Engine bore

[Fro Diesel]

What is the bore of a stock 650 SJ (90) with a .040 bore?
Thanks

 

[Matt_E]

78mm

 

[njfl]

78.016mm assuming that you mean 0.040 inches.

 

[Fro Diesel]

see I'm not sure because i bought the ski from someone else. i would assume inches.

Does this raise it to a 701?

 

[njfl]

Actually, with the 78mm bore it just brings it to 650.

The interesting thing (that a lot of people don't know) is that the stock bore/stroke combination on a "650" is really only 633ccs.

 

[njfl]

see I'm not sure because i bought the ski from someone else. i would assume inches.

Yes, I agree. I'm sure it was inches. I was being funny. 0.040 mm would not be able to be machined on any typical machine shop equipment (tolerances).

 

[Fro Diesel]

hey thanks. i really want to mod my ski. it already has exhaust and some other stuff but i want more power.

 

[jeepmark4x4]

when in doubt bore it out :lmao:

 

[stanton]

Yes, I agree. I'm sure it was inches. I was being funny. 0.040 mm would not be able to be machined on any typical machine shop equipment (tolerances).

BS! thats like .01", common doc for a finish pass.

 

[wayne]

hey thanks. i really want to mod my ski. it already has exhaust and some other stuff but i want more power.

get a 701 and put in it. sell the 650 engine to off set the price.

 

[njfl]

BS! thats like .01", common doc for a finish pass.

Actually it's closer to 0.001" or a mil, so I guess that could still be feasible (I take it this offended you as a machinist, sorry). Regardless, I always find it funny when the metric and English worlds get interrelated like this.

 

[spence]

if the 650 really isnt 650 cc's whats the 701?

 

[njfl]

if the 650 really isnt 650 cc's whats the 701?

The 701 is a true 701. Don't know why they did that with the 650. I can only guess that they did it to keep up with Kawi from a marketing point of view.

 

[Matt_E]

The 701 is a true 701.

Actually, it's 700.77 cc. :fingersx: :haha:

 

[spence]

so are the kawis the same cc's they say?

 

[Matt_E]

Get bore & stroke numbers and figure it out.

It's pretty customary for the OEM's to pad their displacement numbers a bit.
Octane - 777cc
SXR - 781cc
Yamaha 760 - 754
Yamaha 1100 - 1151

 

[spence]

lol i didnt know it was like that. youd think theyd just make it to say 800cc's not 781cc's

 

[Matt_E]

Eh...I don't think I was clear...let's repost this.

Octane 800- actually 777cc
SXR 800 - actually 781cc
Yamaha 760 - actually 754
Yamaha 1100 - actually 1151

 

[RideItLikeYouStoleIt]

lol i didnt know it was like that. youd think theyd just make it to say 800cc's not 781cc's

They do that because to get 800cc's may be a pain for them to do. Its easier for them to reuse connecting rods from another model or pistons or something like that. To get exactly 800 youd need very specific sized strokes and bores. They fudge everything to get the hp, weight etc.. If it saves them $200 a machine to make it 771 instead of lets say 798 then they might just do that.

 

[michael950]

Eh...I don't think I was clear...let's repost this.

Octane 800- actually 777cc
SXR 800 - actually 781cc
Yamaha 760 - actually 754
Yamaha 1100 - actually 1151

They actually call the Octane motor, the "Polaris Marine 777"