Super Jet Need help figuring out boring on this thing.

NVJAY775

My home away from home.
It's a 771 (61x cyl), but I don't know if it has sleeves in it, or if the stock 701 sleeves have been bored into the unknown? Can anyone ID anything on this please? She's seen better days that's for sure. Any option recommendations?

Thanks fellas!
Jay
 

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it looks like Yamaha replacement 84.5mm 64x pistons. You are at 763. 85mm would be 771. If they are stock sleeves, 84.5 is pretty much the limit, noting that some/most builders won't go over 83 on a 61x w/ stock sleeves.
 

NVJAY775

My home away from home.
it looks like Yamaha replacement 84.5mm 64x pistons. You are at 763. 85mm would be 771. If they are stock sleeves, 84.5 is pretty much the limit, noting that some/most builders won't go over 83 on a 61x w/ stock sleeves.
Pistons are 85mm pro-x 771 (my second set lol) I just don't know what the top of the sleeve should look like as far as thickness is concerned. I don't know if these are the stock 61x sleeves bored WAY out, or if it's been re sleeved with big bore sleeves?
 
Get a pic of the bottom of the sleeve where it protrudes into
the cases. Check ur thickness there. 85mm 61x sleeves are gonna be super thin down there.
Also test fit them in a 61x case. If it fits it's most likely 61x. If it hits then it's 62t, am, thicker BB stuff that requires case mods..
 

NVJAY775

My home away from home.
Well... I cooked the top end yesterday after 5 minutes. Was told I would be ok not using race gas mix (for freestyle only), but... No I think. But the pop was nice lmao!! I'll post pics on this later and probably start up a new thread after I get it out and tore down. Although in defense of the recommendation of running pump gas was made assuming my motor had some kind of normal porting, but it always had below average compression for a ported 62t 61x set up. I have no clue who did the porting, but think that was my demise yet again. Should have chucked it a long time ago and not tried to milk it out. Costs more in the long run and now I'm off the water for a while. Got what I paid for lol!!

Lesson learned. If you don't know who did the porting, don't count on anything special other than failure in the near future. I believe these words to be pretty true.

jd91t I'd really dig a pic or two only if it isn't any extra hassle for ya. Thanks much in advance!
 
I don't have an 85mm 61x cyl to take pics of, but I did mic my 81mm X cyl.
OD @ the base where it slides inside the cases is 3.440"
Sleeve thickness also @the case portion is .125"
SO if You have 85mm bore (4mm /.160" over) oem 61x sleeve that take 2mm/.080" from the .125" I'm measuring, and leave you a razor thin .045"/1.1mm...
I measured an 84mm 62t/760 cyl for comparison as well. OD of 3.485" ,and exh side sleeve thickness of .095".
So 62t @85mm would be .075" thick
 
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NVJAY775

My home away from home.
I don't have an 85mm 61x cyl to take pics of, but I did mic my 81mm X cyl.
OD @ the base where it slides inside the cases is 3.440"
Sleeve thickness also @the case portion is .125"
SO if You have 85mm bore (4mm /.160" over) oem 61x sleeve that take 2mm/.080" from the .125" I'm measuring, and leave you a razor thin .045"/1.1mm...
I measured an 84mm 62t/760 cyl for comparison as well. OD of 3.485" ,and exh side sleeve thickness of .095".
So 62t @85mm would be .075" thick
Thanks for all the info! I'll have to do some measuring when I get some time. Been crazy busy...
 

NVJAY775

My home away from home.
That base measument would be a stock 760 64X sleeve.
Thanks for clearing that up! I always wondered what they were. Any idea on why they were installed? Are there any benefits? More of a race set up or freestyle? The guy I got the motor from some years ago was sponsored by pro tec, but did freestyle.

Might give it to my kid this winter if I can get it bored first. Is this a possibility?

Thanks for any other words of wisdom.
 
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