King cat toasted piston help

[tankman720]

Okay here is my deal I just got a king cat last week. All it has is A SLP can and clutching ect. I let it warm up for at least 15 minutes I got spi pistons in it. So im leaning away from cold sieze First ride got .8 of a mile up the trail and the dang think seized on me. I popped the hood and it was HOT underthere. So I got it home and tore into it. the mag side stuck, aluminin melted to cylinder walls. So I popped the PTO side jug off and it looked good. but their was some scaring on the piston and jug so this makes me think that it was starting to get hot or "stick" too. We all know that these 900's run hotter on the MAG side. I have stagered jetting. plugs were nice tan cinamon color. Im trying to figure out why it stuck. I have heard of oil pump, Air bubble in antifreeze, stuck thermostat, or APV valves. from the look of the jug and piston it looked like lack of oil. But I have heard that the valves can look the same. But when I did remove the valves I kinda had to give them a good tug to get them out of the cylinder there was a layer of carbon build up on them also. ? any Ideas ? the guy I bought it from rode it a week earler and it ran fine he said

 

[maddogwfo]

tankman sorry about your issue, same thing happened to me several years ago on my Mod 900 1M and come to find out my cable to the oil pump had to much slack in it, therefore lack of lube and burndown, now I check that there is no slack in cable when applying throttle, just a thought, MADDOGWFO PS what kind of Piston wash on the top of the pistons might tell you something

 

[diggerdown]

If it wasn't for the fact that all the words were spelled right, I would have thought I wrote the post! I just did the same thing, new SPI pistons, bled the cooling system, half dozen heat cycles. Good heat the the rear when I pulled out of the shop, mad a couple loops around the house, nice and easy, headed for the field and gave it about half throttle to launch off a drift and she stuck the mag side tight, tight l tight! Checked the rear exchanger and it was ice cold. Got new re-niced cylinders and putting it back together now with a new thermostate. Now I'm worried about these SPI pistons. I heard good reports so I thought I would give them a try, but I've never stuck a piston that quick and tight, I had to drive it out of the jug. You do have to take a little of the rings to get the proper gap but I wonder if the pistons need more clearance than the factory pistons. Still does not explain the lack of coolant flow, the real culprit. I had trouble last year after unloading and warming it up I headed down the trail and it stopped on me, same thing cold exchanger, I bounced the sled around and got heat at the rear and no more problem the rest of the year. Nothing had been apart since the ride before and yet my flow stopped.

 

[Arcticatdan]

sounds like cooling on both accounts. I have spent a lot of time getting coolant to flow on these 900s. I always check for heat in the rear exchanger at the trailer. Also make sure the over flow tank is full.

 

[01ZRTCAT]

How are both you guys filling and bleeding air from your coolant system?

 

[sumptercat]

happened to a friend of mine, he blew a belt in the past and it twisted the crank slightly, causing a slight vacuum leak and would burn down the mag side piston. figured it out after several repairs.

 

[Scott]

Aftermarket heads? Low octane or compression issues?

What elevation did the previous owner ride it at? What did YOU ride it at when it seized?

Just a bit more info will help us understand.

 

[Fiddy]

did u bleed the oil pump and get all the air out 900 hundreds bleed out kinda slow

 

[tankman720]

I unloaded from a parking lot that was roughly 7000 Ft. It has a Speedwerx head on it. But i got a stock head thats going on if I ever decide to use the nos. I got it all put back together a few days ago the guy I got it from was generous enough to send me a piston to get me by. but in a month or so Im gonna throw a new set of SPI pistons in it. decided against weisco's. When I put it back together to get all the air bubbles out of the coolent system I laid it over on the right side a few times to work all the bubbles out. Gonna go through the oil pump make sure its working properly on monday or tuesday. I may just turn it to premix still debating on that one. need more information? I ran premium fuel in it.

 

[tankman720]

Whats the process of bleeding the oil pump?

 

[tankman720]

Fill my coolant system? is their a process I should do it in please explain

 

[Scott]

On that speedworx head...what is the compression ratio?

GOTTA have perfect fuel if you have high altitude heads running at lower altitudes. 7k feet elevation isn't too bad though if you have good fuel and high compression heads.

 

[tankman720]

I believe its a 14:1 head. Thats what I was told from the guy who I bought it from.

 

[Scott]

Yaw. Gotta run a little race gas in there, especially if it's been ported.

 

[tankman720]

Claims to be a pump gas head. Guy I bought it from ran premium in it. I dont think the issues came from my head. I bet I would of got farther than .8 of a mile. I believe i got a bubble in my coolent. you know more about my sled than I do haha

 

[Scott]

Why? What else do I know about it? LOL

HAS it been ported? Usually people don't run aftermarket domes unless they are porting too.

 

[tankman720]

Lol. How much race gas should I use per tank. and what octane of racegas

 

[Double A]

I lift the front of my sled (head elevation) up higher than the rear cooler if I have torn it apart and need to refill coolant. Fill slow without the t-stat in it. I even fill the t-stat hose up full as possible too... Fill overflow bottle etc. Then I level it out, top it off, put the t-stat in, bolt it down and you should be good. I run my water temp below 150 degrees. I try real hard to make that happen.

I think you had a heat issue and possibly deto too because of that heat factor and low octane/higher compression and a lot of timing as well in the midrange on your sled. I run less timing than stock on mine at midrange rpms.
What are spi piston's?

At 7000 ft would require race gas mix with pump fuel at 14:1 compression I would think. Would definitely require full race gas at a lower elevations. To be safe...I would say.

Edit:Maddogwfo and sumptercat both have good points. It could be a cracked carb boot as well... And there can be a lot more to it. Like jetting... reading plugs properly at different rpm ranges using kill switch, etc. Never assume anything. Make short runs next time and study your plugs at different rpm ranges.
study it the best you can to learn your engine tune and characteristics

Hope you have better days ahead...happy trails!

 

[tankman720]

I went on my first ride the other day with the rebuild and watched it very close. It was fine no issues whatsoever! I ran roughly 4 or 5 gallons of 110 race fuel for safety. it did not miss a beat . . . for a while. on the far inside of the primary clutch their is a plate that bolts to the clutch. the screw or screws worked their way out and caught my cause. I believe my case will be okay I gotta get the clutch off to see. but the clutch is toast. it screwed it all up big time. so now I need a primary clutch. And hopefully it did not tweek my crank. Ugh I got some bad luck. if anyone has a good primary hit me up. thanks

 

[Double A]

I have a 9 post with a new spider in it if that would help you. It is a fixed pin clutch. It may need the sheave to belt clearance adjusted as it has cutler weights in it now... Put your weights and spring in...make offer.
I would sell clutch as is with adjustable weights (65-75 gram) for $200 shipped.

Don't forget to loctite your crank end plate....