Completed 650SX Build - From 50Hp to 60+

[Pro-pulsion]

One thing I need to say before anything else is that most of my ambition and initial mod reference came from kawipilot over at pwct when he posted this thread...

http://www.pwctoday.com/showthread.php?t=157734

Many thanks kawipilot for the awesome thread and the much needed motivation to get started on the modding path.

So to bring everyone up to speed, I bought my ski in early March of 2009. It's a 92 650SX with the blue and white color scheme. I had a laundry list of mods I was originally planning on doing to it but I had to tame it down for now because of the time involved and the lack of experience at the time. So what I have done to the ski up to this point (November 2010) is...

- modified the stock exhaust substantially <-- maximum bottom end gains
- replaced the stock 38mm Keihin carb with a Mikuni SBN44 <-- major improvement and needed for modded exhaust
- replaced the stock reeds with single piece Tony Dukas Racing reeds (had them from my last 92 650SX)
- added in a quick steer turn plate
- removed the water drain from the bottom of the engine and blocked it off
- removed the oil injection (never had a prob with it on the last ski but less weight without a full oil tank)
- replaced the stock ride plate with a Jetsport finned plate <-- better handling and less porpoising
- made a carb and throttle cable adapter for the SBN44
- modified an OceanPro Vortex flame arrestor to fit the SBN
- de-burred and polished the combustion domes
- polished the exhaust ports
- modified the stock intake grate
- replaced the stock impeller with a Skat-Trak 10/18 stainless impeller <--very noticeable hook-up and bottom end gains
- replaced crankcase seals and new head gasket
- rebuilt the fuel valve
- replaced the fuel lines
- added in a primer kit

Other areas that needed attention were...
- clean the hull, engine, and fuel tank thoroughly
- clean up the electrical box (loaded with white corrosion powder)
- repair a bad battery lug connector
- correct kinked hoses (found 3, hose to the waterbox from the stinger, auto bilge hose and water bypass line from the exhaust to the pump)
- some minor painting
- add in some new stainless fasteners and gear clamps

All of the above mentioned mods, had taken me about a year and a half to complete and in some ways are still ongoing. The rest of the postings will take you through the modding experience as it was happening, so getting back to the original posting...

I think that sums up the list...at least as far as I can think of for right now. I was going to mill the head and polish the exhaust ports but the ski right now has 145 compression on both cylinders so I'm not going to bother. Maybe later in the year if I think I want a little more power. I was also going to replace the piston rings and hone the cylinders but again...only if I want more later on down the road. I would like to put a bigger carb on it, new HydroTurf, Skat-Trak stainless impeller and aftermarket intake grate, footholds and handlepole but I'm a little too limitted with affordability right now. If there are any other freebie mods that anyone can think of by all means toss it up, I'm sure there will be lots of thankful people including me hehe :biggrin: Pics will be posted soon, hopefully by the end of Sunday night. Thanks for any suggestions and taking the time to follow this build.

 

[Pro-pulsion]

So I haven't been able to accomplish much. I spent most of the last two days on the road either searching for needed add on parts or nothing to do with the ski entirely. But there is progress. The first few pics are from when I first picked up the ski. The only thing I did at the time was to peel off a couple of little red skull in flames stickers. Other than that I didn't get around to much until just within the last couple of weeks.

 

[Pro-pulsion]

In these two pics you can see the kinked hoses which I believe to be factory flaws. They ran the hoses on too sharp of angles. The other pics are the beginning of the clean-up and repainting. I'm planning on sticking with the factory colors but bringing them inside the hull as well. I'll have more pics hopefully by the middle of the week.

 

[Pro-pulsion]

Oh yeah, I forgot to post a pic of the ski after I took all the unwanted stickers off and cleaned the outside up lol. It looks much nicer without the add on stickers. The warning label on the handle pole was so badly oxidized that it was just an eyesore. I will be putting the odd few stickers on but they'll be something like Skat-Trak and whatever else that is meant for the ski. I'm going to put a couple of Skat-Trak stickers on my truck too lol :cool2:

Update - Ok so it's not much of an update. I ran into some problems trying to remove the flywheel...that sucker is really stuck on there. I hope to have it off and do some clean-up by the weekend. I found what looks like a small slinky type spring all blown up in there and stuck to the magnets. Hopefully it's not going to be a serious issue, or it was but someone has had it repaired and never seen the bits stuck to the magnets. So aside from pulling the intake and exhaust manifolds off, right now the only touch-ups I have done were to continue with some small scale painting and de-burr the intake manifold. In the first pic you'll see the casting slag overhanging into the manifold's ID. I took a Dremel with a fine grit sanding drum and cleaned that off leaving a very small 45 degree chamfer. I'm sure the gains from this will not be noticeable enough when riding, but all of these little things will add up and make a really good machine without sacraficing reliability.

