Invader Oval Race Sled

[Flying Frenchman]

Good Morning Guys,
I am Starting a new thread, so its easier to find!!!!
I am in the process of rebuilding my 81 Invader for Ice Ovals, but all my buddys are telling me that I a am wasting my money souping up my 440 because I will have a hard time competing against the SRX's.  They are encouraging me to find a 340 to soup up. 
All fine and dandy but when I look for replacement pistons and gaskets for a 340, they seem to be discontinued, so again I may be chasing something impossible? 
Please Chime in and give me your opinions.

[gixxer6]

340 parts are definitely harder to come by, but they are out there.   I have a stack of NOS 340 head gaskets if you need some.  All of the other gaskets are the same as the 440s. 

[DougKauer]

You can get 340 pistons on Ebay sometimes, that's where I found mine.

[Flying Frenchman]

Does anyone know if the 440 crank and case are the same as the 340?

[Interceptor398]

Only difference between the 2 motor is the top end.  I have heard the 78 case has a different deck height but have never proved it.

[Flying Frenchman]

So I looked on line for parts catalog and the part number for the 78 is different then 79 -81. 
Is their one year of 340 invaders that was stronger then the rest if so why?

[Interceptor398]

78 was rated 340-52hp and 440-67hp.
79 was  rated 340-53.5hp and 440-68hp.
80 was rated 340-53.5hp and 440-70hp with the LTD 4/6 at 78hp.
81 Invader was 70 hp.  Some of the difference is muffler and jetting.

[sprocket]

You can make a 340 with 90hp Pistons are available just in a different Application a little machining & proper port and polish, pipes, carbs & ignition anything is possible there has been a few people that contacted Wiseco for 340 Kawasaki Pistons in both snowmobiles & also the motorcycle guys asked about the Mach 1,2 & 3 which is a 500 triple free air 2 stroke, sometimes you have to think outside the box

[Flying Frenchman]

Quick question.  Pretty sure the 340 cylinders were cast bore and not nikasil,  is that true.

[kawhead]

340 invader cyl is chrome

[Flying Frenchman]

Has anyone every bored a 340 invader .040 over?  Will it perform with stock exhaust?  If a person did bore it out, which Pistons would work in this?  Looking forward to some input,  Want to make this thing fly!!!!

[gixxer6]

I've never seen over sized Pistons for the 340.  Boring.040 over will change it from a 340 to a 350.  I'm not sure 10cc will make a noticeable difference. 

[Flying Frenchman]

Thanks guys,  Found a good 340 engine.  I was just checking my options before a decide to go big or go home.  Will post pics of the project

[sprocket]

The class for ISR allows you to bore out the engine to 358cc
I went 61.5mm/60mm=356cc the Pistons used are 149M06150 Wiseco. These Pistons are not as tall as your stock Pistons 61.5mm/59.7mm you will have to machine the base to make these work. Stock is 60mm/60mm.
If you need to figure out what you need look up everything 2 stroke they have calculators to figure out what you need very helpful.