Stroked Crank

[MichaelS693]

hey guys, i have two blasters, one that i drag, and the other is my spare parts motor... on my spare parts motor there is a 4 mil stroker crank in it.. i think im going to take that crank out and put it in my bike? is there anything i should be aware of besides making sure it clears and doesnt come out of the sleeve? do you think that the rod is at a different length? i just want to make sure before i swap it that everything will go ok without running into problems.. thanks

[Warnerade]

just be sure you clean the crank before you complete the stroke inside the sleeve

[duke416ex]

Some motors have to be machined in order to take a stroker crank, but I don't know about blasters. Why not just swap the entire motor?

[MichaelS693]

Originally posted by duke416ex
Some motors have to be machined in order to take a stroker crank, but I don't know about blasters. Why not just swap the entire motor?

because the top end in the spare motor is completely gone, its been broken down forever and mine is running.. the spare motor is also 300cc's mine is a 240 and i dont wanna really tear into that motor without knowing alot about the history of it they tore the motor down originally getting the crank out because the bearings went bad in it., they couldnt get the flywheel off so they said screw it and left it apart.. i bought the motor and complete frame with rims and tires for 150 bucks

[wilkin250r]

If I were you, I would try to get the top end from the other motor and clean it up.

There are lots of issues to pay attention to with stroker cranks, especially on 2-stroke engines.

You need to look at the rod length and rod angle, and make sure it will clear the case or if you need to do any machining the provide clearance.

You may need a spacer plate to set the deck height and squish properly.

A stroker crank will throw off all the port timing. This is why I recommend trying to use the top end from the motor that originally had the stroker crank, hopefully the porting was already modified to work with the stroker crank.



These things aren't just a drop-in upgrade, there is a lot of things involved in setting up properly.

[MichaelS693]

Originally posted by wilkin250r
If I were you, I would try to get the top end from the other motor and clean it up.

There are lots of issues to pay attention to with stroker cranks, especially on 2-stroke engines.

You need to look at the rod length and rod angle, and make sure it will clear the case or if you need to do any machining the provide clearance.

You may need a spacer plate to set the deck height and squish properly.

A stroker crank will throw off all the port timing. This is why I recommend trying to use the top end from the motor that originally had the stroker crank, hopefully the porting was already modified to work with the stroker crank.



These things aren't just a drop-in upgrade, there is a lot of things involved in setting up properly.

thanks for the info wilkin.. i know i can always count on your for providing good information. as far as the motors go... they have the same style porting and basically all the same exact work except the spare motor is 300cc and mine is 240cc both were done by trinity with their stage4 porting and head mod. Both motors look exactly the same.. there is no type of spacer plate on the cylinder or head on the spare parts motor from the crank.. looks like it was just dropped in... maybe if i were to take out the entire crank along with the rod and just bolted my piston to it... it would work?:confused:

[wilkin250r]

Maybe, but just because it works doesn't mean it's optimal.

In reality, it's tough to say. Have you talked with Trinity Racing about this, and what characteristics their stage4 porting has, and what effect the stroker will have?

The best, most powerful yet reliable motors are those that are designed with all components in mind to work together and compliment each other.

Like I said, a stroker crank isn't really a "bolt-on" modification all by itself. Porting characteristics are a huge factor in your power delivery, and that stroker crank will change all your port timing. It might work, it might not. You can certainly try.