1999 670 formula getting no air

[Kyle kehn]

My father in law had a crank go bad so be bought a lower end from a 700 and put his block on it kept carbs and pistons and everything else from 670 the only thing he used from 700 was the crank and housing now it Boggs out at 4000 rpm. If I gut the air box it runs good what is wrong?? Do I need to re jet??

 

[olymon]

Two totally different motor styles. Rotary valve 670 versus reed 700 How is that coming together??

Making JIS screws into junk

 

[Bedhead]

This could be interesting to follow........