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Going to a 4 mil crank


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I have a set of jugs on my stock stroke engine that have a good drag/dune port. My question is how exactly will it effect the power range that my bike has now if I go to the 4 mil stroke 5 mil long rod crank. do I need to use a spacer under the jugs for anything other then piston to head clearance because I can cut domes for that. My main concern is port timing and how different it would be. Thanks, Chris

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to keep your port timings correct you will need to run a plate..

 

That would be the worst thing he could do. His cylinders are already ported. Thowing a 2mm thick plate under the cylinders will cause all of the port timings to be advanced. Probably advanced beyond the optimal point. Other wise the guy that ported the cylinders would have opeaned the ports up to that point.

 

The best thing to do would be sell your cylinders and get a set of stock cylinders that havent been ported. You cant have a set of ported cylinders reported for a 4mill crank.

 

If you want to try to run your cylinders that you have now I would get a set of domes that are made for a +4 mill crank. That keeps you from having to put the plate under the cylinders.

 

You will also need 795 series pistons since the crank your going to be putting in is a long rod crank.

 

josh

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A 2mil plate will keep the timings in check...sort of.

SHould be damn close.

 

You use a spacer plate for the crank, 795 series pistons for the long rod...(115 vs. the stock 110mm rod length)

 

Even though you have a 2mil plate to make up for the longer stroke, you'll have to carefully select 2 base gasket thicknesses to make sure everything is in check, deck height, port timing, etc.

 

Honestly, it is better and easier to get stroker domes cut and OEM cylinders ported for a 4 mil long rod crank...

 

A lot of people run a spacer, just asking for air leaks and/or trouble in my book.

 

Your call.

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thanks man, thats what I will do. Anyone got some stock porting jugs, don't really care if they need to be bored or not they will get it no matter. and with that being said my jugs are standard bore and would be a great bolt on for someone that dosen't want to spend alot.

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A 2mil plate will keep the timings in check...sort of.

SHould be damn close.

 

You use a spacer plate for the crank, 795 series pistons for the long rod...(115 vs. the stock 110mm rod length)

 

Even though you have a 2mil plate to make up for the longer stroke, you'll have to carefully select 2 base gasket thicknesses to make sure everything is in check, deck height, port timing, etc.

 

Honestly, it is better and easier to get stroker domes cut and OEM cylinders ported for a 4 mil long rod crank...

 

A lot of people run a spacer, just asking for air leaks and/or trouble in my book.

 

Your call.

dajogejr, so what if I have a simple woods port, and wanted to get it re-ported for a 4mil? Would it not work optimally since it was already ported? I was planning on using cut domes, but did not know about the cylinder re-porting issues??

Edited by Banshee0028
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