650/X-2 winter build 650/750

[dbattersby20]

So, I'm rebuilding my 650sx this winter. The engine lost some compression at the end of the summer and I tried to tear it down to rebuild, but the salt got to it so bad that i couldn't seperate anything except the top and bottom half of case. Rather than waste more time and money getting the engine apart I looked for a used 650 engine. Found one for 300 with with electrics, carbs, exhaust etc, but the guy seemed to always be to busy to meet with me. So i bought a 750 earlier today. Probably starting on tuesday with tearing down the engine to replace gaskets, hone/re-ring, and possibly - get the head milled, flywheel lightened. As far as the engine goes i need to decide what carbs to run, I have the two carbs on there and a mikuni 44 off my 650 engine. I'm also leaning towards using 750 electrics which I'll need to buy. I think I'll probably use stock 650 exhaust for now, but extend the chamber and rework the water. I'll be posting a lot more and more pics during the week.

 

[dbattersby20]

can anyone tell me whether it's a small pin or big pin just by looking. anything 95 and after would be big pin right? so when did they start doing dual carbs... Engine is sitting in my trunk until i go home tuesday so it's not so easy to look around it and check it out.

 

[Twinturbostang]

The bolts on the intake.

 

[dbattersby20]

ok, ill check next time i go to my car, what is it 6 bolts is bp and 4 is sp.

edit: nvm 6 is big and 5 is small. the small has no inner bolts...

 

[Mdavies_02]

Check out my buddies build from last winter.

http://www.pwctoday.com/f16/650sx-build-up-311836.html

He is on the X as Beacom as well, feel free to ask him any questions.

Good luck

Mike

 

[Austin]

Big pin has 12 total, small pin has 10 total (no inner bolts). I think this is what you meant, but just was going to throw it out there just incase. They started the dual carbs from factory on the big pin engines I think.

 

[dbattersby20]

thanks, looked through the thread... looks like he kinda stopped in the middle.

Yea, thats what I meant say... and its a small pin

 

[Mdavies_02]

He may have stopped posting, but his 650/750 ripped this season.

 

[Flatdeckfool]

I have a 650 with a small pin single carb with stock exhaust and I have a 650 with big pin dual carbs with full after market exhaust. Supposedly you can mod the 650 ele but I haven't done it. Currently running the ele box out of a Zxi sit down. If you can get a ele box from a sxi get it. Much smaller

 

[dbattersby20]

Im planning on running the 750 electrics, unless money becomes an issue. In that case than ill run my current 650 electrics. Ill will probably buy the cheapest/best quality ebox bot ill keep on eye out for the sxi one. How does the small pin run on a single carb? I was trying to decide what to to run for carbs... I have the two stock carbs and a mikuni 44 (which i want to get blackjacked) i was thinking about running one 44 and then if i get the motor ported or a nice exhaust ill also add a second 44.

 

[dbattersby20]

Got back from school today for winter break and started to take the engine apart. Ran into a few problems, I knew it needed top end rebuild or at least a hone/ re-ring, but the engine head is pretty messed up (i was planning on getting a ada head or something i just want to be sure of what caused this). Im thinking it was just a lean condition. All the gaskets are thin metal gaskets and the gaskets under the rear carb did not seem to be sealing. The intake took a while to pry off so i don't think that was leaking. The head and exhaust slid off pretty easily but the cylinders are still on there and i haven't been able to budge them yet. I sprayed some penetrating oil on the studs and we'll see if that does anything. Second engine in a row that i haven't been able to free up. This will probably be the last time i buy a used engine. bottom half the the flame arrestor also has a crack in it from hitting up against the tab on the engine head. Will probably be using a different carb set up anyway with pro-k arrestor. After getting the intake off the crank looked like it had a little rust in a few spots, but i don't think i can feel any play so should be good i hope. Clearly there was some water in the engine at some point...

 

[dbattersby20]

since i had a 650 and 750 exhaust mani and head right next to each other i figured i would just take some comparison pictures incase anyone wanted to see something

 

[dbattersby20]

And here's some pieces that will be going back on the ski. The liner in my pump got swollen at the end of the season and the prop started to rub so i got a new pump and 9/17 skat, so now i have a 9/17 skat and a 16. there's also an ocean pro nozzle there and marine ride plate and scoop. Ill probably be getting a top loader style grate though because i ride in a bay which can get pretty choppy at times. where can i get a new ring for the tip of the impeller.

 

[dbattersby20]

After comparing my head to some other posts. Im thinking that something had to have been bouncing around in the chamber.

 

[Austin]

have you checked your crank yet? It almost looks like water came up through the pipe since that cylinder is so rusty.

 

[dbattersby20]

i still haven't gotten the cylinder block off yet. i'm about to go and try again. Looking through the intake there is a little rust on the web ( i think it's called the web), but im thinking i can just clean that up. I'm hoping the bearings are good an nothing is chipped. im wondering what caused all the pits in the head. Hopefully its not from the crank or piston skirt sort of thing. i bought the engine for cheap knowing that i would need a top end rebuild, i didn't think it was from water ingestion though cause the guy i bought it from knew a decent amount about skis so i figured he would have taken the right steps to get the water out asap.

 

[Austin]

Hopefully your crank comes our good. Are both cylinders pitted or is it just the one?

 

[dbattersby20]

both are bad, the rear one is way worse though. The block is going to come off, just waiting on one stud to free up. I think the crank will be good though.

 

[Austin]

Was this a salt water engine?

 

[dbattersby20]

I don't think so. The stud is just a little rusted. My last engine was a salt water engine and now it's a large paperweight