780-890 triple case mods

[Snoghost]

When going to 583 pistons to big bore 780-890 do you have to do the case mods or any skirt mods like you did 617 pistons? thanks

 

[Snoghost]

Big bore 890

Nevermind--Built it last weekend ---runs good

 

[nuttyn01]

The triples with 583 pistons were 925cc engines and ran very well. To answer your question, yes you have to open up the case for the sleeve skirts. Some sleeves for the 890s will fit but some wont. Depends on the o.d. of the sleeve. Some guys say the 925s don't make anymore power for the work involved compared to a ported stock bore. Get the big bore pipes for the elevation and they run very strong.

 

[Bigairhair]

What piston did u use? What year motor? What carbs? What jetting. Tha ks brian