yamaha 2 strokes

[cleve]

asked this question about a year ago and never got a reply. figured i'd try again. does anyone happen to know the difference between the 2004 60 hp and 70 hp 2 stroke? same exact powerhead,weight,lower unit etc. except the 70 rpm range is 5000-6000 where the 60 is 45-5500. could it be the cdi box? the carb? both? just curious,can't seem to find this anywhere.

 

[ianyoung77]

Re: yamaha 2 strokes

I think the carbs and cdi are the same. The reeds are different and I would think probably some exhaust components as well but nothing obvious

 

[robert graham]

Re: yamaha 2 strokes

Maybe the port shapes, size and location,piston skirt design, carb jet sizes, compression ratios on each cylinder, ignition timing. 2 strokes are very easy to tune up or down by the factory. My 90HP 2 stroke Yamaha makes 90HP from 70 cubic inches, all 3 cylinders have slightly different compression ratios. Probably a bad idea to try and "hot-rod" or modify a factory motor unless you were racing and Really knew what you were doing.

 

[cleve]

Re: yamaha 2 strokes

nope,no hot roddin here. just thought maybe it was something simple. there are several 'sister' engines that you could make minor changes to get more horses but i figured that was not the case with these motors or i would have already found out.

 

[seldomseen]

Re: yamaha 2 strokes

The reed stops on the 70 2 stroke allow much more reed opening than the 60. The carbs on the 70 have richer main and secondary jets. The timing on the 70 is 2 degrees less at WOT. These are the main diferences.