Top End Rebuild

[DirtDiggler]

So before my Sand Lake trip in august I'm gonna get a fresh top end done , I haven't pulled a piston before in my blasty , is there a tool you need to remove the wrist pin? or generally will it push out once the retaining rings are pulled out? and does the upper bearing get pressed out as well?


And when I get the cylinder back , I know there is a general break in process for that , I have seen a thread about it on here , any input on that process , like do's and don'ts ?

 

[yb200]

once you get the clips out the wrist pin should slide right out

and the bearing slides right out of the rod

as far as break in run atleast 3 10-15 min heat cycles then ride it nice for a tank of fuel then you will be good to rip

 

[2smoker85]

depends how long the piston has been in there, no special tools needed, i had to bang mine out with a small pin, it isnt hard.

 

[speedracinshift]

like they said should just pop right out after u remove one of the circ clips from the side. if some old pistions some time can be gummed up so it take a little bit more to get it a part. plus when removeing and installing dont forget to cover the bottom hole around the crank with a rag so that the circ clips or any thing can fall into the cases. also make sure all gasket surfices are clean of old gasket or grease. i use brake clean and a scotch pad. also to let me know what days u are ganna be at sandlake i go there all the time.

 

[Blasterdude27]

I've never needed any special tools for rebuilding the top end.

I recently pulled an 18year old piston outta my mojave and the circlip was a bit jammed but a simple tap with a screw driver and a mallet solved that,

 

[DirtDiggler]

like they said should just pop right out after u remove one of the circ clips from the side. if some old pistions some time can be gummed up so it take a little bit more to get it a part. plus when removeing and installing dont forget to cover the bottom hole around the crank with a rag so that the circ clips or any thing can fall into the cases. also make sure all gasket surfices are clean of old gasket or grease. i use brake clean and a scotch pad. also to let me know what days u are ganna be at sandlake i go there all the time.

Right On Bro , we're going August 23rd - 27th , a few of us are going , and bunch of people from work are coming out to camp and hang out too . That would be cool to hook up .

Another Question is this , can I run a stock carb and a Big Bore piston? obviously it can't flow as much air as a 34mm like I plan on getting , but it seems dumb to put in a fresh top end , then turn around and do a big bore like a month later .

 

[brandoz28]

yes you can run the stock carb, it'll be far from optimal to run the 240 with the FMF pipe and the stock carb, you'd probably do better to have the stock cylinder ported and get a 28-30mm OKO

 

[aflawinhumanity]

If the wrist pin dosen't want to come out I use a c-clamp and 2 sockets. One socket that is the same size as the pin to push it through. (I cant think of the size off the top of my head) and another one on the other side for the pin to slide into when it is being pushed out. You dont want to be tapping or hitting on it because you dont want to mess up the rod and bearings

 

[speedracinshift]

i just picked up a full blaster with a 240 kit and the guy hade burnt it up running a stock carb. u can run a stock carb if its jetted right. i would at least run around a 34 mill carb for the diff in power u will get out of it will be worth the money. plus u can pick up a used one for not to much.

 

[speedracinshift]

for sure on the trip i am going mid july so i can jet and brake n my fresh 240. but buy then i will be down to ride agian

 

[DirtDiggler]

for sure on the trip i am going mid july so i can jet and brake n my fresh 240. but buy then i will be down to ride agian

Yeah I'd hate to burn it up , wanna do it right . I'm gonna wait to do the big bore when I can get the 34mm carb and the stroker crank. I'll just go with a fresh top end .

 

[blasterdad]

I had to have a friend hold a board with a hole in it against the side of the piston to drive mine out. The manual says not to do this but we were real careful not to let the rod move from side to side. They do make a wrist pin puller but unless your piston is toast like mine was it should come out fairly easy. The upper rod bearing just slides out. As stated before do the rag thing to keep crap out of your motor!

 

[speedracinshift]

blastard just keep a eye out on cl. i picked up a full roller with a vitos 240 kit newer b1 pipe for 350$

 

[DirtDiggler]

Pulled the Top End Today , it came apart easy , no broken studs . I did a compression test before the tear down and after 2-3 tests , the pressure hovered around 105-111 . Pulled it all apart and the piston was black on the top and had some scratches above the top ring , cylinder looked good , few scratches , nothing terrible . The wrist pin had to be tapped out with a 10mm socket , the top end bearing slid right out . I'll send it out in 2 weeks for the bore/hone and piston kit . should have it back beginning of august to put together and break it in .

 

[DirtDiggler]

whats a proper way to clean up the head? the combustion chamber area is black , can i lightly wire brush it? or steel wool? any other ideas?