Throttle bodies - sticky first, but now fixed

[muzikill]

Yeah so during my rebuild i noticed that the throttle wasnt returning very quick, primarily because the bodies had been sitting (but still covered) in the garage not doing much so the gunky mixture of dust from riding, (because they are more exposed than you think they are under the tank/air filter housing) thick grease and no heat from an engine had caused them to start to seize.

Firstly i took off the throttle cables to take them out of the equation and at least the book of lies is right this time it would be very rare for the cables to be the problem. once off it was easy to see the cables werent the issue as they moved freely when turning the throttle so grime had not travelled up the cable sleeves.

Here is how the bodies look before cleaning them. They are pretty mucky eh?. I disconnected the throttle arms between the front and rear throttle bodies that control the throttle valves as this would help me to discover where the problem lay.

(youtube embedded seems to be not working atm)

http://www.youtube.com/watch?v=JLCtLL90LY8

Ok, so, Front throttle fine, moving back and forth (dont allow it to snap back or else you can damage the throttle valves!). It's the rear thats the issue.

And here's a pic to show how messy it is...

http://farm6.static.flickr.com/5107/5686122375_5669b006b5_z.jpg
(am i allowed to take that nut off to get in more?)

Yup, its partly the fact it did nowt for months and another is it's probably more exposed to the bad elements than the front. If you take a look in next time when you prop your tank up you may catch a glimpse of it. Now here is my solution...

WD40 to clean the areas where the springs are on the pivots (front & rear) liberaly soaked and left to work its way in, tilting the bodies to make sure none of it gets into the areas where the throttle valves are. A cloth underneath to not only catch the dripping solution but it lets you see how much mess comes out when it soaks into the cloth. Whilst doing this i realised that the rear sprung pivot carries a slow return tension and controls how quickly the throttle returns back in revs and at the handle bars it doesn't snap back as fast as the front. Think about it, you turn the throttle and want a quick and controlled action and when you are say, slowing down, you want it to be smooth but not too snappy.
.... i derive, so after much wiggling of the pivots and more wd40 i then reconnected the link rod to recheck the motion and it was a heck of a lot better. Next it was liberal application of gt85 in the same key areas and working in again to get it lubricated. Before reconnection it will be re-greased with moly/oil paste mixture to not only sustain it's good working but as a barrier to prevent this from happening again too quickly.

here is how it looks after reconnecting the rod

http://www.youtube.com/watch?v=06goTyBecYU&feature=player_detailpage

Better! - plus the front throttle body spring now does it's job by acting in conjunction with the back one to control the even travel of the throttle valves whereas before it was being held back slightly by the sticky rear pivot.

Phew! - throttle bodies are very tricky to work on as you dont want to break them. So, sticky throttle? it could be the rear throttle body pivot spring area being gunky!

Hope this is of help to anyone else, comments and corrections welcome :)

[The Flat Badger]

Awesome!

Thanks for this muzikill.

I have had a similar problem since the bike was stored over winter. When it is cold the throttle return is fine once it is up to temp however it is sticky and slow. I was going to start with the cables but after reading this will reach for the liberal application of WD40 instead. I might chuck in a health dose of chain degreaser as well.

[muzikill]

Id expect them to free up when warm not the other way about, if the bodies are still in situ make sure you have them surrounded by rags to soak up the excess degreasing fluid. And choose you grease carefully not too thin and not too thick either in case it doesn't like being cold and turns to lard!

[The Flat Badger]

To be honest, the stick when warm has me a little concerned but I plan to make sure everything is clean, lubricated and in good working order before I start pulling everything to pieces.

I was going to use the same moly/oil mix as you (a tip I got years ago from my machinist grandad) with a small splash of copper grease.

[muzikill]

tbh i wouldnt use any copper grease anywhere near them i might consider spraying them with 3 in 1 silicon lube and thats it. Anything thicker than that and id be inclined to think it will get gunky again. Ive realised that they are not maintainence free.