Problems with my 860

[Redbaronjg]

Hey guys. Need some advice. Got an 08 xp, full motor rebuild about 900 miles ago, 860 with rk tek 14:1 heads. My last trip out I had some issues with the sled, from what I'm seeing on here it sounds like I've got rave problems, going to take the sled in to get codes read and cleared anyway. My big problem that I need to solve is I spent the whole trip retightening spark plugs. At first I thought it was just the new plugs but after tightening them twice I started to figure out I got other issues. I have loosened plugs before, but never noticed it very often, but this trip got ridiculous. Ive always mixed minimum 50% c111, this trip I was at 60% because original plan was to try out the nitrous. My main jets are 440, and are what I've run since the build. I picked up some 460 mains and am going to try that but looking for any advice or info you guys might have. Really just want to finally get this thing dialed in perfect! I have been told my mbrp can needs to go, and probably pick up a skinz can, apparently the mbrp creates back pressure with the 860?? Wasn't aware the can had any affect on back pressure but rk tek recommended getting rid of it. I know this is long but really hoping to hear how other guys are set up. I also want to get some controllers hooked up for some monitoring info, so any advice you guys got there would be appreciated. Anything out there that monitors anything with nitrous? My boondocker kit has a regulator, but would be nice to see hhow much is actually getting fed.. Thanks

 

[slededjr]

What elevation were you riding? Usually detonating loosens plugs, sometimes head bolts as well. With your mixture of fuel what do you think octane was? For monitoring just use egt's. Koso make a nice set. Not too big either. Run a coolant temp gauge too if not already. Did you do plug readings at different throttle levels? Jet size means nothing if not monitoring it.

 

[slededjr]

Do you know what size base gasket is installed? You might have to run a thicker one or a little higher octane.

 

[oler1234]

440 jets.... It takes fuel and air to make power, and you are jetted less than stock.

my BB with twin pipes runs 560 jets and .030 needle shims.
other BB with a single pipe runs 540 and .020 needle shims

every engine is diffrent but I have always found that BB skidoo engines love gas, so feed it to it. For the twin setup anything less than 560 it was a real lack of midrange power. THe single pipe setup we started at 480's and had a similar problem, it was odd to jet up so much but at the end of the day that's what the engine wanted.

 

[slededjr]

Also take the mbrp can and toss it. Run a jaws or factory. As far as pipe, run stock or dyno port. Go with jaws twins if you really want it to rock.

 

[Redbaronjg]

What elevation were you riding? Usually detonating loosens plugs, sometimes head bolts as well. With your mixture of fuel what do you think octane was? For monitoring just use egt's. Koso make a nice set. Not too big either. Run a coolant temp gauge too if not already. Did you do plug readings at different throttle levels? Jet size means nothing if not monitoring it.

All the riding except for trail up and down should e between the 6000-8000 mark. Not sure what the octane would turn out to be, probably a little over 100, I know when the kit was built I was told 40% c111 in the hills and have always run more than that. I checked plugs once in parking lot and once in the hills, tips always looked good and tan, a little dark oil around outside edge of plugs.

 

[Redbaronjg]

Do you know what size base gasket is installed? You might have to run a thicker one or a little higher octane.

Do not know the gasket size. The engine was built by specialty sleds

 

[Redbaronjg]

440 jets.... It takes fuel and air to make power, and you are jetted less than stock.

my BB with twin pipes runs 560 jets and .030 needle shims.
other BB with a single pipe runs 540 and .020 needle shims

every engine is diffrent but I have always found that BB skidoo engines love gas, so feed it to it. For the twin setup anything less than 560 it was a real lack of midrange power. THe single pipe setup we started at 480's and had a similar problem, it was odd to jet up so much but at the end of the day that's what the engine wanted.

I don't even know what stock jets are, 440's are what we're put in when specialty sleds built and tuned it. I asked them recently about it because I want to try the 460's to get rid of my detonating problem and they said most guys running their kits are using between 440's and 480's. 500's sounds like a big number in comparison. I had never considered changing them before cuz I never seemed to have much of an issue, not that I noticed anyways

 

[Redbaronjg]

Also take the mbrp can and toss it. Run a jaws or factory. As far as pipe, run stock or dyno port. Go with jaws twins if you really want it to rock.

Ya, i already got the mbrp can sold now that I know, I think it was the skinz can that rktek recommended, any info on those? Could look into the jaws too. I'm running dynoport pipe, stock y-pipe right now though. I stayed away from twins, everyone I talked to about them said doo's did not match up well with twins

 

[slededjr]

The Jaws BB twins make a huge difference. I have them and holy chit. Totally different sled with them. I found that Dyno port Y pipe, stock pipe and stock can worked the best for me with single set up. I ran 480 ' s with that set up. If you want noise than a jaws can works good too. Not sure about the skin. If Kelley recommended it than it should be OK.

 

[slededjr]

The Jaws twins absolutely rock. Best single I found was dyno port Y pipe, stock pipe and stock can in high elevation. The mbrp is Ok in low elevation. Your octane should be good for that elevation. Do the plugs loosen while up in there or on way up and way down only?

 

[crazy newf]

I got a set of jaws twins for sale blew up bb last season won't need them now put it back stock for a second sled to ride close to home

 

[Redbaronjg]

The Jaws twins absolutely rock. Best single I found was dyno port Y pipe, stock pipe and stock can in high elevation. The mbrp is Ok in low elevation. Your octane should be good for that elevation. Do the plugs loosen while up in there or on way up and way down only?

They loosen at elevation too. Definitely not going back to stock pipe and can, I know that much. Weight savings alone is a big motivator not to. I'll have to track down a can

 

[Redbaronjg]

I got a set of jaws twins for sale blew up bb last season won't need them now put it back stock for a second sled to ride close to home

No thanks. Gonna stick with my dynoport. I've heard way too much bad about twins on doos, probably won't ever go that route, unless something changes.

 

[oler1234]

No thanks. Gonna stick with my dynoport. I've heard way too much bad about twins on doos, probably won't ever go that route, unless something changes.

Really.... Got 8500km on my jaws twins.

 

[deaner]

From the sounds of your plug color it sounds like your jetting is bang on. RK runs super small jetting for some reason. Magic porting, head design, and pistons.

Sounds like detonation

 

[slededjr]

increase your octane and try it again.

 

[tukernater]

Is this a RK-T KIT or just his head and specialty's sled porting.

 

[team-x]

The old turbo pro always backed out plugs and it was always from det even if it didn't throw the det code on the dash. Could try ether running straight race to eliminate the det problem if it is one.

 

[pfi572]

4 years ago I had a 860 RKT 14:1 at 3700ft and above.
Was told to run 450 mains. Put 460's in and tightened it up at 6500 ft. With stock pipe and muffler.
Redone and then 480's with Dyno port pipe , y pipe and specialty can.
Reducer taken out of high elevation pipe so running low elevation pipe.
Mixing 2 gallons 111 with premium.
Sled ran good at final set up but I couldn't come close to running what was suggested for jetting.
Thus also had ECM update from Kelsey.
I would jet it up , take restrictor out of pipe end if it is high elevation pipe.
Change muffler as with some they are restricted more than stock for elevation on stock motor so with that and pipe it could be way to restricted.
My 2 cents and good luck