Boring a 2005 EFI 900 King Cat (Stock M1000 Cylinders?)

507Sledz · Mar 3, 2014

Ok fella's! I was out in the black hills today and looked up the ol 900 efi king cat, I burned up a piston/ scored a cylinder. So being's that happened I want to turn a negative into a positive! I want to bore to a 1000CC. I have heard of guys going to 1050CC but I want reliability. the king cat has plenty of power stock so between a 1000CC and 1050CC. There probably isn't much of a difference. So my questions are:

1. Can I just use M1000 jugs and piston? will they bolt right up?

2. If the the M1000 stock setup doesn't work. what is the best most reliable 1000cc kit for my sled? I don't really want thin cylinder walls.

3. I want to run Twin Jaws exhaust with front dump. So whatever kit works best with that?

4. And any other tips advice you fella's know about that I don't?

Thanks!

Idcatman1 · Mar 3, 2014

1. Can I just use M1000 jugs and piston? will they bolt right up? No, not even close.

2. If the the M1000 stock setup doesn't work. what is the best most reliable 1000cc kit for my sled? I don't really want thin cylinder walls. In my opinion, admittedly biased because I have had lousy luck with Wiseco pistons, which is what most of the big bores use, is to go with stock M 1000 pistons to give you 975 cc. It is smaller than you are wanting but I think the most reliable and also the least expensive because the pistons are cheaper. The pistons are taller though, so you have to put a spacer and an extra base gasket under the cylinder, I have used both an 0.050" or a 0.063 thickness spacer depending on how much compression and port timing I am after.

3. I want to run Twin Jaws exhaust with front dump. So whatever kit works best with that? Can't help you there because I only have experience with a single pipe.

What happened to 4?

5. And any other tips advice you fella's know about that I don't? I have seen some big bores made with 800 cylinders but would not advise that route, the bridge between the main exhaust port and the auxiliary port gets really small and will crack sometimes. Also I am told that the 800 cylinders make less power, don't know that for a fact though. I have had some trouble with head o rings, would advise using stock Arctic Cat ones. They seem to be more flexible than the aftermarkets. The distance between the bore and the o ring groove gets smaller the bigger the bore so I would bet bigger bores would have even more o ring problems. The trouble seems to be worse if you use an aftermarket one piece head. You have to make sure the cylinders are exactly the same height with the shim and extra gasket. I have seen shims and gaskets vary in thickness by several thousanths.

There is my $.02 worth

geo · Mar 4, 2014

Idahocatman1; Does using copper instead of rubber in the cylinder-head groove solve that problem. #5 oring thing.

Idcatman1 · Mar 4, 2014

I have never tried copper, never even thought about it. Hopefully someone who knows will chime in.

timber76 · Mar 4, 2014

What caused the meltdown??

stanredrider · Mar 5, 2014

I ran the 975 on my efi motor and was an all out beast once I got it dialed in with a single pipe. Quickly realized though that I should have gone through my bottom end before I put that much hp to it. Also from my previous mod sled will say it is easier to tune an efi in with a single pipe vs twins, just my opinion.

507Sledz · Mar 5, 2014

RE:

Idcatman1. I fixed number 4! haha oops

timber76. I am not sure what caused the meltdown I am going to break into the motor this weekend. I'll post pictures.

So M1000 are actually 975cc?? About my sled dialing itself in, isn't that what an EFI does by itself? give our take some clutching? If I do all these mods I will be buying digital screens displaying fuel/air, temp, RMP. I'd really like to get my sled bored out to a 1000. There is a guy on youtube that has his kingcat bored to a 1050CC, however I am not sure about the reliability of his sled.

Random Fact: You guys gotta go check out the new ski doo mountain sled. 174" tack with 3" paddles... that's insane!

Thanks for all the info so far.

stanredrider · Mar 5, 2014

Yes M1000 is actually a 975, and the efi will adjust but it isn't enough when you go to a bigger bore. Just takes some time to adjust with a boondocker box or other means, once its set for a specific area you usually don't have to change much, maybe one or two numbers.

Idcatman3 · Mar 5, 2014

M1000 is a 999, it has a 2mm longer stroke than the older 900. (76mm vs 78mm)

The 900 bored to the M1000 piston is a 975.

The EFI is not smart enough to account for larger bore. You'd need a closed system tied into a fuel/air ratio sensor, and the sled EFI systems aren't that smart yet.

The boondocker box (or others) modify the stock map to add fuel where the larger bore demands it, while retaining the percentage change values in the stock map for air temp and pressure.

There are a ton of different big bores for these engines. 925s, 975s, 1010s, 1050s, 1150s, 1160s, 1200s, possibly others that I don't know about. The benefit of the 975 is the ability to use a cheap cast piston that you can get from Cat, rather than Weisco or Speedwerx/D&D/Cutler etc.

