EV Throttle Body Question?

[Tom H]

Simple question that I could not find the answer to.

Does the throttle body have a seal between the TB and the TPS? Or is just the casting or bushing in the casting that seals between them?

Thank you,
Tom

[John A]

No, no seal there. The tps gets any excess fuel on it where it’s situated, maybe contributing to a shorter life so I think it may be a good thing it’s not sealed there.

[Tom H]

John, thank you for your reply. That is what Is what I thought.

But...."maybe contributing to a shorter life so I think it may be a good thing it’s not sealed there" I don't understand why this would be a good thing? I would think sealing it off would make it last longer and that would be a good thing?

Thank you!
Tom

[lucky phil]

John, thank you for your reply. That is what Is what I thought.

But...."maybe contributing to a shorter life so I think it may be a good thing it’s not sealed there" I don't understand why this would be a good thing? I would think sealing it off would make it last longer and that would be a good thing?

Thank you!
Tom

The TPS is a sealed unit in itself. How is it going to get fuel contaminated on top of the Throttle body. Do you mean from an external tank leak on top of the TB?
If you look closely on the older style PF09 you can see the oring around the input which seals against the throttle body internally and in the second image the case sealing.
The later TPS's are fully sealed and not dis assemblable and I would imagine the input would have an oring as the older one. I have one in the workshop I could check. You can see the contamination on the wiper arm that causes the older type to stop working correctly. This is from internally in the sensor due to wear particles. Clean them out and they work fine again. 









Ciao

[Tom H]

Sorry. I just realized I did not ask the question properly. The question should have been:

Does the butterfly shaft of the TPS side TB have a seal at the bottom? Sealing the TB shaft from the rotating part of the TPS?

Like and old 1 barrel carb on a car. The butterfly shaft just rides in the carb casting, No seal. When the casting wears, it can become an air leak around the butterfly shaft.

With the TPS at the bottom of a vertical butterfly shaft on the TB, maybe that is how the TPS gets contaminated by gas or whatever.

Thank you and again sorry for not asking the question correctly,
Tom

[lucky phil]

Sorry. I just realized I did not ask the question properly. The question should have been:

Does the butterfly shaft of the TPS side TB have a seal at the bottom? Sealing the TB shaft from the rotating part of the TPS?

Like and old 1 barrel carb on a car. The butterfly shaft just rides in the carb casting, No seal. When the casting wears, it can become an air leak around the butterfly shaft.

With the TPS at the bottom of a vertical butterfly shaft on the TB, maybe that is how the TPS gets contaminated by gas or whatever.

Thank you and again sorry for not asking the question correctly,
Tom

Yes they do. Here's a thread I did on replacing the TB bushes and seals.

https://www.v11lemans.com/forums/index.php?/topic/22077-throttle-body-rebuild/

Ciao

[Wayne Orwig]

I see more gunked up and damaged TPSs on the EV , where it is under the throttle body. The ones on the CARC and spine frame where they are on top of the TB, tend to be more reliable.

[Tom H]

I read the rebuild thread. It looks like the seal is there just to keep outside air from coming in. The seal does not look like it will hold back any gas from leaking down to the TPS.

Thank you!!!!
Tom

[lucky phil]

I read the rebuild thread. It looks like the seal is there just to keep outside air from coming in. The seal does not look like it will hold back any gas from leaking down to the TPS.

Thank you!!!!
Tom

Yes seals air but it seals fuel leakage as well. Does your bike sometimes drip fuel from the throttle body shaft? You notice it sometimes as a drip marking on the starter cover. If you put your finger on the bottom of the throttle body shaft and its wet with fuel as most Guzzi will be after they've done around 50,000klm or so that's the shaft seal leaking. The L/H is generally more obvious than the right. Unlike Ducati's, Guzzi throttle body shafts are orientated vertically so any fuel that puddles in the intake manifold will run down the shaft and past worn seals and drip when the engine is shut down. Often happens if you start the bike from cold when fuel tends to naturally puddle in the inlet manifold and you shut the bike down again before it's warmed up. V11 Sports do it and they share a common TB with other Guzzis and also Ducati's. Just checked the parts manual for your bike and was surprised to see the TPS mounted under the l/h throttle body as opposed to the r/h top of the TB on a v11 Sport or Daytona/ Centauro. Pretty dumb on Guzzi's part mounting it under the TB's. Believe me the shaft seals leak eventually as I mentioned and that would allow fuel to leak onto the TPS at times. I'll dig out my later PF3 TPS and have a look at its input sealing. With this TB set up I'd avoid starting the bike and not letting it fully warm up before shutting it down. That's when the shaft seals leak the most. My V11 Sport seals have leaked from 40,000 klms.
 

Ciao   

[Tom H]

So... Are you saying that it's double lip seal? Or just the single lip also keeps gas from leaking out? I have seen double lip, one keeps stuff in and the other keeps stuff out.

Is it possible to replace the seal without removing the butterfly shaft?? Kinda scary to remove/install the butterfly screws.

Thank you!!
Tom

[lucky phil]

So... Are you saying that it's double lip seal? Or just the single lip also keeps gas from leaking out? I have seen double lip, one keeps stuff in and the other keeps stuff out.

Is it possible to replace the seal without removing the butterfly shaft?? Kinda scary to remove/install the butterfly screws.

Thank you!!
Tom

It's a single lip seal Tom and in its correct orientation is primarily designed to seal air out. So normally the open side goes outwards because when the engine is running there will be atmospheric pressure on the outside and less than atmospheric in the inlet. Having said all that a seal of this design will also seal fuel and air with a zero differential pressure across it. So it will seal against air leakage while running most effectively but also stop fuel puddling leakage when the engine is stopped which is when it tends to leak past the bushes and a worn seal. Same as when this style of seal is used on an engine or gearbox shaft. Primarily to stop engine or gearbox oil leaking out while running but will seal out environmental stuff like dust and water when its not. Just less effectively than the other way.
Yes you can change the seals without removing the throttle plate but its a job for the bench. I've rebuilt 3 sets of throttle bodies to date. I checked the later style PF03 TPS in the workshop and its not possible to see if its sealed on the input side. If it is it's sealed internally around the rotating spool.

Ciao     

[lucky phil]

I see more gunked up and damaged TPSs on the EV , where it is under the throttle body. The ones on the CARC and spine frame where they are on top of the TB, tend to be more reliable.

Interesting Wayne, I can see why. The shaft seals are pretty notorious for leaking without that many miles on them. I wasn't aware initially this model situated the TPS under the TB. I mean it's about as dumb a thing to do as you can get.

Ciao

[Tom H]

Phil, Thank you!

I don't mind pulling the TB's. I just prefer not to mess with the butterfly screws. Bad things can happen if one should fall out.

Tom

[lucky phil]

Phil, Thank you!

I don't mind pulling the TB's. I just prefer not to mess with the butterfly screws. Bad things can happen if one should fall out.

Tom

As I mentioned Tom I've had 3 Guzzi sets apart now and 1 Ducati set and never seen a loose plate screw. The staking doesn't stop them loosening just falling out so they do a turn or more after undoing before the staking stops them. I'm comfortable with loctite alone.

Ciao