1996 Polaris Scrambler 400 4x4

Zseventy-one

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Cool build, wish I could have shown this to my friend b4 he sold his...think it was a 400, 2 stroke drk green 4x4. Was a nice looking machine and pretty quick. He had trouble keeping it running and eventually sold it. He also has a 900 but that thing is a 1000lb beast.
 

letitsnow

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I did another 2 hour test run yesterday. Everything that I had changed (after the last test run) worked, except the front hub leak - It held for the 1st 1/2 hour, then started leaking pretty bad. I ordered a new sleeve seal and will re-silicone everything up.

The rear shock is still a bit soft, so I added another 1/2 turn of preload. The jetting is now really good. I had over 1 gallon of gas left after my 2 hour run. The tank is a 4 gallon tank, so this is real good.

This is going to be a fun woods racer. :)
 

letitsnow

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I installed the new seal sleeve. This isn't a terrible task, but it isn't easy. After removing the hub I used a dremel to cut a groove in the sleeve. I then used a chisel to break the sleeve loose from the old silicone. After that, the sleeve came off by hand. Here is a pic of the old sleeve.

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A pic of the hub (with sleeve removed) after I cleaned up the old silicone.

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Putting the new sleeve on - you put new silicone on, then tap the sleeve on. It needs to be perfectly aligned with the coil surface, which takes some patience and lots of measuring.
 

letitsnow

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Final weigh day....

With all fluids full, in ready to race/ride mode - it now weighs 532 pounds.
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letitsnow

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I did another 2 hour torture test. Even with a new seal sleeve and all new parts, the hubs still want to leak the hub oil out when being abused. This system just isn't going to work when being abused this badly. If the hub oil didn't leak onto the front brake pads when things flex, i'd leave it as is and just keep adding oil. Oily front brake pads are no good.

I am switching the system over to bearing grease - will add a zerk to the housing and allow it to push grease through all bearings, and then i'll put the plastic cap on the outer end.

Some really smart people have told me not to convert to grease, but I am going to anyways. If it fails, it fails - there is only one way to truly find out... I am using this system in a different way than most, so am banking on the grease working.

I've also ordered a primary clutch spring with the same end rate, but a higher start rate. The one that I have in there now engages at a slightly lower rpm than I need.

Making good progress.
 

letitsnow

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I put the new primary clutch spring in and it works really well. It does make it a bit harder to load/unload (into the back of my s10) because once the clutch engages, it really engages! You have to be paying attention now. While riding, it works great though. I bought the spring from hot seat performance. Their website is easy to use, and no games.

I have done two, 2 hour torture tests now and the hubs (with bearing grease instead of oil) have worked just fine. If anybody else is going to copy this - please remember that my machine is modified so that you can't put it in 2wd. If you used bearing grease in a regular system, it would probably magnify the oem's issue with 4wd engaging on its own with this design.

On to the next issues...
- If I ride harder than maybe 80%, the machine starts to starve for fuel/sputter. It gets better if I loosen the gas cap. The tank has a small vent line, but it must not be big enough to allow gravity to work. I am going to make my own vented gas cap.
- It also sputters a bit in the deep whoops. I am going to T the carb vent lines so that it can get rid of the odd drip of gas (by using gravity in the line that goes down) and also breathe while going through water (by the line that goes up). I've had to do this on dirt bikes in the past.

These last 2 problems are minor, as riding at 80% is fast enough to meet my goals with this machine. It is nice to know that you can wick it up to 100% if needed though. When this machine was stock, riding it at say 30% was all that I could do without crashing.
 

letitsnow

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After making my oem gas cap work as a vented cap, and t'ing the carb vent line - everything is working well.

Here is the underside of the oem gas cap.
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I drilled a hole (a few sizes smaller than the hose) through in the center, and pushed 3/16" fuel line through. Then I installed this rubber baffle from an old gas cap that I had saved.

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Here is the finished product.

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letitsnow

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A couple small items:

- The original airbox-to-carb boot was getting too beat up to trust. Polaris doesn't sell that anymore, but they do sell them for '98+ model years. I bought one (of the 98+ ones) from rmatv. The angle molded into the boot was off slightly. The airbox-to-carb location must have changed slightly in '98. I was able to slot the airbox mounting holes to move it over a bit, and it works fine.

- I replaced the oem porcelain ngk spark plug cap with a rubber ngk cap. This is mostly just because I like the rubber ones better - they seem to handle vibration and impacts better.
 

letitsnow

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I had cut the coolant overflow tank off of the belt air vent and moved it up by the radiator and also replaced the belt air vent with abs pipe before the last couple torture tests. The changes did what I hoped, so now the pieces needed to be finished up/mounted permanently.

Here is a pic that shows the stock (white) piece.

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letitsnow

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Here is the new overflow tank location. I made the mounts out of generic steel banding.

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