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Engine Idle Speed

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smock View Drop Down
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    Posted: Apr/01/2009 at 3:36am
21.4.9 Carburetor
(B) Idle Speed
Any idle speed adjustment, Briggs & Stratton recommends 1750 +/- 100 RPM.

Does anyone know if the wording on this rule means you can change idle speed to whatever you want, or does idle have to be set to 1750 +/- 100 RPM?  From what I gather we can set idle to whatever we would like, I just want to be sure we don't show up to tech and get hosed.

Thanks!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CLReedy21 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/01/2009 at 5:37am
In the past they have suggested that the idle be set there, but it is not enforced as a rule.
 
Just keep in mind that particular idle range is best for the engine, they have a tendency to bog any lower than ~1600, and any higher and you're just burning extra fuel.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote adrive7 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/01/2009 at 8:05am
Idle speed can be whatever you want. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote smock Quote  Post ReplyReply Direct Link To This Post Posted: Apr/01/2009 at 1:14pm
Cool thanks.  Reason for me asking was because we are running a manual tranny w/ an autoclutch this year and we need to find a good idle for where the autoclutch disengages. 
Andrew Smock
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Post Options Post Options   Thanks (0) Thanks(0)   Quote squirrel Quote  Post ReplyReply Direct Link To This Post Posted: Apr/01/2009 at 2:27pm
What kind of auto clutch are you running?  We have tried to run them in the past with not much success.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote smock Quote  Post ReplyReply Direct Link To This Post Posted: Apr/01/2009 at 3:39pm
It's a Suzuki tranny from a quad.  We scrapped the engine half and made a custom input shaft.  5-speed sequential shift w/ reverse.  3 gear selects (hi/lo/superlo).  It has a centrifugal mated with the sequential clutch pack.  We're gonna run it for the first time this weekend - we'll see what happens...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote smock Quote  Post ReplyReply Direct Link To This Post Posted: Apr/01/2009 at 6:05pm
What kind of setup did you run? I think I remember one of your teammates saying you guys ran a Honda 250 tranny these past few years?
Andrew Smock
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Post Options Post Options   Thanks (0) Thanks(0)   Quote delandor Quote  Post ReplyReply Direct Link To This Post Posted: Apr/01/2009 at 8:52pm
Originally posted by squirrel squirrel wrote:

What kind of auto clutch are you running?  We have tried to run them in the past with not much success.


Out of curiosity, what auto clutches have you tried?

We are also running a manual transmission this year. We have a pretty high quality centrifugal kart clutch to go with the setup.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote squirrel Quote  Post ReplyReply Direct Link To This Post Posted: Apr/01/2009 at 11:16pm

Smock

Our current transmission of choice is a Honda CRF 230f. It’s a nice small 6 speed with a good overall spread.

 

Delander

As far as auto clutches go, most recently a revlock which is made for dirt bikes. No matter what we did the thing would slip badly.  I believe Georgia tech ran one last year, he said took some tuning but they got it to work. After talking to them I believe our unit was too small to push our heavier then a dirt bike baja. Did not pursue any further due to the complexity of adding a bigger clutch basket to our transmission.

 

A couple of years ago our team tried to run a tranny with a centrifugal already in it. Something similar to what smock has described. It worked but it never fully put all the power to the ground. 

 

I have looked into a Red Hawk racing go cart clutch just decided I like having a manual clutch.

 

Have you tried the go-cart clutch yet? If so how well does it work?

 

Smock let us know how your trans works out. 

 

 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote smock Quote  Post ReplyReply Direct Link To This Post Posted: Apr/02/2009 at 12:07am
Do you all run any reduction from the engine to the tranny?

We're gonna fire her up on Saturday and run it through the gears, I'll letchya all know what happens.
Andrew Smock
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Post Options Post Options   Thanks (0) Thanks(0)   Quote delandor Quote  Post ReplyReply Direct Link To This Post Posted: Apr/02/2009 at 12:03pm
Squirrel:
We haven't gotten to run our setup yet. We have our drivetrain all together including a 3D printed prototype of our custom case, but we're waiting to get the actual case from CNC and money for shocks, wheels, and brakes.

Smock:
We are running a mild reduction from engine to transmission.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote smock Quote  Post ReplyReply Direct Link To This Post Posted: Apr/02/2009 at 12:37pm
Cool, you guys gonna be at Wisconsin?
Andrew Smock
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Post Options Post Options   Thanks (0) Thanks(0)   Quote delandor Quote  Post ReplyReply Direct Link To This Post Posted: Apr/02/2009 at 5:10pm
Yessir!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote squirrel Quote  Post ReplyReply Direct Link To This Post Posted: Apr/02/2009 at 10:33pm
In the past we used a gates belt setup but now its direct drive.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote delandor Quote  Post ReplyReply Direct Link To This Post Posted: Apr/25/2009 at 1:06am
How is the USF car running with IRS? I know you guys were at Auburn last weekend.

(and smock, are you guys driving yet? How is the drivetrain working out?)

We finally got our case from CNC this week, and will hopefully be testing the drivetrain and shifter with no load tomorrow. First drive 1-2 weeks away. Our team leader is very paranoid about us posting pics, but I might be able to put up a few pretty soon.


Edited by delandor - Apr/25/2009 at 1:07am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote karman1970 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/25/2009 at 2:30am
Go with a multi-plate wet clutch if possible. I've seen a centrifugal like the RevLock for Harleys. Automatic engagement, but retains the ability to disengage with the clutch cable. If I ever built another one, I'd look at that.

We ran a Redhawk last year. It worked, but you can't drive it fast. The friction discs wear fast, too. The factory centrifugal/multi-plate semi-autos work great, but are large and heavy.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote smock Quote  Post ReplyReply Direct Link To This Post Posted: Apr/25/2009 at 2:41am
we've been up and runnin for about 3 weeks now.  did our first official dirt testing last weekend with decent success.  didn't romp on it too hard, just put it through the motions and let everyone take a turn.

tomorrow morning and sunday we head out for round 2 of dirt testing. 

so far so good with the tranny.  i dig having manual control along with the autoclutch.  we ended up gearing down a little lower (from the briggs to tranny) so we could actually get use out of 4th and 5th.  downshifting is working out pretty well for kicking the ass loose around tight turns.  none of our cars in the past have been capable of oversteer, so this year has been a pretty cool crowdpleaser.

we ended up setting idle at 1650 which is working out well for us right now.  we have a 1.5:1 gear ratio going from the engine to the tranny.  at idle we are just low enough to let the centrifugal clutch slip to keep the car from stalling.

i'll throw up some video either tomorrow night or sunday after more testing is done.
Andrew Smock
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Post Options Post Options   Thanks (0) Thanks(0)   Quote smock Quote  Post ReplyReply Direct Link To This Post Posted: Apr/28/2009 at 1:24pm
So we decided to hit an off-camber jump for the hell of it.  Landed on the front left wheel with no post-damage.  Drivetrain is working out really well for us!




Edited by smock - Apr/28/2009 at 1:25pm
Andrew Smock
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