Dallas
05-28-2005, 06:11 PM
I am very new to RC Boats and just got a 31" Prather witha K&B .21 Outboard and it runs perfect except at top speed. If I open the throttle all the way, it will run hard for about 3-4 seconds then it lets off and gets kinda weak and then it will die totally in another 2-3 seconds. Like its running out of fuel. I'm thinking it might be set too lean??? I'd like someonce expertise and if my assumption is correct, which way do i set/turn the fuel adjuster and where about should it be anyway?
Thanks,
Jay
cpiad
11-23-2006, 08:08 AM
I am very new to RC Boats and just got a 31" Prather witha K&B .21 Outboard and it runs perfect except at top speed. If I open the throttle all the way, it will run hard for about 3-4 seconds then it lets off and gets kinda weak and then it will die totally in another 2-3 seconds. Like its running out of fuel. I'm thinking it might be set too lean??? I'd like someonce expertise and if my assumption is correct, which way do i set/turn the fuel adjuster and where about should it be anyway?
Thanks,
Jay
Hi Jay ... Sounds like you are a bit lean ... items 1-6 are just some preliminaries ... a bit more than you asked for .. but I'm waiting for my turkey breast to hit 180 deg F ... you can skip to item 7 and it answers your question more directly ... good luck buddy. Let us know how you get on, please.
1- are you starting/running the outboard clockwise. Outboards (as you probably know) run opposite to their inboard brethren.
1a. Is it possible some water spray is getting into the carb intake? That'll stop it cold.
2 - Also, did you lap the piston into the cylinder? If not ... it will be pretty ight .. while not as tight as an OS .21 ... still tight enought to need some serious running in While some of the newer folk will tell you they run ok right out of the box, I always tear my engines apart brand new and lap the cylinder.
2a. Check your radio controls .. is the throttle responding well? Do you have enough opening at idle to keep the engine running without throttle up?
3 - You might also want to set up a little water line to the running pressure intake and bench run the boat a bit ... gives you a chance to throttle up and throttle down the engine and adjust the needle valve right at the bench.
4 - You might also want to get some carburator cleaner ... remove the needle and spray down the needle hole ...
5 - also .. make sure you are getting good fuel flow into the engine and you're not pulling air in from the connections or the tank(s).
5a. Check your fuel pick up to make sure it doesn't rock itself and starves the engine.
5b. Are you going through glow plugs? Take a look at it .. if its partially or fully burnt out ... the you may need to add another head gasket shim to lower the compression a bit until the engine runs in ... or go to higher nitro fuel.
6 - Are you using at least 20% nitro fuel? Some of the tighter engines just won't run with less % nitro .. they'll start .. but won't stay running ...
7. Start with about 2 1/2 turns from full close ... then see if it'll start for you ... best if you have a water line to the engine and don't race it out of water .. but adjust the needle till you get that nice solid engine sound .. some people call it four-cycling ... but you'll know the sound when you get it .. music to the ears ... then ... try and throttle up the engine a bit ... if it dies on throttle down ... then the engine is probably a little lean .. try opening up the needle valve 1/4 turn at a time ... then try again .. until it stays running on throttle down.
Should get better and better with each run ...