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**rachel** · 02-05-2013, 11:54 AM

if its an HZ-R then yes not sure you can do this if its a non regulated engine ie, not an HZ-R

It also needs a one way valve if it is an HZ-R

**tourerjim** · 02-05-2013, 12:30 PM

Its the HZ Hyper that's all i can see on it, so.! can i just use pipe from cank case to tank or does it need return valve or is it i can't do it this way.???

**Red Devil** · 02-05-2013, 12:45 PM

Iv had a hz r and iv got a hz the hz r is regulated you can see the regulator near the to mixture screws it's a silver thing with some holes in it,the hz hadn't got the hole in the crank case for the fuel tube at it just works from muffler pressure

**tonystevens** · 02-05-2013, 05:29 PM

if your coming off the back plate then yes

**rachel** · 02-05-2013, 05:40 PM

Originally posted by tonystevens View Post

if your coming off the back plate then yes

so what you are saying is you can use crank case pressure , without a one way valve to pressurise the tank on an unregulated engine ? interesting , I haven't seen that one done .

**tonystevens** · 02-05-2013, 05:42 PM

Nope, im saying yes you need a check valve if coming off the crank case which is what he was asking.

Originally posted by rachel View Post

so what you are saying is you can use crank case pressure , without a one way valve to pressurise the tank on an unregulated engine ? interesting , I haven't seen that one done .

**rachel** · 02-05-2013, 05:59 PM

ahhh I see , so just to clarify for future reference , you can use crankcase pressure on a non regulated carb as long as you use a one way valve ?
thanks , it's a new one on me so I want to make sure I understand it :-)

**tonystevens** · 02-05-2013, 06:14 PM

Originally posted by rachel View Post

ahhh I see , so just to clarify for future reference , you can use crankcase pressure on a non regulated carb as long as you use a one way valve ?
thanks , it's a new one on me so I want to make sure I understand it :-)

As far as im aware a non regulated carb will always run off muffler pressure not crankcase pressure, i dont know of a non regulated engine that runs off crank case pressure and if one exists im sure it will use a check valve, you wouldnt want fuel traveling back into your crankcase would you

**chugga-bug** · 02-05-2013, 06:14 PM

Originally posted by rachel View Post

ahhh I see , so just to clarify for future reference , you can use crankcase pressure on a non regulated carb as long as you use a one way valve ?
thanks , it's a new one on me so I want to make sure I understand it :-)

No Rachel. If the engine hasn't got a regulated carb it won't even have a nipple (oo-err!) on the cases.
If you fitted one, and a one way valve to an 'un-regulated' engine tank pressure would be far too high. Hence the use of a regulator.

**chugga-bug** · 02-05-2013, 06:28 PM

The crank case pressure will fluctuate between positive and negative as the piston rises and falls. That's why you need a one way valve, to stop the pressure gained being lost again as soon as the piston is on it's up stroke.
An exhaust pressure system will never give as much pressure, but because of the 2 stroke pipe design, (pressure wave forcing unburnt fuel back through the exhaust port) at no point is there a negative pressure, so the tank remains pressurized without the need of a one way valve. Until the engine stops of course!

**pgkevet** · 02-05-2013, 07:25 PM

And just to add to the story ..you can drill/tap and add a nipple to a normal engine crank case then add a one-way and a regulator. Indeed my blitz avro has this system on a 90sz.
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**rachel** · 02-05-2013, 07:50 PM

Cool just wanted to confirm what I thought ;-)
ie no reg , no crankcase pressure :-)

**tourerjim** · 02-05-2013, 08:14 PM

Originally posted by chugga-bug View Post

The crank case pressure will fluctuate between positive and negative as the piston rises and falls. That's why you need a one way valve, to stop the pressure gained being lost again as soon as the piston is on it's up stroke.
An exhaust pressure system will never give as much pressure, but because of the 2 stroke pipe design, (pressure wave forcing unburnt fuel back through the exhaust port) at no point is there a negative pressure, so the tank remains pressurized without the need of a one way valve. Until the engine stops of course!

This is what i needed to know, I have the carb with the pressure reg but had some bad vibes from the engine so i thought i'd fit the norm os55 carb just to see if vibes are still there" just wanted to know if i could still use same fuel pipe to save changing over to the exhaust setup.
I seem to remember on the old 91's they had the fuel pipe coming off the exhaust & cant remember regulator being used.

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