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  #1  
Old 5 Jun 2010
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Added a vacuum pump and now carb overflows.. Ideas ??

I've been having fuel flow problems with my DRZ and Clark tank.

The fuel doesnt run well, especially with an inline filter.

Well, I added a Mikuni Vacuum pump. The smallest I could find. The fuel starvation problems are over which is great but now the carb overflows after a few seconds.

The floats obviously have to fight harder to close the float valve with pressurised fuel but I don't really fancy playing the "hit and miss" game with trying to set my float height so it doesnt. That's even if I can adjust them enough to fight back the pressure.

Is there another method to compensate for adding a fuel pump when there wasnt one intended ?? A different float valve perhaps ?? A flow restrictor ?

Thanks in advance !!

Ted
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  #2  
Old 5 Jun 2010
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Ted

You could try putting in an other fuel line from the point after the pump and b4 the carb back to the tank as this will reduce the pressure on the carb.. ( just thinking.. you may have to drill a hole in the tank and fit a one way valve for the fuel to return to the tank. Its not a hard job and should only take about an hour.)

Hope this idea helps.

Oneworld Biker..

To old to die young. To young to care.
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  #3  
Old 5 Jun 2010
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Among KLR owners, there've been problems with certain inline filters (and also with their mounting positions), not with others. I think installing a problematic filter, then a problematic fix for the filter, then a problematic fix for the fix....is taking you down a potentially difficult path. Instead, either eliminate the inline filter or find one which works. You might investigate one of the various KLR lists (I use DSN KLR650, a yahoo group which you can easily find) or one of the KLR suppliers (I use Arrowhead Motor Sports in Moab, Utah).

I've got an inline filter and in the 50,000 Third World km since I installed it, it hasn't shown any signs of serving any purpose whatsoever. I'd remove it, but it's easier to just leave it in place. This is the end result you want to achieve on your bike.

enjoy,

Mark
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  #4  
Old 6 Jun 2010
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I agree....

Putting the pump in is probably not the best solution, but i'm a sucker for a challenge !!

The fuel filter needs to be there, especially for African jerry can fuel.

I've removed the pump and changed the filter for a bigger one, hoping it solves the issue but only time will tell.

This Clark tank is crap design. It puts the tap much lower than the carb but very close leaving a very difficult angle for the fuel pipe. It's really hard to accomodate the fuel pipe without a kink, let alone a filter. I've been having problems where the float bowl won't fill and starving the carb on the motorway hence my idea to fit the pump.

The pump eliminated the fuel starvation problems fantastically but added one too...
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  #5  
Old 6 Jun 2010
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Yeh but.....what makes you so sure African fuel is such a big deal? I mean, if you like challenges that's fine, but I've used a lot of fuel out of rusty drums, jerry cans, whiskey bottles, you name it. I never had problems before I installed an inline filter, and I've not had problems since. Plus I've seen some DRZ's, and they don't all have added filters, and I don't notice them dying by the side of the roads left and right.

I do carry a water-separating funnel with a fine screen, but I've used it only a couple of times, usually to pour from my plastic fuel can on windy days (remember Patagonia?). Seems to me this might be a solution to your troubles, serving perfectly without requiring all sorts of complicated modifications, each of which invokes the Law of Unintended Consequences.

Why did you choose a DRZ in the first place? Did it have anything to do with simplicity, straightforward design or proven technologies? Or was it a question of all the available farkles you could install to make it more likely to break down or in other respects misbehave?

Just asking.

Mark
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  #6  
Old 6 Jun 2010
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Quote:
Originally Posted by markharf View Post
Yeh but.....what makes you so sure African fuel is such a big deal? I mean, if you like challenges that's fine, but I've used a lot of fuel out of rusty drums, jerry cans, whiskey bottles, you name it. I never had problems before I installed an inline filter, and I've not had problems since. Plus I've seen some DRZ's, and they don't all have added filters, and I don't notice them dying by the side of the roads left and right.

I do carry a water-separating funnel with a fine screen, but I've used it only a couple of times, usually to pour from my plastic fuel can on windy days (remember Patagonia?). Seems to me this might be a solution to your troubles, serving perfectly without requiring all sorts of complicated modifications, each of which invokes the Law of Unintended Consequences.

Why did you choose a DRZ in the first place? Did it have anything to do with simplicity, straightforward design or proven technologies? Or was it a question of all the available farkles you could install to make it more likely to break down or in other respects misbehave?

Just asking.

Mark
LOL... You do have a way of putting it into perspective. Maybe I will just remove the filter if it still causes me bother.

