Why Power Loss with Uni Filter Intake??

[Danp]

Gents, I finally got a chance to put on my DIY intake. It started fine, but anything after half throttle felt like it was hesitating, missing, flat-spotting, etc. No power. Put the standard airbox back on and it ran fine again.

Total length from carb opening to end of filter is 12". The 1-1/4" pipe itself is 8". Could it be too long, or am I needing to re-jet?

[Miamieddie]

"Both" too long and need to go bigger on main jet. Pipe length no longer than 5" to 6"....

[Danp]

Damn, double mess up on my part then. Was hoping to not have to jet with just the intake mod. How come some people haven't had to and some have? Elevation?

I'm in Ontario Canada by the way. 239m.

[Miamieddie]

Yes and all buggys are differant in looks and personality just like people. if your planning on gutting or getting a high performance exhaused you'll have to rejet again. So get a few sizes bigger jets anyways its all trial and error before you get it right but well worth it. It wont be too bad...Eddie.

[Masteryota]

2nd what has been said above, and elevation plays hell on jetting, we have nice fat air down here, so it makes it a little easier to tune without jetting. I bumped my needle up a notch when I added my 'necktified intake.

[Johnny 5]

Did you oil the filter?

[ckau]

Originally Posted by Danp

Gents,
Total length from carb opening to end of filter is 12". The 1-1/4" pipe itself is 8". Could it be too long, or am I needing to re-jet?

Yes and yes! Before you start over remove the carb and note the jet sizes. Depending on the year of your motor and/or carb, they will have different size jets. Early years, pre '05's may have 114 to 118 jets. The EPA steps in with pollution restrictions so the solution was to lean out the carbs to meet requirements. you could find jet sizes at 108 to 111. With the velocity tube and UNI you will most likely need to go up into the low 20's on jets, approximately 122 range. 127 to 130 if you gut the muffler. exact size depends on your average elevation.
You are increasing air flow by as much as 40% You WILL run lean! Elevation plays a big part in how much jetting you need but regardless you got to re jet! or run the risk of burning up that motor. Those claiming no need to re jet either had early year carbs previously re jetted, got very lucky or didn't pay attention to the adverse effects
Your tube is too long. your loosing velocity. You have to take into account the carb throat length and coupler lengths. Remove the filter and measure the total length while installed on the motor. Slide a ruler inside the tube and gently bump against the carb slide. you should have 7'' +/- to the open end of the tube. Make sure that filter is oiled per instructions! failing to oil properly will greatly reduce efficiency and effect the air/fuel ratio

[Johnny 5]

The intake I made is 1.5 inch diameter, could the 1.1/4 be causing some restriction?

[Miamieddie]

Not sure what ur saying... you don't want ur intake smaller than the opening of ur carb... hope that helps ur question.

[Miamieddie]

If ur intake is bigger than the opening of ur carb. Then ur going to have air leak issues where it clamps to the carb. Because its too big and wont seal right. Hope that helps ur question.

[ckau]

Originally Posted by Johnny 5

The intake I made is 1.5 inch diameter, could the 1.1/4 be causing some restriction?

yea, it will cause a restriction but only in the ability to pass the volume of air. You won't see the full potentials of a velocity tube. It just means you won't jet up quite as much. You'll be jetting for a smaller volume of air but still a improvement over the stock air box.

[Danp]

Hey everyone. My carb intake is 1-1/4", hence the same size tube. The only reason people upsize to 1-1/2" with couplers is because the uni filter opening is 1-1/2". I happened to have a nice gasket that fit over my 1-1/4" tube and makes it fit the uni snug.

Filter seems pre oiled. You can feel it on your fingers when handling the filter.

I've cut the pipe down, now I've got to test it. As for the jetting. My try adjusting the needle first. If now, re jetting I will go.

Thanks.

[Miamieddie]

I gotcha now you should be fine on the intake. Let us know on the jetting test.

[2SlickNick]

Sheesh, I dont think I will change mine out until winter then.... I will just enjoy it now as a stock machine.

[Miamieddie]

Its not that difficult at all its easy breazy... for some reason it seems hard when you put it in writing. ..... trust me I'm no mechanic if I can do it you can do it... Eddie.