lamarkeiko

My Feedback: (1)

This engine is my first gas engine experience, so I don't know if I have an engine problem or just set up and tuning needed.
This engine is new, and has been ran on a stand for about 15 minutes, and ran on the plane for about 45 minutes. The engine has started easily and seems to run fine with good acceleration. The only problem is I cannot get the idle down. With the throttle all the way to the stop, the engine still has a good pull on my 4 Star 120. I don't think it could get airborn, but it would taxi very fast.
Here is what I have for setup.

The idle stop screw has been removed.
The throttle return spring has been unhooked and inactivated.
I'm using an APC 16x8 prop.
Using high octane noethonal fuel with 32-1 mix Still HP Ultra oil per VVRC recommendations.
I have not touched the original settings of the high and low speed needles.
I've checked my throttle servo to make sure it is closing the throttle enough, and it is hitting the stop causing a slight bow in throttle linkage.

I do not know how Walbro carburetors work, but I was expecting to see the engine to quit like a glow engine when at that point.
Would appreciate any help and advice on the matter.
Thanks
Lamar

ahicks

My Feedback: (2)

You can always get an engine to slow by making it richer. That would be my first bet on a new engine.

That said, there's a slight possibility the brass throttle disc may be loose or not centered properly in the carb bore, making it impossible for the carb to close as designed. An intake leak (carb gasket, cracked carb adapter, etc.) could also do what you describe.

Truckracer

My Feedback: (19)

As ahicks suggested, my first suspect would also be the throttle plate. You will have to remove the carb to inspect this and when closed the throttle plate should seal well in the carb bore. Every gas engine I have owned could be killed by closing the throttle completely so closing it enough to achieve a slow idle should not be a problem. If you have to adjust the plate, loosen the retaining screw just enough so the plate can be adjusted ... maybe 1/8 or 1/4 turn. If you go any further, you risk damaging the throttle shaft as the threads on the screw are swaged. After tightening the screw, you can put a tiny dot of green LocTite on the threads if desired.

From there, the only reason for an engine not slowing down enough is an air leak. Make sure all the bolts are tight on the engine and when you inspect the carb, also inspect all the gaskets and the reed assembly. In rare cases, I have heard of a cracked reed housing causing problems such as this.

lamarkeiko

My Feedback: (1)

Before I remove the engine from the plane and remove the carb, should I run it again and try adjusting the high & low speed needles first?

Truckracer

My Feedback: (19)

Yes, that would be a good idea.

kmeyers

Not only should you adjust it but you should close the needles all the way and write down the current settings and report them in this thread. All this is info that will farther problem solving.
once you retune close the needles again and report those settings. Don't be afraid to become more familiar with your engine and the tuning process.

Gizmo-RCU

My Feedback: (27)

About three gallons in and mine developed a loose head as the 4 bolts holding it to the case became loose. Caused constant changing of the carb settings. Tightened it up and all good. These are great little engines and the service is also great, they will help (VVRC) if asked! I use a Xoar 17x6 and exactly the same fuel!

lamarkeiko

My Feedback: (1)

Thanks for the replies back. I'll run it again and try adjusting. I read through my VVRC warranty, and the engine is covered for 2 years. It does say that any dissembly of the engine would void the warranty, so if I can't get it running properly after adjusting the needles, I'll send it back to VVRC. I believe I read that they have good customer support.

Lamar

ahicks

My Feedback: (2)

Lamar, it's your call, but removing the carb for cleaning/inspection is generally not frowned on by an engine manf./dealer - as long as you feel comfortable doing something like that. If I were the tech taking your call at VV, you'd darn sure be safe with me! Very often a quick inspection like that can take care of a problem, saving me the shipping to/from, the hassle of handling the returned engine, and the required paper work...... -Al

Gizmo-RCU

My Feedback: (27)

Do it right , you are only a phone call away and you may be given some good suggestions!

lamarkeiko

My Feedback: (1)

I have an update on my engine idle problem.

I contacted VVRC, and explaned my problem, and they gave me permission to remove the carb for a better look without voiding the warranty. I proceeded to remove the engine from the plane, and once removed, I could see what was causing the problem. I had installed a ball link on my engine throttle arm and the threaded 2-56 shaft of the ball link extended below the nut enough to just barely make contact with the rear of the engine to prevent the throttle arm from closing all the way. I filed about 1/64" off end of threaded shaft to get the clearance I needed. I reinstalled my engine and ran it yesterday, and the high idle problem is gone. Now I just have to get the engine tuned properly.

Lamar

Gizmo-RCU

My Feedback: (27)

Good deal, glad things worked out! After it runs a while it will require a little refined tuning as it loosens up, they all do.

kmeyers

"I've checked my throttle servo to make sure it is closing the throttle enough, and it is hitting the stop causing a slight bow in throttle linkage."

Glad you found it, this is one of those Oops moments.