Ideas how to contain carb spit-back

Alajoyn

Alajoyn

New Member
Anyone have advise on an appropriate air filter system that will better contain the fuel spit-back that is inherent in the HT engine design? I have fuel that accumulates at the bottom of my stock air filter system on the stock NT carb. I realize that with a single cylinder single carb set up on a 2-stroke you'll have this issue, but those of you with custom paint, what do you do to prevent dripping and getting onto the motor and it's fins...except a wipe rag every 5mi or so.

Ideas?

Thanks,
Robert
 
i wipe mine with a rag every 5 miles or so.

actually, i don't think there's a cure for it. if you got a bigger filter to soak it up, it'd just get saturated and have to be cleaned out more often to provide good airflow.

the right mixture helps a lot. i use 100:1 opti 2 oil, and the oil doesn't clog up in the filter and leak out as much.
 
I concur with Bairdco. It's a 2 stroke and intake blow-back is normal. Either live with it or keep a rag handy, or go for a 4 stroke engine.
Some of the more exotic, synthetic oils. Opti-2 is an example will reduce the amount of oil in the intake by some degree but you'll always have it. Sorry, just a fact of life.
Tom
 
Would a plastic overflow tube from the bottom of the air-filter housing going down below the frame help ? (as seen on 4 stroke carbsw on a thread here )
 
On one of my builds I had played with a boost bottle, and put of all things a Right Guard deodorant cap. It matched the color of the bike almost. Last I used pantie hose about 6 plies with a cable tie around the end. It really wasn't all that pretty but the oil was contained between the boost bottle and the added depth of the cap I used.

I think a bigger deeper filter might help but have not tried it without the boost bottle.
And no the boost bottle doesn't give any dramatic power just makes the throttle a little more responsive.
 
Oh yeah, I like the idea of fitting tube to bottom of air filter housing.
I could fabricate a housing that fits tightly around and seals at the carbs front face and make the new housing with a little "basin" with a ferrule fitting soldered to attach a tube to. I can fab it from copper shimming stock and solder it together with an internal flange to press the filter against, then cap it mebe even with the same cover & longer screws. Hmmmm new things to invent.
Thanks for the idea guys.

Robert

Hmmm or would enlongating the intake manifold with a slight "s" help eliminate it??
More to make ya go hmmmm
 
Believe it or not, this is the only instance I'd recommend a boost bottle for a HT. Mine had less spitback with one but no improvement in top end performance or speed.
 
Or you could connect a hose or rubber boot on the end of the aircleaner and run it to a airbox,it contains the oil and gas and holds it in the aircleaner housing. i know this works cause i tryed it.
 
Thinking about the boost bottle,it is a vaccume thing,,,,,so if the tube from the bottom of the air filter was placed in front of the carb intake the vac.from the engine running would suc the oil mix that was collecting in the tube from the bottom of the air filter keeping it clean
 
You would also have to have the aircleaner filter sealed tight up against the housing or gas/oil will leak from the cracks. You also have to have it removable to clean it.
 
There's only one solution to eliminating intake reversion, and that's to fit a reed valve onto the intake port.
This method will not only solve reversion issues but will increase low and mid range rpm performance.

Now if only someone can design and market a reed valve intake conversion system, i'll buy the damm thing at an instant.

Fabian
 
Yeah I know what your talking about.
I have a buddy that designed his own external reed mod for an old Mercury 3cyl outboard in order to increase performance over the stock reed system. I've seen it. Wow it made a difference, Kinda like runnin the old Cleveland 351 heads I used to play with.
Well, a grinder, an aluminum block and lots of epoxy'll get ya there...eventually.

Robert
 
Fabian said:
There's only one solution to eliminating intake reversion, and that's to fit a reed valve onto the intake port.
This method will not only solve reversion issues but will increase low and mid range rpm performance.

Now if only someone can design and market a reed valve intake conversion system, i'll buy the damm thing at an instant.

Fabian
Click to expand...

how is a reed valve work?
 
A reed valve fits in the intake between the carb and the cylinder. This allows fuel to get sucked into the cylinder yet closes to prevent any fuel from going back towards the carb. Basically a reed valve is a one way valve.
 
The reed valve sounds interesting, is there any temperature issues to worry about when attaching stuff to the intake? Just curious as this may need some exploration on a rainy saturday afternoon.
 
Fabian said:
There's only one solution to eliminating intake reversion, and that's to fit a reed valve onto the intake port.
This method will not only solve reversion issues but will increase low and mid range rpm performance.

Now if only someone can design and market a reed valve intake conversion system, i'll buy the damm thing at an instant.

Fabian
Click to expand...
Ya and I would be right behind you!
 
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