boaring out 900 cylinders

[extremsledder]

So I have an idea that came to my mind and I was wondering your guy’s opinions. so my thought is I have a set of 900 cylinders that need to be renicked and my thought was can I take and boar these cylinders out to fit m1000 pistons in them and I have found out that they use the same top bearing, and buy looking on line at where the ring split is it looks close. so my question is has anybody done this or had the 2 pistons side by side and seen if there is a huge difference it height from the pin to the top of the piston and if the ring split will work with the port lay out in the 900, also is there room to boar the 900 cylinders 5.3mm's over without having to sleeve them? or if i was to sleeve them is there room in the sleeves to go that big? because if I was to use these they would have to be nicked anyways just a thought what do you think also the stroke on the 900 is 2mm shorter than the 1000 and is the pistons from the 1000 can be used it works out to being a 974 and that would be cool considering it would be using a stock piston that’s easy to get

 

[Idcatman1]

Yes, lots of guys have done it. The M1000 piston is taller by .080 or .090 inch, ( I can't remember for sure ) so you need a shim and another base gasket or you can just stack base gaskets to raise the cylinder back to the right height. I have used .050 or .063 shims depending on what base gaskets I use, some aftermarket ones are thicker than the stock ones. It also depends a little on how much compression you want to run. I would not bother with sleeves. There is plenty of room to bore for the M1000 pistons. There are kits out there that bore the stock cylinders even farther. I do a mild port job when I do this setup, some do more, I am more concerned with maintaining the low end torque and reliability than with maximum horsepower. My son and I have three 975 engines running plus a 1460 triple with M1000 pistons in it. We have had no piston related troubles that weren't our own fault. I would definitely recommend it as an inexpensive, reliable mod for a 900.

 

[extremsledder]

OK awesome i had figured there had to be someone who had tried this before, and i know what your talking about with the shim under the cylinders as i had a 700 summit with a cundy racing head kit that did this. so when you talk about doing a mild port jod how far do you go and could a person run it with out porting i konw the horse power gain would not be as large, and also what were you useing for pipes?, and were you doing this to carbed or efi sleds ? and specifics would be awsome
thanks Allan

 

[extremsledder]

Also just another question for you seeing that you have experience with these motor would you sujest removing the oil injection, becuse i have the motor tore right down and if i do it i was going to drill the holes in the cse down to the cavity just wondering your personal opinion on this
thanks Allan

 

[Idcatman1]

I enlarge the exhaust boost ports about 2mm in width and 1 in height. Enlarge the middle transfer back to the same height as the sides. I also enlarge the exhaust port outlet to match the size of the exhaust manifold. You could run it without the port work, I have no idea what that would cost in power, I'm guessing not much compared to what I do. I am running a Black Magic single and can on all three of ours. I like it because it is quiet, but they are getting hard to find. I have been in on helping put together one EFI 975. Talk to
Scoop here on Snowest.
I don't really have an opinion on the oil injection. I am still using it on all of ours except the triple. I have changed to EFI oil pumps though, they inject directly into the carb boot instead of mixing in the fuel pump. I have seen a couple crank bearings go out from no oil when a carb jet gets plugged and the rider just kept going on one cylinder.

Hope this helps.

 

[high time]

Actic Engineers ported a stock bore to simular specs and

dynoed a 13 hp gain along with slightly shortened pipe.

Owen

 

[extremsledder]

Ok so the porting would be a help for sure, Idcatman1 so you say to run the efi pump that makes sense so the efi boots can be used on the carbed motor? also right now iam running slp twins on the sled but was thinking that maby a set of the jaws twins would work with the 975, as i have read that the jaws d's i think work well with big boars

 

[high time]

I couldn't get the D-pipe to work till....

I wrapped them. That was a big help in deep powder too, as before when they took a big cool down with snow in the hood, the engine would practically stop.

Owen

 

[Idcatman1]

I didn't mean to sound like I thought the EFI oil pump is a must do, it is just my preference. The throat of the carb boots is different. I bought the oil line fittings and then drilled holes and epoxied them in.

 

[extremsledder]

OK but i get what you mean, and yea i like that at lest if you have a plugged jet you don't lose oil which is a better system i think

 

[ladder08]

Speaking of boring: I have a 1M 600 EFI (2004) that is stock. Are these cylinders plated? In other works if I want to re-ring it, can this be done with simple cylinder hone job? At what point would it need a replate; when bored out to accept larger piston? These sleds are new to me and I'm trying to handle on it, thanks.

 

[Idcatman3]

Yes, all (I believe) current two stroke sled engines use plated cylinders, not sleeves.

Anytime they are bored, they need replated.