but an airlock surely isn't time dependent ?

I always had fuel in the bowl (not complete evaporation), but I am sure some part of the fuel had gone off/became less ignitable. which would make sense if you use an accelerant in the air box and it fires. I don't think a spray in the air box would remove an air lock in the fuel system, or 'fix' fuel starvation. you would still need fuel flow, as well as spray in the air box, to start the engine.

my TT also was completely fine if used every couple of days. but would take a good few minutes of the electric boot if left for a week or so.

I guess you could refit the standard tank and see if your starting problems remain, which would mean the starting problem would not be related to the larger tank.

i can understand fuel flow being an issue when you are running on an open road. but maybe the starting problem is caused by something else. I take it you've removed the fuel cap when experiencing fuel starvation (incase the breather is blocked, I had this too with the TT) ?

cheers

Do you have a vacuum petcock? It should have a PRI (prime) position to fill the carbs before starting. Will it run OK in this position?
Maybe yer petcock/vac line is fecked.

John

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Nostradamus Ate My Hamster

Ted,

Interesting that your mate has no issues with the Safari tank. Does he end up with much fuel left in the tank?

The fuel filter is a PROFILL MAIN PAGE ATV01 I have seen some crap in it so it's doing the job.

Maybe that regulator valve will do the job.

I rarely have any issues starting mine even after a couple of months lay up. Might make a difference that it's an "E" so has different carb.

No vacuum petcock.. Just a standard tap (On/off/reserve)

I don't think he's ever run it dry... He says he has about 4l he can never use.

You E has a pumper carb right ?? You get a prime when you twist the throttle before starting.


Anyway, watch this space.. I'll see if she fires up next week !

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how does you fuel tank compare to this one : Core Racing - Aqualine Fuel Tanks, Larger fuel tanks for Off Road Motorcycles ?

is the fuel tap on yours lower down ? looking at this the fuel pipe seems to go downwards slightly, implying that the carb is lower than the bottom of the tank. though it's very hard to make it out.

FWIW, I had a DRZ-s model with a Clarke tank and an inline fuel filter and never had any problems. Was able to run it to empty and no pump. Here are some pictures of it in Iceland: Iceland TBSdotCom I had to drop it on its left side to get the last of the fuel from the right to near the fuel tap.

I had 2 long pieces of fuel line ((8cm each long?) with the filter in between) and looped them round. Used a bit of racing wire to keep them as high as possible. Also a breather pipe into the fuel cap. The filter was a 2 or 3 quid one off ebay: the smallest I could find.

The only issue I had was on rough ground the side stand would engage (or disengage?) with the side stand kill switch and the bike would stutter. After disabling the kill switch this ceased to be an issue either.

As also suggested by one or 2 others, IMHO you're wasting money/time farting about with random sh*te that's not needed. No other Clarke tank has had a problem and no one apart from you is attempting to use a pump. Save your money and spend it on important stuff like petrol and .

cheers
Chris

PS Never had to prime anything either. Turn ignition on, pull choke, press button with NO throttle.

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Dude,

Not sure if you've sorted this already, and sounds like you've whipped the pump off for the moment anyway but were still interested in solutions for future reference...

It's interesting that the Clarke tanks don't usually need a pump and yours does - unless no one else is using a filter. FWIW, I'm def in favour of having a filter in there. It sounds like the one you have is too restrictive, so my first port of call would be trying a different filter, unless it's already huge - a marginal gravity feed will need a bigger (less restrictive) fuel filter than a pumped system.

If no luck and a pump is still required, plumb the pump in up stream of the filter, otherwise the restriction of the filter may cause vapour to form in the line into the pump, reducing it's effectiveness.

If the pump overwhelms the float valve in the carb, it may be that your float valve is worn - so I'd check that first before doing anything else. How old is the bike? (miles/years?) If the float valve is fine, you need to reduce the feed pressure, and the simplest way to do that is fit a lower pressure pump - I'm thinking a smaller version of the facet pumps commonly used on africa twins.

If you want to persevere with the pulse pump, you will need the "recirc" already suggested. On engine testbeds, we always run a high pressure fuel pump, and then a regulated back-leak to control the pressure. The testbed fuel system has a proper pressure regulator in it, but you should be able to get away with something much simpler.

