860 dropping RPM's

[DenverR1]

My RKT 860 ran awesome the first day with 460 jets and stock can. I've had some problems with the knock sensor since then but I put a brass washer with some silicone under the sensor, also ran half 100 octane and only one knock code today. I've also got a super-q can, and today I had to clicker from 3 up to 6 to get the RPM's up to where they were the first day. I'm running 480 jets but still seems to be running lean (judging by plugs), although I went through a tank of oil before one tank of gas today. Anyway, when I'm climbing the RPM's will hit around 8250 but suddenly fall down to 7000 to 7400 during the climb. Does this sound like my clutching needs to get dialed in? What about having to clicker up to 6 today after having great results at clicker 3? Thanks!

 

[Dootimes2]

Had a problem like this with my 996 mod. Go back to stock can. It will probably run again. If it does the aftermarket can is too restrictive. That was the answer for mine. Also sounds like way too much oil to me.

 

[DenverR1]

Had a problem like this with my 996 mod. Go back to stock can. It will probably run again. If it does the aftermarket can is too restrictive. That was the answer for mine. Also sounds like way too much oil to me.

I went with the Super-Q because Kelsey runs it on his RKT 860 and he recommended it for my setup. But it is weird that I had to clicker up at the same altitude. And I can't figure out the oil thing either because the plugs are gray, even though it's going through that much oil? Clutching?

 

[DenverR1]

I'll try switching out cans again tomorrow, anyone else? Need some opinions!

 

[Dynamo^Joe]

I had a few guys call me up about low rpms like this after they changed to a different muffler; and changed right back and gained rpms back.

DenverR1 writes; I'll try switching out cans again tomorrow, anyone else? Need some opinions!
Joe writes: My question is what was the assessment of the clutch calibration prior to your latest runs with the new exhaust addition?

If the muffler allows the exhaust pipe to run a lower internal pressure - Then the engine won't pump rpms.
In cooke city I put an aaen muffler on my sled and could not get over 6800 rpms. Put back the stock muffler, it ran 8100. I started to taper the aaen muffler outlet and as I continued to choke off the outlet little by little the full throttle rpms would raise. hahaha...then I blew er' up.
....give me a good reason to change out the pistons and got myself a RKTPDI to which flat out fking rawks at 8400 with stock exhaust.

If the clutching was good one day and then the next day not....why blame the clutching when it was not changed?
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About knock sensor washer replacement.
A knock sensor is calibrated for a range of vibration from one frequency to a higher frequency. The knock sensor also responds to the "amplitude" of the frequencies.
There are two ways to change the natural frequency of a "system" 1]stiffen the material (raises frequency out of a range). 2]Add mass (reduces frequency out of a range)
If you were to put a rubber washer under the sensor it should reduce the amplitude of the frequencies below the range the sensor responds to.

 

[winter brew]

I would check all the basics.....exhaust valves opening? DPM solenoid sticking? ANy chance it's overheating? Compression test? Dropping that much RPM is probably more than clutching, especially since it is changing daily.

 

[DenverR1]

I had a few guys call me up about low rpms like this after they changed to a different muffler; and changed right back and gained rpms back.

DenverR1 writes; I'll try switching out cans again tomorrow, anyone else? Need some opinions!
Joe writes: My question is what was the assessment of the clutch calibration prior to your latest runs with the new exhaust addition?

If the muffler allows the exhaust pipe to run a lower internal pressure - Then the engine won't pump rpms.
In cooke city I put an aaen muffler on my sled and could not get over 6800 rpms. Put back the stock muffler, it ran 8100. I started to taper the aaen muffler outlet and as I continued to choke off the outlet little by little the full throttle rpms would raise. hahaha...then I blew er' up.
....give me a good reason to change out the pistons and got myself a RKTPDI to which flat out fking rawks at 8400 with stock exhaust.

If the clutching was good one day and then the next day not....why blame the clutching when it was not changed?
-----------------------------------------------------

About knock sensor washer replacement.
A knock sensor is calibrated for a range of vibration from one frequency to a higher frequency. The knock sensor also responds to the "amplitude" of the frequencies.
There are two ways to change the natural frequency of a "system" 1]stiffen the material (raises frequency out of a range). 2]Add mass (reduces frequency out of a range)
If you were to put a rubber washer under the sensor it should reduce the amplitude of the frequencies below the range the sensor responds to.

I'm not blaming the clutching, I'm asking if it's a possibility. The reason being when I was breaking in the motor I didn't do long pulls so the RPM's never dropped. The RPM's are dropping on longer pulls.

With the knock sensor, doesn't the washer have to be able to hold an electric current? If not, I might try that because I'm still not convinced that the sled isn't dropping the RPM's because of the knock sensor.

I'm really hoping I didn't damage the pistons/rings as it's been running so lean during it's early miles. Thanks for the reply's. Normally I'd give it to my mechanic but I'm finally riding for the first time this year and I'd like to have as many ideas to try as possible.

 

[trinitypowder]

Guess what bro? My first 5 rides on my SHR860 were awesome. A little lean in the middle, but only because my dealer didn't jet the needle as per Big Johns specs. Ride 6 I put a Super Q on and my top end has sucked ever since! Crazy RPM loss, etc. I'm starting to think that maybe the Super Q isn't all that it's cracked up to be for the 860's. I'm going Tuesday for some more tuning. The first thing that is changing is the can. My HPS is going back on. If that doesn't help, than I'll tweak the jetting some more.

