[Ken E]

Heres one for you engine speacialist's. I have a GMS 47 that ran great in a tiger trainer. After I crashed the tiger trainer I bench ran the engine and it still ran good but it wouldn't stop unless I squeesed the fuel line.. So the big question is why won't it stop when the throttle is closed?? any suggestions will be greatly appreciated and will sure be tryed. Ken

[matthew cotton]

I think mabye its leaking and air is getting in feeding the engine.

[nony]

That is not an entirely bad thing, but it is probably sucking air in through the base of the carb, or through the front crankshaft seal

[4*60]

I thought they all did that. We've run into a few that are like that out of the box. I think some silicone was put in the front by the shaft in a couple of cases.

[Ken E]

Thanks guys, this is a cheap and well used engine so I don't want to spend any money on it, any ideas how to stop the front seal from sucking air other than replacing it with a new one. Ken

[nony]

Is it really a problem? If it is not, and the fuel line is accessible, just pinch it off as you did before... In my opinion, it is better to have that situation than have an engine that will not idle at all. You might try loading it up a bit more by putting a larger prop on...

[Wayne MIller]

Hi,

I had problems tuning and poor running of my GMS .47 and started a post (see below). Many people joined in and I think we found a solution. You may want to check it out, it may help in solving your problem.

If nothing else it makes good reading about a bunch of RC guys joining together to solve a common problem.

http://www.rcuniverse.com/forum/m_22...tm.htm#2290854

Hope it helps.

Fly4Fun,

Wayne MIller

[Ken E]

Holy makkeral Wayne, there sure was a lot of reasonable solutions there. I guess I'll have to take the carb off, try taking it apart and put a new o ring and try silicon or something to seal that front seal. but for now it will all have to wait cause it's -23 out there and I'm sure not a cold weather person----- thanks again. Ken

[Wayne MIller]

Hi Ken,

When sealing the carb or muffler joints, I use Permatex "ULTRA COPPER" RTV (room temperature vulcanization) gasket seal. It is good to 371C (700F).

I get mine at Princess Auto and it comes in a 80ml copper coloured tube (similar to a silicon glue tube). It seems to work well. I understand you can get this at almost any automotive store.

Typically, if the motor will not shut down when moving below low throttle, it is caused by an excessive air leak around the carb, or front bearing.

To test for air leaks in a motor, remove the muffler, put a fuel tube on the carb inlet nipple, open the throttle, block the carb throat with your thumb, and the exhaust port with your finger and then blow in the fuel tube. At this point the openings of the carb will be blocked and you will be forcing air into the motor through the fuel intake. NOTE: The tube should be long enough so you can look at the motor while blowing in the tube.

You will hear any air leakage if there is any. If you hear a leak, but can not find the leak, block the above openings as stated above and spray soapy water around the carburettor and front seal. This time when you blow into the tube you will see bubbles where the leak is.

If a small amount of air is leaking out the front propeller shaft bearing seal when air pressure is applied, this is OK, all front seals leak just a little bit.

Hope this helps. Let us know how you make out.

Fly4Fun,

Wayne

[Ken E]

Thanks for the tip Wayne, actually I have some of that Permatex ultra copper in my shop, so as soon as it warms up a little I'll definately give it a try. thanks again. Ken