Ok last weekend my daughters '93 Trailboss just quite running while riding. I found no compression and after taring into it I found a hole in pistion. I currently have the cylinder at a shop. It was backfiring the day before and I adjusted the air screw and backfiring stopped.
I think the spark plug is wrong one (I bought this 2 months ago and have not changed it) I think it is a hot plug any other idea's?
Per my manual it states there should be reeds in the intake! There is nothing there just intake boot.? Is this normal for the '93?
How big is to big for a bore oversize?
It looks like it will be bored to .060 over. Will have have to make any other changes with this big of a bore?

Here is what I found while taring it down:
Looks like it was bored .040 over already.
spark plug: champion N2C with 489 and 6B written on base (Is this a hot plug?
air screw sitting was at 1 3/8 turn out.
a lot of small aluminum pieces in the crankcase from piston.

I found a drain plug on crankcase. Can I flush the crankcase with menerial spirits and oil? Or will I have to split the crankcase to clean it all up?

Does most people use Wiseco Pistons? What about Namura Pistons? I have found both with complete kits that I will need.

 

Can anyone help?

 

what is it running for a main jet??

 

well i couldnt find the plug number, but its a 145 main and it has no reeds. you could use kerose to clean out the base and it wouldnt hurt anything. its running way to lean/hot to burn a hole in the piston. guessing the air screw should be no more then 1 1/2 turns i beleave. i wouldnt go more .60 over if you can go that much on that cylinder.(shop should be able to tell ya) and wisco is a good choice for a piston. hope this helps.

 

X2 on what stendori just told you.
The only thing that will make a "religious piston" is being lean. WHY it's lean is anybody's guess. Jetting, air leak. clogged jet, venting problem.................... On and on and on...........

 

thanks for the replies, Ok I'll have to go through the carb and clean it up. I do have a new plug that is correct per the manual. The manual states that the air screw should be 1 turn out. So maybe something in carb/jet.
Did some research and it also states that early detonation also causes holes in pistons along with lean mixture. So I should check timing right?

I did notice the plug was very 'clean'. I'll look at it in more detail this weekend.

 

air screw at 1 sounds right about right. if the plug was whitish color thats not a good thing on a 2 stroke. you need to check everything to make sure theres no air leaks as well.

 

Check the amount of side to side movement on your primary clutch. If that is excessive you will take out the seal and suck air in there. If so a complete rebuild is in order all the way down to the crank bearings. Doc

 

Ok I got a chance to work on it this past weekend. I cleaned the carb, very little dirt in bottom. The main jet is 145 as stated above. There is no side to side movement on primary clutch (crank), Drlang thanks for your input, I did not think of check that. The shop bored it out to 60 over, I should get it tomorrow. I just ordered my wisco piston tonight.
I flushed the crankcase. Here is a question on the crankcase. There was no oil in the bottom but everything wet with oil when I took apart. Do I need to add some (just alittle) or just make sure everything is wet? What about putting some in and after running just a little pull the drain? If you block off the oil mixer (mine is not) then do you have to put oil in the crankcase?
Doc did you adjust your timing any? The old plug is hard to read but do believe is was running lean. On a rebuild is there any special I need to do for break in?

 

it should be put together w/ assambly lube so it will have some lube while the start up is the hardest on any engine. you run 1 tank of premix gas thru w/ the oil injection is a good break in and not to hold one rpm too long and not too long full throttle.