Need some advice on a running issue with my 1991 KX500 please..

[Lon]

Ok,long story short..
I just got the bike about 3 weeks ago and the big guy was a mess,17 year old kid had it for a month and about run it into the ground..
Guy told me the bike needed the rear shock rebuilt and rear caliper rebuilt,well he was soo full of it..Picked the bike up around 9pm so was dark out,bike needed ALOT more than I was told when I looked it over the next day..
Missing spacers in the rear wheel,rear shock bracket wasn't even hooked up/bolted to the frame where it gos between the frame/engine case..He needed alot of love and getting it..First pic is when I first picked it up and 2nd pic is the first day I took it out,you can see a HUGE difference after I replaced and fixed the shock..





Anyways,you can see it was in pretty ruff shape when I got it..Knowing I needed to add all the missing parts,I bought a 1993 KX500 basket case that I planned to build so I had 2 KX500's and glad I bought it because it turned into my parts bike  ..Guy told me it has a brand new top end and the bike does,heres how I found out..Took it for a test ride down the street after replacing parts and once warmed up,I cracked it open full throttle in 3rd gear and felt like something was choking the engine..Parked it and looked everything over real good,arm that opens/closes the power valve was missing so I grabed one off the parts bike..Before putting it on,I tried pulling the rod to open the power valve...It was stuck and wouldn't even open 1/4 ways..Blocked off the piston so I didn't spray it and hit each side of the power valves with PB-Blaster thinking its gummed up with carbon..After working it in/out for 20ish mins,its fully opening..Put the arm on and hit the trails thinking everything its all good..Well has the same issue but seems a little better,I think..So im guessing the power valve is the reason im having wide open throttle issues correct?The bike was a mess when I got it so im guessing he had the power valve apart when the top end was done,could it be installed wrong?Never had a issue like this and never had to mess with a power valve..Just feels like it choking/fueling up if I try a wide open throttle run..
Thanks in adv guys  ..

[Lon]

BTW,
Is it true that I can pull the cover off along with the black boot then start the bike..Throttle it a few times in neutral and see if the arm/power valve rod is moving??If so,how far should the rod come out?Im guessing it comes out all the way so the power valves fully open?

[Foxx4Beaver]

BTW,
Is it true that I can pull the cover off along with the black boot then start the bike..Throttle it a few times in neutral and see if the arm/power valve rod is moving??

yes you can...

I know you probably don't want to hear it, but you're probably gonna have to pull the jug and inspect the KIPS...for wear, broken parts, heavy carbon build-up, or hopefully just mis-aligned valves.

[Lon]

BTW,
Is it true that I can pull the cover off along with the black boot then start the bike..Throttle it a few times in neutral and see if the arm/power valve rod is moving??

yes you can...

I know you probably don't want to hear it, but you're probably gonna have to pull the jug and inspect the KIPS...for wear, broken parts, heavy carbon build-up, or hopefully just mis-aligned valves.

Honestly,im glad to hear that lol..I kinda thought it was the power valve so already started thinking about buying a top end gasket set but wanted to ask and be sure first..  ..I do have one other question..Is it ok to still ride it until my gaskets show up?Thanks man    ....

[sandblaster]

That is tough to answer...
Could make things worse by riding it but probably not much.
Get a Cometic top end gasket kit or OEM.
If your valves were stuck chances are the top end has a lot of hours on it.
Inspect it carefully before you reassemble.

[brooksie]

Prevention is better than cure! (and cheaper!!!)

Pull the top end off, might be a good clean is all it needs. A few gaskets is a cheap price for the piece of mind it buys you.

[Lon]

That is tough to answer...
Could make things worse by riding it but probably not much.
Get a Cometic top end gasket kit or OEM.
If your valves were stuck chances are the top end has a lot of hours on it.
Inspect it carefully before you reassemble.

Top end is brand new 

[Lon]

BTW,
I am pulling the jug and checking the power valves for sure,just ordered the top end gasket set..Im about to take the cover/boot off the power valve then start the bike and see if its moving and how far its moving...I'll also take some videos and post them,that way you guys can see whats going on...Thanks for the replys guys    ..

Not sure why but this site is moving turtle slow for some reason...

[Foxx4Beaver]

Is it ok to still ride it until my gaskets show up?Thanks man    ....

I myself wouldn't ride it until it's squared away....remember, you/we don't even know what the problem is yet.

[sandblaster]

Remember, a new piston is not a new top end... It's just a new piston, rings, and bearing...
That is normal maintenance.
Having trouble with your exhaust valves right after a new piston is installed is telling us that there is something not quite right.
When you get the top off, check for cracks around the intake and exhaust bridges...
Look for any discoloration of the plating... Discoloration is often a sign that the plating is done or close to being done.
Remove your exhaust valves and look for broken or chipped teeth.
Remember, that exhaust valve assembly should move as smooth as butter if it's working right.
Something else to check for while you have it apart is your reed pedals.
Make sure they sit flat with no gaps and make sure they are not cracked or frayed around the edges.

[Lon]

I don't know how to post a video on here yet but heres the link   -------->   https://www.youtube.com/watch?v=EirlCkrFbZw

[Foxx4Beaver]

not the most crystal clear vid, but they do "appear" to be opening/closing fully.

[Lon]

not the most crystal clear vid, but they do "appear" to be opening/closing fully.

I tried but its super hard trying to hold the phone,flash light and move the power valve rod at the same time lol...Well heres the running video and looks like everything is working like it should but not 100% sure as I never saw one moving while running lol..
Next step is to put everything back together the pull the carb/reed cage and check reeds..Then i'll pull the carb bowl off and check jets...What it feels like is its loading up pretty good past 1/2 throttle and you can hear it in the video,well I hope you can..
Heres the running video---->   https://www.youtube.com/watch?v=rNtzX-MUjho   ..

[Foxx4Beaver]

What it feels like is its loading up pretty good past 1/2 throttle and you can hear it in the video,well I hope you can..
Heres the running video---->   https://www.youtube.com/watch?v=rNtzX-MUjho   ..

funny...one of the 1st things I noticed in your 1st vid, was how much black spooge was around the exhaust outlet/cylinder, like it was running extremely rich.

Definitely pull the carb and find out exactly what your current jetting is...Main, Pilot,
look at the needle closely, and post the numbers and letters that're stamped into it, so we know which needle is in there, and what position the needle clip is in too.

it also "looked" like your governor rod seal was leaking too...the rod you were pulling in and out in the 1st vid.

[reklessj]

 +1.   I had similar symptoms mine was a bad coil. Get your carb cleaned up check your jetting and start testing electronics. I believe it was sandblaster who did a write up about testing and specs that's what got me pointed in the right direction