I have a 30 zenoah clone in a mono last time I took it to the lake was running good but now I get 2 or 3 laps and the engine stalls, when I try starting it kicks over first pull but again it stalls after a couple of laps. I have tried adjusting the carb in small incriments but no luck, the carb is a 257. Any suggestions would be much appreciated.

It sounds to me like you're running out of gas. Is your tank properly vented? Are you running a clunk in a hard tank or are you using a gas bag? Is your engine properly cooled?

I'm thinking basically what Steve is. If you're using an IV bag it may have hardened and won't collapse allowing it to run lean until it quits.

I'm using an iv bag, I made sure it was full the weather was pretty warm 38 C. When I checked the spark plug it was a dark brown colour, and dry is that running too lean? Sometimes the revs would go up and down before stalling. I will change the bag and check the cabi for dirt. Thanks for your imput guys.

Trying to upload a video doesn't seem to be working

Are you burping the bag? Making sure all the air is getting out before you run? You might want to change the carb diaphragm also.

With a dark brown plug ( good ) and 38C air temp, I'm thinking fresh/cool air restriction, or possible water cooling problems.
A 257 will usually do well on 2 1/4 to 2 1/2 low needle and 7/8 to 1 high needle. Run your hull with no hatch to give it plenty of fresh air for a test, and make sure your water is going into the cooling cap low, and exiting high ( to eliminate trapped air pockets ), with strong flow. Another thing to look at is your iso block/intake manifold. They can get hot and warp slightly causing an air leak and eratic RPM. Too long mounting bolts can cause air leaks as well. Sometimes they can be removed and flat sanded, but they are known for being "iffy". It's the reason a lot of guys use aftermarket aluminum manifolds. Oversize prop loads can be a problem at temps like that, so make sure the eng. can rev freely.

Thanks for your feedback hot rod some things I will consider my main consern was running too lean and cooking the bearings and engine I have some footage but it doesn't seem to be up loading to this site

It's fairly easy to upload videos here. Usually hit the Reply To Topic button then click on the film strip in the toolbar next to the eBay logo then copy and paste a link from You Tube, Vimeo, etc.

If you have already had it uploaded to any of those why wouldn't you just post the link right in the text ?

You tube,


or Vimeo,
vimeo.com/15305700

Upload it to one of those and just copy and paste the link provided.