Airbox?

[Metalface.]

I don't have what I think of as an airbox, just the black cover in the photo.

Do I need a different type of airbox I'm confused?

[gatekeeper]

the bellmouths of the carbs or throttle bodies must be enclosed

[little chud]

can you post a picture with the seat off, then we can see what is under it.

jc

[Eddy Wright]

The top of the seat can form part of the airbox.

[Metalface.]

the bellmouths of the carbs or throttle bodies must be enclosed

They are but not enough I think.

The top of the seat can form part of the airbox.

I'm still confused.

can you post a picture with the seat off, then we can see what is under it.

jc

Here it is, as you can see its a Thundercat.

[ianw]

Is that one of Colin Jacobs chassis?

[Metalface.]

I believe it is yes.

[Big Tim]

It's Bill Crook's old bike as far as I can see. Probably the last un-modified (unspoilt) chassis built by Colin Jacobs between 1991 & 1994. The very last one he built was the one currently owned by Steve Ramsden, and built for Howard Langham in the Winter of 1995, which is also still running Thundercat / FZR motors, but was different to the majority of the F2's Colin built.

The black fibre glass engine cover unfortunately will most likely not fulfil the criteria of being an "air box". Although the flat slide Keihin carburetors work absolutely perfectly without an enclosed airbox (in fact, most likely, better), unfortunately the regulations are written as such, that you have to run one. The written word from the ACU handbook is -

18.9 AIRBOX
An airbox must be used with all four-stroke engines.
The airbox intake sizes are restricted as follows
If 1 intake is used a maximum of 103mm lnternal Diameter is permitted
If 2 intakes are used a maximum of 73mm Internal Diameter per intake is permitted or
equivalent area if none circular section(s) are used measured within 50mm of the point of entry
into the airbox.
The airbox must completely close around the induction bell-mouths.
The carburettors or throttle-bodies may be entirely within the airbox.
The engine must have a closed breather system.
The engine breather must be connected and discharge in the airbox. only. (by a sealed catch tank if required)
The airbox must cover and collect fluids discharged from the bell-mouths.
The airbox must be constructed in such a way as to prevent any oil discharged in the airbox from spilling on the track.
The oil containment must hold a minimum of 1000 cc of oil.
The airbox must be sealed to prevent spillage of oil or fuel.

[Metalface.]

Thats what I thought and yes it is Bills outfit.

[oldbelly]

You can make an undertray to go around the carb rubbers or the carb trumpets. Make this a proper seal to the engine cover and you have a legal airbox. This will make the volume as large as possible. You will have to seal the vent off at the front and bring the air in ( to the front ) as two tubes. Link these two tubes to the fairing via two ducts and it should work OK. Tims right though the old Yams woked better as you have them on Bills bike now.

[Metalface.]

Thanks, I think I'd rather do it like you said, its a shame I can't just use the vent at the front though, ah well

[lovingit]

This was my thundercat airbox

Carbs inside

[Metalface.]

Thanks for the pic, nice bike too.

You will have to seal the vent off at the front and bring the air in ( to the front ) as two tubes. Link these two tubes to the fairing via two ducts and it should work OK.

Is there somewhere I can buy the right diameter tubes from or is there something to pinch the tubes and ducts off like a car or something, just wondered before I start fabricating?

[steve-e]

Put an ask in 'the sidecar paddock' someone will have some

[Metalface.]

Its alright I'll figure it out, I'm sure other people have to.