300/440/550 Js550 bore questions

[Js550FTW]

Hey guys I want to say thanks for everyone who helped me on the forums. I got my ski in the water and it's running like a champ. But I got a question about boring one if these things. I just got a couple of questions about them.

1.) how much can you bore them out

2.) Is it a good mod to do for the money

3.) does it make a noticeable difference in power

I'm wondering this because this winter I'm gonna have to do a top end rebuild. So if it's worth it I may want to bore it and get a little more power outta it for next season.

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[kswiatk]

1. 2mm
2. not in this case
3. only slight if you are doing a big bore, but you cannot big bore 550s

Boring should only been done to fit larger pistons in case you score the cylinder, not for any performance gain because it will not be noticeable.
If you want more power, get the engine ported through a reputable porter, or skip the rebuild all together and buy a 650 engine

 

[Js550FTW]

Thanks. I'm thinking of sticking with the old 550 engine just because I heard you can't race em if they have an engine swap

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