2 cycle engine issue

[CAP1]

i already stated i had no 2 stroke experience.

 i asked a simple question. answer it, or don't type.

[icepac]

When the electrode is near hot enough to melt into liquid, it is every easy for act of combustion to influence the very flexible electrode to move.

[CAP1]

now was that so hard?

 you brought up something i was overlooking....and to be honest, i hadn't thought that compression pressure could/would ever be able to do that.

 i ain't the arrogant @#% you think i am.

[j500ss]

Helbent
Just out of curiousity, what NGK plug are you using?  Just curious is all.  If ya wouldn't mind just post both numbers on the box end flap.  I am a pretty avid snowmobiler, have had my share of 2 strokes apart and rebuilt myself.   

If the piston is hitting the grounding strip on the plug, you will see it plain as day with the plug out.  If its getting hot enough to melt it together, the top of the piston will be nice and clean, maybe even a whiteish color. That's a pretty decent indication of lean. 

If it is due to lean out, there are a number of possibilities then.  Carb sync, carb passages plugged, air leakage, or even exhaust leakage can do it.   

Go with your plan, your on the right starting track for sure   

[PAKFRONT]

When the electrode is near hot enough to melt into liquid, it is every easy for act of combustion to influence the very flexible electrode to move.

(Image removed from quote.)

Yes that is possible, I have seen that before too, far worse than that actually, lol.. But by the time that happens, you should already be hearing the KNACK KNACK KNACK sounds of detonation.. I have a 490 2 stroke race bike that a single NOS piston costs $800,(if you can find one) running 50:1 Spectro, race gas and 13.5 comp, and 2.2mm BTDC timing.. That's the ragged edge on an aircooled 2stroke man.. Gets real spendy when ya make a booboo in tuning.. After a lifetime, I don't make many.. I keep a tuning logbook for my different bikes, so I don't forget how they have been altered last! Gettin feeble minded too..

I kinda regret saying anything at all, without having it in front of me.. I am making a few assumptions, that the guy knows what he is doing for one, he sounds OK to me.. And all things being equal and straight up, as said with the motor.. Being as the big end went prematurely, (rod kit), so that usually means a vacuum leak at the intake port.. But again, injector motors usually squirt the oil right at the rod bearing.. I am assuming the builder made the correct moves to prevent an overlean, blah blah blah.. Without having the thing in front of me, I can only go by what the guy says..

Watercraft and whatnot are an odd combo of tech, like an Outboard/Motorcycle/Snowmachine hybrid kinda deal.. Interesting lineage/parentage of the machines too..

[FX1]

For 15 years i road and raced in expert limited and super stock class in region 5. I would go back to pre mix and do a compression test to see if their is any issues. I cant remember a time were i experienced a problem with the piston hitting the plug. You might get lucky and be able to use the gasket if you need to pop the head. O ring heads were a gift from the gods when they first came out..

[helbent]

Lots of advice and I appreciate all of it fellas 

Dont know when I am going home, but it looks like I have a few things to try.

I was thinking return to premix also, thanks, persuaded me.  Will test cpmression also

[helbent]

OK, got home, put 3 new plugs in and premixed fuel.  Ran it in driveway, front cylinder seemed cold.  Put it in water and its definately down a cyl.  Guess Ill have to crack it open and see whats wrong.

[zack1234]

I have a 1974 lambretta with a high compression nicosil alloy barrell and head 180cc, exspansion chamber clubman. ( I have broke two cranks using this kit )

From my experience of skimmed barrel head it might be that you require a thicker gasket to the cylinder head.

with the Mugello skimmed/or squished head you are supplied with various head gaskets depending on how far you want to increase the compression.

Compression closing the gap seems a little excessive, if such pressure was excerted on the plug it would strip the alloy head plug thread before cloing the gap. ( i have had this happen where by the plug becomes a bullet and fire's across the workshop)
I have seen melted plugs and squashed plugs but not from compression.

My Lambretta require a new up gear and ugraded clutch to cope with increased compresson.

Is there variants of spark plugs for said barrel?

I would be interested to see pics of you stripping barrel down, many heas together might be able to help you with this problem.

I remember rebuilding my engine and forgetting to put my a new roller bearing in the crank it still looks at me that caged bearing when I am looking for something

[morfiend]

 Nice Bike Zack,   would you post a pic of it for me,I was in my prime when those were new,might breath some life into this old codger!



   

[helbent]

Well, had a piston down.  Scarred up the cyl so i had it sleeved, other 2 honed, ordered new parts that my machinist broke and finally got it all back together last night.  Came home tonight and went to fire it up.  Fired up after a bit priming, ran it for about 15 minutes.  I noticed some water come out an exhaust connection so i shut down and tightened those bolts.  Went to refire it up and I am getting a whirring sound from what i think is the magneto.  the starter is not moving and this part is after the start button and before batt, CDI, starter, and everything else.

thoughts on that?  thx <S>

[helbent]

Well, had a piston down.  Scarred up the cyl so i had it sleeved, other 2 honed, ordered new parts that my machinist broke and finally got it all back together last night.  Came home tonight and went to fire it up.  Fired up after a bit priming, ran it for about 15 minutes.  I noticed some water come out an exhaust connection so i shut down and tightened those bolts.  Went to refire it up and I am getting a whirring sound from what i think is the magneto.  the starter is not moving and this "whirring" part is after the start button and before batt, CDI, starter, and everything else.

thoughts on that?  thx <S>

[helbent]

woops

ok its not that magneto nor ignition coil

[SIK1]

The whirring sound is probably the starter spinning. It sounds like it's not engaging the starter gear for some reason or another.

[helbent]

not the starter.  thinking a celinoid