97 polaris scrambler 400 4x4 won't start?
 

Hello All,

Please help me out! I recently got this quad and rebuilt the motor. It ran for 3 laps around my home then started to bog down and was backfiring a bit, then shut down. After investigating I found a small crack in the lower outside of the jug near the front left bolt flange. So I took it to a competent shop and had it repaired. I put it back together a d it still will not start. I cleaned the carb, changed the gas. The plug has really good spark, but it seems like under compression it has no spark because the plug is soaked when I remove it. I tried disconnecting the black wire from the rev limiter and still nothing. I seen the etc was touching the electrodes and it shouldn't be. Did I fry the rev limiter? Please lend me any help.

Thanks,

Just adjust the throttle cable adjuster to where you have about an 1/8" free play at the thumb lever. Pull the throttle cap if you have to see if the contacts are apart.Doesn't matter about the rev limiter,you don't want it anyway. Keep the black wire unplugged. Then see if it will crank. If it doesn't recheck compression. Plus you need to bleed the 10 mm bleed screw on the head if you haven't done so. This could have caused the original over heating as many people forget to do this.

Old polaris tech,

Thanks for your reply. I adjusted cable and still nothing. Bleed screw on the head and still nothing. Did not check the compression as I just put the jug back on with new gaskets and all so I assume I can rule that out. It is just weird that it will just crank and crank and it will not fire. I get the occasional backfire and it wants the try to start but nothing. I have a ton of spark when I check it. And then I put it back in and take it back out it is soaked with gas. What would kill the spark while in the cylinder? How does the etc affect it starting? Should the little blue sensor in the throttle box have the button pushed in at idle or no? I am kinda out of ideas lol.

Don't assume you have good compression! Check it out first.If compression is decent,at least 130psi or so on a new bore(140psi or more even better) you could be having crank seal leakage stopping it from running if you just did a top end only. If seals are leaking it can't allow enough air in the lower crank case to atomize the mixture properly and you'll end up with a wet,fouled spark plug.Plus if you just cleaned the carb and didn't install a new carb kit or at least a needle and seat and have the float arm parallel with the carb body,you could be just getting too much fuel into the cylinder.

Good idea! I will see if I can get ahold of a tester to check the compression before tearing the motor back down. I am also going to try the carb kit. If it is getting too much gas wouldn't it be coming out the overflow? The thoughts of the crank seals make me cringe cause I would have to split the case and the is not fun, so I am hoping for good compression. I will let you know what happens.

Hi all,

After digging in I found the compression to be 135psi on the cylinder which is good with my rebuild. Still wasn't getting it to start though. I pulled the flywheel cause I had a hunch that it broke the woodruff key and was out if time. After struggling to get it off I found that it was in fact ruined on the inside bore. The flywheel had spun on the crankshaft but the key never broke. It pretty well trashed the flywheel, so a replacement is in the mail. I will keep you posted on whether or not this new flywheel makes her fire up.

Hi all,

Was wondering if anyone knows the size of the woodruff key for this quad?
I know the polaris part number (3081543), but don't know the exact size?

It's a 5mm woodruff key used on nearly all Polaris atv models. Plus if you have part of the old one left you can match it up at good hardware stores like Ace,etc.3081543 KEY WOODRUFF $4.59 Make sure the shaft isn't damaged and the flywheel magnets are tight. If not they can trash a stator.