TRX250R.ORG
Workshop => Carburetor, Intake, and Exhaust => Topic started by: Bowtie316 on October 18, 2013, 10:15:02 PM
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I just thought I would share the results of some testingthat I carried out.
I followed the same procedure that KSRRider2 used, 10 oz in a clear plastic bottle, and used a stop watch to record the amount of time it took to fill to the 10 oz line. Here are my results;
These are with stock petcock, stock tank and hoses.
With 90 degree visu-filter, Petcock in on position, full tank of gas, - 32.18 seconds to the mark.
For the rest of the testing, no filter was used.
Petcock in ON position, half tank of gas – 18.88 seconds to the mark.
Petcock in ON position, full tank of gas – 17.22 seconds to the mark.
Petcock on RES position, full tank of gas – 17.09 seconds to the mark.
Then I ground the stop off the plate on the petcock so I could use the ON+RES mod position.
Petcock in new ON+RESposition, full tank of gas – 12.19 and backed that up with an 11.76.
Then I drilled the gas cap vent holes to 5/32” (2 on bottom and the nipple hole).
Petcock on ON+RES position, full tank of gas – 11.72 seconds to the mark.
Petcock on ON+RES, full tank of gas, No Gas Cap – 11.43 seconds to the mark.
I tried it again with a short hose and a piston shaped vent that is on my sons TTR90, and came up with around 13 seconds (I didn’t write it down).
So based on my results, I conclude that the ON+RES mod is a good one, but the pingel still flows much more. The drilled cap didn’t make much change but It would make more difference if you had a pingel and were flowing in the 6 second range.
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them guzzlers work damn good. probly way overkill for a gas engine though
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I run a pingel and love it!!!
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this idea probably has no real benefit, but its late and im just thinking about this
you could put a small check valve on the vent tube and pressurize the tank with a couple pounds of pressure before say a drag race to have added pressure???
not sure what it would do but just a thought
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Then I ground the stop off the plate on the petcock so I could use the ON+RES mod position.
Petcock in new ON+RESposition, full tank of gas – 12.19 and backed that up with an 11.76.
How ironic! I planned on doing this mod today. That's a significant, improvement.
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How ironic! I planned on doing this mod today. That's a significant, improvement.
Yes, I was impressed, you can see and hear the difference switching from ON to ON+RES and the test data backs it up.
Word of caution though, this mod is best done with an empty tank. I did it with a full tank and the petcock did not keep the fuel shut off so I had it draining into a gas can. Not a big deal.
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Comparing two different petcocks. Looks to be a mod on the left. Is this a factor?
(http://i532.photobucket.com/albums/ee328/RideRed187/250R%20Pics%20Parts/null_zps0bdca92f.jpg)[/URL]
(http://i532.photobucket.com/albums/ee328/RideRed187/250R%20Pics%20Parts/null_zpsd883aa5f.jpg) (http://s532.photobucket.com/user/RideRed187/media/250R%20Pics%20Parts/null_zpsd883aa5f.jpg.html)
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Comparing two different petcocks. Looks to be a mod on the left. Is this a factor?
(http://i532.photobucket.com/albums/ee328/RideRed187/250R%20Pics%20Parts/null_zps0bdca92f.jpg)[/URL]
(http://i532.photobucket.com/albums/ee328/RideRed187/250R%20Pics%20Parts/null_zpsd883aa5f.jpg) (http://s532.photobucket.com/user/RideRed187/media/250R%20Pics%20Parts/null_zpsd883aa5f.jpg.html)
Yeah I'm sure that would help too. What size are those holes? I might have to give it a try and continue the experiment.
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Stock cock .195 Bored out cock .235
That's a 20.5% increase in volume. :beguiled: Fuel bowl should fill with those numbers!
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I did that exactly like the pic with my last petcock when I rebuilt it.
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I did that exactly like the pic with my last petcock when I rebuilt it.
That's so funny Wes! It was yours! :joyous:
(http://i532.photobucket.com/albums/ee328/RideRed187/Random%20Pics/null_zps5c60b6a6.jpg) (http://s532.photobucket.com/user/RideRed187/media/Random%20Pics/null_zps5c60b6a6.jpg.html)
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Haha! Well there ya go! You should check the flow rate on it
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hey been throwing that idea out for years, we have done that since the 90's and even use that mod on alky setups
I did the same style tests where I timed it, don't have the numbers anymore but they were very much like yours with a significant improvement by grinding the tab off running both.
I just drill and tap a 1/8 pipe-3/8 hose fitting into the gas cap for a vent
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Yes rsss396, it was your post from a long time ago that made me want to try it. It definitely works. Thanks!
