Rebuilding motor

[87jarmshee]

OK i was out trail riding and i took a jump and landed in a small puddle and just at the landing it started knocking like crazy... so i cut it off and towed it back to the truck...i havent opened it up yet but im planning on completly rebuilding it anyway... I do mainly trail and the ocassional drag race (against freinds) but i have absolutley no clue what i need... i just ordered my clymer manual.. what parts should i replace and who is a good sponser to work with... i konw my way around engines and i can do just about anything but never worked on a two stroke.. im also looking for a little more umph shall i say...

 

heres what i have

motofast 2-1 carb with a lectron flatslide carb..(wanna get rid of)

motofast 2-1 pipe (wanna get rid of this loud ass thing too)

other than that its stock

 

what all is needed to run a 4mm long rod crank...

im lloking to do cool head and some porting billet impeller and a new clutch... what else do i need

 

so if you guys could point me in the right direction to get my shee back on the trail i would greatly appreciate it...

[Jereme6655]

Since your interested in goin with a 4mill and porting and a rebuild and all that fun stuff i'd suggest you call Jeff at F.A.S.T. Racing. He's a sponsor here and has a great reputation. He has everything that you need for your problem.....from your pistons for that rebuild all the way to different pipes for you to run.

 

www.farmandsandtoys.com

or

785-364-5325

[jbooker82]

what all is needed to run a 4mm long rod crank...

 

4 mill long rod crank

Wiseco 795 Series Pisons

Cut Stroker domes

Cool Head

 

Port job

 

The port job is not required but in order to gain the most out of a 4 mill it is. A stock stroke ported banshee will run circles around a non ported 4 mill. Once you port your cylinders for a stock stroke crank they cannot be ported for a 4 mill. So you kind of need to decide wich road to go down and stick with it.

 

A 4 mill is a great engine and I would deffinatly do it. If your in need of a rebuild there isnt a better time to do it. That way your not replacing good parts with other good parts.

[87jarmshee]

!!!!!!!!!!!!!!!!!!!!UPDATE!!!!!!!!!!!!!!!!!!!!!!

 

i pulled the motor and the head is all scored up and the right piston looks like it got chewed on by a pit bull and the left piston looks like it got chewed on by a shitzu.. the right side crank bearing has a ton of play in it..

 

i wanna rebuild this myself and learn about these motors...(of course send out what i need to send out)

 

i really wanna do the 4mm stroker but im not sure of all that i need to do it... is there a great diffrence between a standard stroke and the 4mm..

 

i mainly do trail riding..

[jbooker82]

!!!!!!!!!!!!!!!!!!!!UPDATE!!!!!!!!!!!!!!!!!!!!!!

 

i pulled the motor and the head is all scored up and the right piston looks like it got chewed on by a pit bull and the left piston looks like it got chewed on by a shitzu.. the right side crank bearing has a ton of play in it..

 

i wanna rebuild this myself and learn about these motors...(of course send out what i need to send out)

 

i really wanna do the 4mm stroker but im not sure of all that i need to do it... is there a great diffrence between a standard stroke and the 4mm..

 

i mainly do trail riding..

 

There is no better time to do the 4 mill build then. It is going to cost you about same amount. The only way you would do it cheaper doing a stock stroke setup with a used crank.

 

A 4 mill long rod crank from FAST is only 35 bucks more than a hot rods stock stroke crank. 50 bucks more if you have FAST do a stronger weld on the crank pins. I wouldn't run a cheaper no name crank. Hot Rods is a really good crank for the price. You want a long rod stroker crank. A standard or short rod 4mill will put more side load on the pistons wich can cause the piston skirts to break. The long rod is a reliability mod not a hp mod.

http://www.farmandsandtoys.com/partdetail.asp?partid=78

 

Next you need some pistons. You need to run 795 series wiseco pistons. They have the crank pin moved up 5mm closer to the top of the piston. This is because the long rod crank has conecting rods that are 5mm longer than the stock rod. You have to run these pistons wether your builing a 4mill long rod, or a stock stroke long rod.

 

Third you need to do some kind of head moddification. You can have your oem head rechambered, or run a pair of cool head domes that are for a 4 mill. The 4 mill crank makes the pistons fall 2mm farther down in to the bore. It also causes them to pop up 2mm farther out of the cylinder. So you need to clearance the head so you don't have contact being made. The other option is to put a 2mm thick aluminum spacer plate under the cylinders. This will raise the cylinders and keep the piston from hitting the cylinder head as well. It isn't the best method. Most guys prefer to run a cut head. It is more reliable instead of haveing double base gaskets sandwitching an alumnum plate.

