Reading plugs on 2 stroke

gizmoe107 · 10-25-2009, 10:53 PM

How do you read the plugs on a 2 stroke? I have a recently rebuilt (pistons, rings, rebored cylinders) 94 Montego with a 640 engine. The mag side plug is dry and the pto side is wet. Which one is right? With a single carb how can they be different? Compression is still good (130 - 140 psi), but ski is bogging and won't take the throttle. Any ideas?

dank · 10-25-2009, 11:30 PM

If you have a single carb and it is clean and set to the same settings as it once ran well with then the carb may not be the problem. Could be a broke reed pedal from being hydro locked or a bad spark plug, plug boot or coil?

Carb Tuning

engr146 · 10-26-2009, 07:34 PM

http://www.vintagesleds.com/library/manuals/misc/Two-stroke%20Tuner's%20Handbook.pdf

2 stroke Handbook Guide

gizmoe107 · 10-26-2009, 11:50 PM

engr146 - thanks for the great reference document. A great discussion on the theories of tuning 2 strokes. Being an engineer myself I can appreciate this kind of detail.

dank - engine was running well before it started losing power. Ignition appears to be ok, but will try new plugs. Reeds are ok as well. I assume the plugs should be dry, not wet. Could it be a vacuum leak? I'll be pressure testing soon.

Thanks.

PrickofMisery · 10-26-2009, 11:54 PM

The plugs should be dry and a nice even toasty brown color.

However to get a correct reading the motor must be operated under load and at high RPM then shut down. Reading plugs after running on the hose or idling in th driveway is not a accurate indication. With that being said in any case one should not be dry and the other wet.

EDIT- Not the best chart but you get the idea

PrickofMisery · 10-27-2009, 12:11 AM

http://images.google.com/imgres?imgu...%3Den%26sa%3DG

Krispy · 10-27-2009, 01:40 PM

Quote:

Originally Posted by engr146

http://www.vintagesleds.com/library/...20Handbook.pdf

2 stroke Handbook Guide

Great bit of reading! Thanks!

lownrangr · 10-27-2009, 02:30 PM

Yeah, good illustrations.

I winterized my 1100R yesterday and i checked the plugs and damn, they are abso-freakin-lutely perfect. I love my motor.

engr146 · 10-27-2009, 04:24 PM

THX ,for sample sheet,I'am a power plant engineer,I can rebuild a steam turbine,But I have a long way to go understanding 2 cycle engines and troubleshooting them,I have learned so much from this forum.and learn more everyday!!

Quote:

Originally Posted by gizmoe107

engr146 - thanks for the great reference document. A great discussion on the theories of tuning 2 strokes. Being an engineer myself I can appreciate this kind of detail.

dank - engine was running well before it started losing power. Ignition appears to be ok, but will try new plugs. Reeds are ok as well. I assume the plugs should be dry, not wet. Could it be a vacuum leak? I'll be pressure testing soon.

Thanks.