Finally some progress

[rgvkid]

Got it! Thanks I'll give it a try. Gonna try the carb cleaner tip, hopefully its just the gasket.

I just realized that the clutch on the 3.5 is the same shaft diameter as the 6.5 clone i have. I could just swap it but i want to get the 3.5 running and usable jsut in case i want to use it later on another project.

 

[shake this]

Keep me informed on what you find out on the 3.5, I might need it on my 5hp.

 

[rgvkid]

Dang! I couldn't figure out what was wrong with the 3.5 Briggs. I changed the fuel pump gasket again, changed the oil, which was really dirty, and still couldn't get it not to die down.
It would start up and sound fine but the revs would go up and down then after about 30 seconds it would die down. I'd have to wait a bit, or keep pulling till i got tired, for it to start up again. I finally got frustrated with it and took it off the kart and pulled out a 2.5 HP Harbor Freight motor i bought awhile ago. I degoved the 2.5 to use on a bicycle project but never got to it or started it after degoving it. So i was a lil worried if it would even start up.

The 2.5 has a 1/2 shaft so I took the clutch off the 3.5 Briggs and i used a piece of 5/8 16gauge tubing to sleeve over the 1/2in. shaft on the 2.5 so i could use the clutch. Sleeving the shaft worked great. I had to cut out a slot on the sleeve for the keyway on the clutch and i drilled a hole for the set screw. I'll have to take some pics when i pull it apart tomorrow.

It was a bit of extra work to use the 2.5 because i also had to drill new holes on the engine mount, its a different bolt pattern then the 3.5. I also mounted the 6.5 clone i have just to see how it looks and that thing is way to big for a 7 year old first time kart. I'll save it for her brothers Offroad Jumper that i want to build.

I'll try and post some video that i shot of the test run. I work at night so its not very clear and not much light. I'll shoot some more video in the day.

The 2.5 feels Great when in motion and it really picks up speed! Sucks on take off though, I don't think that clutch would last very long pushing someone over 150lbs at stop and go driving. Im gonna make an exhaust and do a filter mod later.

I wonder if the 3.5 is having problems because of the exhaust i made. I used the threaded end of the muffler and then sleeved and welded it into a 1in. pipe extension, then welded the other end of the 1in. pipe to the exhaust. So it flows out the engine, through the 5/8 threaded nipple, then into a 1in pipe then back into the 5/8 muffler. I wonder if the 1in pipe is acting as a chamber and making back pressure? Im gonna buy another muffler and screw it on directly to the engine, without the extension, and see if that makes a difference. If thats not the problem then i don't know what it is and hate to have to pay a lawn mower shop to tell me whats wrong with it.

Oh well, The 2.5 will do good for now. I'll try and shoot some more video tomorrow in the daylight. My knees are shot from working on the ground, as you can see in the video. Im gonna have to build a rack to work on the karts form now on.

 

[rgvkid]

The video doesn't do it justice. Its a blast once you get up to speed. My next build will have suspension to soften up knicking the corner of the speed bumps. It was hard to get it up to full speed because of the obstacles. I won't be able to take it to an open lot till the weekend

http://www.youtube.com/watch?v=NwbwZ_17OrI

 

[shake this]

I'll be working on mine this weekend. I'll post up any usefull information I might uncover that could be helpful to your 3.5

 

[rgvkid]

Thanks Shake. What are the symptoms that yours is having?

 

[shake this]

Starts fine, idles fine and even runs fine at times. However, for no reason at all it sometimes just dies as if you hit the kill switch. You can be going wide open throttle or just be getting back in the cart after starting it when it happens. It only does it when you give it gas. I’ve never had it die just from idling. I have a few ideas of what it could be. First is I tore the gasket from the carb to the tank and had to use a blank gasket kit and cut a new one out. It could be picking up trash from the tank or just dirt still in the carb. I think it’s the first two because I don’t have any problems staring it (other then chocking it a little) after it dies.

 

[rgvkid]

Sounds similar to what mine was doing. This is the tutorial I used to rebuild the carb. Most important is using the wire to clean inside the valve. Also, I don't remember if he did this on the video, I pop off the screened inlet and cleaned teh inside of it but be careful because the plastic tube is brittle and can crack easily. Another thing i would do before hand is get a new gas tank gasket and the fuel pump diaphragm/gasket. The Fuel pump diaohragm runs between $2-$7 depending where you get it so call ahead of time to your local lawnmower repair shops to shop around.

DO Not Get Carb Cleaner On the Fuel Pump Gasket! It corrodes the gasket instantly. I found that out the hard way and had to go get another gasket.

I hope we can figure out whats wrong with the engines.

 

[shake this]

Good information provided. I hope to come back after this weekend with some good info as well. It just sucks because the engine runs strong and then bam...dies for no reason. The only difference is, I'm not having the issues starting it back up like you.

 

[rgvkid]

Yah the start up issues baffles me, Almost like if its flooded and needs to get teh gas out.

I just read on a lawn mower forum about a similar issue. The engine would run for a bit then bog down and shut off. He put in some Mystery Marvels additive in the gas and it cured the problem. Im gonna try taht today since i have some of the stuff in the shop. I use it in my oil changes for my truck.

