I just bought my second Suzuki Savage LS650. Anyway, I started rebuilding the carburetor and had a very difficult time getting the air/fuel mixture screw out, I mean a very difficult time! Screwed it in three full turns and backed it out 3 full turns, and then someone put the brakes on hard! Used WD-40 and ground the sides of a new screwdriver to fit hole
and fit what was left of the slot on brass needle. Anyway, finally got it out!
I have ordered two new air/fuel mixture screws. Question: what are the threads? I think they are M6 X 0.75 but not sure. I want to run a tap to clean up threads, good or bad idea?  

When the factory installs the screw they dimple the outer threads, which I assume is their way of assuring that it does not fall out from vibration,
As if it needed it.  I've never had one come loose on me.

I bought a 'lighted' magnifying lens from Harbor Freight. Put the bad pilot adjusting screw (air fuel mixture) under the magnifier and put a MM ruler next to threads. Top of one thread to top off next thread (pitch) is 0.5 MM.
So it is a M6 X 0.5
I am waiting for the new adjusting screws and will try using oil and 'gently' screwing into carburetor. Threads on adjusting screw seem rounded, and outer most, top thread did look as if it had been hit.
The threads in carburetor looked good. Will see what happens.
If I need to buy a M6 X 0.5 tap, does anyone know who sells the tap & die?

The 6 x 0.5 aluminum threads for the idle fuel screw can become corroded, and it makes it nearly impossible to get the old screw out - and just as hard to get a new screw in without ruining it. The new brass screw is too soft to restore the aluminum threads - and the brass screw slot doesn't allow you to monkey around with it too much.

I have cleaned up the aluminum threads with a tap....and it works great.  The spring and O-ring keep the idle fuel screw in place.

I have a tap.....you can use it provide you pay shipping both ways, and put a small deposit so that I get it back....I believe it was about $12 when I bought it.  (I bought the tap at a local hardware store that caters to contractors - and it has a very nice selection of taps and dies).

A dremel cut off disk , used right, will make a bolt into a thread chaser.
Just a slice into the bolt and Bob's your uncle.

justin_o_guy2 wrote on 12/21/17 at 18:49:46:



That does work well on a hardened steel bolt - it doesn't work on these soft brass fuel mixture screws.

I'm sure I'd never suggest that with brass.
I've been using bolts for such a trick for years. They don't cost near as much as a tap.

I received the taps today and also received new brass air/fuel needle valve. Cleaned the threads with tap and put new needle valve in. Put Carb back on and started her up. Seem to run OK, then noticed smoke and oil leak under exhaust, at head.  As I mentioned before, I just bought LS650 and have found quite a bit wrong. So, I wasn't surprised to find a 'nut' missing under the exhaust, M8 X coarse thread. Looks like it has been off quite awhile. The nut on rear of engine was there. I found a nut that fit, put it on and tightened.  Anyway, started up and ran it. To cold to run outside, -11 degrees F. Otherwise, I would take it for a drive. Question: Should the head bolts be re-torqued? Am I wasting my time and should tear engine down for Head gasket?  :'( :'(