The reason I put a filter in is because the carb has a very fine filter under the float bowl. I had the same one in my XT and it kept gumming up in South America when I ran without an inline filter.

It's a lot easier to clean an inline filter than a carb filter. The tank does have a filter, but it's not very fine (like my Acerbis XT one which allowed the carb filter to block)


You do make a VERY good point though. Why am I over complicating things on a bike I bought for simplicity !!!! ???? !!!! ????

I've removed the pump and fitted a larger, higher flow rate filter and looped the fuel line to take out tight angles. I'll see if that cures my problems.

I still would like to run with the pump if I can find a simple, easy fix for the overflow.. Even if I don't use the pump, i'd love to find a way to use one just for reference reasons. There are times where a pump maybe needed (auxilary tanks etc) and I'd like to have the knowledge and knowhow to do it...

Thanks for the reality check though, I needed it !!
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  #7  
Old 6 Jun 2010
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Ted, have you actually run the tank dry while riding the bike?

I mentioned in another post that I have a similar problem with my CCM tank and I lashed up a means of pressurising the tank to get the last few litres through. In reality though the amount that's left in the tank when you stop is less than you'd expect as all the sloshing around tends to keep the fuel moving through for longer than you'd think. My "level with the carb" amount is about 4 litres but the bike only stops when there's just 2 / 2.5 litres left.

You only need the pump to get that last bit into the carb. The rest of the time the it's extra weight and complexity. In your position I'd dump the pump and make sure I had a small container - say 1 litre, (maybe a petrol stove bottle or something like that) that was going to be my absolute last ditch fuel reserve. I'd fit a fuel tap to the end opposite the filler. When times got hard that 1 litre or whatever would go in the tank first. When the bike stopped with a few litres left in the main tank I'd drain it into the bottle and connect that to the carb with some fuel line. Fix it somewhere higher than the carb and run the bike on that as a substitute fuel tank until you're absolutely out of fuel. Then walk.

The only extra weight is a fuel tap. The fuel line will be the tank breather pipe that goes down the headstock which you'll have anyway.
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  #8  
Old 6 Jun 2010
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My problem isn't getting the last few litres, the carb cant/wont fill up quick enough under it's own pressure, even when it's full... On one occasion, i couldn't ride faster than 45mph or the bike would be starved of fuel.... Float height is correct, carb is immaculate inside.

It's a fuel flow, vaccum, air lock problem somewhere. Fitting the vaccum pump is the only thing thats solved it upto now.

The bike won't start if it's been left over a week without manually priming the carb.

I've changed the filter/pipe set up and see if that solves it...
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  #9  
Old 6 Jun 2010
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Are there filters fitted to the fuel tap? It may be those, that are restricting the flow. Instead of a filter why not install a trap ? I have a glass see through filter but with the filter removed. The glass bit is down low so any sediment or water is trapped in the glass bowl. Most crud is heavier than petrol.

fuel line runs, tap to trap which is lower than the carb. then trap up to carb. Any sediment remains in the trap and can easily be seen. Both input and exit to trap are higher than the bottom of the trap.

This system presents no restriction to fuel flow, just uses gravity to trap sediment, water etc.
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  #10  
Old 6 Jun 2010
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Quote:
Originally Posted by oldbmw View Post
Are there filters fitted to the fuel tap? It may be those, that are restricting the flow. Instead of a filter why not install a trap ? I have a glass see through filter but with the filter removed. The glass bit is down low so any sediment or water is trapped in the glass bowl. Most crud is heavier than petrol.

fuel line runs, tap to trap which is lower than the carb. then trap up to carb. Any sediment remains in the trap and can easily be seen. Both input and exit to trap are higher than the bottom of the trap.

This system presents no restriction to fuel flow, just uses gravity to trap sediment, water etc.
Theres a filter on the tap in the carb but it flows nicely out of there. I've fitted a large transparent fuel filter which will hopefully sort the problem.

I might use your "trap" idea right next to the carb, to see if fuel is coming through.

I would use clear pvc fuel line but the problem is it doesnt stay clear for long. It becomes opaque and brittle over time.
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  #11  
Old 6 Jun 2010
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Ted,

Just some thoughts.........

The fuel demand is variable but I assume your pump runs a constant pressure/flow.

As suggested by someone else, I think maybe you need a bypass to let fuel back to the tank that isn't needed by the carb. (does that make sense ??)

