What is the best primary spring to put in a 1997 xcr 440 with valves. Currently have a blue(120-300) in. Stock was a almond/gold(150-290). Would a almond/red be a good option. I have S51H weights in it, if this helps. With a silver, 50-34 helix in secondary. Any help. Hotseat has been no help. Say sled is not new enough for us to test.

Almond/red will engage it too high, if you use the stock profile weights, use the almond/gold, with the S55R weights, stock R8, and silver/blue #2 or 3. The hot seat kit specs for that sled were hot seat black, W2 weights (heavy tip 49 grams), black secondary #3, and HSP34 helix (same as R8). Gear it 20/39, or 21/41, and reshim the primary clutch for a 3211074 overdrive belt. Run it 8-8300 rpm. Also install 159 P4 nozzles (needle Jets), if it doesn't have them already, and run 2 of the metal shims under the y-pipe donut. If you want to run the almond/red, get some S55H, #1322004, and use a silver/blue#2, or a blue/orange #2 secondary. A steeper helix, like a R12, HSP50/36S, or HSP34X would work with the heavier weight set-up. The S51H are too light, you do not want to rev 8500, like the newer engines.

what spring can I run with the S51H weights. A blue

You need to have at least 5000 rpm engagement, and will need more helix most likely to keep the rpm down to 8300 max with those weights. I would say almond/blue, or stock almond/gold.

polaris spec say 4200 for engagement.

Are you sure that is for the valved sled? That spec sounds more like the XC piston port spec. Our 98's with valves needed 5-5500 to have any launch, and not have a boggy feeling at low end.

that was for a 97 xcr 440 domestic twin with exhaust valves. almond/gold with S53R, silver/blue/50-34 helix. 97 has smaller bore but longer stroke than 98, unless 97 got updated engine, which mine has not.