 

[Pro-pulsion]

Ok, so things are taking a little longer than hoped for. I was hoping to lighten my flywheel today and polish the exhaust ports but because I have a severely corroded stud I can't remove the cylinders. I spent the day trying to free it up and put the flywheel down. Still never broke the cylinders free from the stud so that will be my weekend project. On the upside though, I managed to clean and rebuild the starter bendix and polish the domes. I was also going to mill the head but somebody beat me to it.

When looking at the head, you'll notice a very slightly raised portion around the domes. Typically on a stock 650sx this portion is around .060", mine is around .002". The nice thing when looking into this is that the pistons are really clean as are the cylinders and the crank seals were installed with the springs facing out. This is also the way Group K rebuilds engines so whom ever rebuilt this ski knew what they were doing.

But getting back to the heads since that was today's job, I used a countersink bit in the drill and removed the barbs around the spark plug ports. Then I cleaned the domes out with a 3M medium scrub pad and went onto sanding. I used 240 grit Emery Cloth to remove as many imperfections as I could then up to 600 grit sand paper to make the final polish. All in all, I think today was a good day even though I was limitted to what I accomplished. The domes took about 2 hours to polish, the cylinders I spent about 3 hours on trying to break them free from that stud and the bendix took about 2 hours to disassemble, clean and rebuild.

 

[Pro-pulsion]

Hey hey, so I'm really really stuck with this whole cylinder deal. I've tried everything...put a ton of heat to the cylinder around the stud, three different types of penetrating oil, made jam nuts to thread out the stud if possible and nothing is working. It really sucks and to see that the engine had been worked on in the not too distant past just adds insult to injury. These cylinders should not be that corroded and seized to the studs when the cylinders were removed what seems to be fairly recently.

But getting back to the mod work. This past weekend I took the manifolds in to work and bored them out. So now I have the intake manifold opened up to 42mm and the exhaust manifold to 44mm. Additionally when I was there we used the mill and put a 45 degree 44mm diameter chamfer on the head pipe to port match it to the exhaust manifold. There are still some other little things to do and more will come as the mods are completed. Most of the exhaust mod work is done but I want to get the whole set-up finished before I post pics on it. Anyway here are the all manifolds before and after modding.

 

[Pro-pulsion]

The first two were the before, these ones are the after.

 

[Pro-pulsion]

Finally! I managed to get my cylinders off and made some real progress. Today I polished the exhaust ports. I didn't change the dimensions such as height, width or angle on the cylinder wall. But I did smooth out the angles a bit. I always thought that factory porting was very precise and clean but I was way off. The PTO port had a much nicer angle flow but much worse port match to the sleeve. It took about a total of 4 hours to get them at where they are right now. I plan on spending another 2 or 3 on them with 600 grit sandpaper and then 1200 to really give a mirror finish. The extra finish might or might not matter but I prefer it. Here are the before and after pics.

 

[Pro-pulsion]

I guess it's time for some more updating. Things have been a little bit hectic over the last month or so. Anyway, I have about 99% of the exhaust mod work done. I just have to plug one water fitting and figure out how much hose I will need for the new set-up. In the first two pics you will see the welded up water injection port. The second shows the 1/8th inch hole (down from the stock 1/4 inch size) drilled.

Next up is the old head pipe gasket, I used the Dremel with a sanding drum to oversize the inside diameter to a slightly larger one than the new bored out size of the pipe. And yeah I did re-use it lol, but I added some OMC Gelseal (Anearobic flange sealant) to both sides of it so it should be fine. I've done this in the past with a 100% sucess rate of a solid seal. Additionally on the head pipe, there is a flat spot which I used to add the new water fitting to (as per instructed from another fellow modder), but I am going to change this fitting to a 90 degree fitting to allow for more clearance between the hood and a better finished look. That's about as far as I have made it with the exhaust for now but technically speaking, it's pretty well finished. The only other mod I still have to get a pic of is the water injection fitting I had welded onto the stinger.

