87 250r issues

Lucky13 · #1 (**permalink**) 05-01-2008

Ok so here's the deal. I bought this 250r in Feb of 2007, did some work to the carb and got it all cleaned up and running. I never thought to take anything apart like the top end or even just the head. he had a mutt of a carb on there so I replaced it with stock(because he told me the bike was all stock minus the pipe).

So i put a stock 34mm carb on and jetted it at stock settings. Bike always ran great!

Well just in the last few months I've been fouling plugs left and right. So I take it apart to see what the deal is and first, find that I have a broken reed....

and second, I find out that A, I'm pretty sure the piston is in backwards. B, its got a 75 on the top of the piston but it measures 66.675mm??, and 3, I think i was in the process of frying it because it had started what coulda been a major meltdown.

and here is the head, if it helps.

So, since this appears to be just a normal stock piston, what would cause it to start wearing like that on the top?? I run castor 927 at 40:1.....is it just not jetted properly or.....?

superevil · #2 (**permalink**) 05-01-2008

I think the "in" is supposed to face the intake,but the top of the piston looks fine to me just replace the reeds.

Bad Ass Honda 250r · #3 (**permalink**) 05-01-2008

well i would get a piston for it... just to be on the safe side.. there cheep on fleabay...

Lucky13 · #4 (**permalink**) 05-01-2008

the top of the piston is like down to the rings on the side right there............(not the IN side the other side)

so i know i need to get a new piston and rings, but what causes a piston to do that?

Bad Ass Honda 250r · #5 (**permalink**) 05-01-2008

well getting hot as hell is what causes the piston do to that... but i would get some v-force 2 reeds... and put a new piston and rings in it and jet it accordingly and you should be good to go...

Lucky13 · #6 (**permalink**) 05-02-2008

pardon my ignorance. but what causes it to get hot as hell....what can I change because I obviously thought it was running just fine but this is actually what it was doing in there.

trx · #7 (**permalink**) 05-02-2008

WILL it gets hot on the exhaust side becouse of lack of lube on that side becouse the reeds were sucking in too much air were it was broken but it looks like it was running good though jetting looks fine

superevil · #8 (**permalink**) 05-02-2008

i didnt notice the top of the piston opposite the "in" being down..oops

fulltiltrider · #9 (**permalink**) 05-02-2008

Looks like it snagged a ring on the exhaust port at one time. Take the cylinder off, flush out the bottom end and see if you find your piece of reed or your piece of piston lol. Cant tell on the jetting due to the broken reed.

Id just bore it to the next size. You have plenty of life left in that cylinder at 66.75.

oldschoolzuk · #10 (**permalink**) 05-02-2008

Could be also she ran out of antifreeze somewhere along the line.Definetly get a new piston and rings and have your cylinder honed or bored depending on how bad it is.On oem pistons the arrow faces exhaust .Also when you do rebuild be sure to place the headgasket correctly.Try to use oem bottem and head gaskets as they are vastly superior to the aftermarket ones...........