Where is your pump located ?
Would a "T" in the pipe just before the carb, running back to the pipe on the inlet side of the pump provide a bypass loop ?? Maybe with an adjustable restrictor.

Perhaps there is a pressure reducing valve available. I can't believe this is an isolated problem.

I will be interested in you conclusions because I have a bigger tank to fit to my Dr Zed and that has an outlet way below the carb.

As far as filters go, I have a filter bag/screen that sits in the top of the tank.

Regards

BYT
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  #12  
Old 6 Jun 2010
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Quote:
Originally Posted by Big Yellow Tractor View Post
Ted,

Just some thoughts.........

The fuel demand is variable but I assume your pump runs a constant pressure/flow.

As suggested by someone else, I think maybe you need a bypass to let fuel back to the tank that isn't needed by the carb. (does that make sense ??)

Where is your pump located ?
Would a "T" in the pipe just before the carb, running back to the pipe on the inlet side of the pump provide a bypass loop ?? Maybe with an adjustable restrictor.


Perhaps there is a pressure reducing valve available. I can't believe this is an isolated problem.

I will be interested in you conclusions because I have a bigger tank to fit to my Dr Zed and that has an outlet way below the carb.

As far as filters go, I have a filter bag/screen that sits in the top of the tank.

Regards

BYT
A fuel bypass does make sense but I'm worried about making things even more complicated. A bypass could end up giving less flow to the carb than having no pump at all. Having allsorts of T-pieces, pipework, bypasses and valves sounds like a nightmare to set up and get working properly.

I remember reading on a forum something about your float valve which needs to be modded or changed but I can't for the life of me find it again.

If I can do without the pump, I will... I need to wait a week or so with the DRZ dormant and see if I get the same problem than before I changed the filter/pipes. I used to have to open the drain screw on the carb to get the fuel moving again or give a squirt of power start in the airbox to get things going.

After the bike started cutting out on my on the motorway, I stripped and cleaned the carb out and set the float a little higher which stopped the problem (for now). It still wouldnt start if left a while though. Im guessing once the fuel in the bowl evaporates, its not refilling sufficiently.


What bag/filter do you have on your tank ?? home made affair ?? Pictures ?

Have you ever had any starting , starvation problems with your tank ?? My mate has a 28L Safari (no inline filters) and has no issues at all.
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  #13  
Old 6 Jun 2010
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"I need to wait a week or so with the DRZ dormant and see if I get the same problem than before I changed the filter/pipes. I used to have to open the drain screw on the carb to get the fuel moving again or give a squirt of power start in the airbox to get things going."

I used to get that symptom on my TT. I always just assumed it was the fuel in the bowl 'going off' somehow. obviously with the leccy start you can just keep the button on, but I found it fired first time if I drained the old fuel first.

isn't the battery on the drz quite weak ? maybe you've upgraded. but if not could it just not have a fat enough spark to ignite old-ish fuel ? are you definite that there's no fuel between the tank and the carb, after a layup of a week ?

maybe you have two problems that are not strictly caused by the same thing ?
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Old 6 Jun 2010
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Look what I've just found on ebay !!

Any experinces ?????

Carburettor Fuel Regulator on eBay (end time 08-Jun-10 20:14:18 BST)



It looks a bit "MEATY" for my little DRZ but it is adjustable !!

Last resort I think...
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  #15  
Old 6 Jun 2010
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Quote:
Originally Posted by DougieB View Post
"I need to wait a week or so with the DRZ dormant and see if I get the same problem than before I changed the filter/pipes. I used to have to open the drain screw on the carb to get the fuel moving again or give a squirt of power start in the airbox to get things going."

I used to get that symptom on my TT. I always just assumed it was the fuel in the bowl 'going off' somehow. obviously with the leccy start you can just keep the button on, but I found it fired first time if I drained the old fuel first.

isn't the battery on the drz quite weak ? maybe you've upgraded. but if not could it just not have a fat enough spark to ignite old-ish fuel ? are you definite that there's no fuel between the tank and the carb, after a layup of a week ?

maybe you have two problems that are not strictly caused by the same thing ?
The fuel has always been fresh and I uprated my battery to a big fat 10ah one ! LOTS OF POWER !

Its not uncommon for fuel to evaporate out the bowl.. Im CERTAIN its fuel flow problem as the bike will fire up perfectly if used every few days, but longer than a week and it would be a bitch. The carb is vented fine !

I cant be certain of if there was fuel in the line... If I pulled the line off at the carb, fuel would piss out but then it would as all restriction has been removed.

Right old head scratcher isnt it !!
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