weedy engine won't stay running

[builder bob]

I have a homelite sx135 bandit weed eater engine that i'm going to use for an r/c boat. it sometimes runs but only if I fiddle with the mix screws and then it'll only run a minut before it dies. I don't know which screw is which. it's a zama carb 'cause I haven't found a walbro yet. the engine has a new spark plug, makes a spark, has good compression, gets gas, and the muffler isn't plugged up. what is the specific function of the two screws (which is low end and which is the main mix)?

also how can I make the fuel line connecters on the carb a little bigger so the lines from the fuel bag stop leaking there?

 

[B man]

You need the muffler. its a two stroke. it works with the back pressure off the muffler

 

[landuse]

what is the specific function of the two screws (which is low end and which is the main mix)?

also how can I make the fuel line connecters on the carb a little bigger so the lines from the fuel bag stop leaking there?

The main jet is closest to the engine and the low end is next to it.

For the fuel lines, I would suggest getting the correct size lines and not mess with the carb connections. You are more likely to stuff them up. Fuel line should cost only a few cents/dollars ( a new carb would be a bit more than that)

 

[Doc Sprocket]

Most of the time I have come across crotchety/non-running weedies it is due to a bad fuel line. For some reason, they seem to use really cheap line and it only takes a couple years to degrade. If there are small cracks in the line, it will not draw the fuel reliably- pulling air bubbles will cause stalling.

 

[builder bob]

You need the muffler. its a two stroke. it works with the back pressure off the muffler

muffler is on

The main jet is closest to the engine and the low end is next to it.

For the fuel lines, I would suggest getting the correct size lines and not mess with the carb connections. You are more likely to stuff them up. Fuel line should cost only a few cents/dollars ( a new carb would be a bit more than that)

woops I had it backwards! the problem with getting lines that fit the carb is that I won't be able to attach them to the bag I think. i'll try and find some any way. what's a good starting point for the two screws?

Most of the time I have come across crotchety/non-running weedies it is due to a bad fuel line. For some reason, they seem to use really cheap line and it only takes a couple years to degrade. If there are small cracks in the line, it will not draw the fuel reliably- pulling air bubbles will cause stalling.

the fuel lines are new tygon tubing hooked to an IV bag set up for R/C use and I've made shur the carb is getting fuel by letting a little drip from the carb into a pan.

 

[builder bob]

got the engine running great! I found a thing about cleaning the carb that's on this engine and at the end of it it said to back both screws out 1 and 1/2 turns and start on full throttle. started first pull like that and I've tuned it a little better then that. i'm a little afraid to tune it with no load and very little cooling. I saw a few sparks coming out of the exhaust when running wide open. does that mean that it's going to fast and there's flame in the muffler? I know that I had the engine going faster than I've ever gotten a gas engine to go.

I also fixed the fuel leak with zip ties and aluminum foil so now my boat's all set!

edit: woops, drive system's all set

 

[Doc Sprocket]

I wanna see this boat!

 

[souperman000]

 

[landuse]

I saw a few sparks coming out of the exhaust when running wide open. does that mean that it's going to fast and there's flame in the muffler?

I also fixed the fuel leak with zip ties and aluminum foil so now my boat's all set!

The sparks just mean that you probably don't have a spark arrestor screen in your muffler

 

[builder bob]

The sparks just mean that you probably don't have a spark arrestor screen in your muffler

oh few, it was getting me worried. I want to make a tuned pipe for this engine so do I need to get some of that screen?

I'll get some pics soon. here's a thread of my progress: http://www.rcgroups.com/forums/showthread.php?t=1698383 all the real progress is at the end.

 

[landuse]

oh few, it was getting me worried. I want to make a tuned pipe for this engine so do I need to get some of that screen?

I'll get some pics soon. here's a thread of my progress: http://www.rcgroups.com/forums/showthread.php?t=1698383 all the progress is at the end.

With it being a 2 stroke, you are going to have to be careful with just slapping any old pipe on there hoping it will work. You are seriously going to have to do your maths and tune that pipe properly

 

[builder bob]

I've got some software for mufflers and tuned pipes. my problem is that I haven't found a program that can print the templates for the parts. I might also get this one: http://buildandclick.com/html/all_products.html

 

[builder bob]

pics

 

[Doc Sprocket]

Oh, COOL! Did you build the hull yourself? What's the projected top speed?

 

[builder bob]

yep, built the hull myself. I hope it'll do at least 40 mph. I still need a servo and remot before it can be driven. there's a few other parts that will make it faster but I don't have to have. probably will have the boat done by March 17!

 

[OzFab]

yep, built the hull myself.

With all those nice tools you have, that doesn't surprise me

 

[Doc Sprocket]

Looks good. Did you use pre-engineered plans, or did you develop the design yourself?

 

[builder bob]

With all those nice tools you have, that doesn't surprise me

thanks, my dad's a carpenter so I get to use all his awesome tools. still wish I could weld though.

Looks good. Did you use pre-engineered plans, or did you develop the design yourself?

found the plans online but they have some serious problems (such as nothing being the correct size).