Engine problem

[cobbadiggabuddyblooo]

I'll take a wild stab in the dark here and this is no way confirmation on it's purpose.
Could this be because your engine breather which contains oil and fumes is also routed into the airbox so maybe this is used as a rust inhibitor because its a steel frame???? With the breather running from the frame back to the air box..

[Con Rod]

I think that vent is to allow air flow into the frame to rather than water from the airbox

[Planx]

Hmm, I never thought of it being there to vent the frame, but it does sound plausible. There is a filter in the pipe between the frame and the airbox. Does that suggest that it's sucking into the aibox rather than venting out? That would make sense in the frame venting theory, I guess.

[alextrx850]

This reminds me to the FUNGS bike build that I was involved in where we found one of these so called frame breather things.....Fungs bike was a 96 model from memory, earlier than my own 96 model, but my frame doesn't have this vent tube...at all.
Also if you follow the frame, the tubeing will be blanked off on the joins by the welds and the frame pipe work....basically, if water was poured in at the tube referred to...it won't flow all the way through...so I'm buggered to what it is..
But the theme wasn't continued.
These photos will show the thingy.

Someone reckoned it was a BOY bike as it had an extra appendage....silly Sods.!

[Planx]

Yes, this is a '96 bike too. Interestingly, the bike that I dismantled for its engine didn't have this connection. The pipe from the air box was a long one with an in-line filter, which was threaded down behind the engine and was just open to air at the bottom. I can't make up my mind whether to use the frame connection or to fit the long open pipe.

[QuickDraw]

That drain/vent at the airbox does have vacuum when the engine is running. I don't have a hose off mine ATM. And being on the intake side of the filter, putting a filtered hose on it has been on my to-do list for a while.

My guess is that the frame connection is a way of ensuring no muck gets sucked in, but was changed in later models possibly because of the potential for internal corrosion(?)

[Planx]

putting a filtered hose on it has been on my to-do list for a while

I think I have a spare one you can have if you want it.

[QuickDraw]

Thanx Planx. I think I've got sufficient bits here if I have a proper look. I'm actually soon to fit my FCR's (ex-Kev), so I may well run without the airbox altogether. Cheers tho.

[davamb]

Sorry to digress but this reminds me of a racing anecdote from Vic Alford (if memory serves) and concerns a Porsche 917 racer at Le Mans. This was back in the pre-monocoque days when the chassis were still largely tubular affairs. These Porsche frames were permanently pressurised and a gauge attached where the driver could see it - the idea being that any frame cracks would result in the pressure dropping. With rather Germanic nonchalance, Vic had been duly instructed to make his way back to the pits should there be any problems and report his observations to the engineers. His actual thoughts were something along the lines of "bugger that, if that needle goes to zero, I'm parking this f**ker and walking back to the pits!"