VA

My Feedback: (1)

Hey all
I have a DOA MDS .68 that will not start. When O inject some fuel into the carb via syringe it blips to life and dies. When I put the starter on the prop the fuel runs through the line, and no start. Should i ditch the carb?>?? Or is there an OS or other equivelent I can buy instead of a new engine that will bring this engine to life. I use it in my 60 stick. Went vertical with 7/8 throttle. I want to ressurect this engine that was dormint for 1 season and gummed up, was cleaned and still wont start. I am using 10% fuel and a hot glowplug fyi. Thanks for any help in advance.

VA

My Feedback: (1)

I mean is their a carb I can put on the engine that is still available that will fit.

mtwister

I'd be willing to bet that your low speed circuit is gummed up. Pull the low speed needle, blow fuel through it, and blow air through it. Reset the low speed, and I'm sure you'll be fine.

Flyboy Dave

My Feedback: (21)

Rather than taking the carb completely apart to clean it, take the high speed
needle out of the carb. Open then throttle wide open. Blow air or fuel, or both
through where the high speed needle went in. This should blow any lint or other
debris through the nozzle, and clear out the carb.

You can get a can of carb cleaner from the auto parts store to blast through the
carb if you don't have compressed air.

FBD.

Weekendflyer

My Feedback: (3)

I would still back the low end needle out and blow through it ,I just went through this and it didnt clear up until I had blowen out both needles

Flyboy Dave

My Feedback: (21)

Yes, I agree....open the low end needle two full turns....open the carb to full throttle, and
give a blast of the carb cleaner into the main needle hole. This will give plenty of opening
to clear out the nozzle in any case....

FBD.

speedster 1919

My Feedback: (3)

Keep in mind your MDS doesn't like nitro and 10% would be MAX and it is proven the FOX RC LONG idle bar plug is the perfect plug. You had it running last season so you probably know this. Did you put new fuel line on. Fuel line degrade over time and develope pin holes and tears were they bend at tank nipple. I now replace tubing after winter storage because too many times this was a problem on first start up.

tukkus

My Feedback: (2)

my MDS .68 ran like crud with the stock plug and 15% nitro....i then read up on it in here and tried what most recommended which was low nitro(in my case i used 5%) and a Fox idle plug, then the engine came to life

speedster 1919

My Feedback: (3)

DAM It's purely amazing what an old FOX RCLONG can do at $2.35 a copy and almost everybody else wants to throw $6-$9 OS and ENYA plugs at engines............IT proves not all engines are NITRO HOGS................

Hobbsy

My Feedback: (102)

Almost any two stroke will run fine on the Fox idle bar plug.

NM2K

My Feedback: (14)

If you can find one that isn't DOA in the pack.


Ed Cregger

buzzingb

My Feedback: (2)

Dried castor can accumulate in the needle valve area over time especially if the engine isn't used very much. I had this happen just recently and I blowedfuel throught it but it didn't come out I resorted to cleaning phisically but I didn't have any carb or other such solvent on hand. I can say that several blast of glow fuel didn't clean it out as I had the carb off the engine and could actually see the blockage under a bright light. Now If I had soaked the carb in glow fuel or methanol for a period of time it might have disolved it but I didn't take that much time and tried to blow it out with fuel with no luck. Trash and other material can get lodged in these little carbs too. The carb is so simple and has so few parts why not just take it apart and give it a good cleaning and inspecting? Once (last year) I had a Thunder Tiger 42 that had a shard of aluminum in the needle valve area that was a result of the jett being pressed into the carb housing. The jett base scrapped a small piece of aluminum off and it was trapped in the needle area. The engine would run normally most of the time but on occasion when the aluminum flake vibrated into a position to block some of the fuel flow problem. It would start running lean and make me think the needle needed richening up or there was a tank or fule line issue, go figure. Now, no amount of blowing or carb cleaner would have resolved this. Good Luck and happy flying.

Hobbsy

My Feedback: (102)

I never had that happen

Flyboy Dave

My Feedback: (21)

The only problem I ever had with idle bar plugs was getting the engine to idle with them.
Although the engine will run fine at speed with them, the idle will suffer when you block
the fire from the fuel by putting a barrier in front of the glow element.

I had this proven to me 20 years ago.

FBD.

RaceCity

FBD...are you trying to start a fight? <GGGGG>

Idle bar plugs were designed with baffle piston/loop scavenged engines in mind, and "blocking the fire from the fuel" was the whole idea.