 

[Dynamo^Joe]

Once i got closer (about 2 jets sizes) to jetting for my engine it started to rpm.
When I was farther away in jetting it would always hang out about 200 rpms low. I have piston drop in but I swear that it seems with higher revving engines you need to be close on the jetting before engine starts to rpm correctly....even with other vendor's products (twin pipes as an example)

 

[Gros Chien]

My RKT 860 ran awesome the first day with 460 jets and stock can. I've had some problems with the knock sensor since then but I put a brass washer with some silicone under the sensor, also ran half 100 octane and only one knock code today. I've also got a super-q can, and today I had to clicker from 3 up to 6 to get the RPM's up to where they were the first day. I'm running 480 jets but still seems to be running lean (judging by plugs), although I went through a tank of oil before one tank of gas today. Anyway, when I'm climbing the RPM's will hit around 8250 but suddenly fall down to 7000 to 7400 during the climb. Does this sound like my clutching needs to get dialed in? What about having to clicker up to 6 today after having great results at clicker 3? Thanks!

Sounds like one of the RAVE valves is stock in that gluemy sh!t that sticks in there. Try clean'em up

 

[DenverR1]

Guess what bro? My first 5 rides on my SHR860 were awesome. A little lean in the middle, but only because my dealer didn't jet the needle as per Big Johns specs. Ride 6 I put a Super Q on and my top end has sucked ever since! Crazy RPM loss, etc. I'm starting to think that maybe the Super Q isn't all that it's cracked up to be for the 860's. I'm going Tuesday for some more tuning. The first thing that is changing is the can. My HPS is going back on. If that doesn't help, than I'll tweak the jetting some more.

I'm going to switch back out tomorrow. Hopefully putting the stock suitcase back in will help. I'm still not convinced that the can would make it do what it's doing. I clickered up to 6 which made the RPM's get up to 8250, and the low torque is great. But when doing a long pull climb it would stay around 8000 to 8250 for almost the whole climb, then suddenly die out and drop to around 7000. I was getting highmarked by everyone! Still wondering about the knock sensor problem, maybe the sled is going into preservation mode on the long climbs.

And does anyone know if a rubber washer will work under the knock sensor or does it have to be a washer that conducts an electric current?

 

[madmax]

My RKT 860 bogged like crazy on on the deep powder days with the stock can. With tthe Super Q it runs perfect. Its really running well. I'm guessing since you are running 460-480 jets you do not have the ECM reflash from RKT? What clutching do you have in it? There is also a BRP oil adjust spec for the oil cable, most are adjusted from the factory very rich. You need to check that and all you clutch moving parts.

 

[Gros Chien]

sounds like go stock or wack!!!

 

[DenverR1]

My RKT 860 bogged like crazy on on the deep powder days with the stock can. With tthe Super Q it runs perfect. Its really running well. I'm guessing since you are running 460-480 jets you do not have the ECM reflash from RKT? What clutching do you have in it? There is also a BRP oil adjust spec for the oil cable, most are adjusted from the factory very rich. You need to check that and all you clutch moving parts.

I've got the RKT reflash. But last week when I was getting the knock sensor I jetted it up to see if it would help. It didn't, but yesterday I kept the 480's in because it had run lean for a while and I wanted to go easy on it. Tomorrow I'll put 460's back in with the stocker and see what happens. And I'll adjust the oil cable. How much should I adjust it to start with?

 

[MontanaPowder]

Rkt 860

I run mine with super q and am very happy with rpms. I am waiting now for my ecm to come back. I understand with the ecm you jet down to smaller size. If you were lean most likely in mid range, do you have it shimmed? How much?

Was the outside temp up from your last rides?

From what Kelsey has posted it sounds like you should talk with him first but your mains seem way rich for ecm reprogram, check with Kelsey though.

 

[Dootimes2]

Hope it works. I know on my 996 it would take off like a rocket and then fall on it's face when motor was loaded at full throttle. Thing would not get out of it's own way. Would not keep up to a phazer. Tried everything. Spent 5 hours on the hill with an exact duplicate motor that ran very well.Pulled his carbs and put them on mine ( he had dial a jets ) ran every jet combo and nothing. Used his clutches and carbs and notning. My carbs and clutches his can and we had a winner. Another friend had a m7 with a 800 kit that did the exact same thing mine did and the only fix was the stock can. Go figure, may not be your problem but maybe.

 

[madmax]

from what i understand the deto sensor does need to be grounded to the head. . ]ou can use a rubber washer as the bolt through the deto sensor will give the current needed.

 

[trinitypowder]

You guys that say you have no problem with the Super Q on your 860s, are you running holes in the back of the box??? Under a load in powder, mine will keep 8200 for about 1-2 secs before dropping off. I didn't get to check the HPS in the deep pow because it was early season, no pow to load the motor. We'll see in a day or two

 

[madmax]

You mean holes in the airbox? If so yes. Got a couple 2.5" flow rites back there.

 

[MontanaPowder]

Rkt 860

I have two 3" holes in upper box to a outlet behind windshield same effect I believe as mmax. My super q was very strong with the airbox holes compared to bro xp with jaws can. I could pull one 10mm set screw more with a 2.5 track. Just seems to work great. On my rkt drop in 04 rev nothing but stock would work, Kelsey runs it and suggested it last year so I did it.

Really like the power of 860. Just messing with clutching a bit went to a 160*290 from 130*260 seems and dropped from clicker 3 to 2 with same set screw in primary. It is a handful in acceleration, just need deeper snow now.

I looped it last weekend.