Kx 85 not running right in powrrband

[locko90]

Hey all,
really need some help with Me kx 85, ever since I've had this bike I've had problems with it's powerband, when its about to hit power band it starts to rev out of time and can't gain higher revs sorta sounds like it's hitting a rev limiter.

I'm running the fuel at 32:1 now.

I can't test compression on bike but it does feel pretty low and very easy to kick over.

I havnt checked condition of reed valves, and I haven't checked power valve as I'm unsure on how to do that or if that could be the problem.
I'm not sure how to take the muffler appart and clean that. Would that be worth doing?

Today I cleaned the air filter and box it was filthy and dirty it had fuel and dirt in the air box, could it be that the carbs blocked with dirt now (I did clean the carb but didn't think the air box would be that bad and i didn't realise the air box was so easy to take off and clean) also the air filter had nearly no oil on it, I put heaps on today though. Didn't fix Problem though.

So was wondering what could be causing the engine to run like this?

Oh just remembered that the muffler has oil coming out the back of it what could cause that and could that be part of the problem?

 

[china911]

if you have never had it running right its hard to know how it should behave . All 2 strokes need to run like clockwork. Check the easy accessible items first , your manifold (any cracks)and the reeds that sit between the carb and the manifold . exhaust expansion chamber washer (may be leaking) , put a fresh standard plug in .(oem specs).
Check your clutch lever and adjuster (may be slipping ) if adjust to tight without slack. These items are simple.to do .. good luck

 

[locko90]

Yeah it sucks that I've never had it running right the poor things been abused I think it could really do with a new piston and rings and cylinder hone (don't have the money for that ) but next time im able to I'll check the condition of the reeds and hopefully that's what's causing it to run like ****,
Does anyone know how to clean the power valve on these bikes would it be worth checking the power valve or how to take apart the muffler and clean or repack?

 

[LEO DPRO 037]

I run my kx80/100cc at 40:1.
Thats 25ml of oil to every litre of fuel maybe 32:1 is too much oil?

Check this chart, how much oil have you been adding to every litre?

 

[china911]

probably best you get a diagram/manual for the power valve . you need to see if it is moving and not seized ,broken or washer split. With the muffler (if its the removable type) it may be riveted or bolted at the rear end cap . muffler packing pulls out like a sleeve. l usually shove a bit of timber or broom stick into the end cap hole and jiggle it out , tap the sides .Try not to be keen with a screw driver ,you wll make a mess of your muffler. Give it a good wash in petrol /solvent . wrap the new pack tight like a kebab and secure with some wire on the ends and the middle . It needs to fit back in neatly so you have to be precise.

 

[locko90]

Yeah well I used to run it at 50:1 that seemed to run pretty good but I went to 32 cuz that's what it says to run it at in the user manual. I'll give 40:1 a try. I think with changing fuel ratio I have to tune carb ?
I'm kinda thinking the power valve could use cleaning reeds need checking and muffler needs cleaning if I could get any advice on doin this that would be awesome.

 

[locko90]

It's got really low compression... Could that cause it to run out of time at high rpm or would it be the power valve not working properly possibly carboned up or reeds worn out and can't open and close good enough.. I'm trying to read up on causes to this problem but I'm not really finding much... Pretty fustrsting

 

[my67xr]

Changing the fuel/oil ratio it may need to be rejetted
The carby does need to be tuned to suit the new fuel/oil ratio too
Have you checked the plug ? might be fouled if you haven't tuned the carby
Have a look here for the power valve adjustment- bike bogs when it hits the powerband - Kawasaki 2-Stroke - ThumperTalk
kx clutch and KIPS check

 

[locko90]

sweet bro!! thanks alot man that's what I was hoping to find!! looking at the "kx clutch and kips check" link and its a step by step guide to servicing the kips! cheers mate thanks!!

 

[locko90]

hey mate, i have a small question, cuz of my inexperience in changing pistons in motorbikes (never done before)...

would i be able to just remove the cylinder and clean out the power valves and reinstall the cylinder back on to old piston and rings with out honing cylinder.

i know changing the piston and getting the cylinder honed would be better, only problem I just wont have the money for that anytime soon.

i just have a feeling that the power valves are the problem, i think that they are just not opening up completely and causing it to run crap at high rpm.

would this be worth doing or should i just replace piston when i service power valves??

any opinions on this subject would be most helpful.

 

[my67xr]

You could do it that way depending on what you find while its apart.
You'll most likely need a gasket set minimum.

If it all look's good inside you could just re ring it too, depending on what piston it has they cost from $30 and up
Scotchbrite the bore to deglaze it etc

A new top end rebuild kit would be around $150 for everything, a go for something like a Wossner forged piston etc

 

[locko90]

thanks for the reply mate!!,

I think ill just take the engine off the frame, that way ill be able to inspect the power valves and not have to take the cylinder off.:thumbup:

Im not sure how i would measure the torque needed for the cylinder bolts, do i need a special tool for that??

since im taking the engine off the frame im thinking i may as well give the frame a new coat of paint and clean the bike up

I looked at the kips today and its actually leaking oil out of it, that would be an indication that something's wrong yeah?

heres a pic of the kips

 

[locko90]

I found out that the power valve shaft was put back together incorrectly by previous owner... And I'm thinking that's whats causing it to run really shiat in powerband.. the mark on the power valve shaft isn't in line with the mark on the case.