GS450 GS425 swap?

[chrisw123]

I have 1980 gs 450L that has a bad bottom end (Crank shot). I have a GS425 with a Good bottom end my question is can I use the top end from my 450 on the 425 bottom end? I wasnt sure if they would interchange or not can somebody HELP

 

[Guest]

Depends on the years of the engines.

I believe all 1980 and so on 400cc-450-500cc's blocks with plain bearings can interchange anything in the base and the differences between them are in the head and the cylinder bore sizes only. (from everything I've discovered)

However the 425 is a roller bearing motor, most 425's that I have seen were made up to the year 1979. In that case very little is interchangeable.


Certain parts may fit but you'll notice certain oil passages do not lign up if you swap your head and cylinder to the good base.


What kind of crank bearings are in the 425? plain?

The 79 base has a different stroke than the 4xx base after 1980

 

[Guest]

+1 to Mekanix, roller bearing bottom end won't work to the best of my knowledge.

However, the whole 425 should bolt straight in...

 

[chrisw123]

I am not sure if the motor has plain or roller bearings, I bought this GS450L because it was flawless shape and didnt hear it run so when I cleaned the carbs and got it running it had a knock in it when I pulled it apart the rod bearing on the left side was completely gone, Everything else was fine so a buddy of mine had a really good motor off of a 425 but the cylinder head and cylinder was missing so rather than have to tear down I was going to put the head and cylinder off of my 450 on the 425 bottom end and rebuild the 450 bottom end this winter

 

[Guest]

Bugger, that doesn't help. Might have to bring the bottom end rebuild forward...

 

[SteveN]

Hey ChrisW, where are you located? I have what is supposedly a good engine with a sticky valve from a 450 I can sell cheap. I'm in CT