rstearman

My Feedback: (185)

Just picked up a used RCS 140 (22cc) Gasoline Engine that I ran for the first time today on a test stand .

The engine ran great but I can not kill the engine with the throttle. the lowest it will go is a fast idle.

Here are something I tried:

Tried riching up the low needle but then it just ran too rich
Pulled the carb and checked the butterfly to see if it was shutting all the way, and it is, No day light showing through it when it's closed
Tried a bigger prop and it still no luck, it just ran better.
The intake gasket looks very good, pretty sure it's not a vacuum leak. Sprayed carb cleaner around the intake and the engine did not change rpms.

I'm wondering if it has too large of carburetor on it. The carburetor on the engine is a Walbro WT225a 013.


Does any have any suggestions?

Thank you

captinjohn

Do not use carb cleaner to check for a vacume leak...if there is a leak,the carb cleaner will thin out the lube in your engine when its runing. Use WD 40 it at least has a lubricating effect! Capt,n

yak-54

Hi
do you see the big bolt open it all the way out you can remove it if you want
your engine will be just fine

ilan

rstearman

My Feedback: (185)

Thanks for the advice but I use an outboard engine cleaner that has lube and is safe for two stoke engines.

rstearman

My Feedback: (185)

HI Ilan

The carb doesn't have an idle screw and the arm on the throttle shaft has been removed.

ahicks

My Feedback: (2)

It's obvious that it's leaking air from somewhere, right? You just need to figure out where?

How used? Could it be sucking air through worn throttle shaft openings? Do you see fuel stains or excess mess by the front bearing? Base gasket?

Propane torch that's not lit can often get you pointed in the right direction as well?

MetallicaJunkie

thats a new one to me....how would you use a propane torn to find a leak/?

rangerfredbob

My Feedback: (13)

you let the engine suck in the propane of the unlit torch, just like the starting fluid/carb cleaner/WD 40 method without the liquid part

captinjohn

Some engines will speed up more if there is a leak...right when you spray the WD40. Maybe with propane too?

CK1

My Feedback: (60)

Way back in the mid to late seventies and into the early eighties in the auto repair buisness we used propane enrichment to diagnose various carb issues and vacuum leaks. It worked well but could be dangerous . I have seen a few distributor caps blow off from loading up with propane . Thank God for newer and safer technology .
Use WD 40 it is much safer than propane

ahicks

My Feedback: (2)

A running engine is going to disperse propane to the point it's not very dangerous at all. It's not something I would try for long in garage or enclosed area, but otherwise, I doubt you'll even smell it unless getting really carried away. How long is it going to take you to move that burner around all the suspicious areas found on a model engine? Seconds? a minute?

BTW, guess what you're using for a propellant in many spray cans? Propane. WD-40 used to use it, not sure if they still do or not.....

rstearman

My Feedback: (185)

I agree, it has to be a vacuum leak. I'll install some new intake gaskets this week and see if that solves the problem .

Thanks for all help guys,

Scota4570

Maybe the previous owner filed the butterfly?

Cyberwolf

My Feedback: (4)

A couple of ideas one is the throttle return spring still in place?

With the idle arm removed the butterfly shaft can get turned over.
Looking down thru the ventury with the choke open do you see screw heads or screw threads?

rstearman

My Feedback: (185)

Well I pulled the carb off and everything looks good, The head of the butterfly screw is facing the engine, and the butterfly shaft spin all the way around.

I decide to pull the carburetor adapter plate off and I think I found the leak. The carburetor adapter plate is made out if thin aluminium and if the carburetor mounting screws are over tighten it warps the plate creating a gap between the engine and adapter plate. I straightened out the plate last night and will give it a try later.

rstearman

My Feedback: (185)

Well that was it, a vacuum leak. Thanks ahicks for keeping me on track.

I started engine and it ran very rich at low idle. After adjusting the low end needle in an entire turn the engine now idles down to a nice slow idle.
As an extra bonus the engine also seems to have a little more top end .


While we're on the subject I have another question.

I went to the local small engine repair shop to buy a new intake gasket, but they where unable to find one with just the carburetor part number. They needed to
know what the carburetor came off of. e.g. chainsaw, leaf blower etc. so they could look it up in their parts book.

Does any one know of a common part number to use for an intake gasket for a Walbro wt-225?

Thanks again
Rick

Len Todd

You might try this Ebay store for a gasket. http://stores.ebay.com/RC-Laser-Cut-Gasket-CoThey have a lot of RC plane engine gaskets, ship quick and are not very expensive.

av8tor1977

My Feedback: (6)

I make almost all my gaskets out of cardboard stock, like the backs of notebook pads, etc. Harbor Freight sells a hole punch set that I have found invaluable for making the holes in the gaskets. Been doing it for 40 years...

AV8TOR

Truckracer

My Feedback: (19)

A carb gasket for a WT series carb is pretty much the same regardless of what it was used on. Yes there are a few variations. Any shop worth their salt should have dozens of them on a peg somewhere. Sounds like you got a parts guy that was less than knowledgeable! As others have said, you can easily make one. Fiber gasket material from the auto parts store is relatively cheap .... don't use cork as it compresses too much and simply won't work well. Yes, card stock will work well too.

Maybe if you go in with the carb and old gasket in hand they can match yours?

Len Todd

I am used to making my own car and truck sized gaskets out in the bush.It is the tiny holes right next to the edge of these RC toys' tiny gaskets that always gets me. To me, making these little buggers myself doesn't seem worth the effort. I tend to stock the frequently used expendable parts right on my own shelves. Getting replacement stock here is relatively cheap and quick, which I realize may not always be the case for everyone. Let's face it. I was a spoiled kid!