Does anyone know what the bore size is on a 426 piston?

I'm not wanting to resleave.

 

426cc is the biggest you can go in the stock 400ex sleeve.....I dont know the size......

 

It makes it 88mm or .120 of an inch. I would only go to a 416 (87mm .080 of inch) with stock sleeve. Going with a 426 would make it too thin for reliability. If you really want power; get it resleeved and go with 440 cc or 89 mm.

 

I disagree

 

I beg to differ, This 426 of mine is fantastic. I ride it to the limits and it never skipped a beat. Besides the 88mm is a lighter weight piston as compared to a 89mm.

 

Did you guys change your cam to the XR400 when doing a 426 kit? I just went with the 426 and my machine shop is saying to replace the springs with a RD Valve Spring kit. Is this true?

Thanks

B

 

LL_---I was just responding with what i have heard about the 426 with no sleeve. I hope you dont have any problems. RGB----I did install the XR400 cam and TitaniumValve springs (RD Heavy Duty) when I had it bored to a 416. It feels like a whole new bike! It will easily pull the front up in 4th gear with stock gearing!

 

I already have bored it to 416 with a white Brothers Cam and I just looking for a little more (cheap) power.
I plan on buying a new Carb before the race season starts, But I have a chance to sell/trade my 416 Piston and cylinder for a stock one so I can start again.

 

I understand you were sharing info like me. Hey guys here's how I look at it! I figure I build it up the first time , if it blows, I'll make it badder and better next time? Positive outlooks!! Have fun!!

 

Milkbone how do you like those shaved fenders? and is that 416 a revver of a bike somewhat like a 2 stroke.RGB XR400 cam here also.