Many use them with good results. I have tried them in a couple of 670's and found them very aggressive. They really go downhill fast which upshifts quicly. Good for drags, not so great for off trail. In my opinion you almost need a reverse angle helix for them.
I have tried to the 280's, don,t like the way they work. Stick with the 286 ramps, a 200-290 or 200-320 spring, as much pin wieght as it takes to get your desired rpm, a straight 50 helix or a 50-47. Its all in in the testing.
Here is the set up I ran in my 97 MXZ 670. 280 ramps, Erlandson yellow (240/320) spring, Black ice 44/40 (black ice numbers) helix, Doo 067 belt. I thought it worked excellent. It is true it did not back shift the best but it pulled so hard on the lake it was worth it. Also, you may be able to add a bit of pin weight. My experience is to NOT gear down this sled. It likes the stock gears pretty well. (I weighed about 185 at the time). The 280 ramps do not seem to work as good in the 99 670HO that I have now!
A couple more pointers: Run the track as loose as possible, shorten up the limiter strap. (If studded properly you should still be able to hook up good with the limiter strap shortened up. The difference between a short and long limiter strap is a good 7 mph on top end! (My experience on ice with a radar gun) That 97 kicked butt! It now belongs to someone else that i ride with and it WILL take my HO in some conditions although I beat him overall.
The 280's are a drag ramp plain and simple, they shift out like a ton of bricks and dont pull hard on top end at all, try a set of 287's and mag arms this will have great top end pull and and they are a little more laid down compared to the 286's there not as agressive as a 280 on the bottom but the 287's with mag arms will rock also. But if all your looking for is a drag setup 280's are the ticket and use shallow cams in the secondary 50-44 50-40 the 287 setup is a good trail setup.
You also need to watch those yellow 240/320 erlandson springs, theyre junk IMO. Way too long and they take a set and sack out fast. Youre much better off running a 200/350 doo spring and changing pin weight.If you insist on running the erlandson spring change it often. Like was posted the 280 is a great drag ramp but a very lzy trail ramp. I personally feel the px ramp is the ticket in the 670.
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