Need Information on Throttle/Clutch

[buddhabrat]

Hey guys. I just got a go-kart from a friend in trade for some computer work I did for his wife. It has a 3.5HP Briggs and Stratton Engine, and is built on an O'Reilly auto parts store frame. He said the clutch was bad, and it needs to have the throttle cable hooked up to the engine. It used to have a 5HP engine that came with it and was replaced with the 3.5HP engine (without switching the clutch). My question is...I have NEVER had a Kart, and have not the first clue as how I am going to approach this project. Any help/advice would be great. Thanks in advance.

[robertdjung]

Cool, you're in the right place.

Look at the throttle on the engine. There's either a bunch of linkage, or there's a direct connect. Got a camera? Take a bunch of photos and post them.

If the clutch is bad, maybe it burned up the shoes or something. Cheap enough -- just take it off and measure the output shaft on the engine. It's probably either 5/8 or ... i think 3/4. I forget off the top of my head.

With that info you can order a new one. Here's some more info about clutches (http://www.diygokarts.com/go-kart/clutch-centrifugal.html).

[buddhabrat]

Okay, got some more info:

It's a Briggs and Stratton Model 91212 3.5 HP engine. Looks like a direct connect throttle on the engine. Since it is a replacement engine, there is no where for me to attach the throttle cable. I'll post some pictures, maybe that will help. It will need a new clutch, any advice on what to buy there? The current configuration is: 15in tires, 10 teeth on current (bad) clutch), and 60 teeth on sprocket. Motor is rated at 3300RPM, did a calculation, and comes to roughly 24.5MPH with current setup. Which is fine, as I am rebuilding this for my two sons (10 and 11 yo's, speed is not a need here). I want to say shaft is 3/4", at least that what the spec's say for the engine. I need answers pretty fast, gonna strip it down for sanding/primer/paint tommorrow. Trying to complete for their "big" present from the fat reindeer driver.

http://img1.putfile.com/thumb/12/33619414455.jpg (http://www.putfile.com/pic.php?img=4164203)

http://img1.putfile.com/thumb/12/33619414478.jpg (http://www.putfile.com/pic.php?img=4164202)

http://img1.putfile.com/thumb/12/33619414489.jpg (http://www.putfile.com/pic.php?img=4164201)

http://img1.putfile.com/thumb/12/33619414391.jpg (http://www.putfile.com/pic.php?img=4164200)

[robertdjung]

OK, I've got good and bad news.

That engine is a little underpowered -- but it's really the carbuerator setup that is lacking on that model. See this page about go kart engines (http://www.diygokarts.com/engine/3-hp-briggs-engine.html). Basically, the carb doesn't have a high-speed setting, meaning the throttle response is really cruddy on that engine.

The good news is that you can buy a new engine for cheap. Here's one for 200, but I know you can get them cheaper at pep boys. http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_47829_47829

Anyway -- if you want to run that engine (and there's nothing wrong with doing it) then we can get you going. And the plus side is that your kids will have something more to look forward to -- a new engine!

So, to hook the throttle up --

part "A" is the butterfly. That regulates the air flow. Air flow regulates how much suction. Suction (through the carb) regulates how much gas flow. More open, the faster it runs.

part "B" needs to be torn off unless there's some way to hook your cable up to it. I doubt it --- it looks like that came off a tiller. A tiller engine doesn't have a throttle cable a lot of times -- you adjust it right there on the engine, which is what "B" looks like to me, the throttle. You need to get rid of that so that you can hook the cable up.

On another look -- i appears that "B" controls a choke. Can someone else look at this? If that's the choke, then you want it closed when trying to start the engine cold, and all the way open all other times. If that linkage just does the choke, then leave it. If it controls the throttle, you may need to mod it.

If you can, take some more pics of the carb, I think that the choke is integrated with the same handle as the throttle. They need to be indepenedent because your throttle cable needs a place to hook up.

OK, looking at "C" (pic 2) That's what currently controlling your throttle. That looks like something air flow operated. You want to disconnect that so that the thing "A" is controlled by the throttle cable.

Basically, you're really going to want a better engine. This one will work, it will just be slow.

[buddhabrat]

Well, as I said, slow is JUST fine. Don't need any trips to the emergency room, so slow is good. So, how would I go about hooking the throttle cable up to that? The problem I see is having feedback to the throttle pedal. Are there kits to hook the cable up to the carb? And if so, where would I start looking? Again, thanks for all the help.

[robertdjung]

Anyone else got some photos of their throttle setups?

I just checked my info and I can see that this definitely needs more pics. If you would be so kind, would you take more as you hook this whole thing up so we could use the for future questions?

Check: http://www.diygokarts.com/kart-plans/plans-brakethrottle.html

Figure 4 and 5 show the beginning of the throttle hook up. There's a rod that's connected to the pedal, but it could just as easily be a cable.

You need to put a return spring on the setup. I put one on the rod (fig 5) and one again on the engine, which is just for safety in case the throttle assembly broke.

Then you need to route the cable. I took mine and did something like what you see in the attached photo. That's a bad drawing of the cable coming up the back, and then there's a mount on my engine, and then that's the little cable coming out of the sheathe.

However, look at "D" and that's where this whole mess is connecting down probably to the governor, and then to that little throttle control box. If you can, use that linkage and hook in to the system somewhere. I'd dump the governor, because it's really going to kill the throttle response, and maybe even kill the engine when you floor it, i'm unsure.

Keep taking photos, we'll get this worked out!

[Burning Rubber]

my throttle cable setup is just the cable in a hole screwed in on the carburetor lever that operates the butterfly or whatever its called. But then again, i don't have a clutch. Anyway talking about the choke, would i need to use that always? or only on a cold start?

[buddhabrat]

Well, I plan on changing the clutch this weekend, and I'm going to start work on the throttle situation. I'll make sure and take photo's to document what I do, and what I needed to get it to work out. I'll post back with results.