 

Fourth. Porting. Porting 2 stroke cylinders is not like porting a head on a 4 stroke. The name of the game doing 4 stroke heads is to improve flow. When you open ports up on a 2 stroke your changing when the air and fuel come in and when the exhaust goes out. Porting a 2 stroke is like putting a camshaft in 4 stroke. The ports need to be certian shapes and sizes. There angles are import to. That way you dont have fresh air and fuel being blown out the exhaust port. Porting should be left to the professionals.

 

You need to order your pistons from the guy you have do the port job. You send him your cylinders, they come back ported, and bored with the correct size of piston. That way he can port the cylinders. Measure the bore and get the right size pistons off the shelf and bore your jugs to the correct bore. If you have to bore most builders like to do it after the cylinder has been ported. That way if they have any slip ups and nick the cylinder the bore will take care of it.

 

If your getting a bran new crank there isnt a better time to do a 4 mill. It has a stronger midrange wich is nice for trail riding. Just call some site sponcers. Let them know what you want to do, type of riding you do, rider weight. Talk to them with what pipes work best with there port jobs. Dont buy a set until you know what the guy who ports the cylinders recomends.

[87jarmshee]

There is no better time to do the 4 mill build then. It is going to cost you about same amount. The only way you would do it cheaper doing a stock stroke setup with a used crank.

 

A 4 mill long rod crank from FAST is only 35 bucks more than a hot rods stock stroke crank. 50 bucks more if you have FAST do a stronger weld on the crank pins. I wouldn't run a cheaper no name crank. Hot Rods is a really good crank for the price. You want a long rod stroker crank. A standard or short rod 4mill will put more side load on the pistons wich can cause the piston skirts to break. The long rod is a reliability mod not a hp mod.

http://www.farmandsandtoys.com/partdetail.asp?partid=78

 

Next you need some pistons. You need to run 795 series wiseco pistons. They have the crank pin moved up 5mm closer to the top of the piston. This is because the long rod crank has conecting rods that are 5mm longer than the stock rod. You have to run these pistons wether your builing a 4mill long rod, or a stock stroke long rod.

 

Third you need to do some kind of head moddification. You can have your oem head rechambered, or run a pair of cool head domes that are for a 4 mill. The 4 mill crank makes the pistons fall 2mm farther down in to the bore. It also causes them to pop up 2mm farther out of the cylinder. So you need to clearance the head so you don't have contact being made. The other option is to put a 2mm thick aluminum spacer plate under the cylinders. This will raise the cylinders and keep the piston from hitting the cylinder head as well. It isn't the best method. Most guys prefer to run a cut head. It is more reliable instead of haveing double base gaskets sandwitching an alumnum plate.

 

Fourth. Porting. Porting 2 stroke cylinders is not like porting a head on a 4 stroke. The name of the game doing 4 stroke heads is to improve flow. When you open ports up on a 2 stroke your changing when the air and fuel come in and when the exhaust goes out. Porting a 2 stroke is like putting a camshaft in 4 stroke. The ports need to be certian shapes and sizes. There angles are import to. That way you dont have fresh air and fuel being blown out the exhaust port. Porting should be left to the professionals.

 

You need to order your pistons from the guy you have do the port job. You send him your cylinders, they come back ported, and bored with the correct size of piston. That way he can port the cylinders. Measure the bore and get the right size pistons off the shelf and bore your jugs to the correct bore. If you have to bore most builders like to do it after the cylinder has been ported. That way if they have any slip ups and nick the cylinder the bore will take care of it.

 

If your getting a bran new crank there isnt a better time to do a 4 mill. It has a stronger midrange wich is nice for trail riding. Just call some site sponcers. Let them know what you want to do, type of riding you do, rider weight. Talk to them with what pipes work best with there port jobs. Dont buy a set until you know what the guy who ports the cylinders recomends.

 

 

dude your my hero... i going to try to upload pictures later

[87jarmshee]

[87jarmshee]

any idea on how that all this carnage happened...

[jbooker82]

That dammage looks pretty standard. Any pieces of the skirt broke off? Missing any scews in the reed cage? Any rolers bearings missin from the crank shaft or upper conecting rod bearings ?Just looks like something got on top of the piston. If part of the skirt is broke off that is usually due to the bore bing to large and the piston rocking in the bore.

 

Clean the tops of the piston off with a wire brush. See if there is any numbers on the top.