[G-daddy]

I have a 2009 polaris rmk 700cfi with the 155 track on it and a little over 3000 miles. The guy I bought it from had the engine melt down on him so he rebuilt it from bottom up putting high quality aftermarket parts in it. He also went through the clutch and clutched it for mid-mn trail riding as well as put the mesh side panel on it to help with cooling. Now the problem is that after the rebuild it has a heavy bog when you pin the throttle (sometimes will come out of it if you feather the throttle a little), when you slowly accelerate the bog will come on after about 15-20 seconds of WOT. The guy I bought it from went through a couple things, got frustrated with it, thought it was the tps and put it up for sale. Long story short I bought it for a good price thinking I could fix it for a couple hundred bucks and have a good sled with a fresh rebuild… not quite. I checked the tps, good. I cleaned the power valves and replaced the bellows (orange ones). Clutch has
10-66 weights. Replaced fuel filter (which seemed to help for a little bit). Replaced spark plugs with oem. Compression was good last time I checked it. I’m not sure where to go from here, the bog has been seeming to get worse lately and I really would like to figure this thing out. Any help is greatly appreciate! Thanks in advance for all the help!

 

[BC_Dan]

Have you looked at the clutches? I would make sure you don't have a weak spring or maybe something is binding...

 

[G-daddy]

I looked through the primary clutch and it seemed all good I haven’t checked the secondary clutch as of yet, what would I be looking for? Broken spring?
If I had a bad bearing on the driveshaft would that cause a bog on the top end? The other thought I had was a failing fuel pump, would that cause it to bog sometimes or all the time?

 

[Yamaha440]

Fuel starvation could cause of the bog, but the 20 second delay is odd; if the pump can't handle higher flows, it should show up very quickly. Delayed onset of fuel starvation is pretty much limited to carbs, as they have some reserve in the float bowls before they go dry. Once a fuel injection system loses fuel pressure, the effect is immediate.

The clutches could be upshifting too quickly once they reach higher speeds, loading the engine too much (causing the bog). This would be inherent to the tuneup, so they'd look fine in an inspection. The weights in the primary and the helix in the secondary are progressive, so their shifting characteristics vary with speed (and load for the secondary, as it's torque sensing). At higher speeds does the sled like to cruise at (relatively) low RPM/lack response?

I've had a similar issue where I'd lose 500-700 rpm after 10-20 seconds WOT, fixing an exhaust restriction helped a lot (baffle broke off). The rest was swapping the helix to one with a shallower angle at full shift, causing the clutches to upshift less aggressively at higher speeds.

If you can adjust secondary spring preload, you could try adding some. If it helps, the issue is likely the clutch tuneup, and you'll want to lower the final angle of your helix.

If it's otherwise stock, it might not be a bad idea to return the clutching to stock and start from there. Clutching can be pretty complicated, and sorting out someone else's work without any documentation makes that doubly so.

 

[BC_Dan]

The 700 in this flavor is CFI, (Crossfire Injection) no carbs. I would get the fuel pressure tested to make sure that is in spec. The secondary is a Team secondary, there may be different springs he could try to adjust preload, but those are pretty dependable. The previous owner may have put in a wrong spring, so I would want to verify that what he did is what you want.

 

[G-daddy]

So first off, I’m not very experienced with clutches, I’ve never really adjusted one before so I have no idea what I’d be adjusting and how much in the secondary. As far as the helix, again, I’m sorry, but if you explain a little more on what I’d be looking for that’d be great, unfortunately clutches are kind of a mystery to me😅. As for exhaust baffle, the sled does have an aftermarket MBRP can, how would you check for a broke baffle, just look in the mouth of the can? As for fuel pressure, is there a special hook up I need or if I just bought a standard gas pressure kit would that work. Also what is stock pressure for these sleds? I’ll try to pull the secondary clutch off today and look through it to make sure the spring and rollers are good. Again thanks so much for your help guys, I appreciate it!

 

[Yamaha440]

I saw the baffle looking in the can, it's a perforated tube that had come loose, leaving a gap between inlet and baffle. It also rattled when I shook it!

Clutching can be pretty complicated, with 7-8 variables to tune and multiple ways to achieve the same goals. If you can get a copy of AAEN's clutch tuning handbook, that's a good way to get into the world of clutching.

The helix is one of those variables. The two sheaves contact each other through the helix via a set of rollers, and a spring preloads the sheaves to be closed at rest. The angle of the helix controls how much of that spring pressure acts along the axis of the clutch, and a variable profile allows that behavior to vary with ratio. Lower angles provide more belt pressure, slower upshifting, faster backshifting. Higher angles produce less belt pressure, faster upshifting, slower backshifting. Shift RPM is also affected, but the shifting characteristics/belt pressure should be tuned through the secondary clutch, and shift RPM through the primary clutch.

A team helix looks like this, the surface the roller contacts is to the left:

As for the fuel pressure questions, I can't answer anything specific for Polaris, but an automotive fuel pressure tester should work or be able to be adapted. You can rent those for free at most auto parts stores.

 

[BC_Dan]

Team secondaries are very easy to adjust for deflection. There is a small nut on an adjusting screw. It turns in to increase deflection and out to reduce deflection. Before loosening the nut to turn the screw in, use the belt removal tool to push the sheaves apart a little. That way, there is no force on the adjusting screw when you turn it in. The screw is pretty small and is easy to strip if you were to try to turn it against the internal spring pressure that is causing the sheaves to close. The biggest problem I have had with Team clutches is getting the dang thing apart. There are 6 torx screws that are VERY easy to strip. It may be helpful to have an impact tool (the kind you hit with a hammer) to get them loose. I've had to drill off the heads on more than a couple of those pesky things over the years.