The next step will be to drill them out and time that. Not sure when that will happen though, got other junk to work on.
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Stock cock .195 Bored out cock .235
That's a 20.5% increase in volume. :beguiled: Fuel bowl should fill with those numbers!
Going from .195" to .235" is an increase in DIAMETER of 20.5%
Going from .195" to .235" is an increase in AREA of 45%
If there are not any restrictions above or below the .235 diameter hole you should have an increase in VOLUME (flow rate) of about 45%.
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Going from .195" to .235" is an increase in DIAMETER of 20.5%
Going from .195" to .235" is an increase in AREA of 45%
If there are not any restrictions above or below the .235 diameter hole you should have an increase in VOLUME (flow rate) of about 45%.
Running a CR250 petcock that has been drilled out is a cheap mod for those on a budget. You lose the res though.
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I also run a modded stock petcock. I ground the tab off and run it pulling from both feeds.
I have a 44mm Lectron/stock clear bowl and 363 Sphinx that is making 70HP. The carb does not run dry while running the hills.
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High performance engines should NEVER run the pet cock in the ON position unless it has been modified to flow fuel through the Reserve and On port of the pet cock simultaneously. Do not risk starving the ON stand-pipe pick up even for a second or two when the fuel gets low and the fuel "slosh" does not keep the stand-pipe submerged 100% of the time.
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this idea probably has no real benefit, but its late and im just thinking about this
you could put a small check valve on the vent tube and pressurize the tank with a couple pounds of pressure before say a drag race to have added pressure???
not sure what it would do but just a thought
Increasing the tank pressure will increase the flow. 1 psi of pressure at the float valve will approximately double the fuel flow over what you would have with a gravity feed system when the fuel tank is full. A fuel level in the gas tank that is 1 foot above the the float valve will produce approximately 0.4 to 0.5 psi at the float valve.
The float valves on the majority of the PJ or PWK type of Keihin carburetor are sized for gravity feed. Float valves sized for gravity feed will stop holding as the pressure approaches 1 psi. When the float valve stops holding, the fuel level will rise causing an extreme rich condition in addition to fuel overflowing out of the vent lines. The float valve seat on the Keihin carbs cannot be replaced with different sizes like the Mikuni carbs. Mikuni offers this feature of replaceable seat sizes to accommodate a wide range of fuel pressures to the carb.
Sizing the seat size with the correct fuel pressure to get maximum flow sometimes takes a lot of testing to find the right combination. I often use variable fuel pressure systems to offer low pressure when the fuel demand is low and higher pressure at higher fuel demands on the methanol systems.
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So how do you perform this mod for ON+RES?
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So how do you perform this mod for ON+RES?
Good question, I should have included it in the original post. Basically you just take the retainer plate (the one that says on - off- res) off, and grind out the stop so it will let the valve travel all the way around. Then you just turn it forward, 180 degrees from off. That allows it to feed from on+res simultaneously.
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Good question, I should have included it in the original post. Basically you just take the retainer plate (the one that says on - off- res) off, and grind out the stop so it will let the valve travel all the way around. Then you just turn it forward, 180 degrees from off. That allows it to feed from on+res simultaneously.
Cool deal. Thanks. I think I am going to do this mod and drill mine out also.
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when you remove the tab and position the valve so it is 180 from off the half circle relief cut into the back of the valve is now positioned so both the res and on is exposed.
not sure if you can see the relief very well in this pic but that may make you understand better
(http://i39.tinypic.com/1496xk6.jpg)
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I only see a red X.
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hows that
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hows that
Dave, call me the stupid one, but what part are you actually grinding on? The pic looks good; is there any way to add an arrow pointing to what you are grinding?
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Dave, call me the stupid one, but what part are you actually grinding on? The pic looks good; is there any way to add an arrow pointing to what you are grinding?
Do you want us to grind it for you too, Jk.
(http://i851.photobucket.com/albums/ab73/bowtie316/gasmod_zps090f575b.png) (http://s851.photobucket.com/user/bowtie316/media/gasmod_zps090f575b.png.html)
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Somehow missed that from the first pic. Yes, mod it for me Bowtie, that would be just fine. LOL
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Neato
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I freakin love it. I have two petcocks so I can play with one. Problem is that it leaks out the front. Maybe those two washer things under the plate that tells you what position you're in are in wrong? It has two tabs on it but maybe they go in differently. I bought the tank on eBay but decided to clean it out. The petcock had goop in it and I'm glad I cleaned it out. Never tested it for leaks but it does now. I'd like to get it fixed so I can mod it and the one on my R.
I like the number results from testing.