KX85 wont fire ???? Please Help Newbie !

1st Hello Everyone!, long time reader...1st time poster.

Purchased my son a used 03' KX85 a couple months ago....he has ridden it 7 or 8 times now and is getting a little braver each lap....his bike was bogging down in the low end so I decided to replace the reeds and re-jet the carb.

Boysen - Power Reeds

Re-Jet - 138 Main - 42 Pilot (from stock 140 - 45) NAPE Needle 2nd position

removed cleaned and Repacked Pro circut R304 silencer

Well now I cant get it started (Bruised my foot trying to get it to crank !)

Started a couple times and ran breifly, still bogged on the low end - ran great up top, but started sputtering, then backfired a few times and died. Like i said ran breifly......now I cant even get it to think about firing, when I did try it sounded like it was loaded up, give it a little throttle chokes and dies......

What I've done since and what has been checked.

New Plug (tried 2)

Removed cleaned the carb (twice) all passages (air and carb cleaner)

Put the old reeds back in - No difference - reinstalled the power reeds

Spark tested - OK

Plugs are Wet

Silencer is open (packing didnt get caught up in it - still wide open

Changed the gaskets, O-rings and springs on the exhaust manifold.

New Air filter

Checked Compression (155psi)

Could the backfire have damaged the stator Key or could this thing get out of sync?

I say I have spark - it aint a lightning bolt, but still visable - How can I check if I'm getting enough juice to the plug?

What can I do to rule out the kill switch - just disconect the wires ?

Any help or suggestions would be greatly appreciated...Thanks!

get some starter fluid and get it fired up

also check the main jet if its clogged it wont start

Is it realy hard to kick over? honestly all i can think of is that theres something(broken off piece of metal mabey???) jammed somewere in there thats make it so there too much pressure on the gears to get them spinning nicely. I'll be the first to admit i'm a lil new to this buti'd like to be any help if possible and to learn as much as i can. as for the kill switch thing, sounds very probable. but the only way i can think to rule it out is to get a new switch. For your sake i hope nothing got jammed in there, sounds costly.

Starter fluid is the worst thing in the world.

Did you try new gas and pre-mix. Could have water in gas.

Thanks Guys....I'll try the starter fluid tonight, see if that helps. Seems to crank easy like it did before......but after 20 or 30 kicks and no luck my foot (even in boots) and breath give out.

Removed the Main jet - it's new and open, no gas leaking from the overflow, so I dont think it's a stuck float.

Seems to be getting gas and fire.....I'm really baffled unless the timining or fire is out of sync?

Don't use starter fluid. It's not good for the engine especially 2 strokes.

Ok Thanks - I'll nix the starter fluid. Plugs are wet, so I'm sure it's getting fuel

When it did TRY to start - white smoke, cough, die (like it was loaded up and needed to be rung out). only did it a couple times after the 1st run. but now it wont even do that?

Try new gas and pre mix. Clean out carb again, look for water. If that doesn't do it, check the power valve. They are know to get gummed up and stick open. When is the last time top end was done? I would pull off top end and take a look. If it's ok, put some new rings in while it's off.

Can you smell gas? Is it getting gas (fuel line)?

All electrical connections good and tight? (worked on a buddy's 4 wheeler for hours, found a loose wire)

Bad Stator?

Spark plug cap?


Not sure how to test for good spark/weak spark

try push starting it... bump it into 2nd or 3rd and see if she will light up....

try push starting it... bump it into 2nd or 3rd and see if she will light up....

Why bump start it. If there is a minor problem with the top end like a stuck ring, that may cause more damage. I believe the compression should be around 170 on a stock motor for that bike. I have to look at my sons service manual.

Compression should be 165.

a bad carb will do that and if there is water in there it will do white smoke as for the main jet i see you have already changed that good

I've still got a strong feeling there is some sort of short in the kill switch, i've seen that happen 2 or 3 times. Look up "how to test kill switch for short" if nothing comesup put in dirt bike or your model dirtbike into the search. i think this is worth looking into because a short should be easy and probably cheap to fix. NSF is right though starter fluid is terrible on dirtbikes, it's definately a last resort.

check your reed valve intake boots for damage

It just came to me how to test the kill switch. Unscrew your spark plug and reattach to the black thing that attaches to the top. Makes sure you ground the spark plug to the motor or something and obviously don't touch it. Then kick it over there should be a fat blue spark. Then try it with the killswitch on and off and see if it's working if it doesn't spark you probably either have a kill switch or coil problem. And I believe that narrows it down.

Just an Update.....still not runnin.

I did test the Kill switch and everything seems to be functioning as it should. Spark, hold swith - no Spark (Thanks for the idea ! it worked perfect)

I'll get back on it tonight. My plan,

Drain the fuel tank - Clean and put new fuel in it (32:1)

Take the carb back off and proceed to do a complete forensic operation on it.....

check the reed cage and reeds again, just to make sure everything looks as it should.

un-hook and clean "all" grounds - reinstall.

Kick it, smile at my ability to come back from the dark side and bring this thing back to life !! Wish me luck.

If none of that seems to do the trick, I think I'll need to conceed that the bike has beat me this round and take er to a qualified shop !!

Thanks again for everyones response, If you think of enything else I should look at while i'm in there let me know....

I may be wrong, but it almost sounds like it is getting too much fuel. Is it possible the float height is so jacked up that it is getting way too much fuel?

Sounds like you are getting all the essentials...air....fuel....spark

With a dry plug and gas in the carb, but the fuel petcock shut off, can you get it to fire and stay running?.. Have you double checked the slide, throttle cable, needle position, etc. How about the choke opening and closing...is that operating properly? Put back together properly?

Sorry....just thinking off the top of my head. I apologize if you have looked at all these things already.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now