Topic: Different float needle seat on carb 2

[derelicte]

My '74 750 came with a gutted mac exhaust (completely open) and pod filters.  I want to go back to a stock airbox and have a superstrapp exhaust ready to mount in the spring.  I've got the carbs apart for cleaning and rejetting if necessary...  A few questions so far.  The #2 carb has a different float needle seat than the other 3, it has sort of a bumpout on the bottom (#2 is on the left in both photos below).  Would the other 3 be the stock parts?  The #2 is the only one with keihin markings. 





Next odd thing - the float in one of the bowls was corroded and the tab bent to a point where it did not even touch the needle when fully "floated" (tried to show this in the last pic).  Why wasn't that carb leaking all over the place?  Bike idled fine but otherwise ran like crap when I started it up this fall.  Its possible I did this taking the bowl off but I was careful (i thought) not to bump anything.  Last question - currently there are stock idle jets and 130 mains.  I am not sure what the mains were stock (shop manual says 120 but I wasn't sure of the years) - what would you recommend?  Never messed with this before but based on a formula I found somewhere on here I was thinking 125?

[ekpent]

The stock main jet would have been around #110 or #105 on the 74. That 'bump out' needle seat looks like a later model that has a built in fuel filter on it.If it is they do pull out.

[derelicte]

Wow, if that's the case what was this doing with 130s?  I read if you're running the stock airbox with an aftermarket exhaust you can run stock jetting - should I go closer to 110s?

[ekpent]

I would start with at least a #110. You may find it works or you may need larger depending on the pipe etc. The bikes in 74 were jetted pretty lean at the time because of the fuel crisis etc.Also not all engines are the same and there are diffences in jetting that suite each engine best. The main is used most at higher rpm's where the needle is for midrange and it also is fully adjustable with different notches to vary height. I would set them up close to stock,see how it runs,check the plug color and take it from there as far as fine tuning.One thing of note its better to maybe be a little rich than too lean as the gas actually works to cool the engine in an air cooled engine. Good Luck on them.

[derelicte]

Appreciate the help.  I'll probably get some 115s in that case.  If I recall the needle was in the middle position on the carb I checked. 

[lucky]

Some kind of stupid repair.

Just get 4 new float needles and seats!!

End of story. Those look old and beat up anyway.

And No ...you cannot polish them into being serviceable. Forget that.