Walmart has Carb cleaner for about $1.50, cheapest around. Also they sell teh Mystery Marvel additive.

One more thing, if you have rust in the tank, you can dip it into a container full of Sulphuric Acid, leave it for about 15-20min and it will clean up the rust in the tank probably the paint also. Just be careful using it cause the fumes can be very dangerous to the lungs. YOu can buy the acid by the gallon from local pool supply. Works great.

 

[rgvkid]

Made some additions last night and did a few test runs before tear down. I replaced the stock exhaust and the new one sounds much better and will breathe alot better once i do an air filter mode.

I did have a problem with the engine shutting off whenever I make sharp right turns. It has to be a fuel problem but not sure how to fix it. I filled up the tank till it was full, but it would still shut down when make right turns. It might be the gas in the carb being shifted to one side but not really sure how this carb works, i have yet to take it apart. Any ideas on this?

I also extended the chain guard for safety.

My girlfriend and I work pretty late so I thought some Headlights would be cool since we would probably be hitting the parking lots closer to dusk. The Bike flag is always good.

 

[fowler]

would the shutting down problem not be the low oil shut off switch.
as in u turn corner and the oil sloshes away from the switch.

 

[anderkart]

Fowlers right, you'll probably find a single wire exiting the front of your engine that plugs into the kill switch harness. Just unplug that one wire and keep an eye on your oil level.

Here's what your low oil sensor looks like inside the engine:

 

[shake this]

Worked on mine all day long. I know what's wrong, just not how to fix it. It's not picking up fuel regularly. I can play with the throttle and when it starts to bog, spray a quick shot of starting fluid into the carb and it'll pick back up. If I don't give it a quick shot, it will stall out.

I'm thinking of just picking up a Harbor Freight clone and calling it good.

Your kart looks awesome rgvkid.

 

[newrider3]

Worked on mine all day long. I know what's wrong, just not how to fix it. It's not picking up fuel regularly. I can play with the throttle and when it starts to bog, spray a quick shot of starting fluid into the carb and it'll pick back up. If I don't give it a quick shot, it will stall out.

Briggs tank-style carb? Check to see that the plastic fuel pickup tubes are intact and not clogged. Also check the carb diaphragm.

 

[shake this]

Yes, its the tank style. The pickup tube is clean, replaced the gasket between the carb and the tank but not the diaphragm . Guess that's the last thing to try. I even removed the spong looking stuff in the tanking thinking it might be breaking up and clogging the carb but nope.

 

[Blazkowiez]

Picture.

 

[rgvkid]

Awesome, thanks guys for the pics. I'll remove the wire today.

Shake, i gave up on the 3.5 til i get this kart completed. I'll get back on it later and keep you posted of any changes.

Are you building the kart for yourself? How much do you weigh? The 6.5 from harbor freight will put out alot of power but is pretty bulky. The good thing is it has the same bolt pattern as my Briggs 3.5, not sure about the 5.5. Keep me posted on how yours is working out.

 

[shake this]

Im building it for my daughter who is turning 8 this month. I'm going to end up building a jack shaft for it because the 5hp now is even to much. I've got one last shot and the Briggs, I'm going to replace the diaphragm but if that doesn't fix the problem then I'll have no choice but to get the 6.5 for now. At least it will be up and running and we can drive it around until I can spend more time on the Briggs. I have another kart that I can stick the 6.5 on if I can get the the Briggs to run right.

It's so sad because its a great running little engine when it's getting gas but I can't have it stalling out every 5-10 minutes.

 

[rgvkid]

The oil Plug did the trick. Thanks guys.

Shake, I hear you on the Jack shaft. It was sketchy even on the 3.5 Briggs. Im even thinking of putting the adjustable stop on the 2.5. Its Quick, once it gets up to speed. For sure im finding a wide open parking lot for her first ride. Its sketchy riding that fast with your head so close to steel Truck bumpers.

The clutch has a 10 Tooth and the Rear has a 60 tooth, If that helps any. Im running it with a New #35 chain, which needs to be adjusted again after its 5th Test Run. I couldn't tell you exactly what i've topped it out at yet. But all my life I've ridden and built dirt bikes up to superbikes and this little Kart is a blast! I can't wait to get it out to an Open lot and really see what it can do. Im trying to get it to spin out in a complete 180 degrees, so far I've only been able to get it about 140-130 Degrees on Fairly smooth concrete. Not sure yet how it will react on asphalt but it feels Really stable.

So the 5.5 would have been plenty power for your 8yr. I put the 6.5 on just for looks, and it was way to big for her first engine. With a jack shaft you could get alot out of the 2.5 from harbor freight and the on sale price with 20% Coupon price is Great. Granted, I don't know how a 2.5 feels that hasn't been degoverned. But it wasn't difficult at all to degovern the engine. It also gave me a good chance to get to know the internals. I'll take apart my 3.5 if i have to, It'll give me a chance to get to familiar with these engines and trouble shooting.

Be careful not to get carb cleaner on the new Diaphragm. I had to buy 2 of them, The first one $6 Dang! Phone shopped for the second one, $2 just a mile down the road.