507Sledz · Mar 6, 2014

RE:

Im confused. So the stock m1000 piston is a 999cc but if I want to put stock m1000 pistons in my king cat I need to bore my jugs to 975cc? I feel like there somehow is a 999-975 = 24CC difference?

Lets say I do the 1010CC kit for this sled. How much are pistons? and would my motor become more prone to melt downs?

Also If I want to put High Comp Heads on, How will I match them up once I have my pistons bored?

Do you need to do anything to the crank once you bore?

Thanks for all the Info

Reeb · Mar 7, 2014

By the sounds of it, you should probably just run it stock and ride it till you trade her in.

Idcatman3 · Mar 7, 2014

Ok.

The M1000 piston has a 90.3mm diameter.
The stock 900 piston has an 85mm diameter.

An M1000 has a 78mm stroke, the King Cat has a 76mm stroke.

Displacement is calculated (in cubic centimeters) by taking half the bore, times PI (~3.14), squaring that number, multiplying by the stroke, and number of cylinders.

For the stock 900:
8.5 cm bore / 2 = 4.25 cm
PI = 3.14
stroke = 7.6 cm
number of cylinders = 2

Displacement = 862.52 cc (stock 900)

For a stock M1000
9.03 cm bore / 2 = 4.515 cm
PI = 3.14
stroke = 7.8 cm
number of cylinders = 2

Displacement = 999.06 cc (stock 1000)

Now a bored 900:
9.03 cm bore / 2 = 4.515 cm
PI = 3.14
stroke = 7.6 cm
number of cylinders = 2

Displacement = 973.44 cc (bored 900)

Idcatman1 · Mar 7, 2014

Lets try one more angle of attack here. Displacement of an engine is a function of bore multiplied by stroke. An engine with a longer stroke but the same bore will have a larger displacement. In this case it is better to work with centimeters so you don't have to convert from cubic millimeters to cubic centimeters (CCs ) when you are finished. Starting over- the M 1000 piston has a diameter of 90.3 millimeters or 9.03 centimeters. If you remember from high school math how to get the area of a circle it is radius squared times Pi ( 3.14159 ). So Diameter divided by two gives radius. 9.03 divided by two is 4.515 squared is 20.38+ times Pi is 64.04+. That is the area of the bore of the cylinder is square centimeters. To get volume you multiply by the stroke of the engine, 7.6 centimeters for the 900 engine, 7.8 for the M 1000. So 7.6 times the 64.04 is 486.72+. Multiply that by 2 because you have two cylinders and have been figuring volume for one so 973.4 cubic centimeters rounded to 975 because it is easier to say.
Take that 64.04 area of the bore and multiply by the M 1000 stroke of 7.8 gives you 999.05 cubic centimeters. That is how you end up with two different displacements in two different engines with the same piston.

You need to make sure your crank is in good shape before you start modifying, more power will put more stress on parts. Anything not quite right will fail faster with more stress.

You bore the cylinders, not the pistons.

You match heads to the bore by having the diameter of the combustion chamber cut on a lathe or milling machine to match the same bore of the cylinder. They also need to be cut to have enough clearance between the top of the piston and the head.

Unless you are on good terms with a machine shop that is familiar with doing this kind of work I would have to agree with Reeb.

I had most of this written about an hour ago when the power blipped. I thought I had lost it all. In the meantime I see my son, Idcatman3, has chimed in with his teaching moment. I was hoping he would do so.

Hope this helps.

Qreiff · Mar 7, 2014

And that is good information!

rdr99 · Mar 7, 2014

I would do what Reeb posted.

507Sledz · Mar 7, 2014

RE:

Reeb - My sled is already not stock, I enjoy modifying my sleds, just so happens I have never done a bore before. I have rebuilt plenty of motors, but with all stock parts. Their is something about taking a 2005 sled and kicking someones *ss up a chute with a brand new sled (because they traded their old one in) Thanks for your helpful comment however!!

ound:

Idcatman1 & 3 - Thanks for the information, and thanks for taking the time to type it up for a rookie like myself, totally makes sense now! Haha yes I remember my high school math! I managed to make it through college... Somehow!!

Rob davis · Mar 7, 2014

i have culter 1150 top end for sale jugs head and power vavles

507Sledz · Mar 8, 2014

RE:

How much?

Reeb · Mar 8, 2014

507Sledz said:
Reeb - My sled is already not stock, I enjoy modifying my sleds, just so happens I have never done a bore before. I have rebuilt plenty of motors, but with all stock parts. Their is something about taking a 2005 sled and kicking someones *ss up a chute with a brand new sled (because they traded their old one in) Thanks for your helpful comment however!!ound:

Then by all means, have at her! Update us on your progress and what you decide on!

timber76 · Mar 8, 2014

Anyone have any ideas why an ununmodified EFI would seize up?

Boring a 2005 EFI 900 King Cat (Stock M1000 Cylinders?)

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