Idle Mixture Screw Cap

[geneborg]

I am reworking two sets of carbs to get one good set. The "new to me" carb bodies still have the cap covering the "pre-set" idle misture screw. The old set has had it already removed. I believe both sets to be 1980s or at least the newer versions. What years did they have the caps?
****I know I have read when researching the best way to remove the cap. How about some suggestions how best to do so without doing any damage??****
Then the other question is, should I leave the cap in & alone on a set of preset 30 year old carbs? Who know what has been done in the past and how that preset will work on a different year engine.

[fredintoon]

Rip them out

Then the other question is, should I leave the cap in & alone on a set of preset 30 year old carbs? Who know what has been done in the past and how that preset will work on a different year engine.

Hi Gene,
if the plugs are still there the needles and their associated narrow passages have a 30 year collection of crud in them. Best you clean it out.

[tinman905]

I just finished rebuilding my 80SG carbs .I was having a hard time removing the plugs so I just drilled them out. Once the drill bit dug in it spun the plug out. I was looking on MikesXS for some replacements but you have to buy them in a kit.

[motoman]

Tinman, what I did couple years ago: went to to True-Value and in those specialty boxes got four of the plastic plugs U would use to plug an already drilled in a body panel, etc. Popped those in to keep the crud out and they are still there. Just pop them out when sync. carbs. If one becomes a little loose, just replace. Simple and cheap fix!

[boyat68]

Those plugs are really not needed as they were originally placed to keep diddling hands from changing those factory settings to conform to the then EPA rules. Remember this was the same period when auto carbs had plastic plugs to prevent someone from changing the air fuel ratio. Even though the 80 kits come with plugs, they can be left out. This makes the synching job easier as those air screws need to be tuned for optimum performance while on the bike and putting those plugs in while the carbs are installed is a difficult task.

[DGXSER]

I am reworking two sets of carbs to get one good set. The "new to me" carb bodies still have the cap covering the "pre-set" idle misture screw. The old set has had it already removed. I believe both sets to be 1980s or at least the newer versions. What years did they have the caps?
****I know I have read when researching the best way to remove the cap. How about some suggestions how best to do so without doing any damage??****
Then the other question is, should I leave the cap in & alone on a set of preset 30 year old carbs? Who know what has been done in the past and how that preset will work on a different year engine.

To remove or not, well, how dirty was the rest of the carb? As Fred stated, there is 30 years of build up under there most likely, unless someone before you pulled the plug, cleaned and reinstalled. Also, this is one of the few methods of tuning the bike and the carbs. Me, I would pull them, remove the jet screws and clean it good, then reinstall without the plugs.

[TopCatGr58]

I posted a how to a while back, but will be faster for me to retype it than to search for it! :ROLLEYES:

I used a fairly small drill bit, put a piece of tape about a 1/4" from the end of the bit, and then drill slowly and gently into the caps, after about 1/8" into them, you should break thru, so just don't push too hard so when it pops thru it won't damage the tops of the pilot screws. Then get a sheet metal screw, screw it into the cap enough for it to get a bite, and then use a pair of pliers to grasp the screw and wriggle the cap loose and out. It may come loose during drilling, but with a small bit, probably not.

Be aware there are small rubber and metal washers down inside the screw tunnel, they sometimes get stuck down there, may need a small dental pick to get them out. You can get replacements from MikesXS if you loose them, or if they are damaged.
T.C.

[tinman905]

When I drilled my plugs out there wasn't much crap in there but the idle screws were tight coming out .One trip through my new ultrasonic cleaner and they went back in like "butter" .I haven't replaced the caps yet but might do the same as Motoman. Good idea !

[lvrsnr]

one thing I have found to prevent damage to the needle when drilling them out is to use a left handed drill bit, then even if you slip and the drill contacts the needle it screws it out not in

[fredintoon]

Re-plugging the needles

Y'know the rubber plugs you get with carb. rebuild kits, the plugs that seal up the pilot jet holes in carbs where the pilot jets are internally fed from the main jet gallery so if you don't use them you run rich but if you use them on carbs where the pilot jet is directly fed from the floatbowl the pilot jet gets no gas at all but they include the plugs in that kit too anyway?
Don't throw them out. They will also fit in the hole atop the mixture needle where the brass plug used to be to make a perfect dirt seal.