Star 90 Shake Rattle and Roll

[DaveinWA]

I have a '77 (I think) Star 90 Model 906S4A that whenever I try to get up on plane starts hammering/jumping and making a terrible racket. It starts fine and idles fine. I changed the plugs and it seemed OK but then started doing it again. A friend suggested changing spark plug caps which made it far worse. If I'm reading the service manual right the correct firing order is simply top to bottom 1 thru 4. We checked the coils and they're all firing. Any ideas? Bad plug maybe?

 

[force01]

Re: Star 90 Shake Rattle and Roll

Dave,<br />It sounds like you are jumping the clutch dog. It is probably too late but try to adjust it to where forward gear is favored. If it still jumps out you have to disassemble the gear box and change the clutch dog and the forward gear. thanks, bret<br /><br /> If you need further assistance please email me @ forcepower01@yahoo.com. thanks,Bret