Anybody out there have any info on GMS engines, regarding reliability, power, etc? I am considering buying a GMS 1.20 for my next P-51 project and their price is right but I don't know much about these engines.

Thanx, Mark

The GMS 120 is not as highly tuned as some of the smaller GMS engines. Its a rather mild runner
Undoubtedly this has prompted your inquiry?

GMS 1.20 Aero
Ringed, Double Ball Bearing
$119.99 each
Save Buy 2 for just $199.98 $189.98 (94.99 ea)
with $10.00 off
That's Only $94.99 Each

This 141 engine is made by the same company and has a little more power?
http://www3.towerhobbies.com/cgi-bin...&I=LXFV80&P=ML

The GMS 1.20 2-stroke is the finest 1.20-sized glow engine on the market... at the $94.99 price point, anyway.

I've run some of GMS's smaller engines and I thought they were quite powerful and a great value. The 1.20 in particular has a bit of a reputation for being difficult to tune. If you're not very, very comfortable with breaking in and tuning 2-stroke engines, you might want to consider another choice. If you have some tuning experience, however, the GMS 1.20 is a bargain.

Can you be more specific about why they are difficult to tune? Is it setting the idle or hi speed adjustment? Or is it that the engine has unreliable performance? Please advise.

Thanx, Mark

If you buy a GMS 1.20, there's a better than even chance that it will run very rich in the mid range (1/4 to 3/4 throttle), especially in-flight, even if your low speed and high speed needles are adjusted correctly. It appears that at least some of these engines suffer a carb calibration problem in the mid range throttle zone.

We have one flying at our field. It has a Pitts style muffler fitted (this may or may not be contributing to the problem) and despite tuning it as lean as possible, we cannot get rid of the mid range richness. Running an OS type F plug helped make the engine a little more resilient against the stumbles and occasional flame-outs caused by this mid range richness.

The engine at least now provides reasonably reliable service, but its mid range richness would drive me insane if I owned it.

Would crimping the fuel line or using a smaller ID line, thus lowering total fuel flow; fix the midrange problems in engines with bad fuel metering carbs??

i have a well used gms 76 that is a great performer.
unlimited in most 60 size aerobats. BUT!

like big ed said. you better be ready for a long breakin period.
and the low end needle is very touchy.

once the engine seats in provided you break it in corectlly
it ll be fine. mine will idle all day and never misses.
low end is around 5/8 turn out

I find that you MUST lean the low end more than you would normally, using standard tuning proceedures, on the 1.20 GMS and then richen the high end up a bit more than you would normally.

This cures the mid range transition problems once the engine is broken in.