XP big bores - lets compare

[tntm7]

Good to know the above... The problem I have with it is that my sled doesn't make any "Short Runs" and it seems like right when I need it, 45 sec into a long pull in the mountains that is when you get that seat of the pants feel that the sled has stopped pulling and is turning into a turtle.

You can try clutching it to run slightly over peak hp RPM, you will loose a little bit at the bottom but wont heat soak as bad and gain lots at the top of the hill.
Its not a 100% but worth the try if your heat soaking real bad. Dont get crazy, like 75-100rpm

 

[Insaneboltrounder/sjohns]

Hey TNT... how did that T 860 go after you "fixed: it. sj

 

[tntm7]

I have not rode it yet, but those who have say it runs real well.

 

[triple7]

Hey TNT... how did that T 860 go after you "fixed: it. sj

Turbo 860?? Or ET 860?? Just clarifyin...

So back to the hot soak thing. In theory then if I am running 100 deg water temp and piston/cylinder temps are 300 or above the motor is hot soaked?? And if I raise water temp to 160, piston/cylinder temps would have to be 360 to be hot soaked??

So correct me if I am wrong, what you are basically saying is that on a long pull the 800r motor is building too much piston/cylinder heat and that is causing it to drop horsepower which would lead to a drop in rpm and trackspeed...correct??

So, what is the best way to get a handle on this?? Richen the jetting?? Raise or lower water temps?? More oil??

Thanks alot, tons of good info on here!!

Jake

 

[DaveB]

I second that!, when I first saw the 860 BB title on this I thought to myself "Isnt that horse already Dead?". But Everyone has given excellent info and brought up good questions.

thanks

My sled still sucks. Hahaha.

Looking in another direction.....what about sending the ECM for a re-curve? Are there different things that can be done? I guess I would have to ask Split Second Ralph what he recommends, but I would like to take away all potential "limp mode excuses" from the ECM if that is possible. Once the ECM is re-programmed, can you still adjust up and down with the dealer BUDS....or will that undo any reprogramming?

 

[byeatts]

1 more time...LOL

IMHO...nothing more...the rings werent the reason, the extreme ignition timing and very small exhaust port (with valves closed at cruise speed, read slow traffic) was/is the problem...

At WOT with full fuel/less timing and a full exhaust port wasnt/isnt the problem...

In my 860 kit I modify the valves (bigger opening when closed), modify the side port valves (alot bigger than stock when closed), better head design (IMHO), alot larger exhaust port/sub ports and with a bigger bore stock timing becomes less...I actually bump it 1 degree to match my motor...BJ

I spoke with an individual yesterday who purchased BJ,s 860 kit. Comments were they were really happy with the package. Everything is included to complete this build with detailed instructions, The components looked top notch, This indivdual sees all types of builds and indicated it is an impressive package.He also is involved with all differant brand Ski Doo kits so this is an un-biased opinion. They also commented that it idles smoother than a stocker.Has not had it on the hill yet.BJ you owe me lunch!

 

[tntm7]

Turbo 860?? Or ET 860?? Just clarifyin...

So back to the hot soak thing. In theory then if I am running 100 deg water temp and piston/cylinder temps are 300 or above the motor is hot soaked?? And if I raise water temp to 160, piston/cylinder temps would have to be 360 to be hot soaked??

So correct me if I am wrong, what you are basically saying is that on a long pull the 800r motor is building too much piston/cylinder heat and that is causing it to drop horsepower which would lead to a drop in rpm and trackspeed...correct??

So, what is the best way to get a handle on this?? Richen the jetting?? Raise or lower water temps?? More oil??

Thanks alot, tons of good info on here!!

Jake

The only real cure is to not make HP, no one is willing to do that. But there are things you can do to slow it down. More oil is great start, correct squish and quinch band on the head, little on the rich side, 50-100rpm high on clutching from peak hp, higher octain fuel, better quality oil.
Oils that have failed all my tests, Blue marble, Skidoo semi synth-aka golden spectro, cat none apv oil valvaline 2 stroke.
Still the best and only complete molecule chain oil is Castor bean oil. But in cold weather creates many other problems so hard to use.
On my big hp outboards we use a fat or washdown button, its where we spray the gas solenoid of the nitrious system with no nitrious to fuel wash the piston before we shut it down to reduce piston wear or siezed pistons from long hard nitrious pulls.

 

[Insaneboltrounder/sjohns]

Hmmm thats a pretty interesting use of the n2o button. I used to do that when on the trail and my midrange was getting too hot. Bottle valves were off of course.

Whats that you say about oil??????????? Superblumarble failed???????

