sxr piston closing spark plug gap

[ticega306]

Friends SXR 800
b-pipe, flame arrestors, rejetted carbs, otherwise stock.

in front cylinder, piston keeps closing the spark plug gap. Sometimes it closes it enough to loose spark completley. what could cause this?

if piston is over reaching, i suspect a failed/failing rod bearing. could that be it? i don't hear any rattling so bearing hasn't failed completely. what else could it be? i don't think it could be a crank bearing, cause after regapping plug it idles smooth and steady. but once its in the water and he gets on the gas, it eventually looses power and ultimately dies (pull ski in and gap is closed again)

trying to get a better idea before we open up...

 

[Motorheads5]

Are you using the correct plug ?

 

[ticega306]

i believe so BR8ES
no problems for about a year so definitely not the wrong plug...

 

[Motorheads5]

I don't know what's going on I would think if you had a bearing going bad it would be over with by now, can you see any contact on the top of the piston ?
maybe someone else can help sorry no Idea !

 

[ticega306]

thanx anyways,
could not really see any contact on piston, but only looked through spark plug hole (end of day, not much light)
first thing we'll do is pull the head. see what the pistons look like. i'll post some pics if i can take some

 

[X2Pilot]

Please post your findings...funny a friend had the exact issue on the front cylinder of his SXi last sunday...I am curious. I am also under the impression that if the bearings were that shot that it would have failed completely already...

 

[Motorheads5]

Please post your findings...funny a friend had the exact issue on the front cylinder of his SXi last sunday...I am curious. I am also under the impression that if the bearings were that shot that it would have failed completely already...

I would think if you had a bearing going bad it would be over with by now.

Yeah what's up I am very curious.

 

[ticega306]

have not yet posted any findings cause I have not yet had anytime to work on the ski personaly. Hopefully that will change this weekend and I'll let u all kbow what's up...

By the way does anyone know where I can get a digital copy of the service manual for the sxr??

 

[Shonuff]

http://www.drmikesandy.com/X-H20/X-H20.htm

 

[ticega306]

Thanx I'll get to work and let u all know...

 

[ticega306]

we're working on the ski right now...so far we've confirmed that the piston rings are shot (that was expected) pulling the cylinders right now (they are scored pretty bad)...i'll keep posting as we progress...pics to follow soon

 

[ticega306]

since we already know we're looking at new pistons, cylinders and head...anyone have good suggestions on a place to purchase those parts.
not necessarily looking for aftermarket, stock should be fine...

 

[redsxr800]

sure its not supposed to be br8hs the shorter one ? cant remenber whats what right now. h and e are same plug two different length threads
the only thing that should stick out of the head on inside is the electrode. if you see any threads its to long.