Piston oil holes + a few question.

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eddie1

Member
Oct 17, 2007
39
0
ok i just got my wisco piston infrom motosport and the direction say drill holes into the band new piston.

personally I don't see my self drilling into a $100 piston.

Is this real nessisary to do?

ALSO

I put my tire back on the rim today and some of the tire lip isn't fully all over the rim or not fully seated. the tire it self is 100% on just not seated perfectly. will be riding allow it to set it self into place or this a problem?

ALSO

Any tips on rebuild the topend. This is my very first time on a 2-stroke bike rebuild and i can afford for any thing to go wronge or to hinder engine life. so any hint or trick or tips are very much needed.

Thank

Ed
 

IndyMX

Crash Test Dummy
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Jul 18, 2006
5,548
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eddie1 said:
Any tips on rebuild the topend. This is my very first time on a 2-stroke bike rebuild and i can afford for any thing to go wronge or to hinder engine life. so any hint or trick or tips are very much needed.

Thank

Ed
Click to expand...


Yeah, follow the directions that came with your piston..

If it says you need to drill the hole, drill it...

Otherwise you're going to be back asking why the piston seized on the exhaust bridge.
 
F

FruDaddy

Member
Aug 21, 2005
2,854
0
Wiseco know more about engines and piston design than either you or I, it might be a good idea to trust them. If you cannot find it in yourself to do that, try calling them and asking them why you need to drill the hole, and what will happen if you don't.
 
E

eddie1

Member
Oct 17, 2007
39
0
ok so the directions say................................

"Drill .375 apart starting .300 below the bottom ring, and between the pencil lines."

can any help me with ways of marking the .300 and .375 measurements. I personally have no idea how long those are and no way of knows im pretty much drawling a blank.

ALSO

Do I drill the hole all the way through the piston till the drill bit shows through into the center of the piston or do I just put like a little knott in the piston
 

IndyMX

Crash Test Dummy
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Jul 18, 2006
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Amo, IN
.25 is 1/4th inch, .125 is 1/8th inch, so .375 is 3/8th's inch.

So, just between 1/4 and 3/8ths below the ring, drill a 3/8th's inch hole.

Drill thru the piston. So that oil from below will get to the exhaust bridge.
 
E

eddie1

Member
Oct 17, 2007
39
0
ok so i don't screw it up lemmi get the straight

Drill a hole 1/4 - 3/8ths from bottom of the piston ring(But the paper says .300 so wouldn't that ahve ot be a exact spot not a range to choose from?)
and

from the first hole I drill move down 3/8ths exackly and drill another.

*Sorry for the annoying questions just worried about messing it up.*
 

IndyMX

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Jul 18, 2006
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Oooh.. I just reread your previous post.. .375 apart, does it mention the size of the holes?

I have no idea what .300 is in fraction, so a bit more than 1/4 (.250) and 3/8 (.375)... Just shy of 5/16".

Just my thinking, but if you are as close as possible, it should be ok.
 
E

eddie1

Member
Oct 17, 2007
39
0
ok thanks for the help.

any tips or tricks tp putting a motor back together?

probly going to assemble it tonight
 
B

bwood

Member
Mar 21, 2004
135
0
Drilling the hole is only required if your cylinder has an exhaust bridge (looks like 2 exhaust ports side by side). I usually have seen these in 125s. Ok, next I'm going from memory. You should install the piston temporarly and slowly move the piston up and down. While doing this use a pencil and mark the piston as it moves (mark it on both sides). Now remove the piston and find the center between the 2 lines and make a center mark. Using you directions, measure from top and bottom to find where to drill the hole(s), (some piston require more than 1 hole). If I remember correctly, the hole should 1/8" dia. Clean it all up and reinstall. The holes are to allow proper lubrication to the friction point of the piston ring and the exhaust bridge. If you dont do this, the bridge will fail and the ring will literally eat away at the alum bridge. Reread your instructions again one step at a time.
 

IndyMX

Crash Test Dummy
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Jul 18, 2006
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Amo, IN
Tips.. main tip.. Take your time.

Lay out all the parts on a clean surface first. Make sure you have everything there that needs to go back in..

It's a real drag to be torquing head bolts, and notice a part laying on the bench that should be under that head bolt. I do that way too much for my comfort.

Make sure everything is CLEAN.

Lube the parts that move, and Loctite the things that shouldn't move.

Did I mention, Take your time!
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
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Merrillville,Indiana
.300"= about 5/16"=7.62mm. Set the piston on something soft and use a center punch to exactly locate where to drill. Ideally, hold it in a vice(soft jaws or rags) and drill it with a drill press. Deburr inside and out.
 

Pete Payne

MX-Tech Suspension Agent
Nov 3, 2000
933
38
bwood has it right , this is a practice for a bridged exhaust port only . It is intended to give the exhaust bridge a little extra lube and cooling to hep it not seize against the piston .
 
E

eddie1

Member
Oct 17, 2007
39
0
ok installed piston, everything went great started in 4 kicks. Broke in the motor runs like a champ, heck pops wheelies in 4 gear with out droppen clutch, Thanks for the help.

Sure i'll be poppen in again soon with more questions
 
E

eddie1

Member
Oct 17, 2007
39
0
doesn't answer you question but....

Any one new like was who all "o my god i'll never be able todo this" it actualy very easy and simple long as you have a drill press, vice, rag, and debur tool. Took me and my uncle(ised his tools so have to include him) at the very most 10 minutes from wlking into the garage to walking out.
 
T

TWRT

Member
Sep 13, 2001
249
0
The yamaha 250 2-stroke does not need the holes. I believe the honda 250's have the bridge talked about. I have replaced many pistons in 2000 and up YZ 250's. I guess it couldn't hurt, but the YZ 250's do not have the exhaust port bridge.
 
B

bwood

Member
Mar 21, 2004
135
0
I have only seen the bridges on the 125's. I know 96,99 Cr250s don't have the bridge and same for 95 and 99 KX250.
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
Well, some 250's have them then. I know the early CR250's, and the 02-04 have it, and the suzuki's. But, it is predominately on 80's to 125's. And we were only talking about the exhaust bridge. Some, have bridges on the intake side. They do not need holes for lube, but still need to be properly relieved. Bridge: 1/8 to 1/4 inch wide and the height of the port, usually right in the middle. If it gets a hone and the bridges do not get hit, then that is a good sign. If it has the exhaust bridge, it has to get lubed(holes in the piston)and relieved, at least .0015 more than the bore.
 
G

gthoma23

Member
Apr 24, 2008
86
0
i bought a used '03 CR250 last summer. got bored cause i didn't have a job so i tore it apart. found out i had a wiseco piston. also found out the guy that owned it before me never drilled the holes. and my exhaust bridge was pretty jacked. if u seach threw my threads u'll see pics and everythin. i was runnin the right mixture and was all good.

and fyi, the drilling isn't that hard. just make sure to clamp it done in soft jaws and use a punch. and always start with the smallest bit you can find...otherwise it will wonder like mine.
 
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