Would I need to rejet my bike?


16 replies to this topic
  • RobbieM16

Posted June 05, 2011 - 01:42 PM

#1

2003 YZ450f coming from stock, going to a hotrods stroker crankshaft assy, possibly a big bore kit.. Would jetting need to be changed with either application? I heard with a stroker crankshaft timing sometimes needs to be different, dont think its true but ?

  • grayracer513

Posted June 05, 2011 - 02:31 PM

#2

It is true that ignition timing may need changing with a stroker, and also that the jetting may need to be adjusted.

One thing that will absolutely have to be done is a balance job. Don't skip that.

  • RobbieM16

Posted June 05, 2011 - 03:26 PM

#3

Is it not balanced before Hotrods sends them out? Also is it a pain in the ass re adjusting, tuning the bike for the stroker than just using a regular crank or is it worth it?

  • grayracer513

Posted June 05, 2011 - 03:58 PM

#4

What piston should they balance it for?

No it's not balanced. Whether the jetting is problematic or not varies quite a bit.

  • RobbieM16

Posted June 05, 2011 - 07:36 PM

#5

Yea good point,, where would I bring the crank to get this done?

  • grayracer513

Posted June 06, 2011 - 06:55 AM

#6

You'll have to do a little searching for that. Google engine balancing in your area first, and try to find a shop that has experience with balancing single cylinder engines. If you can't find something local, check with Engine Dynamics.

  • RobbieM16

Posted June 07, 2011 - 02:33 PM

#7

OK does it need to be trued? or BALANCED? Just making sure.. Apparently it just needs to be trued? Its a brand new crank

  • grayracer513

Posted June 07, 2011 - 02:55 PM

#8

Balanced. Otherwise, it will vibrate like a CR500 with a bent crank.

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  • RobbieM16

Posted June 07, 2011 - 03:13 PM

#9

OK I've never heard of this before so don't mind the questions..
Is it just the stroker crank that needs this done?
If its with every new crank, stroker or not, how do you go about balancing it for a new piston if you change from OEM to lets say, Wiseco piston?
Balancing is shaving/taking materials off the crank?

  • grayracer513

Posted June 07, 2011 - 04:15 PM

#10

The best results are had with any crank if it's balanced for any change in the weight of the piston. One would hope that the Hot Rods stroker cranks would be balanced for at least an average weight stock bore size piston, but I don't know that they are, and the reports I've seen here would suggest that they aren't, or that the aren't done very well.

Changing the balance is normally done by drilling or grinding at the heavy spots, but sometimes that's not enough, and slugs of a tungsten alloy (used to be known as "Mallory Metal") are added to the light spots. Strokers exaggerate the weight of the piston by increasing its velocity at any given RPM.

  • RobbieM16

Posted June 07, 2011 - 07:24 PM

#11

OK. Looks like I'll send it out to get balanced.

  • RobbieM16

Posted June 07, 2011 - 07:27 PM

#12

Ill need to send my piston out too?

  • grayracer513

Posted June 07, 2011 - 07:55 PM

#13

Check with the shop you send it to. Normally, they would need the complete crank, piston, wrist pin, circlips, rings, the balancer shaft with weights, and the balancer gears.

  • Deadend

Posted June 07, 2011 - 09:02 PM

#14

The best results are had with any crank if it's balanced for any change in the weight of the piston. One would hope that the Hot Rods stroker cranks would be balanced for at least an average weight stock bore size piston, but I don't know that they are, and the reports I've seen here would suggest that they aren't, or that the aren't done very well.

Changing the balance is normally done by drilling or grinding at the heavy spots, but sometimes that's not enough, and slugs of a tungsten alloy (used to be known as "Mallory Metal") are added to the light spots. Strokers exaggerate the weight of the piston by increasing its velocity at any given RPM.


:ride:

  • RobbieM16

Posted June 08, 2011 - 12:57 PM

#15

:ride:


? Is this false or what? I don't wanna send it out if it's not nessicary, I mean if its a must ill do it but I dont got time to do it for the fun of it..

  • salemonkey

Posted June 08, 2011 - 01:46 PM

#16

? Is this false or what? I don't wanna send it out if it's not nessicary, I mean if its a must ill do it but I dont got time to do it for the fun of it..


hes bowing down for giving out good quick knowledge. grayracer is a moderator for this section of thumpertalk and gives out non bullshit advice. if he is giving you advice i would definitly consider it and at least look into it. if your putting a stroker kit on with full rebuild this is not the time to cut corners. they do this on all types of motors and is nothing new. you hear a lot of people call it balance and blueprinting and should be done on anymotor that gets in the high rpm's.
also reread what grayracer said to you. he even explained why you should be more prone to balancing a stroker.

  • RobbieM16

Posted June 08, 2011 - 03:18 PM

#17

OK well I did some research / calling around on it today, I called Bondi Engines and they said it's not nessicary to do so with a brand new crank going onto a cylinder works bigbore, or a stock piston. It should only be trued to make sure it's as is when left factory which I will get done. I called Hotrods after, and they said the same thing. They told me a bit of vibration is normal with the stroker cranks, and should be expected balanced or not





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