Oh man now thats funny , where are those losers that insist that sheet is the be all end all???? Oh wait... you musta leaned the motor out 9 sizes like the idiots at mb used to suggest you could

 

[tntm7]

actually two buttons, one activates both nitrous and fuel, the other only fuel,
The boodocker box has that ability but if you choose that option you cant get nitrious when you want it without changing the box.
I would like to washdown the motor with fuel before I lifted after one of my empty the whole bottle in one shot hill climbs.

 

[tntm7]

ok I need some help from some of you old school Snowesters, on the top right there is green squares, mine used to be red now its all green, whats that all about?

 

[byeatts]

ok I need some help from some of you old school Snowesters, on the top right there is green squares, mine used to be red now its all green, whats that all about?

The light to Dark green "bar" indicates the % of time your on the Nitrous button..

 

[tntm7]

OOOOH it shouldnt be green, IM always on it. Thats why im making room to carry three for next season.
Your doo in trouble, lmaoi

 

[winter brew]

Red is the Polaris riders.....green is Cat.

 

[diamonddave]

Red is the Polaris riders.....green is Cat.

So you're a Cat dude WB??

 

[triple7]

LMAO the green means you are clearly a cat guy on the bottle!! LOL anyway, how do you avoid hot soak on your kitty when the button is down for long periods of time?? Have you seen the addition of narrow squish/quench heads cause more hot soak issue with doos??

Not being a dink but what is the idea behind your buddy engineering the motor with a chamber *** backwards to what the Big Four use on their hotrod motors??

 

[tntm7]

The doo guys are still basically rotary valve guys at heart and they have taken there rotory valve background and experience to the reed motor. If you search around you will see that its not only doo. that runs a narrow squish clearance, TM and KTM does as well as I. If your motor is setup to rev high over 8000 rpm they dont like wide squish bands, its hard to get a motor to rev free with wide squish band.
HOW do i keep the heat soak out of my Cat on 1 min nitrious pulls, TRUTH, I dont. If you look at my pistons they will scare most, the wash is more like what wash, there dark to the edge and then some.
I only run 1050 max egt's without nitrious and only 1025 on nitrious. I also pull timing on the bottle, my probes are not in center of the exhaust and there 6" from the center of the piston. But i still premix at about 60to1 and I use 3 quarts of oil to 11 gallons of fuel on average from my injection. I shortened the arm on my injector pump and adjusted the cable so it has less oil at low rpm and more oil 3/4 throttle and above. I wont even bat an eye to hold my nitrious button down till the bottle is empty in one long hard pull. I have no carbon build up in my exhaust ports and my valves stay clean. But I still have a major heat soak problem and thats all I can do to reduce it.

 

[tntm7]

So you're a Cat dude WB??

Ya I just like my little m7, we get along well, I trust it and know it. But Have to say this yr with a bad shoulder I am finally missing Reverse.

 

[triple7]

The doo guys are still basically rotary valve guys at heart and they have taken there rotory valve background and experience to the reed motor. If you search around you will see that its not only doo. that runs a narrow squish clearance, TM and KTM does as well as I. If your motor is setup to rev high over 8000 rpm they dont like wide squish bands, its hard to get a motor to rev free with wide squish band.
HOW do i keep the heat soak out of my Cat on 1 min nitrious pulls, TRUTH, I dont. If you look at my pistons they will scare most, the wash is more like what wash, there dark to the edge and then some.
I only run 1050 max egt's without nitrious and only 1025 on nitrious. I also pull timing on the bottle, my probes are not in center of the exhaust and there 6" from the center of the piston. But i still premix at about 60to1 and I use 3 quarts of oil to 11 gallons of fuel on average from my injection. I shortened the arm on my injector pump and adjusted the cable so it has less oil at low rpm and more oil 3/4 throttle and above. I wont even bat an eye to hold my nitrious button down till the bottle is empty in one long hard pull. I have no carbon build up in my exhaust ports and my valves stay clean. But I still have a major heat soak problem and thats all I can do to reduce it.

I suppose I wasnt clear. I mean why does doo use a tophat shaped chamber. With super wide outer edge and a deep dish center?? The overall chamber shape is nothing like that of the Big Four.

And DAMN thats alot of oil!!

 

[tntm7]

the 800r has very aggresive port timing, they had to do everything they could to get that grunt power back into that motor that so many doo fans have come to love. they also had a problem with pistons wholing, so you do what you have to keep the heat out of the pistons.
the 06 m7 chamber is very similar to the 800r chamber if my memory serves me correct.

 

[triple7]

Hmm, so basically it comes down to keeping heat towards the center of the slug...because they used identicle chamber shape in every motor they have built in the past.

So, in a round about sort of way my ring failures could definatly be related to working my motor hard and running a conventional chamber shape?? I could be overheating the ring because I am no longer focusing the heat in the middle of the piston as much as stock. By overheating the ring it would be possible that I dont have enough ring end gap and the ends are touching under extreme use?? Does that sound plausible??