switching brass floats for plastic ones , float height ?

[TDodge7]

i have a set of 79 carbs with bad brass floats , if i buy the plastic floats from mikes xs do i keep the floats set to 1979 specs of 25.7mm or would i change the float height to match the 23.0mm height from a 1980 model that actually used the plastic floats.

[DiverRay]

Keep the floats to the '79 spec. You may STILL have to adjust them one side or the other for top performance and economy.

[foreda]

Plastic floats

I agree with DiverRay, you will probably need to tweak the floats. I had to tweak mine to get em right.

[dbeardslee]

I switched to the plastic ones and have them set right about where the brass ones were. Keep and eye on your plugs. If they show signs of fouling or running too rich, lower (installed-on-the-bike orientation) the floats 1mm or so. If it runs lean, go the other way 1mm. Spec is 24.7 to 26.7mm, so it's basically normal. What do you use as a gauge when setting your float height?

[81xsproject]

I did fuel height testing a while back with BOTH types of floats. They can be set exactly the same. Set the floats to stock 79 float heights, 25.7mm.

[TDodge7]

awesome , so then is there any difference between the floats mikesxs sells and the floats that would be in a 1980 set of special carbs ? because my set of 1980 carbs is going nowhere fast and my 79 set of carbs has 2 popped brass floats . i was just gonna switch em . and i assume i would still have to use the non viton tipped needle valves even tho i'm upgrading to the 80 style floats ?

[DGXSER]

Should be able to switch floats but seats on the 78-79 are different than the 80's as you should see. The 79 screwed in the 80 popped in with an o-ring and clamped down. I would keep the needle valve with the seat.

[TDodge7]

yeah , thought so . well here's hoping these 79 carbs end up working better than my horrible 1980 carbs .

[dbeardslee]

You can use the viton tipped needles in the 78/79 carbs. I've got 'em in mine with the plastic floats. I also installed XV920 seats. The hole is .001" larger than the stock seats, and they have an integral screen at the bottom. Not sure I needed to as I had them in the stock seats previously and they were working fine, but some members have reported needles sticking when installed with stock seats. Personally I think the viton-tipped needles are a much better design, and provide a better seal than the metal to metal seal you get with stock. Depending on how deformed the viton is, they may work with your existing seats. Don's absolutely right though - normally you want to keep a used needle with the seat it was mated to.