KX 65 Engine Problems

[rsaxa]

I bought my son a KX 65 2004, after two months the lower portion of the rod threw a roller bearing and it ate the cylinder, head and piston. Took it back to the shop where I bought it and they fixed it, I had to pay half ($500). It has been 4 months since and not much ride time, I am in the army and had to move to Japan, that every time the eng gets a little throttle and I do mean a little and you let the throttle go, you can hear a whining noise. Not high pitched but a low growl. I won’t rev the eng no more than a quarter cause I don’t want to buy another cylinder, head and piston. I was going to take it apart myself (first time for me). Does anyone have a good manual, that they could email me (everything is in Japanese here), and does anyone have any pictures of cases being split??

Thanks,
Bob

 

[Ol'89r]

does anyone have any pictures of cases being split??

Thanks,
Bob

Bob.

Don't have any pictures, but we could probably walk you through it. You may want to remove the cylinder first and check your piston clearance. While the cylinder is off, you can check for excessive movement in the lower end.

The noise you are hearing may just be a little piston noise on deceleration. If the noise is excessive, it may be wise to pull the cylinder. :cool:

Just my $ .02

 

[rsaxa]

I don't want to sound like a complete idiot, but what is piston clearance? I think the diameter of the piston and the room it has between the cylinder. I removed the head and the cylinder to find that the lower end has no play. The sound that I heard, a low buzz when I let off of the throttle could have been piston slap? I have heard piston slap, usually I only hear that at an idle. The sound did not seem to be clanky but more of a buzz, but low in tone and volume. Any help is greatly appreciated.

Thanks,
Bob

 

[Bodge]

How does the lower end feel through its stroke? Does it have any side to side play? No play at all dosnt sound right.

 

[Ol'89r]

what is piston clearance? I think the diameter of the piston and the room it has between the cylinder.
Thanks,
Bob

Bob.

That's exactly what it is. Measure the diameter of the piston down near the bottom of the piston skirt. Measure from front to rear of the piston. Then measure the bore of the cylinder, also from front to rear. The difference is your piston clearance. Cant remember the exact clearance on the 65 but, it should be around .002 or less. Also inspect the piston and cylinder bore for excessive wear marks or scratches. (Signs of seizure).

To check your lower end, grab the rod with both hands and bring it to the top of the stroke. While resting the heels of your hands on the engine base gasket surface, try moving the rod straight up and down. If you feel any movement or hear a clicking sound in the rod, the big end could be worn. You should get some side to side movement in the rod, just not any up and down movement.

Like Bodge said, check the crank through the whole stroke. Rotate the crank and feel for any roughness in the bearings. Check the little washers on the bottom end of the rod for discoloration or signs of heat. Both washers should be the same thickness and should be a copper color. If one is thinner than the other or they are black or burnt looking, the crank needs to be rebuilt.

When you replace the top end be sure to buy a new set of rings for the piston and hone the cylinder. You can use Scotchbright for this if you don't have a hone.

Don't feel like an idiot if you find nothing wrong. It's better to be safe than sorry. :cool:

 

[Radiator Ron]

without hearing it, its hard to say. Make sure nothing on the bike is vibrating, somtimes it can sound like an engine problem. Other than that, i dont believe a low growl would be a rod or piston. This engine has an interference fit on both main bearings, if improperly assembled excess side preload will cause bearing failure.