 

[Pro-pulsion]

Moving right along, I removed the old reed valves and changed them up with a solid one piece reed and stop plate raisers. This allows the reeds to open that extra little bit further and dump in that extra bit of fuel :cool2: Afterward I went out to a local metal supply store and asked the guy if he had any little scrap bits and pieces kicking around he wouldn't mind parting with. That's where I picked up the stainless steel tubing I used to make the stinger fitting (which will be shown later) and also a foot of 1/4 inch aluminum round bar.

I used the aluminum round bar to make a plug for the intake manifold where the old oil injection fitting was mounted. But to make it fit I had to cut it down to about an inch long, chuck it in a cordless hand drill, lock a mildly coarse file into the vise and turn it down also on a slight angle. Once I angled it down enough to work I coated it with copper gasket compound and tapped it in good and snug. The third pic shows how it looks from the inside of the intake manifold. I could have made it fit much more closely to the true inside diameter but there won't be any air leaks and that little bit of surface difference won't have any real bearing on the quality of the air flow.

Update, the silicone on the aluminum intake plug was eventually allowing an extremely slight amount of by-pass, so I ended up JB Welding it in place.

 

[Pro-pulsion]

Time to get into the crankcase. To block off the oil injection I grabbed up a small 2x3 x 1/4 inch thick piece of aluminum plate, this was also scrap material from the metal shear. It isn't overly precise mainly because I didn't have the engine at the time I made it...would have been nice to plot the stud distance out but oh well, it's on and sealed with gasket sealant. It was easy to make, I used an end mill at work to do it but a hacksaw or jigsaw and coarse file will due as good of a job if not better with a little time put into it. Pics will come for this as well...it's tough stopping to document all the steps lol...but worth it if even one person finds it useful or has fun following the build.

Continuing on, the water drain on the bottom of the crank needed to be removed and the ports plugged. I originally made a block-off plate for this but found the info from another modder to be a lot better of a method. One thing about around here is that stainless metric fasteners seem to be ridiculously rare...I don't understand it as I do live in Canada where we supposedly took to the metric system...but there are alternatives. The modder I followed suggests using 2 8mm diameter by 12mm long stainless bolts. I couldn't find these fasteners at any of the 8 hardware/fastener specialty shops around here. So I went with the next closest thing, 2 5/16 x 1/2 inch stainless bolts, mixed up some Permatex cold weld (same as JB, Devcon, Loctite cold welds), coated the threads and around the uderside of the hex portion and threaded them in. No tapping threads as this will send shavings into the engine, just coat them and force thread them in with the ratchet. That's all for the engine and for now, here are some pics of the port blocking job and a quick peak at the inside of the hull all cleaned up and with a touch of new color. More to come later.

 

[Pro-pulsion]

Ok, so here are the last stages of my mod works until I either blow the ski up or get ahead a little over the course of the winter. So for this mod, I cut out the middle bar in the stock intake grate. I just used a tiny hack-saw for small area plumbing work that I had kicking around (it's about time it had a purpose) A little change of this mod from what I have read in the past is that I changed the angle of the curved portion at the back of the grate, to be a little more aggressive and I sharpened the edges to cut the water instead of jamming through it. Also I gave the curved area a bit more of an opening to allow the additional amount of water in and keep that pump loaded. Think of it as looking like the wide mouth beer cans, less glug and more chug lol. I'm not sure if this will help but it can't hurt. I also read recently that by just putting a stainless washer in between the ride plate and the hull only at the back two bolts (closest to the rear of the ski) it will help to reduce porpoising, I'm going to try it and see, for how cheap the washers are why not.

 

[Pro-pulsion]

I promised pics showing the added water fitting onto the stinger and my home made injection block-off plate. I'm not sure if the original fittings have calibrated hole sizes or not but I pre-drilled the hole to match the size of the others. I used a #27 drill bit which I think works out to something like .144" I was reading on several postings about running new through-hull fittings and what not to get rid of the bypassed water coming from the T between the head pipe and stinger on the new cooling line set-up. I'm not a fan of cutting into a hull and adding holes unless it's going to be for something necessary like foot holds. So instead I used the original bypass fitting already in the hull which gets plumbed out to the pump housing. As for the bypass port on the first stainless section of the exhaust cone, I tapped it with a #8-32 tap, bought a stainless screw, washer and lock washer, and coated the screw with copper silicone because it has the highest gas/oil/heat resistance rating.

