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Post by silas on Jun 5, 2012 18:39:52 GMT -5
Hi people. I have been looking around for quite a while and compiling information on an electric fuel pump conversion for my yy250t. Most seem to use the 42s type pump, but I went with an Airtex 8016s. My concern is the orientation of the pump. The most I have gathered on this pump is that the pump inlet should NOT be higher than the outlet.
The tank is in the rear, under the seat. I know the pump should be close to the tank, but should the pump be mounted vertically or horizontally? Does it matter?
Thanks for the help.
-Silas
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Post by chromestarhustler on Jun 5, 2012 20:24:10 GMT -5
is your tank above the carb? if so you dont need a pump,
installing a pump would just steal juice from the cooling fan, which is of major importance and the head lights.
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Post by silas on Jun 5, 2012 21:32:29 GMT -5
Yeah, I'd say it is above the carb or about level; it's a 2008 Jonway 250, with the tank in the rear, under the seat. People are always saying that you can't let it get below 1/2 tank and all that jazz.
I couldn't seem to find anything distinguishing the vacuum pump from a vacuum valve. It's the smaller, half-dollar sized unit mounted on the left rear of the frame. I always have trouble with it losing its prime over a day or so. I end up having to disconnect the fuel line from the carb, and emulating the vacuum pulse on the vacuum port to get it primed to the carb again. It seems to operate as a pump.
I do wonder whether or not I would really need a pump, but I don't want anymore of this tank too low, vapor-lock, losing prime b/s. The current draw does concern me.
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Post by leo on Jun 5, 2012 22:01:08 GMT -5
my tank outlet is 6 inches above the carb inlet.
the only problems i've noticed is when the tank is about 3/4 empty.
i find it sometimes hesitates around curves and up and down hills.
on level ground the carb can completely drain the tank at speed with no problems.
i'm running with 1/4" fuel line and a manual valve.
to answer the OPs question:
yes, orientation is important with some electric pumps.
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Post by chromestarhustler on Jun 5, 2012 22:19:54 GMT -5
run a vacuum fuel pump one off a 250 like 54b or vog will have an easy time keeping your engine supplied with fuel thanks to the higher tank location. is an easy splice in, no electric draw, and the engine has the vacuum to tun it.
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Post by silas on Jun 5, 2012 22:39:52 GMT -5
Okay, I do have a dual-out Mikuni pump from my ultralight that I could use. With a vacuum pump, could I possibly mount it close to the carb as opposed to the tank to keep the fuel ready near the carb? In other words, will a vacuum pump PULL fuel unlike an electric pump?
Thank you all for the help with this.
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Post by onilegion on Jun 6, 2012 1:41:01 GMT -5
Hi silas, Depending on the model of course, vacuum pulse pumps have lift rating in the range of 6"-10", for pumps used on 4t engines. They do however push better than they draw (but this is also limited by the fact that you are pumping a fluid with a relatively high vapor pressure, ie gasoline), and work best when the inlet is fed with a small head pressure, which you should already have due to the high placement of your tank. During the early years of the Chinese scooter boom, many manufacturers went overboard with the sizing of the vacuum pumps on their scooters, thinking, we guess, that this would insure a steady fuel supply pressure. Unfortunately these pumps are driven from the rather small-volume pulse from the intake manifold on a 4t engine, rather then the crankcase pulse on a 2t engine. These intake manifold pulses are so small that they barely tickled the diaphragms of these larger pumps and fuel starvation at WOT was common. The solution was quite simple: use a vacuum pulse pump whose pulse-volume needs match those that can be derived from the intake manifold pulse. In other words: use a smaller pump (which they eventually did). Here is a great little pump that Kohler, B&S, Kawasaki, etc. use on small engines that are in the 17-25hp range. Kohler uses them on their V-twin Command series, so they are plenty strong enough to use on any of the 250cc Chinese clone scooter engines. We use them on both of our scoots with a combined mileage of over 14K and have never had a single issue with them. They might come in a bag that says Kohler or B&S, but they are actually made by Mikuni. They are so compact that they literally fit in the palm of your hand but they provide enough flow to always keep up with our rather highly modified CFMOTO 244cc engine, even when it is screaming at 8,000 rpm. www.jackssmallengines.com/Products/KOHLER/Fuel-Pumps-Diaphragms/808656/321923Hope this helps, onilegion <>< |
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Post by silas on Jun 6, 2012 16:37:30 GMT -5
Hi, and thanks for the good info, onilegion. That Kohler pump does seem like a good idea. I sure am giving second thoughts to an electric pump, but I am going to do some tests on the charging system before I decide.
And the Mikuni pump I spoke of is a rather large pump and came from a 2cyl/2stroke. I'm going to do some tests on that as well.
Silas
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Post by chromestarhustler on Jun 7, 2012 16:38:52 GMT -5
never had a single problem with any of the 08 250 fuel pumps, not even at 80mph. use whatever vacuum pump you want but mount it under the tank so the supply side is gravity fed. and then its pumped into your carb. \
but the more i think about it, it sounds like your float level is low, you can run the tank dry on flat ground but curves and up and down motion makes you run dry. sounds like the fuel float is closing too early and running the carb almost dry before it can pick back up again.
at full tank the gravity is enough to keep the fuel slowly flowing in. at 3/4 the float can over come the fuel flow and cut off the feed, and your almost running out of fuel.
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Post by leo on Jun 8, 2012 14:24:17 GMT -5
but the more i think about it, it sounds like your float level is low, you can run the tank dry on flat ground but curves and up and down motion makes you run dry. sounds like the fuel float is closing too early and running the carb almost dry before it can pick back up again. i gave the carb a hillbilly adjustment soon after i got it. removed and disassembled the carb and adjusted the needle tang to where the float seam was parallel to the carb body when upside down. |
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Post by Scooter Elements on Jun 8, 2012 15:32:38 GMT -5
Mikuni Vacuum Fuel Pumps work great! 14L an hour and there are others that flow even more Attachments:
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Post by silas on Jun 8, 2012 15:36:21 GMT -5
I have a rectangular dual-out Mikuni like the one pictured. I am going to test with it as well.
Not quite sure on which pump I want to use, but I should certainly check that float like you all are talking about. We don't have hills here, but if I'm going down the test road at medium speed and slow down to turn, that is when it runs out of fuel (I think).
Silas
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