650sx build by: my650sux

20161024_180159.jpg I have made leaps and bounds in my project. The things I changed were carb settings, cooling water flow, gas tank check valve and pump nozzle size. This thing is starting to rip, and I like it! So my carb settings needed a much lower pop off, I read for days and ordered a 95g and 2.0 needle seat. Installed these to get a pop off pressure of 16psi (lower than expected) LS120 and HS145. I then took the aluminum nozzle apart that I bought on ebay and started measuring, my stock nozzle was 84mm this one was 80mm. I rolled up a piece of 1/8" aluminum to be 84mm and modified the aluminum nozzle. Because this nozzle was originally to small, it was causing low speed cavitation and an awesome top speed (not what I wanted).
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20161028_185807.jpg The pics are before cutting the nozzle to length and adding repads for tapping m6x1.25.

I then moved on to the cooling system, because I installed dual cooling and I'm running in 50 something degree water the engine was never getting warm. I used small ball valves to control the water flowing though the dry pipe jackets and out of the head to the pisser. In addition to this I tapped into the water flow (pre exhaust manifold) and routed it to my water box for less sound (with ball valve).

I'm also experimenting on where to place the gopro, I had it on my had pole and the video is shaky but you can tell this think is starting to rip! The powerband hits right away and goes all the way to rev limit.

After making changes to my cooling system I used an inferred thermometer to check exhaust and engine temps. My engine was anywhere from high 130's to 158 depending on where I shot with the thermometer. The dry exhaust was much hotter (as planned with ball valves) in the 180 degree range. It seems as though things are really starting to come together.
 
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Mad skills. I know many guy hate the 650sx, it was my first ski when i was 14 I always wanted Yamaha type power, I did every mod to it you could think of, ended up with a 750pjs motor in it and it still didn't have that 61x pull. Eventually broke the ski beyond what I thought was worth repairing and bought a superjet but the I still have a soft spot for 650.

I think this is an awesome build and it sounds amazing!! Keep up the good work
 
@Blaine Mac,
Thank you for the compliment, I too grew up on the js440,650sx,x2 and js550. After ridding a few aftermarket hulls you realize how slippery and tipsy the 650sx hull is. I'm sure that this could be fixed by a rockered front end tubbies exc. but there are to many options on the market to invest a whole lot into it. I am more interested in something to mess with in my garage and fabricate parts for. I have learned so much from this build, maybe one day I can make a product that others would be interested in. #goals Soon I will be buying an aftermarket hull and will make some new parts to fit that hull. I would really like to make a hydro-formed exhaust that would lay in the belly of the boat to keep weight down low. The current dry pipe pulls hard mid to top but lacks the low end hit that I desire. I plan to do some math and then play with different designs until I get the desired result. I rode a krash with 1000cc power valve engine the other day and it was a beast! I need less power than that but more than I have currently. My 701 needs more compression and a different pipe to get what I'm wanting. ADA head w/33mm domes, twin 38's and different exhaust here we come!
 
IMG_0773.JPG IMG_0788.JPG IMG_0804.JPG IMG_0812.JPG IMG_0819.JPG After a lot of overtime I had the hull of my dreams built. It's built from reflections carbon fiber. Jeff Blair did the hull build and I have been working on everything else. Because I'm waiting on some gaskets I am not running my ported 61x, I grabbed another one off the shelf and slapped an ada 33mm head on it. I spent quite a bit on parts this time because I want a show piece. Here are a few pictures of my progress, once I get my trim and steering cable length correct I'll be ready to set the motor in.
 
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