I have a 99 scrambler 400 that has never given me an issue as far as starting and running.

I ran it around the block a few times and parked it outside, uncovered for about 2 weeks. It is now 20 degress. I started it up to plow, and with the choke it ran for about 5 seconds...i goosed it as it tried to die and it did. This happened about 5 or 6 more times til it wouldnt even start...not even try...choke or none....but it would backfire like a mf'er.

So i took it in my garage and am letting it warm up. It SHOULD be warm now, but no go

What should I do next?

I guess logic would tell me to remove the spark plug...


anything else?

 

your logic is correct. check to see if the bike is fouled or not.

 

I just dug a little deeper...the plug is wet, but not fouled...i left it out so everything dries up some...might take a while since i was cranking for 60 secs+


Also, i found the coolant res. to be bone dry. it always leaked a little visibly, but never enough to affect the level. this is very wierd to me. i had some polaris antifeeze somehere, but cant find it. does a normal 50/50 blend work okay? this really concerns me

 

Okay....


So I took the plug out and it was very wet....dryed it off....let everything air out for about 6 hours. Put the plug back in...and same scenario....got it 'started' for about 3 seconds...then died. The started for about 3 seconds...then died....then crank crank crank crank


ideas? it ran great til i let it sit for a bit

 

do a compression check.Could have a blown head gasket

 

well, i drained the gas, added a 1/4 bottle of gasline antifreeze, and new gas, and she fired right up


now to find out wtf is going on with the coolant!

what should compression be on this motor?

 

Very minimum psi is 100 better if 120+

 

is mean your plug is wet w/ coolant and not gas then you have a head gasket leak possiable.

 

im starting to wonder if this is the problem. after it ran for about 20 seconds, i shut it off, hooked up my plow, and went to bed. this morning i checked coolant and it is indeed to the top of the radiator, but the overflow is dry...when its cold....i added a bit more and intended to run it with the cap off to purge.


well, same thing happened....started up for about 5 seconds, cut out....started for 3 seconds, cut out...then BAAAAAAAM big backfire....then started for 3 seconds etc etc


eventually i was able to goose it enough to stay running and i've let it idle now for a good 20 mins. white smoke out the muffler seems a little excessive, but it could be my imagination


IF there is a head gasket leak, it would make sense that it could be leaking into the spark plug chamber, and making it tough to keep ignition going? perhaps that's why it ran okay, but then after sitting overnight had the same problem? or, maybe all the old gas wasnt out...after all.....the gas appeared to be the big issue here because once it was drained and refilled with heet-treated gas, it ran okay.


i'll compression test later and post results

i should do it cold at full throttle, right?

 

well, i tested compression (what a mf'in PITA to get that thing threaded in there with the tube getting in the way)

110psi after 3 or 4 seconds cranking 2 times, 2nd time with a little throttle


So.....what's that tell me? it's good i guess, but is there a possibility still of a head gasket leak?