tue Jun 20, 2017 1:47 pm
by MK
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.

Re: Mystery carbs Mikuni 26mm's

Posted: Tue Jun 20, 2017 9:08 pm
by JonW
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.

Re: Mystery carbs Mikuni 26mm's

Posted: Wed Jun 21, 2017 2:38 am
by LC Cnd
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).

Re: Mystery carbs Mikuni 26mm's

Posted: Wed Jun 21, 2017 6:34 am
by waltmil
Now I am confused. The float bowls are what get swapped, not the floats!

Re: Mystery carbs Mikuni 26mm's

Posted: Wed Jun 21, 2017 6:34 am
by graham heise
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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Re: Mystery carbs Mikuni 26mm's

Posted: Wed Jun 21, 2017 6:35 am
by graham heise
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Re: Mystery carbs Mikuni 26mm's

Posted: Thu Jun 22, 2017 1:17 am
by LC Cnd
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.