You'd need two t-pieces, one upstream and one downstream of the pump, with a piece of pipe between the two "short-circuiting" the pump. You then put a restriction in that "short circuit" pipe (or ideally in the end of one of the t-pieces) and that way there is still some pressure rise across the pump - it's still helping. You'd need to do some experimenting with the size of hole required in the "bypass" route to stop the float bowl overfilling. Maybe start with a bit of brass with a 1mm hole in it. If the float bowl still overflows at idle, drill it out to 1.5mm. You get the idea. With a bit of luck, there's a hole size that stops it overflowing at idle (large vacuum "pulses" and min fuel demand) which still provides enough fuel to the carb at rated power (small vacuum "pulses" and max fuel demand).

That is the solution, but it's adding loads of complexity (six pipes, a filter, a pump, an orifice, two tee-pieces) where there used to just be a pipe, so you want to be sure you really need it before putting it in...

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Cheers dude.. Very imformative if a little complex !!

You're right ... The pump is a solution but I should be finding the problem.

I'm 95% sure its down to fuel flow. I have a large transparent fuel filter inline now. As long as that is full, the bike seems to start ok. ! If I leave it a few days with the tap off, the filter seems to empty a little (where ?) and then it won't start.

I have to turn the tap on, crank it over a few times then the filter with fill REALLY SLOWLY and then the bike will start.. Still takes a lot of cranking though.

It really doesn't help that I changed the exhaust, jetting, airbox and tank all at the same time. And because its a problem that only sometimes raises it's head, it's very hard to diagnose.

The reason I don't think it's the float valve or jetting is because when it starts, it runs perfectly and then will start effortlessly as long as it's run regularly.

It's a wierd one !!

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With the bike parked and the fuel off, fuel will slowly evaporate out of the carb, which is normal. With the tap on, the carb would be constantly replenshed from the tank (which is why you have a tap), but with it off, the pressure in the line will drop. This allows some of the fuel in the pipe to evaporate, forming a bit of vapour which collects in the filter (there'll also be some collecting up by the tap if that's a bit higher than the top of the filter).

Once the tap's back on, the pressure in the fuel line will rise again and the fuel vapour will condense back into liquid (the bubble disappears).

When you turn the tap on, the carb can refill, but as it's not a vacuum tap like the OE one, I'm surprised you have to crank for ages to get it to fire. If you park it for a week with the tap off (or however long it takes to get a good "bubble" in the filter) what happens if you turn the tap on and leave it for 2 minutes? Does the filter fill up without cranking the engine? If it does, key on and crank it, should start quickly...

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I've just got back from a week in Cyprus.

I left the bike with the tap on.

The fitler was full and the bike started up second crank !!

Seems the new filter and routing has helped the fuel flow... For now anyway

Cheers for all input... Hopefully I won't have to update this thread anymore. lol

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I have just re read through this thread and realise now it was a starting problem.

I think it is a non problem.

Many bikes including nearly all old Brit bikes need you to switch on the fuel a couple of minutes before trying to start. A lot got around this by having a manual float valve to completly fill the carb. A cold engine is difficult to start when with a weak mixture. What I do on my Enfield is this.
When returning from a ride, switch off fuel in the lane to my house and put away the bike. IE drain the carb by using what fuel is in there.
When I next want to ride, I turn on the fuel tap before getting the bike out and putting on my gear. IE allow it time to fill fully.
Turn the motor over on the kickstart to free clutch, then another time or two to position piston just after TDC on the power stroke. Using NO throttle swing the kickstart. It is unusual for it not to start first time and that is a lean burn motor. In winter when it is really cold I will sometimes use the choke (which isn't a choke at all but an enriching circuit).
You really need to allow petrol vapours time and opportunity to get into the cylinders. If you dont you will end up blaming the bike for poor starting which is what happened to a lot of old brit bikes. Adding electronic ignition, electric start or worry beads will not help.

Well, maybe if you have a big battery an electronic ignition system -might- just give you a slightly bigger spark to improve your chances of firing a weak mix.

A tenner says you do!
Hope you enjoyed Cyprus, you missed a good Ripley meet.

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Did it rain ?? I bet I missed the only dry Ripley meeting in years !

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Quote:
Originally Posted by *Touring Ted*

Cheers for all input... Hopefully I won't have to update this thread anymore. lol


A tenner says you do!
Hope you enjoyed Cyprus, you missed a good Ripley meet.

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'He who laughs last, was too slow to get the joke'
Never confuse the map with the journey.

hahaha very funny... I'll post the cheque from middle of the sahara.

I hope it doesn't get lost

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Did some trips.
Rode some bikes.
Fix them for a living.
Can't say anymore.