This is where it all comes to an end...unless I can afford to start on some winter projects such as foot holds. All in all I spent around 110 bucks in total. The ski fired up for the first time tonight since I've owned it, and does it ever sound good. I am very stoked to get out on the water with it. My first start I wanted to get some lube in there as it had sat since last August. So it's first taste of fuel/oil was nothing more than a good heavy dose of fogging oil. Initially it was rough and choppy and sputtering but once the cobwebs worked themselves out it had a good, clean and consistent idle. After that I went to the pumps and bought up 23L(5 Imp. Gal.) of Sunoco Ultra 94, mixed it up with a rich mixture of Maxima Marine Pro (650mL:23L) and dumped in enough to give it a half a tank. Turned on the 'ol choke and after a few minutes of cranking to prime up the lines boom...the beast sparked up and lives! Well, until I can do more fun things to this ski, thanks to all that have followed my build, or read some of it, or are using some of the info to do their own. It's a ton of fun and worth every part of it when you get to see your work in action, thanks again guys n' gals :biggthumpup:

Update, I had to remove the plastic grommets on the oil injection plate as the heat made them soft and squish down. This also made the nuts loosen off. I also made a solid cork gasket and placed new nuts just larger than the studs on as my spacers, a washer next and then the original nuts. Seems to be holding out just fine.

 

[Pro-pulsion]

Today was the first test with all the new mods. What a difference, from a ski that ran stock speeds of about 37mph, I was passing my buddy on his SPi which GPS'd at 44mph. I figure the old 650 is clocking out at about 46-47mph now and with buckets of more blast behind it. The stock set-up I remember was a pig to do jumps with but the new configuration had enough wallop behind it to get some good air off of about a 2ft wake. I also noticed when climbing back on after a spill (and there were several of them) that hitting the throttle made pulling up into the pan almost impossible without letting off. The cooling was great, the engine did run about double the temp from stock but I always remembered the stock set-up almost always being cool to touch after a run...it ran way too cold before. Plus routing the bypass line from the T at the head pipe and down to the original through-hull fitting near the bilge on the stock set-up worked great. The hull stayed very dry and everything was just on the money today. The low speed will need to be fine tuned a bit more but all I can say is wow...what an amazing difference. I hope everyone that owns one of these skis decides to pick up on these mods because they are soo worth it. Have fun with this stuff guys n' gals, it was well worth the effort.

Forgot something, the 2, 5/16 stainless washers I put in between the ride plate and the hull closest to the nozzle exit, made a huge difference. They tamed the porpoising of that ski to an unreal amount. I took it down a mile+ of light chop and very little front end bounce. Most of the time there was none at all. Absolutely the cheapest, easiest and most effective handling mod you can do. I very highly recommend anyone with a stock ride plate to do this simple trick.

 

[D-Roc]

hey man just seen this build. very nice work restoring the ski.

 

[six5hooSX]

nice

 

[Pro-pulsion]

Right on, thanks bro...I bought it in March and finished it yesterday haha.

 

[ATS_Aaron]

Nice job! Makes me want to un-tarp the 650SX in the corner of my shop.

Aaron

 

[Pro-pulsion]

It was a fun build, you should haul the 'ol beast out and do some updates to it. If it's running, take it out first and bring back the memories of how low key it is, then mod it and post the differences. I'd really like to see what the impressions are of the before and after.

 

[Standup Rider]

Your 650sx sounds awesome. I am a proud owner of a 1990 650sx. I just picked up a 1988 X2 which has the same motor as the 650sx. The motor needs a new top end but I cannot get the cylinder off. I see you have had the same problem and was wondering how you got it off. I have been spraying pb blaster on it and have had my fiance pulling on tie downs I hooked around the cylinder while hitting it with a hammer. I was hitting it so hard I started crushing the water jacket and it still won't budge. I don't want to pry too hard on the tabs as I don't want to crack the cases. The motor shows little to no corrosion so it must be those cylinder dowels holding it up. At this point I just want to get it off and if I have to buy one off ebay I don't mind but it's driving me crazy that I can't get it off when my crankshaft is still good and the motor has good spark. I'd appreciate any help you could offer as I just want to put in a new piston and rings so I can ride this thing.