Hitchcocks Forum

Could one of you kind gents, (ladies?), do me a great favour and do a test drain of your fuel tap to ascertain the flow rate.
When I tested mine I was getting 250ml per minute which I thought was quite low and with various thoughts whizzing through my head wondered if this was'normal' or a possible contributor to leaning out at extended higher revs due to flow.
Thanks hugely.

Mike

Hi
I don't think the flow rate has anything to do with your carburation problems. At the rate your tap is flowing you are flowing a gallon in about 18 minutes unless my arithmetic is at fault again. If your bike only did 60 to the gallon it would take an hour to use it at 60MPH. Imagine the bore of the fuel tap and then the main jet, unless there is a severe blockage it will always flow much more fuel than the main jet can pass.
Edward

You're most likely right, (and I'm not questioning your maths, especially first thing in the morning, too much thought required)
It's primarily to put my mind at ease on another thought that crossed my mind among the various things I now want to check before riding it again.
If I know that other 350 owners are getting similar flow then I'd be able to relax on that score.

Well, the bike's outside and there's a measuring jug handy in the garage so I just tested my 350 for you, Mike. I got the same result as you - 250 ml in one minute. (Well, a tiny bit less, actually).

Tom

Thankyou hugely Tom, you are an absolute gent and that certainly puts my mind at ease regarding adequate flow.
Next thing I'll be checking is the oil pump so covers off that for a visual inspection as soon ass i can.

---------- are the fuel taps different then on the 350 compared to the 500 Classic ?? If you want to see fuel gobbled up just watch those top-fueler dragsters go. You wouldn't want to meet them in a pub !!! Just as a rough "for-instance" when I was grass-tracking a BSA C15 on straight Methanol the fuel/air mix is in the order of 7:1 ie approx twice the vol. to that of petrol. A half-gallon fuel tank gave just enough for a 4-lap race + time in the pits. It used to take me a weeks worth of overtime just to pay for a Sunday's racing. On a Mk1 Concentric the rule-of thumb was to double all intermediate jet sizes (using a methanol needle) and a 1/8" drill down the main jet !! ( plus a sneaky shot of nitro. ----if you were careful).

If you're worried about slow flow rate try a Lightning 535 tap,it's a hi-flow type.
Jack.

I was mainly concerned that mine was slower than it should be, having had a couple of folks verify theirs is the same I'm happy enough.
I'm used to seeing flow rates of 1/2L minute, (plus pump assistance), on most sport bikes I've worked with, I know strip tuned machines for straightlining use taps that deliver something like 1L per minute minimum.
Overall, if others are getting the same, it's good enough to discount it as a possible reason for leaning out at extended throttle runs.
500 taps look the same, it'd be interesting to see what yours flows Alan!

I have said this before, drain a full tank into a jerry can, see how long it takes, half an hour. Even at flat chat an Enfield couldn't empty a tank in half an hour and if it did you would be extremly unhappy with your mpg rate. Enfields do about 70/80 mpg so if you said a 3 gallon tank that would take nearly 3 hours to empty as a rough guess

And just to add to this, 250mls per minute equals 15 litres an hour