Hesitation On Acceleration

[CoyCaller]

I just got done port and shaving the eyebrows on the kids' gokart.
There is definately an improvement in performance. (I found out that the block is aluminum, I assumed it was cast.)

I have a problem though. The engine idles great and when you wind it up to governor speed and beyond it is good but getting there is a little shakey.

When I punch the throttle, it is either loading up or starving for fuel. Seems better if I choke it just a little (very little). I'm guessing I need more fuel, if so, how do i accomplish that.

I can feather the throttle and get through it but it would be nice for the kids and me if I didn't need to follow them around and start it every time they killed it.

 

[freakboy]

you need to re jet the carburetor start one size up from what is in there now and keep going till it bogs out then go one size down.

 

[BAMBY]

i assume since you did the eyebrows, you have a briggs.

1. the shakyness... on my briggs 5hp, i know the vibrations your talking about, they get even worse if you go a little higher than the governor lets you, but once you get past 4200rpm, it smooths out like its on a cloud or something... its weird, but i run mine up in the 4800-5200 range all the time now that i realized it quits shaking once you get up in the revs... maybe yours is similar...

2. if you have the briggs 5hp, (dont know about others) there is a mixture screw on the side of the carb thats closest to the flywheel. if you turn it counterclockwise, it will let more fuel in. all you should need is 1/2 turn MAX 1/8 or a quarter should do it!

gratz on the eyebrows... i remeber when i did that, i can vouch for the gain in power, also helped me get my revs to where they are today...

good luck. hope i helped.
BAMBY

ps. do what u want, but if your kids are riding in this beast, i would not recommend getting the revs as high as i mentioned. for safety reasons of course. (even though mine has held up.)

 

[CoyCaller]

Thanks Bamby. It's just a 3.5 hp Briggs. I ran the RPMs up, and it was shakey but I adjusted the mixture screw and it smoothed out but I still have the hesitation immediately when I hit the gas. As soon as I get through the hesitation with a little feathering of the throttle is is as smooth as glass.

FreakBoy, Do you still think the jets are the problem? How do I go about knowing what I have and finding what I need?

Thanks to you both!

 

[EagleTalons]

i assume since you did the eyebrows, you have a briggs.

1. the shakyness... on my briggs 5hp, i know the vibrations your talking about, they get even worse if you go a little higher than the governor lets you, but once you get past 4200rpm, it smooths out like its on a cloud or something... its weird, but i run mine up in the 4800-5200 range all the time now that i realized it quits shaking once you get up in the revs... maybe yours is similar...

2. if you have the briggs 5hp, (dont know about others) there is a mixture screw on the side of the carb thats closest to the flywheel. if you turn it counterclockwise, it will let more fuel in. all you should need is 1/2 turn MAX 1/8 or a quarter should do it!

gratz on the eyebrows... i remeber when i did that, i can vouch for the gain in power, also helped me get my revs to where they are today...

good luck. hope i helped.
BAMBY

ps. do what u want, but if your kids are riding in this beast, i would not recommend getting the revs as high as i mentioned. for safety reasons of course. (even though mine has held up.)

How fast are you going at your top rpms?

 

[BAMBY]

glad i helped... mine always bogs a little, but i try to be fuel efficient to by not opening that screw up too much. nothing bad will happen except more carbon build up over time and worse emissions. i just have to pay for my gas so i try to conserve... lol

@eagletalons...
10tooth clutch
60tooth rear
50in tire circumfrence
max rpm i ever hit was 5380
usuall i go 5100 about tho.

this gets me to hmm lets see... goes to speed calc...
5100rpm=40.24mph
5380rpm=42.45mph

BAMBY

 

[freakboy]

You should be fine now. the only time you really need to open up the jets is on a newer carburetor that has all the emissions crap and dont have adjustments. so you should be fine now. on older carbs the only time you need to open them up is if the adjustment needles dont go far enough.

 

[EagleTalons]

glad i helped... mine always bogs a little, but i try to be fuel efficient to by not opening that screw up too much. nothing bad will happen except more carbon build up over time and worse emissions. i just have to pay for my gas so i try to conserve... lol

@eagletalons...
10tooth clutch
60tooth rear
50in tire circumfrence
max rpm i ever hit was 5380
usuall i go 5100 about tho.

this gets me to hmm lets see... goes to speed calc...
5100rpm=40.24mph
5380rpm=42.45mph

BAMBY

Ah, I hit 42 mph on my doodle bug just the other day! On gravel on top of that! It was kinda scary going that fast that close to the ground.

 

[freakboy]

yeah any real amount of speed anywere close to the ground seems like its tripple the speed ur going.

 

[CoyCaller]

I took the kids out for a test run on their go kart. I ported it and sanded down the eyebrows. Solved the hesitation problem by speeding up the idle a little (idle is still slow enough not to actuate the clutch).

That little 3.5 briggs hauls two 40 lbs kids really well. It doesn't sit their and lug its guts out to get rolling now. It will even get me rolling. Amazing what a little modification will do.

Riding beside them, out in the grass on the four wheeler, I clocked them at 19mph governor speed. Too fast for a 5 and 8 yr old but we were in a mowed meadow, what could happen, right?:rolleyes3:

Anyway thanks for the tips guys!

As soon as i lay my hands on a 5 hp briggs, it's on. Daddy is building a kart from the motor up.

Has anybody seen the kart plans on http://www.spidercarts.com?

I like the Black Widow.

 

[EagleTalons]

Well...I fell off my minibike a few minutes ago on gravel. It did a burn out for some reason and fell sideways and drove with me on it for a few feet at about 10 miles an hour! Everyone is afraid of me going 40 mph but, its the start off that gets ya haha!

Bent my pull start too.

 

[CoyCaller]

Well...I fell off my minibike a few minutes ago on gravel. It did a burn out for some reason and fell sideways and drove with me on it for a few feet at about 10 miles an hour! Everyone is afraid of me going 40 mph but, its the start off that gets ya haha!

Bent my pull start too.

Try some training wheels.

Worked for my four year old. LOL

 

[BAMBY]

@coycaller
glad to hear you guys are all having a blast on the kart!
Black widow is kinda cool... i like th x frame thing goin on... whats with 2 wheels in each corner tho? so you can use cheap 3$ harbor freight wheels???

yeah couple months ago i welded footpegs (in addition to my front foot pegs) on my mini bike right over the back axle. easier to do wheelies... but my throttle is a brake lever from a bicycle... so not being experienced with wheelies when i got the front end up, i got scared and held on tighter therefore making me floor the throttle... needless to say i got tossed of the back like garbage and hit the pavement... big shower of sparks from the rear sprocket when the bike tipped over after i fell off.

PS @ eagle talons... that 42mph was on my minibike, so it wasnt too close (not like a kart) to the ground... going that fast is now natural to me...

 

[CoyCaller]

The dual tires are cool but probably not too practical.

The Black widow will probably be my next Kart.

Simple, Yet practical.

After that I want to build the Tarantula!

Suspension would be nice on any Kart.