Burned up Right Cylinder

[someone82]

To start off this forum is great! I want to thank all you guys for all the great information I've gotten on this board it's really helped me learn about the banshee and 2 strokes in general. But now it is time for me to ask for some help.

 

This weekend I took my banshee for her first real ride up (bought the quad last month) at gorman and she was running great for the whole first ride, up untill some water got into the carbs (running pods). The motor tried to hydralock on me but I was able to keep it going; I cleared her out and she was fine again.

 

Rode it for another 30 mins and got back to camp. We took about a 30 min break and I told my buddy to take her for a spin (he was pissed that I was out running his raptor). He didn't get more than 100 ft from camp when he shifted into second and it just died. He tired to kick it over but it locked up.

 

Once I got it home I noticed the right spark plug was backed out about half way so I pulled the head off to discover the crown of the right piston beat to crap. Pulled the jug to find the intake side of the piston skirt to be completely gone. Pcs of the piston were wedged in between the crank and the case, being the cause of locking up the motor. Surpriselinly the sleeve took no damage at all!

 

By the way the left cylinder was fine.

 

Long story short I can tell my right cylinder was running hot/lean but I never had any indication of it while riding (motor was smooth and had plenty of power. What does 2 stroke detonation sound like?). What should I look for what might have caused this. I noticed on the bottom side of the jug the rubber plug (what is the purpose of this?) that goes into the water jacket was torn to pieces (possible air bubble in the water jacket?).

 

 

Here are my specs:

 

96 banshee, the motor was rebuilt (before i bought it with really no hours on it) with wiseco 64.5 pistons, jugs have a mild port, klein pwk 28's w/ pod filters (don't know the jetting yet), reed spacers, boyeson reeds in stock cages, stock head milled .020, ngk iriduim BR7EIX plugs (had a nice chocolate burn on the plugs, maybe too hot of a plug?), and toomey t5's. Stock timing and cdi. 32:1 91 oct fuel mix w/yamalube.

 

I myself had the head milled (motor had a bad head gasket on it when i got it) and put in the reed spacers (for clearence) and checked for air leaks, but never found any. Also before this the cylinders had 145 psi even.

 

thanks,

matt

 

if you guys want to see pictures i can get some up tonight.

[IrideA250R]

7's are too hot of a plug, I would run 8's.

 

It's possible you damaged the piston when you sucked in the water. Hot piston + cold water = cracked intake skirt. It then let go when your buddy was riding it and locked the thing up.

[BansheeDan]

well imo the br7 plug is part of the issue....

stock shee's run br8 and alot of the guys with big motors run br9's

 

and you did say it was the right cyl??

what about the crank seal being bad??

 

 

 

 

 

 

Dan

[someone82]

well imo the br7 plug is part of the issue....

and you did say it was the right cyl??

what about the crank seal being bad??

 

I had a feeling the br7's might have been part of the problem. (But left cyl was fine, no signs of detonation and the plug was good) I ran them because of my rich oil mixture to help burn off extra carbon deposits (did this in some of my rotory motors). How sensivtive are two strokes to plug heat ranges?

 

Yes it was the right cyl and I don't know about the crank seal, I haven't pulled the case apart yet and i never did a leak down on the motor before hand, only compression tests.

 

I just remebered tho, when I drained the oil from the tranny I had a slight "pressure release" sound? :shrug:

 

thanks again,

matt

[2001Stroker]

32:1 is what most people mix, with BR8 plugs. Actually, that's what Yamaha calls for. IMO, Yamalube is junk. I have a few quarts of it in my shed. I only use it for my leaf blower and weedeater. I use Maxima SuperM in the Banshee. It's a smokeless synthetic blend. I love it. If you don't know, Maxima is the company that makes Castor927.

 

As far as sucking up water, it doesn't compress. I'm sure that could cause some serious damage to a piston, and if it sucks up enough, it COULD bend rods. In a 4-stroke, water in a cylinder can also bend valves. So, if you ever suck it up again, kill it. Pull the spark plugs, and let it dry out, and dry the filters. That's why I just bought Outerwears for my pods. I don't want this happening.

[someone82]

Here are the pictures of the piston:

 

 

 

[IrideA250R]

you can tell the piston crown temps were very high due to the oil burned onto the underside of the piston. Rebuild it, ditch those 7 heat range plugs for some 8's or 9's, and run a nice 32:1 mixture. It wouldn't hurt to leakdown test the motor when you have it all back together too.

Edited April 21, 2008 by IrideA250R