Uniflow Modification

[Monkey Wrench]

Has anyone that has done the uniflow modification on their Savage (one-way valve in pressure line trick) noticed an increase in the likelihood of their engine hydrolocking or hydrolocking very, very easily?

I have a Savage with a Wasp .28 in it, and I have gone through 2 OWB's and a pull starter in one week because it locks so often and so fast! I just started experiencing these problems when I did the mod to prevent the 1/2 tank lean and am wondering if anyone else has experienced this?

I'm going to take the one-way valve out and try it, see if that changes anything.

Thanks in advance!

 

[sweetdiesel]

Yes it can hydrolock easier upon priming because it is a closed system. You need to be more careful with priming.

You can also think of it as being easier to prime.



edit, I recall you having flooding problems before the uniflow though, or am I having a senior moment?

 

[digger]

I started to do it to one of mine a couple of years ago.
Bought the little valve. Then I was searching around some posts on different places, and it seemed like more trouble than it was worth.

Made a lot of sense when I read about it.
Would be easy to flood the engine and you would have to take the line off everytime you stopped because there would still be pressure on it.


I think the uni-flow mod is the bic pen in the fuel tank? Or am I having a "moment?"
Not trying to be an ass.

 

[sweetdiesel]

I've seen very mixed results with the uniflow, and yes it does make it easier to flood, which in turn will make it harder to start.

My apologies if I offended you with my senior moment comment digger. It was all in fun. pps:

 

[jon2]

I actually had to play with my needles more after the uniflow mod since themod constantly had a flow of fuel than without. Still was better for me. It just loaded up more.

 

[wanabedriver]

I was reading that people completly ditch the uniflow idea, and instead just get a HUGE fuel filter, which solves the problem.

I'm trying to make a 'Apparently it works because" statement, but I seriously can't think of why. The 1/2 tank leaning is caused when the fuel's surface area changes, but that would mean there would be more pressure per area, meaning there would be more fuel fed into the engine, causing a rich sydrome...

Anyway, an alternative was to just go ahead and make the pressure line longer to tone down the pipe pressure, but it cannot be too long, because it will bog the engine down. I can figure out how that method works.

BTW, link to where I was reading on a different forum.


EDIT: Apparently the large fuel filter idea works, because it's along the lines of a dual tank mod. Basically, it's mounting a fuel source at the carb height or higher, making it gravity fed.

 

[Monkey Wrench]

I think the uni-flow mod is the bic pen in the fuel tank? Or am I having a "moment?"
Not trying to be an ass.

Yup! That's the one, Digger.


Thanks for the insights, everyone! I really appreciate it! I think I'll see the results by taking it off and then go from there.

 

[NvNitro]

For me it's not so much hydrolocking, But I find my self priming more often when I stop. I tend to like the Uni-flow method right now. Didn't know if I had the lean at half tank when I got it, But heard so many horror stories I just went to the mod before the first fire up, and have liked it so far.

 

[sweetdiesel]

I was reading that people completly ditch the uniflow idea, and instead just get a HUGE fuel filter, which solves the problem.

BTW, link to where I was reading on a different forum.


EDIT: Apparently the large fuel filter idea works, because it's along the lines of a dual tank mod. Basically, it's mounting a fuel source at the carb height or higher, making it gravity fed.

I used to run dual dyamite big daddy fuel filters at the top of the rear shock tower. I would still get the half tank lean. Or is there an even bigger fuel flter out there?

Don't forget the other no cost solution. Tune your engine at a half tank. That way when it is full you will run slightly rich and nearly empty will be slightly lean.

 

[Monkey Wrench]

I think, and I stress THINK, one of the reasons for the quick hydrolocking may be related to the inner gasket on the LSN being shot. Also would answer the "why can't this {BLEEP} {BLEEP} thing get tuned!"

Thanks again for the assist, fellas! Much obliged to you all!

 

[wanabedriver]

I used to run dual dyamite big daddy fuel filters at the top of the rear shock tower. I would still get the half tank lean. Or is there an even bigger fuel flter out there?

:shrug: I personally haven't tried it, so I can't say what to make it work.

 

[rossb]

I've been running my Uniflow setup with great results for over 2 years and 8 gallons. The only downside is you need to be careful when leaving fuel in the the tank with the motor off. The motor can easily flood. I either empty the tank back into my fuel bottle or I just crack the lid of my gas tank.

Pictures of the install here:
http://www.rbartick.com/hpi/buildidx.htm

 

[MEGA MAXX]

i tried the mod, it worked but the truck ran really badly..

i took it off and it ran great, but, i left the bit of bic pen in the lid and it solved the problem, never got any leaning, i think it must of just helped force the pressure into the tank...

 

[jon2]

Make sure that you don't have a tube in your tank too long. I did that initially and my savage ran like crap. Check for that as well.

 

[SumoDethRat]

Make sure that you don't have a tube in your tank too long. I did that initially and my savage ran like crap. Check for that as well.

How long would be too long??? I just did the mod since my dog chewed a pen.

 

[jon2]

How long would be too long??? I just did the mod since my dog chewed a pen.

If you read the link for the uniflow mod, the measurements are given. Also to add make sure that the end of the line rests at the very bottom level of the tank.I just trimmed about 3mm.

 

[NvNitro]

How long would be too long??? I just did the mod since my dog chewed a pen.

Just keep it off the tank floor by about 1/8 of inch. That should be fine. I run mine that way, have no problems.

 

[Savage_man]

I was reading that people completly ditch the uniflow idea, and instead just get a HUGE fuel filter, which solves the problem.

I'm trying to make a 'Apparently it works because" statement, but I seriously can't think of why. The 1/2 tank leaning is caused when the fuel's surface area changes, but that would mean there would be more pressure per area, meaning there would be more fuel fed into the engine, causing a rich sydrome...

Anyway, an alternative was to just go ahead and make the pressure line longer to tone down the pipe pressure, but it cannot be too long, because it will bog the engine down. I can figure out how that method works.

BTW, link to where I was reading on a different forum.


EDIT: Apparently the large fuel filter idea works, because it's along the lines of a dual tank mod. Basically, it's mounting a fuel source at the carb height or higher, making it gravity fed.

Hey there, hope to clear this up a little. I know the physics part: it is the height of the fuel in the tank. the way to calc pressure from gravity on the fuel is (desity of fuel)*(height)*(gravity). Now just throw out the variables g and d, ((consants)) that leaves h. as h varies because the tank runs down, the fuel pressure diminishes. If we could get a flat tank that runs length of the body, then problem solved. I am thinking about this one.