[Larry Sapp]

I just purchased a 86 Yamaha 70 hp , it idles fine in neutral but when I shift into forward it shakes at low rpm's ! My question , is this normal for this engine ( 3 cyl. )? It smooths out fine once the throttle is increased and runs good WOT... TIA L.E.S.

[rodbolt]

Hello its hard to estimate excessive shaking without seeing it. some of those motors shook some when idleing. you may try moving the carb pilot screws in or out 1/8 at a time and see if it smooths out any. keep posting and let us know

[Larry Sapp]

Thanks Rodbolt for your responce ! Here's a little more info , the bottom carb was leaking so I to it to repair shop ,they cleaned carbs and replaced water pump impeller... (impeller was insurance on my part). I would think the carbs would be adjusted correctly at the shop but I doubt they engage shifter while running.....As I said in my post the engine runs good so maybe this is normal for this engine . I will purchase a Clymer manual before attempting any tweeking on my own . Thanks Again L.E.S.

[lonewolf5347]

L.E.S.I have a 90 hp yamaha 2003 and it seems that at idle there is a liitle shaking to the engine but onces in gear the problem is gone.What I did to correct the problem was to increase the idle speed a little and increase the low speed jets or pilot screws.Factory setting on the low speed jets were around 1 1/2 turns out now it seems to run great at idle with about 1 3/4 turns out on pilot screws

[Larry Sapp]

Thanks Lonewolf5347 for your reply and info.... L.E.S.