Paint inside throttle body????

roadriderg

roadriderg

Joined
Oct 18, 2007
Messages
891
Location
Huntington Beach, Calif
Bike
2004 st1300
STOC #
7468
I am doing my fpr replacement and in my throttle bodys they are painted black on one side of the butterfly valve in the throttle body throat. I see from pictures that this is common on all the bikes.

What is the purpose of the paint ,and can it be removed?? Or should it be removed.

Gary
:04biker:
 
It's not paint, it's a molybdenum coating that creates a seal between the edge of the butterfly and the surface of the throttle body housing when the throttle is closed. It also serves as a non-stick surface to keep dirt from building up and preventing the seal from forming.

You don't want to remove it, and you also don't want to apply carburetor cleaner, which will dissolve the coating.

--Mark
 
I've only ever had my nose in a handful of different throttle bodies, but they all used the same technique.

You can't have the butterfly making contact with the throat because it would bind, and eventually would probably shed bits of metal into the intake. Once it was worn down enough not to stick, there would always be a path for air to be sucked in, even with the throttle fully closed.

--Mark
 
Blrfl said:
I've only ever had my nose in a handful of different throttle bodies, but they all used the same technique.

You can't have the butterfly making contact with the throat because it would bind, and eventually would probably shed bits of metal into the intake. Once it was worn down enough not to stick, there would always be a path for air to be sucked in, even with the throttle fully closed.

--Mark
Click to expand...

Good splainin, thanks. Since the idle air bypasses the butterfly that makes sense. The XX had carbs and since you adjust the sync. by moving the butterflies, they always had a slight opening.
 
When they stopped venting the crankcase to atmosphere and sending the vapors through the intake you would notice severe buildup on the throttle plates (big problem with FI) This caused the plates to stick at idle. Coating the area around the throttle plate was added to prevent this. A throttle stop screw is used to keep the plates from fully seating against the throttle body. Without the stop screw, letting the throttle snap shut would jam the plate into the housing.
 
Unbelievable!:hat2:

CABINPETE said:
When they stopped venting the crankcase to atmosphere and sending the vapors through the intake you would notice severe buildup on the throttle plates (big problem with FI) This caused the plates to stick at idle. Coating the area around the throttle plate was added to prevent this. A throttle stop screw is used to keep the plates from fully seating against the throttle body. Without the stop screw, letting the throttle snap shut would jam the plate into the housing.
Click to expand...

Cabinpete!

You are dead on with your statement! The coating is more to prevent sticking from deposit build up while the stop screw is used to keep it from jamming mechanically! Your mention of the stop screw saved me some grief today!

As I was reading this thread, it occurred to me that I've been trying to figure out why the gas pedal sticks in my daughters new (to her 98 Civic) car! It only happens after the car comes to a stop and the throttle has closed. Every time you push on the gas from a stop, there is a slight resistance before the pedal moves causing a mild jerky start. It's much worse the 1st time you give it gas after the car has set long enough to cool off. That 1st couple of starts for my new to driving daughter are more than a little jerky and it's bad enough that she has commented about it. Funny thing about it is that other than moving off of closed throttle, the accelerator works nice and easy and smooth as glass through out the rest of the range to wide open!!

So far i've lubricated the pedal and linkage assembly inside the car. Checked for obstructions through out the throttle system. Checked the accelerator cable adjustment and went so far as to spray wd-40 on the throttle body area (which- by the way- is a huge no no as the lube attracts dirt which sooner than later gums up the linkage anyway!!!! Now I need to clean the throttle body linkage with brake clean!:rolleyes:) just to see if the problem was there! Nothing fixed it. I initially looked for a stop screw but being unfamiliar with this particular linkage, didn't see one to adjust. However, after reading your post, I went out and took another long look at the throttle body to see if I'd missed something! ( I really wasn't looking forward to tearing the throttle body off the car to clean it as I have very little time right now for this silly stuff!) Well, low and behold,,,still don't see a stop screw,,,but by golly, there is a hole where one ought to be!! It was no wonder I didn't see it before! I wasn't looking for an empty hole!

After a quick walk to the hardware store next to my work place and 34 cents later, I had a new set screw! A little loc-tite and 15 minutes of tweaking during lunch and wah-la!!! THANKS PETE!:woo No more sticky gas pedal!!!!

And to think a motorcycle thread lent me a hand with a CAGE! At least it was a Honda Civic!!!! :clap2:
 
Tom,

If you still have a problem with the throttle stop screw backing off. Remove the screw and spin a nut on it. Reinstall and tighten the added jam nut.
Base throttle stop settings are contact plus 1/16 to 1/8 turn in then lock.
If you go in too far and open the throttle plate excessively it can tax the idle system.
To check idle compensation, if it's an auto, put it in drive you should see the idle drop slightly then return also turn the AC compressor on, if equipped, and the same thing should happen. Same thing with an electrical load, turning on lights, etc.
If operating properly the idle system will compensate for load.
 
Unbelievable!:hat2:
Well, I used a high strength loc-tite (red) on the set screw. I'm sure it's a smidgen high but the car is is idling about 50 rpm more than it was. It still fluctuates and returns to a steady idle speed so I think I'm safe. I'm a bit afraid to readjust now that the loc-tite is set. Also I'm really lacking time to fix it if I strip the hole trying to break the set screw loose. Maybe in the spring and I have more time and the warmth to deal with it! Sure am glad you know where to adjust it to! If a problem does crop up, I'll dig into it and double check the setting.

Thanks again!!


CABINPETE said:
Tom,

If you still have a problem with the throttle stop screw backing off. Remove the screw and spin a nut on it. Reinstall and tighten the added jam nut.
Base throttle stop settings are contact plus 1/16 to 1/8 turn in then lock.
If you go in too far and open the throttle plate excessively it can tax the idle system.
To check idle compensation, if it's an auto, put it in drive you should see the idle drop slightly then return also turn the AC compressor on, if equipped, and the same thing should happen. Same thing with an electrical load, turning on lights, etc.
If operating properly the idle system will compensate for load.
Click to expand...
 
Tom B. said:
Unbelievable!:hat2:
Well, I used a high strength loc-tite (red) on the set screw. I'm sure it's a smidgen high but the car is is idling about 50 rpm more than it was. It still fluctuates and returns to a steady idle speed so I think I'm safe. I'm a bit afraid to readjust now that the loc-tite is set. Also I'm really lacking time to fix it if I strip the hole trying to break the set screw loose. Maybe in the spring and I have more time and the warmth to deal with it! Sure am glad you know where to adjust it to! If a problem does crop up, I'll dig into it and double check the setting.

Thanks again!!
Click to expand...

If it's red loc-tite you might want to leave it alone. If you do need to adjust, heat the screw with a soldering iron, safer then a torch.
 
CABINPETE said:
If it's red loc-tite you might want to leave it alone. If you do need to adjust, heat the screw with a soldering iron, safer then a torch.
Click to expand...

Hey! The soldering iron is a good ideal! Thanks for that titbit! Always something great to learn here at ST-Owners!!! Idle is about 850-900, est off the tach in the dash. Should be ok. The idle solenoids seem to be working better and the transmission even seems to shift better, almost as if the TPS was out of sink with the trans...then again, it might just be me...:doh1:

Sorry about pirating the thread,,,it IS about throttle bodies though!:a13:
 
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