Anybody come across this before

[Rob Farmer]

Thunders gearbox breather has been plugged using a small piece of threaded rod. Clearly deliberately but I cannot see why

Especially as the small v has been sealed as well

 

[brassmonkey001]

I would imagine that it might have been leaking out of the breather.

 

[Steptoe]

For serious use in sandy places. i.e. desert racing. Does the front engine cover also have the vents sealed up ??

Thunder has bought a thrashed to within it's life ex racer.

 

[John Armstrong]

Is it of the Dessert Storm? In which case shouldn't the output shaft hole be sealed as it's a para?

Don't know about the speedo drive breather though, maybe it was put in to stop leaks if it was posted somewhere?

 

[Thunder]

For serious use in sandy places. i.e. desert racing. Does the front engine cover also have the vents sealed up ??

Thunder has bought a thrashed to within it's life ex racer.

No front engine cover does not have the vents sealed up, bikes had some interesting additions and is currently being worked on

Out of interest if the breathers are blocked for serious use in sandy places, how would the gearbox breathe or is not essential?

 

[John Armstrong]

Air filter looks "normal" too.

I guess the gearbox would breath out of the next easiest place, like a seal

 

[MattW]

Out of interest if the breathers are blocked for serious use in sandy places, how would the gearbox breathe or is not essential?

I was wondering that too?...

I guess if you really, really managed to seal it up, it'd force oil past the seals in the end. I'd be more inclined to fit a remote breather with a filter on it (but waddooIknow - desert bike builder, I am not )

 

[John Armstrong]

I guess if you really, really managed to seal it up, it'd force oil past the seals in the end. I'd be more inclined to fit a remote breather with a filter on it (but waddooIknow - desert bike builder, I am not )

The other thought is, is the breather there to allow excess pressure out, or air in, or both If it's out only then fitting a NRV would work, I think, or if both ways, an in-line fuel filter?

 

[MattW]

The other thought is, is the breather there to allow excess pressure out, or air in, or both If it's out only then fitting a NRV would work, I think, or if both ways, an in-line fuel filter?

In and out I'd have thought, as it heats and cools. Clue's in the name I guess

 

[Steptoe]

, how would the gearbox breathe or is not essential?

I guess the gearbox would breath out of the next easiest place, like a seal

I was wondering that too?...

I guess if you really, really managed to seal it up, it'd force oil past the seals in the end. I'd be more inclined to fit a remote breather with a filter on it (but waddooIknow - desert bike builder, I am not )

Drill the bolt on top of the gearbox, the one under the air filter. The one that is filtered so no dust/sand can enter.

You new airhead boys have a lot to learn. .

 

[Garry H]

The gearbox needs to breath or the seals are going to blow...
I made this for my off road bike and ran a breather pipe up under the tank..I also removed the vented bolt and replaced it with a solid one...
Result is even after deep wading there is never any water whatsoever in the gearbox oil

 

[Thunder]

Drill the bolt on top of the gearbox, the one under the air filter. The one that is filtered so no dust/sand can enter.

You new airhead boys have a lot to learn. .

Makes sense

 

[MattW]

Drill the bolt on top of the gearbox, the one under the air filter. The one that is filtered so no dust/sand can enter.

Ahh - I knew there'd be a simple solution

You new airhead boys have a lot to learn. .

You're not wrong there! - however, I'm not an airhead boy yet....

 

[John Armstrong]

Makes sense

We are not worthy

 

[AliBaba]

Drill the bolt on top of the gearbox, the one under the air filter. The one that is filtered so no dust/sand can enter.

I’ve never heard of this nor have I seen it on a desert bike.

Not sure if it’s a good idea to make vacuum in gearbox in sandy conditions. It doesn’t make much sense when riding in water either, when the air filter gets flooded with water the cold gearbox will suck water.

Personally I think the best solution is a breather-tube with the inlet below the point it’s attached to the gearbox.

 

[Steptoe]

I’ve never heard of this nor have I seen it on a desert bike.


Not sure if it’s a good idea to make vacuum in gearbox in sandy conditions. It doesn’t make much sense when riding in water either, when the air filter gets flooded with water the cold gearbox will suck water.

.

Water flooded engines in desert racing I like it. I helped build two bikes for the pharoes rally and rally of tunis back in the late eighties, both finished. And both had breathers on top of the gearbox, and both front engine cases were sealed.

A breather hole is a breather hole, water can enter wherever it is. But on top of the gearbox is the highest point.

 

[AliBaba]

Water flooded engines in desert racing I like it.

I have flooded my engine in both Niger and Sudan, it happens. In Sahel you might find lots of water crossings. Even Morocco has been terribly wet the last six months or so.

I helped build two bikes for the pharoes rally and rally of tunis back in the late eighties, both finished.
And both had breathers on top of the gearbox, and both front engine cases were sealed.

Personally I wouldn’t seal the front engine cover. It provides cooling for an already stressed alternator, but rallies are during the cold season.
There are other ways to control dust in that area if you find it necessary.
Quite a lot of water gets out through the holes, I don’t see any point in having the alternator, diode-board and beancan surrounded by boiling water.

A breather hole is a breather hole, water can enter wherever it is. But on top of the gearbox is the highest point.

Yes it can but your choice was to move it….
With a tube you can go higher then the gearbox, but it’s no point doing it. Just make sure the tube points downwards, below the entrance to the gearbox.

I’m not saying that it doesn’t work, but personally I would have done it different.

 

[(RIP) Proff]

Drill the bolt on top of the gearbox, the one under the air filter. The one that is filtered so no dust/sand can enter.

You new airhead boys have a lot to learn. .

Beat me to it "O" Guru of the Airheads
Common racing mod as well after Scrutineers used to say it was an oil leak after a few laps at high speed on track..
IIRC we drilled a 1/64th hole in the top g/box bolt...
Broke a lot of drills tho'

 

[Rob Farmer]

Beat me to it "O" Guru of the Airheads

Feck off! That's blindingly obvious though fundementaly flawed if it was applied in it's simplest form. The question related to the particular mod on the breather on Thunders bike.

It seems a lot of trouble to go to when a simple undrilled bolt to easily be inserted instead. I suspect that the intention was to allow it to still breath, though slightly restricted, but reduce the size of the particles that could get through.

I was hoping that somebody would chirp in and say that it was a particlar mod carried out by somebody in particular.

As a side issue does anybody know who stamps the letter "I" next to the gearbox number when they rebuild gearboxes?

 

[abrasion]

Rob.
Engine was originally tweaked by Andrew Sexton not sure what else he had a hand in.He might be able to help as he remebers the bike pretty well.