how to tell if engine is running lean?

[bigJake]

I see lots of warning in posts that running lean will destroy the engine. Is there an easy way to tell if the engine is lean, gray/white sparkplugs?

 

[Dr Honda]

Yep... if things seem like they are running good... just pull the spark plugs, and they will give you a general idea of the health of the engine. With a 2-stroke... and if I'm doing the tuning... I like to run it just a little rich. (dark plugs) It helps cool the piston crowns. BUT... on a 2-stroke... overly rich is bad too. If you have a lot of extra fuel leaving the combustion chamber... you will overheat the piston crown at the exhaust port... and you will load the rings, and head with carbon.

On a 2-stroke... I like to see plugs that range from a dark brown, to a light black. (but no gloss)

ALSO.... since most of the seadoo engines just use O-rings for the head gaskets... you can pop off the head, and look at the piston wash. Other groups talk a lot about piston wash... but for some reason... we don't. Here's a pic I've posted int he past.

When you read piston wash... you are are looking for the clean crowns. Basically... the cool, wet incoming fuel keeps the edges clean, at the intake ports. The picture above is exaggerated... but it gives you an idea. My personal preference would be a light clean spot at each of the ports... and extend in about 15% past the edge of the piston.

 

[bigJake]

On a 2-stroke... I like to see plugs that range from a dark brown, to a light black. (but no gloss)
.

Thanks Doc, can you clarify "no gloss"? My plugs are always wet/oily. Do you mean wipe the wet stuff off and the dried deposits on the electrode should not be glossy?

you got me curious now, if its that easy to pull the head off (no gasket to replace). I'll do that next time up to the lake (heading home in a couple hrs)

 

[Dr Honda]

If they are glossy... either the plugs are....

1) Too cool for the engien
2) Too much oil
3) Way too rich
4) low compression

OR...

5) You ride your ski like an old woman, and you aren't burning them clean. :rofl:


after I get a shower... I go pull a plug out of my ski and post a pic. You read them after pulling them out. Don't wipe them.

Last thing... if the plugs are old... don't try to read them. If you want to "Read a Plug"... then put in a new set... go ride for an hour or so... and check them. You can target an RPM range... but you need new plugs... hold the throttle at the RPM (this is in the water) then chop the ignition without releasing the throttle. But if you need that kind of tuning... then a wide band O2 system is what you want to use.

 

[bigJake]

If they are glossy... either the plugs are....

1) Too cool for the engien
2) Too much oil
3) Way too rich
4) low compression

OR...

5) You ride your ski like an old woman, and you aren't burning them clean. :rofl:


after I get a shower... I go pull a plug out of my ski and post a pic. You read them after pulling them out. Don't wipe them.

Last thing... if the plugs are old... don't try to read them. If you want to "Read a Plug"... then put in a new set... go ride for an hour or so... and check them. You can target an RPM range... but you need new plugs... hold the throttle at the RPM (this is in the water) then chop the ignition without releasing the throttle. But if you need that kind of tuning... then a wide band O2 system is what you want to use.

well i sure don't ride like an old woman. I GOT A NEED FOR SPEED, YEEH HAH!
but i do have that other variable that you guys are going to yell at me for -
when I first bought the ski and converted to amsoil, cause that's what my marina sells. i bought amsoil injector instead of interceptor. Injector is supposedly rated for both tcw-3 and api-tc but it is ashless, i drained it out and now use interceptor, but don't want to wast $80 worth of oil so mix in a little trying to use up the 2 gallons i have. so i'm sure that is causing me to run a little dirty. yes, the amsoil tech assured me the two were compatible to mix.

I know you guys are going to say what is $80 vs a $1000 (actually X2) engine. But I thought if I just cleaned my raves pretty often I'd be ok.

but that wouldn't explain why they are always so wet.

 

[Dr Honda]

The Amsoil Interceptor is fine. The snowmobile guys use it... and that's the real test since they are pushing power-valve engines as hard as us... but they are doing it sucking in cold air. (Hard on the engine)


OK... I changed my Tempo hoses, and cleaned the carbs a couple weeks ago... and these plugs have about 3 tanks of fuel on them. I would say they are dam near perfect for my liking. The PTO plug (the one on the right) will almost always be lighter since the crank twists on the 800 engines, and you get a degree more timing in the rear jug. After looking at these... I opened the high needle about an 1/8th of a turn to richen up the PTO. (so PTO 1/8 turn: MAG 0 Turns)

you can see that the base (metal) part of the plug is wet from oil... but the electrodes and ceramic are dry (ish)

 

[stevexp2]

But if you need that kind of tuning... then a wide band O2 system is what you want to use.

WHAT?? On a 2 stroke?

 

[Dr Honda]

WHAT?? On a 2 stroke?

Yes. We do it all the time for race engines. The o2 sensor doesn't live long... but if you need to be tuned on the ragged edge... then it's worth the $60.

Generally, it's not worth it for a recreational PWC since the OEM jetting is good, and the cost for the sensor, and welding a bung into the pipe isn't worth it.

 

[stevexp2]

OK, that was a new one on me. We have always used an egt for tuning because of the issues of O2 sensor accuracy in an oil burning 2 stroke, the 2 strokes scavenging characteristics and the fact that almost no-one has ever implemented closed loop injection on a 2 stroke (Ski or Sno).

I'm never too old to learn.