(For the un-initiated, a baffle piston motor shoots raw fuel directly at the plug....hence the idle bar plug)

Fox plugs are fine...for some engines. I've never seen a problem with one in 30+ years. It works in your engine, or it doesn't.

FWIW....I've stood right alongside Katrina (the girl who makes Fox plugs) and watched her make them. They're Individually hand made, and tested good when they go in the pack!

Despite what some might say....Fox puts customer satisfaction at the top of the list.

Here's a pic to prove it!!

Buy Fox!!

speedster 1919

My Feedback: (3)

Well ED I did have 2 new plugs last summer that ran fine for one flight and upon second use they lost their coil contact . I didn't bother to return at 2.35 a copy. And upon all the different sizes and brands I run I don't experience an RPM drop at Idle when igniter is removed.

Flyboy Dave

My Feedback: (21)

Race....idlebar plugs came about by Duke Fox in an attempt to keep his crummy
carbs from throwing droplets of fuel into the combustion chamber and drowning
the plug. They were not invented because of loop scavenged engines like the K&B's.

Loop scavenged engines with a decent carb run fine without idlebar plugs.

http://www.rcuniverse.com/forum/m_25...tm.htm#2544578

quote:

ORIGINAL: hobbsy

OK, why are you guys so biased against idlebar plug s. This ought to be interesting.

Hobbs....I never had any luck with the idle bars, even on the loop scavanged
K&B .61. When I started out, I surmised that the regular plug s were for non
carburetor engines, and the idle bars were for the r/c carbs with throttles.

One day I was working with a fussy engine, and a friend advised me to use a non
idle bar plug . He said "why block the fire from the fuel with a chunk of metal"?
It made sense to me, and it worked like a charm. Then I tried regular plug s in other
engines....same story, they ran.... and especially idled better.

I chucked the few idlebar plug s I had, and never used one again.

FBD.

quote:

ORIGINAL: gcb

FBD,

When the idle-bar plug s became available they really helped...but carbs were
very primative by today's standards.

George

That was my understanding too, George....that the idle bars kept the coil
from getting doused with excess fuel/oil, and to keep from putting the fire out.
I guess I never had an engine that slung droplets at the plug .

Fast forward 25 years or so....a couple years ago I put this OS .61 RF
pattern motor into the old Super Kaos. (the third engine in the plane, four now,
that one chucked the liner) The engine had been bench run only. It has the
7L carb. The engine would start up and run great, but on landing the engine
would die out....wouldn't hold an idle.

From the time I chopped the throttle on the downwind landing leg, to the time
the plane touched down was about 20 seconds. Then it would die. I played
with the carb for months....adjusted it back and forth dozens of times. Same
story, it would start instantly, and run perfectly....but die on landing. I was tired
of having to walk out and get the plane all the time....and I'm the field "tuner".

Finally I decided to try a new Miracle Plug (one of my favorites) to see if that
would help....I had seen them do miracles before ! I pulled the old plug out, and
KABOOM....there was the problem right in front of my eyes. Somehow it got
passed me....a darned idle bar plug . I stood up and threw it as far as I could
out into the the desert.

Needless to say, I put a regular plug in it, and the problem was cured, and ended
a few months of frustration.

FBD.

I don't think there is a variance in the heat range of idle bar plug s, Hobbs.

It's interesting to note that OS Engines does'nt appear to offer an idle bar
plug ....I wonder why that is ?

Dave.

Check plug s&FVPROFIL=++&search3=Go">this out.

It looks like Fox is still the only one to produce idle bar plug s, a throwback
to the early days of r/c. Fox probably had the worst carbs as well, and
needed the "droplet blocker" plug s.

Edit: Oops....J&Z makes one.

Dave.

Sport_Pilot

Fox didn't invent them. I think Champion invented them. K&B has their own idle bar plugs, you needed them on at least some of their baffled engines not the loop scavenged ones. I think MDS is the only looped scavanged engines that need them. I had to use idle bar plugs on my first R/C engine a baffled Supertigre Blue Head .60. That engine had a fine carb. As did many Fox's especially the MK series carb, almost a copy of a Supertigre carb with crude needles. My Fox .50 runs great with an OS #8 plug and 5% fuel.

Sport_Pilot

Her is the K&B line of glow plugs. Notice the two idle bar plugs in the line.

http://www.mecoa.com/acc/glowplug/glowplug.htm