Mudgy

Hi All,

Been a while since I visited here.
I have a mate's boat in my garage today, he says it hasn't been run for a year. I don't think he drained the fuel (bad man!)
It is a fibreglass Enforcer hull with a Zenoah (260 I think - not too sure, as I prefer nitros)
I noticed the choke was still on by a small amount, and since I have made a new choke lever from an old servo horn (now I can turn the damn thing on and off)
I fired it up, tuned the high needle like a chainsaw (lean - peak revs, then richened off a bit to drop the peak revs down a bit) about 1.5 - 1.75 turns out.
Carb is a Walbro.
I now have the idle speed up a bit, just to see where the low needle is best.
It seems good at 1 - 1.5 turns out.
However, after doing this, and settling the idle speed back down, the engine will run very well on a burst of power, but allowing it to come down to idle it revs lower than how I've set it.
Have I just made high end a little too rich?
or is the carb needing disassembly?
It's as though it floods a little when the butterfly drops to idle/closed (open by 1 or 2 mm still.)

fuel is new, plug is a good browny grey. Spark is fat.
I know it's a fuel issue, but I'm running out of ideas.

Anyone???

arrowshark

My Feedback: (1)

I WOULD RECOMMEND TAKING THE CARB OFF DISASEMBLE AND CLEAN MAKE SURE YOU DONT HAVE ANY AIR SUCKING BETWWEN CARB AND MANIFOLD CHECK YOUR FUEL LINES FOR LEAKS IT WOULD BE GOOD TO REPLACE THEM DUE TO THE AMOUNT OF TIME SITTING THERE RESET ALL SETTINGS TO SPEC AND RETEST.
THIS SHOULD BE A START AND GOOD LUCK MATE!!!!

dwr9

If the boat has been sitting that long and he didn't drain the fuel out, did you take the carb apart? If not, you should, to see what junk has accumulated in there. There is a screen that probably needs to be cleaned and the diaphragm may very well need replacing also. Personally the first thing I do is remove the choke and fill the holes from the choke shaft with silicone. Just hold your finger over the end of the carb and slowly pull it over a couple times til your finger has fuel on it and it should then start up easily in a couple pulls. Also you should remove the idle screw and throw it away. You need to be able to totally close the throttle and shut the engine down with the transmitter for safety reasons. Doug

Slow Motion

It's almost impossible to bench set a boat carb with no load on the eng, particularly the high needle. This must be done at the run site.

ken0276

My Feedback: (2)

Don't know that Carb you are running, you might check those settings if yours is one of these.

Stock Walbro WT-644 carb

High = 1 1/2 turns
Low = 1 1/2 turns

Stock Walbro WT-603 carb
High = 1 1/2 turns
Low = 1 5/8 turns

Walbro WT-488 big bore carb
High = 1 1/8 turns
Low = 1 1/2 turns

Walbro WT-257 big bore carb
High = 1 1/8 turns
Low = 2 turns

Walbro WT-813 big bore carb
High = 1 1/2 turns
Low = 1 1/2 turns

Mudgy

Thanks fellas, for your help... i will get the No of the carb toy you tomorrow...
As you said, the bench test is far different to the "real world" of a boat IN THE WATER

I have a 1/4 scale drag car powered by a Poulan 44cc chainsaw motor, and I find myself drawing parallels to the tuning of this.
The pipe on this is the size of a Baseball Bat-
I also have had numerous Nitro on and off road cars for the last 10 years.
I am also a fully qualified Auto Electrician, but gave the game away in 1994 to pursue a career in Industrial Automated Packaging Equipment...so you see, no dumb ass when it comes to technical challenges!

I just needed some feedback to be sure I was going in the right direction.

I will disassemble the carb (and get the number) tomorrow, and see if the screen is blocked with old fuel varnish,
and I will also check the needle and seat. Probably a dose of Clean-R-Carb or Contact Cleaner will help here.
The seals for the carb to Spacer to Engine are good. No air leaks will be present here. (Gaskets are all good, and all bolts are "torqued" up.)

thanks for the tips, gents!

Happy New Year to all!!!!!

Believe It

While you have the carb off... pull the isolator off the motor (are you using the stock one?) and put it on a flat surface (like glass table top). You'd be suprised how quick they warp... ive had brand NEW ones come in the package warped. This will cause a air leak...

Mudgy

All those bits seem good....is the idle meant to be low (like on cars), or a bit higher? It has a clutch, and when I had the idle high (to tune in the L needle), things seemed better.
I just don't want to swim "the Channel" in distance before it's tuned![sm=drowning.gif][sm=drowning.gif]