How to: Replace the o-rings in Mikuni float bowls.

[97tiger885]

I have now replaced the two o-rings in the Mikuni carb float bowl assembly.  It was relatively easy. Here are some pix of the procedure.

First, remove the gas from the carbs.  I ran my engine with the petcock off until the engine stalled.  I removed the carbs and turned them upside down.  This got rid of the small amount of gas remaining in the carbs.

Turn the carbs upside down.



There are two phillips head screws holding the float bowl onto the carb body.  Remove these and pull off the float bowl.





The large o-ring should come off with the float bowl.



Pull the float assembly off.



Here is a shot of the carb body with the float removed.



Turn the float onto its side.  You will see the two posts with the o-rings.



I used a tweezer to pull off the o-rings.  The new ones will roll on easily.

Put the float back in.



Put the float bowl back on.



Done.

The only complication I had was that 3 of the 6 phillips head screws stripped.  I used penetrating oil on each of the  6 screws and tapped lightly on each with a screwdriver and hammer.  The carbs sat overnight in my bathroom.  Three released fairly easily.   The other three did not.  For those, I used  a cutting wheel on a dremel and cut a large slot for a slotted screwdriver.  I used more penetrating oil and the last three released.  I replaced all 6 screws with allen heads.

Here is what the phillips head should look like.



Here is what one looked like after cutting a slot.



Here is a replacement.



One carb has an adjustment knob which makes getting to one of the phillips head screws a bit difficult.



Remove the phillip head and this knob will pull away making access to the float bowl mounting screw easier.

[Sin_Tiger]

I've found in the past, heating the carbs with a hairdryer the alloy cools faster than the steel screws, along with some Plus Gas (works better  than WD40 with alloy in my opinion) usually does the trick. Hey you've got the carbs in the bathroom already

[97tiger885]

I've found in the past, heating the carbs with a hairdryer the alloy cools faster than the steel screws, along with some Plus Gas (works better  than WD40 with alloy in my opinion) usually does the trick. Hey you've got the carbs in the bathroom already

Heating had occurred to me, but I feared setting my carbs, hair and house on fire.  I will try that next time I take the float bowls off.

[Sin_Tiger]