Tool for adjusting the idle mixture screw

When I cleaned my carbs several years ago after I got my ST1100, I couldn't budge the idle mixture screws. Never saw a "half circle" end of a mixture screw before or since either, BTW. I tried to make a home brew tool to turn the screws, but it didn't work. They seemed really tight. So, I just left them as they were and the bike seems to run fine.

But I just read about the 40 vs. 38 EPA idle jets and may switch them over to the 40's ( drill out my 38's ) some day but won't do this unless I can find a tool to adjust the idle mixture screws after the change.

Where can I get a proper tool ?

To borrow or to buy, Jim? It has a Honda part number so most any Honda parts source. The PN is in the manual or I can go dig it up for you...

John

John OoSTerhuis said:

To borrow or to buy, Jim? It has a Honda part number so most any Honda parts source. The PN is in the manual or I can go dig it up for you...

John

Click to expand...

Thanks for the offer John. I may take you up on that next winter. I think I'll let them be for this next season - Got plenty to do this spring ( fork work, timing belt, etc. ), and the bike runs pretty good now. What I didn't understand is why the mixture screws were so darn tight. I couldn't budge any of them. Am I missing something, here ?? Like I said in my first post, the ends look like half a circle. Does that sound correct , or is that some kind of a cover over the ends of the idle mixture screws , etc. ??

Jim Van said:

the ends look like half a circle

Click to expand...

It's normal.... you can get a tool to fit it. However, if you run some fuel cleaners through the carbs, you may find they are best left alone. My '99 has 97K on the clock... when I first got the bike with 64K, the carbs were very dirty. I cleaned the jets and bowls, left the idle mixture screws alone because of the special tool needed. After assembly and a couple cans more of "Seafoam" the bike runs perfectly and get about 50 mpg.
BTW... I have a special tool now, and haven't used it yet.

John OoSTerhuis said:

To borrow or to buy, Jim? It has a Honda part number so most any Honda parts source. The PN is in the manual or I can go dig it up for you...

John

Click to expand...

Wow !! Just looked on the web for the tool - $74 !!!

Maybe I'll try again to make my own.

John : When you have a few spare minutes, could you please take a picture of the end of the tool so I can see exactly what I need to fabricate ??

I'm away from my desktop. I can post a picture that I have of the tool later but the pilot screw shape that it was designed for is usually described as "D shaped." I believe the Canadian version carbs have cross-tip/Phillips pilot screws. The key to the special tool is the flex shaft which is required to adjust the pilot screws in-situ/engine running. See the schematics in the shop manual. This "idle drop procedure" also requires an expensive, accurate rpm meter which is the main reason I haven't ever done it. Well that, and the fact that my ST1100 runs just fine.

I recall that some folks have attempted to make their own tool. Fairly easy to use a piece of correctly sized metal tubing and put a dent in the side to work the D shape. IINM, a 22cal shell worked for one fellow. Those handmade tools worked on carbs off the bike, but I don't know of anyone successfully duplicating the flex shaft and actually doing the procedure.

Regards, John
via iPhone 4S

Here is a picture of the Bit for the Motion pro tool, as John says you need something Flexible to reach the carbs on the Bike.
http://www.motionpro.com/motorcycle/partno/08-0242/

Read the note below the picture regarding use on an ST1100

Slydynbye said:

Here is a picture of the Bit for the Motion pro tool, as John says you need something Flexible to reach the carbs on the Bike.
http://www.motionpro.com/motorcycle/partno/08-0242/

Click to expand...

Looks like a standard bit, thus might fit into an angled carburettor tool/set:

Here's the USA version of the Honda Special Tool (07MMA-MT3010A / WRENCH PILOT SCREW), about $47 from Ron Ayers:


http://www.st-riders.net/coppermine/displayimage.php?pid=1080


http://www.st-riders.net/coppermine/displayimage.php?pid=1081

I can see that the MotionPro bit wouldn't work on the ST carbs very well, if at all. The Honda tool's tip is quite thin-walled in comparison.



For folks that just want to manually adjust the pilot screws to a set number of turns while the carbs are off the bike, if you can get your handmade bit to work, you could do what I've heard reported: count the number of turn inward to the stop, next remove the pilot screws completely, and then cut a slot in their heads so you can have the option to use a plain flat-tip screwdriver bit in the future.

FWIW YMMV

John

The flex shaft section is important -- when used, the tip is placed in the ramp on the carb body leading up to the pilot screw, the tool is then pushed to bend the shaft and slide the tip down the ramp to engage the D-shaped head of the screw. The tool can (needs to) operate with a 90? bend in it.

What I used is a section of brake line and formed the shape of the "D" on one end and flattened the other end to fit a flat blade screwdriver.
You will have to set them with the carbs off the bike. Plenty of discussions on that in the former MY_MC Forum by some really knowledgeable guys.
On my old 93 ST, I used the #40 Pilots jets and on the main jets went with the #128's but can't find my notes on where I set the pilot screw.
The other thing is to raise the jet needle by placing a small washer on the jet needle. This is so that it will come on a little sooner when rolling on the throttle.
There is a lot more to it than that,,,,,, but just throwing it out there because if you get it right you will make some improvements on how the bike runs.

NOTE: This is basically the way the bikes are set up by the factory when shipping to Canada.


I think that I'm going to have to invest in the Honda Special Tool (07MMA-MT3010A / WRENCH PILOT SCREW)..
Not sure if the pics will give you a good idea of the way I made my pilot screw tool or not but I also attached a pic of what I'm working on today.
It is the old carb off the 93 I used to own.

Thanks, Guys. Yup, That's what I saw when I had the carbs off my ST. But I still don't understand why I couldn't budge those adjustment screws. They were tight !! I tried to make a tool using a piece of brass tubing ......

Jim Van said:

Thanks, Guys. Yup, That's what I saw when I had the carbs off my ST. But I still don't understand why I couldn't budge those adjustment screws. They were tight !! I tried to make a tool using a piece of brass tubing ......

Click to expand...

A shot PB blaster can be of help.

John OoSTerhuis said:

Here's the USA version of the Honda Special Tool (07MMA-MT3010A / WRENCH PILOT SCREW), about $47 from Ron Ayers

Click to expand...

I tried to order this tool today and it is now super seceded by part number 07mma-mt3010b and it is $69.07 instead of the $47 as listed from Ron Ayers.

I'm away from my desktop. Maybe try Service Honda? Or ask to borrow a fellow STOCer's tool, here or ST-Riders? I know there's a couple of them out there...

There's never been enough interest/need or I'd have gotten one and made it a STOC loaner like all my other free loaner kits.

John
via iPhone 4S

Grabcon said:

I tried to order this tool today and it is now super seceded by part number 07mma-mt3010b and it is $69.07 instead of the $47 as listed from Ron Ayers.

Click to expand...

I bet that $47 price was a typo - the 4 & 7 may have been switched around.

Maybe. But I have a hard time springing 70 bucks for a flexible screw driver with a "D" socket on the end.

Jim Van said:

I bet that $47 price was a typo - the 4 & 7 may have been switched around.

Click to expand...

Grabcon said:

Maybe. But I have a hard time springing 70 bucks for a flexible screw driver with a "D" socket on the end.

Click to expand...

+10 ..... I'm retired and on a fixed income. Can't even afford razor blades to shave.

Me too. I just got my first hair cut in five months. Didn't want to buy another helmet so I cut the hair. $20 vs. $400