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| Fuel tap http://www.kawi2strokes.com/forum/viewtopic.php?f=14&t=14206 |
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| Author: | DGA [ Sat Jul 18, 2020 2:24 pm ] |
| Post subject: | Fuel tap |
My H2B has the stock fuel tap, which I would like to keep. I have never ridden an H2 before this bike, so I really didn't know what to expect, and nothing to compare it to except my H1 from 40 years ago. With either the stock carbs or the TM34s I have on it now, and my large, midrange pipes on it, it makes sudden, exciting power at 5k but seems to sign off at 6500 rpm. This becomes a bit sucky on the freeway or any decent straight road, where going much over 100 it just does not want to pull anymore. I just accepted it as how these bikes are, and that my midrange pipes are hurting the top end, but that was sort of intentional, I never wanted to beat this motor too hard. I had noticed a sort of slow down on occasion, like a sieze, but it wasn't, it would just stop pulling at random, usually after I had beaten it a bit. I had a think about it and wondered if the fuel tap was a restriction because of vacuum loss, and the carb bowl levels were getting low, so I tried riding with it on prime. Oh yes, much better, revs on up, and just keeps going past 6500 easily. So I can ride it on prime, but I then lose the reserve function, which I do use, and this bike certainly likes it's fuel. I know some run the Pingel tap, but I would like to keep the stock tap if possible. Any ideas? I don't think a vacuum check valve is a good idea, and I don't want to forget to shut the fuel off with an open flow tap. |
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| Author: | Jim [ Sat Jul 18, 2020 3:00 pm ] |
| Post subject: | Re: Fuel tap |
Usually a stock petcock can flow way more than even the most modified engine can use, so I'd look for something preventing full flow in the lines, or maybe a partially clogged tank screen, etc.. |
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| Author: | DGA [ Sat Jul 18, 2020 4:35 pm ] |
| Post subject: | Re: Fuel tap |
Jim wrote: Usually a stock petcock can flow way more than even the most modified engine can use, so I'd look for something preventing full flow in the lines, or maybe a partially clogged tank screen, etc.. It's all rebuilt, new screens, lines, tank clean and shiny. I switch it over while riding and then feel a difference. Vacuum gets too low at high throttle openings for too long and the diaphragm shuts off fuel flow and the carb bowls start to empty. Takes more flow to lift the lower fuel levels in the bowls, so acts like a lean condition. I have 260 main jets, which would usually be sort of rich. |
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| Author: | Ja-Moo [ Sun Jul 19, 2020 8:45 am ] |
| Post subject: | Re: Fuel tap |
It would be a very rare problem if it was low vacuum, as this is the first I have heard of it. Check your gas cap vent, the gaskets swell cutting off the vent. and get those screens off, use big inline filters. |
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| Author: | DGA [ Sun Jul 19, 2020 1:32 pm ] |
| Post subject: | Re: Fuel tap |
Remember, I have TM34s on it, and had to add a vacuum port to operate the vacuum tap. I drilled that up high in the carb body in hopes it would be behind the slide for as long as possible. Maybe this isn't as good as the stock VM30 position. |
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| Author: | Jim [ Sun Jul 19, 2020 1:44 pm ] |
| Post subject: | Re: Fuel tap |
DGA wrote: Remember, I have TM34s on it, and had to add a vacuum port to operate the vacuum tap. I drilled that up high in the carb body in hopes it would be behind the slide for as long as possible. Maybe this isn't as good as the stock VM30 position. That could be. |
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| Author: | Ja-Moo [ Mon Jul 20, 2020 10:05 am ] |
| Post subject: | Re: Fuel tap |
If you look closely, there is a divot for drilling right before the rubber manifold. And I have run 38's no problem. |
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| Author: | DGA [ Mon Jul 20, 2020 10:21 am ] |
| Post subject: | Re: Fuel tap |
Here's where I put the vacuum fitting. In any case, the issue still stands, and I guess I will leave the tap on prime for riding and shut it off when parked, and use the odometer for range. |
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| Author: | H2RTuner [ Mon Jul 20, 2020 3:09 pm ] |
| Post subject: | Re: Fuel tap |
I do a vacuum fitting in all my carbs, no matter where they will sit on the engine, so I can use a mercury manometer to set the carb balance at both idle and off idle (2,000 rpm's). I use the rubber block off plugs from a Z1, KZ900/KZ1,000 to block the two non fuel valve feed carbs when done with the balancing. A lot easier than using a Uni-Syn, and much more accurate then fingers feeling the slides. There used to be kits under warranty for the Z1, with threaded fittings, to replace the pressed in ones that always fell out (there was an FDM on this, don't know if Dale has it on the resources site, it is for a 4 stroke Kawasaki). |
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