KDXRIDER.NET

i recently brought a 1991 KDX 250 and the engine made a slight knocking noise, it didnt sound like big end or crank bearings and when listening to the engine with a stethoscope the noise could only be heard on the cylinder and head area.

i suspected little end bearing or piston slap...

compression at this point with the engine warm was 180 psi and it ran and started very well.

now its apart the big end has no play and neither does the little end...

neither the piston or bore look particularly worn but i dont have a spec about wear limits or piston and bore clearence.

the guy also gave me a spare cylinder and a new and used piston but these pistons are different by being about 5mm taller and the wrist pin being 18mm rather than 19mm..... the cylinder is also different as there is a removable blanking plate just above the exhaust and the exhaust mounting is a different shape and size.

could any one offer an opinion to the knocking noise or help with any specs.... both much appreciated

sorry for the long post

thanks all

matt

KIPS... KDX's make noise.

The knocking is probably just Kips noise. Very common, nothing to worry about. If it makes the noise at idle, but goes away when you rev it, it's the KIPS vavles doing what they should. If the noise increases as you rev it, then it's most likely piston slap.

Now that you have it apart you need to replace the rings at the very least. I would go ahead and put a new piston in it. Have no idea on the pistons he gave you, except that they obviously are not the correct pistons.


*edit*

Dang, Inda beat me to it.....

pics?

wow thanks for the quick replys... dont think it is the kips valves as they dont have enough play to rattle around and it doesn't go away when revved... stayed almost a constant volume but was at engine speed.

i also have a kmx 125 with a similar kips engine which is almost silent so pretty sure its not that.

i am after the piston and bore sizes as there is no point replacing the piston if its the bore that is worn.

any one know of a manual download for the kdx?

cant wait to get it on the road but cant legally as i have 2 months left of my 33hp restriction so have some time to sort it out.

manual: TOP LEFT and RIGHT of this site.
what's that 33 hp restriction??? You in Europe or something?

yes from the UK... if you do you test under the age of 21 you are limited to 33hp for 2 years.

tried the manual but they took my money and it wont me download.

i measured the piston and bore today with clearences from a kmx 200 as the bore diameter is the same... it is not any where the wear limits although the rings were so i replaced them but it is still knocking.... just going to use it as is i think.

thanks for all the help.

It's not a download it's is an online manual. Log in and look at the manual. Print as needed

My KDX250 has the same noise. It is the KIPS. I thought it was weird when I first bought it too. Nothing to worry about.

I've never noticed mine making any such noise...does this mean my KIPS is potentially gummed up? There is no power loss anywhere in the rev range yet...I guess I should pull it apart soon.

Yes it means it's potentially gummed up.

Yes. And it's better to have a loud KIPS rattle than no KIPS rattle...



Little joke from another thread.