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Old Sep 07, 2003, 09:37 AM
Registered User
Cincinnati, OH
Joined Jul 2003
280 Posts
Using crankcase vent to pressurize fuel tank

I recently purchased a Saito 72 and would like to add a flex pipe to the setup. The flex pipe that would fit my application the best doesn't come with a pressure fitting. A number of people have told me that they've used the crankcase vent fitting to pressurize their fuel tanks for years without problems. I've also read that they recommend connecting anything to this fitting other than a drain tube.

Can anyone offer some insight into this? I'm sure that I could add a pressure fitting to the new flex pipe, but if the crankcase vent would work without harming anything, I'll use that.

Thanks!
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Old Sep 08, 2003, 08:56 AM
Voices through wires? Ha!
Chas's Avatar
Joined Feb 2003
1,659 Posts
In the beginning, verily it is said,
DON'T blocketh the VENT with ANYTHING.

OS. Ch 2. v1.

Chas
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Old Sep 10, 2003, 07:08 AM
Say no to ARFs
Heavy Date's Avatar
Manchester Municipal, New Hampshire, United States
Joined Sep 2003
159 Posts
If you use the vent on the tank, the crankcase will pressurize and the engine will quit on you. Guess how I know!

The options are, use a pump, or use the muffler to pressurize the tank.

I have seen models with tuned pipes run fuel tubing well over a foot from the end of the muffler to the tank, so I don't think the distance is an issue.

Let us know how it works out.
Hans
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Old Sep 10, 2003, 07:35 AM
Registered User
Cincinnati, OH
Joined Jul 2003
280 Posts
I've decided to go with installing a fitting on the tube. The only other question is where. The unit I want has a right angle solid metal manifold, which attaches to the flexible section. Does the fitting have to go at or near the end of the pipe? I would prefer that it's located on the solid pipe up near the engine.

Thanks!
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Old Sep 10, 2003, 07:38 AM
Say no to ARFs
Heavy Date's Avatar
Manchester Municipal, New Hampshire, United States
Joined Sep 2003
159 Posts
I don't think it matters much where along the tube the fitting is, but I could be wrong. Hope someone else knows for sure.
Hans
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Old Sep 26, 2003, 10:35 PM
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fredericksburg va
Joined Apr 2003
14 Posts
you can use the crank case nipple but you will need to use a needle ass. so you can regulate how much pressure you need
thats the way it is on my satio 300 twin it keeps the fuel flow the same from full tank to the last drop. i don't think you will get much
bennefit on the flex tube because they half little or no back pressure.if you call horzon just order the "pump ass."for the 300
twin with dual carbs all it realy is a needel valve ass. simple but
works great.
roy
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Old Sep 27, 2003, 08:10 PM
Hi ya! Car ride!?
Sport Flyer's Avatar
Portage La Prairie, Manitoba Canada
Joined Sep 2003
734 Posts
Is there any harm in using a splitter to hook the crankcase vent to the muffler pressure line? Just curious as I'm installing a OS 70 Surpass into a cowled installation on a Jamara Ford Flivver and was planning on doing this. I didn't want the crankcase line to just vent into cowl area.

Thanks,
Kelly
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Old Sep 27, 2003, 09:04 PM
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fredericksburg va
Joined Apr 2003
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i don't think you want to hook both up if i'm following you i think one will cancell the other out i would use one or the other but on the os 70 if i rember right it has a muffler so that might have enough back pressure.try and see is about the only real test to see what happens.just one other thought the simpler you keep lines and the least amount the better the more complex the plumbing the more chance for problems.
roy
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Old Sep 28, 2003, 08:40 AM
Hi ya! Car ride!?
Sport Flyer's Avatar
Portage La Prairie, Manitoba Canada
Joined Sep 2003
734 Posts
Hi Roy. I just figured to keep the crankcase tap from spitting into the cowl I'd tee it into the muffler pressure tap line. Not a good idea? Better to vent it outside the cowl area then?
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