08 860R Popping Plugs

[Ekim]

An update to this post.I believe I was detonating down low. 2000'. Upgraded fuel and have not fouled a plug. As well the carb set was very lean at wot. Re-Jetting to 490 mains and will try again. Have my oil injection set to about a litre and a half for a full tank of fuel. Running Castrol snowmobile oil. Should I be running less or more with this oil? Thanks

 

[MtnMaster]

a litre and a half per 40L tank is a little rich, but you're definitely safe. And, you shouldn't foul plugs at that.... Do you have any intake mods done? 490 seems a little rich for an SHR BB. Did you start at 470 like BJ recommends?

 

[ryan#1]

I had a broken wire in my ignition coil last year that caused my sled to run really erratic. Would run and then miss than run again then die then restart and run fine (likely as wire was coming loose). The BRP computer picked it up right away when they hooked it up. Mine would completely die and then restart and the gauge cluster would go all hay wire too. Might be worth checking into if you run out of ideas.

On my BB (RKT/Specialty) i've always run 30% or so race mix and it is never had a problem (other than above) although has 14:1 heads. Mine probably burns at least a litre and a half oil per tank too.

 

[oler1234]

490's are not too small if its a strong runner... hell i am running a 560 and its right on the edge. I know the single pipe BB we have out in our group, 1 runs a 490 and the other is a 520.

 

[MtnMaster]

BJ recommends to start at 470 on the SHR BB, and with vforce reeds and dynoport exhaust its bang on. Kelsey recommends 460's in the RKT 860!!

 

[bayman]

460's seem crazy low. With my Terra Alps kit, single pipe, Ted suggested 500 and shim the needle as a start point.

 

[boots]

Im surprised bj even told you anything he told me 480 at one point then he stopped helping once he fixed his kit that cratered at 500 miles. Wouldn't even stand behind his product. Just check your plugs and go from that. If you can get a hold of mots in Edmonton he used to make kits and helped me out.


Sent from my iPhone

 

[pfi572]

Jetting that that any builder gives you is a best guess. These motors all run different due to load ,elevation,fuel and so on. Always start rich and work your way down.
I let one builder talk me into his lean jetting and i should have known better and it was to lean. Jetted back up 4 sizes and good to go. He couldn't understand why either.
Others that jetted low with his kit all blue up due to lean mid range and detonation and kept blaming it on the nikasil company.
Keep these motors runing on the richer side as fuel helps cool them. IMO

 

[Ekim]

I have Boyesen Reeds and Pods for my intake, Dynoport modified Y-pipe from RK Tek, stock pipe and after market can. BJ recommended 470 yes, but I am finding they are way too lean. I am going to try the 490's and hope they are better. I have roughly 300km's on the motor and have had white plugs at all elevations at WOT. As far as consistency goes the motor has run the same since day one. No changes in power or reliability once I figured out I needed more octane. No more fouled plugs. Thanks for the inputs

 

[tukernater]

I have Boyesen Reeds and Pods for my intake, Dynoport modified Y-pipe from RK Tek, stock pipe and after market can. BJ recommended 470 yes, but I am finding they are way too lean. I am going to try the 490's and hope they are better. I have roughly 300km's on the motor and have had white plugs at all elevations at WOT. As far as consistency goes the motor has run the same since day one. No changes in power or reliability once I figured out I needed more octane. No more fouled plugs. Thanks for the inputs

Wow small jets Trygstad 872 started 660-640 settled at 600-580 best tool is a bore scope it PITA first couple of rides but takes the guess work out of jetting.

 

[cdnemsguy]

Wow small jets Trygstad 872 started 660-640 settled at 600-580 best tool is a bore scope it PITA first couple of rides but takes the guess work out of jetting.

Absolutely get a bore scope and take a look at the wash on the piston. Shoot for around 2/3 inch from the side and good coloring. I was on this after each shorter ride after my RK Tek kit just to be sure. Looking good so far. IMO plugs are only to find detonation, not a great sign of jetting.

 

[tukernater]

Absolutely get a bore scope and take a look at the wash on the piston. Shoot for around 2/3 inch from the side and good coloring. I was on this after each shorter ride after my RK Tek kit just to be sure. Looking good so far. IMO plugs are only to find detonation, not a great sign of jetting.

Yep learnt lots with the bore scope lots of thing I've over looked and or never noticed before? best tool in my tool boxs.

 

[oler1234]

Wow small jets Trygstad 872 started 660-640 settled at 600-580 best tool is a bore scope it PITA first couple of rides but takes the guess work out of jetting.

Ever do a leak down test on you build??? 600+ is the first i have heard of, sounds extremely high. more or less and leak somewhere and you are compensating with jet. could be wrong though. 580 is the biggest i have seen in a build.

 

[09 860 gade]

If you have your valve open on your heated carbs you will foul plugs like crazy

 

[09 860 gade]

Let me know if the valve is open

 

[Ekim]

Opened valve only once I realized, or thought, I was lean. Figured warmer charge would help compensate for the leaness. Have not fouled a plug with the valve open. I am heating my carbs currently with no fouling. I will shut them off with the 490's and see where I am from there. Do not own a bore scope, but will find one and inspect piston wash. Does anyone have a picture of good piston wash compared to bad piston wash?

 

[cdnemsguy]

Opened valve only once I realized, or thought, I was lean. Figured warmer charge would help compensate for the leaness. Have not fouled a plug with the valve open. I am heating my carbs currently with no fouling. I will shut them off with the 490's and see where I am from there. Do not own a bore scope, but will find one and inspect piston wash. Does anyone have a picture of good piston wash compared to bad piston wash?

I have pictures but give me a minute to get them transfered over. Good but not bad wash on my RK Tek piece. Stay tuned...

 

[cdnemsguy]

 

[cdnemsguy]

Not the best pics but the arrow to the left is the exhaust side on pics 2 and 3. The first one is of the wash on the intake side. Dont have a great side wash view but you can see the side and imagine how the wash goes. This is a pretty good burn IMO.

 

[Ekim]

Blew up my motor today. Still turns over, so I believe it is a crank bearing. Very rough when running. Bad vibrations. Anyone got a guess? Still has compression and runs, but you can feel vibrations in your feet and through the bars.