Ducati Sporting Club UK > DesmoDue Race Series > DesmoDue - General Questions and Chat > Lack of petrol flowing

[ells]

Out at Oulton yesterday and a previous afliction reared its head. After a few laps (5/6) the old girl ran out of puff at turn 2. As they had limited marshalls I tried to limp home and after knickerbrok she suddenly had a second wind!

Second session and the same happened again


Now I had an issue at Snetterton last year thta felt like a fuel issue, I had the carbs stripped and rebuilt and set up for the new pipes in time for Cadwell and it were fine at the end of last year. Now the Mrs did drain my tank to the bottom for the petrol!

Got the bike out today, started to drain the tank and what started as a good flow turned into a trickle. Then after unscrewing the petrol cap (replacement race item) the flow was restored!

I suspect either
1. there is rubbish in the float bowl again
or
2. The flow is not enough

Its a monster tank with the vacuum pump (which I thought we bypassed but I may be wrong). How does the air get back in the tank to replace the fuel going out of the tank so we dont get a vacuum? There seems to be no hole in the race fuel cap although there looks like a mini ball bearing (0.5 to 1mmm in size). The SS tanks used to have a pipe on the top with a valve? What does the monster get?

Am I looking at the right thing or am I going to have to pull the carbs kff to look at the float bowl.

Tried blowing through the fuel cap to see how air could get in and it did not seem to work.

Very puzzled bloke

[chris.p]

Originally Posted by ells

Out at Oulton yesterday and a previous afliction reared its head. After a few laps (5/6) the old girl ran out of puff at turn 2. As they had limited marshalls I tried to limp home and after knickerbrok she suddenly had a second wind!

Second session and the same happened again


Now I had an issue at Snetterton last year thta felt like a fuel issue, I had the carbs stripped and rebuilt and set up for the new pipes in time for Cadwell and it were fine at the end of last year. Now the Mrs did drain my tank to the bottom for the petrol!

Got the bike out today, started to drain the tank and what started as a good flow turned into a trickle. Then after unscrewing the petrol cap (replacement race item) the flow was restored!

I suspect either
1. there is rubbish in the float bowl again
or
2. The flow is not enough

Its a monster tank with the vacuum pump (which I thought we bypassed but I may be wrong). How does the air get back in the tank to replace the fuel going out of the tank so we dont get a vacuum? There seems to be no hole in the race fuel cap although there looks like a mini ball bearing (0.5 to 1mmm in size). The SS tanks used to have a pipe on the top with a valve? What does the monster get?

Am I looking at the right thing or am I going to have to pull the carbs kff to look at the float bowl.

Tried blowing through the fuel cap to see how air could get in and it did not seem to work.

Very puzzled bloke

Hi Mark,
I do believe it may be your tank not being able to breath, remove the filler dap and remove the ball bearing, replace and try again, this is what happened when I put a Chinese one on my 748.


Chris

[ells]

Having chatted to local mechanic he too suspects the lack of the tank to breathe. Cant see any way to remove the ball bearings but will have a good look.

Cut open and inspected the fuel filter. Learnt its ok to blow through the fuel filter but sucking is a silly thing to do.

Little bit of rubbish on the tank side of the filter (need new filter now I have cut it open.)

Tried blowing past the ball bearing from both sides but to no avail. Definatelt lack of air. Get a good old hiss when I open the cap. I suppose drilling out the ball bearing is not acceptable on a race bike.

Cheers
Mark

[chris.p]

Originally Posted by ells

Having chatted to local mechanic he too suspects the lack of the tank to breathe. Cant see any way to remove the ball bearings but will have a good look.

Cut open and inspected the fuel filter. Learnt its ok to blow through the fuel filter but sucking is a silly thing to do.

Little bit of rubbish on the tank side of the filter (need new filter now I have cut it open.)

Tried blowing past the ball bearing from both sides but to no avail. Definatelt lack of air. Get a good old hiss when I open the cap. I suppose drilling out the ball bearing is not acceptable on a race bike.

Cheers
Mark

Drilled mine out, so do not see why you cant.

Chris

[numbskull]

I drilled a hole in the filler cap on my race bike.

Never failed scrutineering or let out too much petrol during a race!

[ells]

Woo Hoo,
out with the drill then. Cheers Chris and Neal

Mark

[skidlids]

Although two scrutineers now know about it

[chris.p]

Originally Posted by skidlids

Although two scrutineers now know about it

Spoilsport


Chris

[chris.p]

Maybe buying a new filler cap unit may be needed to keep the scrutes happy


Chris

[numbskull]

Originally Posted by skidlids

Although two scrutineers now know about it

And one of them is using it this year I believe?