Piston look ok to u?

[Brandon H.]

I have my 1994 KX 125 completely torn apart to inspect, replace, and paint anything I think needs it. So far every bearing and seal looks great, got cleaned and repacked, every single part on the bike cleaned.... it took HOURS!! But it will look like a brand new bike once done. I am about to paint the cylinder and head, and the bottom end needs a new rod bearing and rod, and I will do new crank bearings and seals. I already have all the gaskets and a new piston ring.

Anyways right now what I want to know is if my piston looks ok to you guys?? I can't afford a new one at the moment, and I don't own a mic so I haven't checked to see if its in spec... yet. I will include pics of the cylinder tomorrow after its been painted to see if you guys think the insides are good.

 

[Brandon H.]

http://i5.photobucket.com/albums/y173/Brandon10251988/100_2005.jpg
http://i5.photobucket.com/albums/y173/Brandon10251988/100_2002.jpg
http://i5.photobucket.com/albums/y173/Brandon10251988/100_2000.jpg
http://i5.photobucket.com/albums/y173/Brandon10251988/100_1994.jpg
http://i5.photobucket.com/albums/y173/Brandon10251988/100_1992.jpg
http://i5.photobucket.com/albums/y173/Brandon10251988/100_1981.jpg
http://i5.photobucket.com/albums/y173/Brandon10251988/100_1982.jpg
http://i5.photobucket.com/albums/y173/Brandon10251988/100_1977.jpg
http://i5.photobucket.com/albums/y173/Brandon10251988/100_1975.jpg

I also found out that my cylinder isn't nickel plated.... I though it was the whole time, so I guess I am a newb lol. You can see surface rust in this pic from cleaning.... not to worry though it was so little that my finger was enough to get it all off.
http://i5.photobucket.com/albums/y173/Brandon10251988/100_1984.jpg
http://i5.photobucket.com/albums/y173/Brandon10251988/100_1986.jpg


Sorry guys, got a error message saying too many pics, so I made them URL's

 

[RM 125]

hey guy dont paint that unless u want your bike to overheat

 

[Brandon H.]

Why not its water cooled?

 

[julien_d]

Paint's not going to hurt anything, although it probably won't stay on there long.

Piston looks pretty tired, I don't think I'd put it back together without a new one. A fresh piston is relatively inexpensive insurance considering all the work you're putting into it now.

No way we can tell anything about your cylinder looking at pictures through the ports. Take a shot straight down through the bore.

 

[sr5bidder]

hey carefull plating will rust!! put a magnet on the inside of your cylinder and check it that way
you should also be able to see from the top a sleeve if it is not plated

eric gorr has some good reading on his site (sample of books) I would suggest you read that stuff!! pay attension to the part about the ring guide pins when reinstalling the piston

 

[mathd]

instead to spend the $ on high temp paint that wont last long, and will just make it look bad after some wear.
i suggest you buy a piston instead, its tear apart and piston is not that expensive.

I cant comment on the cylinder, i lack knowledges for this part.

 

[rmc_olderthandirt]

put a magnet on the inside of your cylinder and check it that way
/QUOTE]


What is the magnet supposed to check?

Rod

 

[Brandon H.]

put a magnet on the inside of your cylinder and check it that way
/QUOTE]


What is the magnet supposed to check?

Rod

If the cylinder is iron.

Well crap then I guess its time to save up more $$$ for a new piston. I understand u can't see the cylinder in that pic, I already taped the cylinder for paint and didn't have a pic. I was just saying if u look close u can see the rust. I should have a pic of the inside of the cylinder in a few hours. On a side not I just painted the cylinder (aluminum color) and the head, it looks good. The frame should be done this weekend.

 

[dirt bike dave]

You have a two stroke 125 cc race motor. Piston and rings do not last long.

Your factory service manual probably recommends replacing the piston several times during a race season.

It looks like you spent a lot of time cleaning the piston up,and on other cosmetic stuff. IMO, you should replace the piston if there is any chance it has a lot of hours on it, even if it measures within spec.

BTW, if you put it back in, it may well run great. Lots of pistons with way too many hours on them will run great, right up to the point they break. Then you hope the carnage does not take out the crank, cases, power valves, cylinder, etc... Basically, if your piston shatters because it is beyond its service life, it can cost far more to fix the bike than it is worth.

 

[Brandon H.]

Ok, I will get a new piston, rod w/bearings, crank bearings, and seals. I already have a engine gasket kit and piston ring. Just need to find someplace cheap to put the rod on the crank for me. I also need help finding a cheap flywheel puller to remove the flywheel. CaHills wants $35 to pull the flywheel.

I also got pics of the cylinder, but they did not turn out good so I wont post them and just wait till my buddy can MIC it.

How many hours of riding (average rider thats trail riding) should a piston last?
How many hours of riding (average rider thats trail riding) should a cylinder last before needing redone both sleeved/iron, and nickel.
I don't own a service manual, but I need one.

 

[whenfoxforks-ruled]

Rod, I thought plated/chrome bores are not magnetic? Brandon, the hour life of them parts are model specific, in the manual. Roughly, a new top end every 15 hours,could be less? Stock. Modded will be shorter. Is an hour how you ride the same as a pro racer? They rebuilt theirs every race, a little over an hour. Screaming wfo up and down the roads and bye bye engine? Putt putting under the power band may extend the hours, and harm other parts. Its a state of the art, 125 2 stroke mx race bike after all. I would send the top end complete, and the crank to Eric, http://www.eric-gorr.com/

 

[Brandon H.]

Yeah I have talked to Eric, and I am thinking about just sending him the top end and crank to him. He has really good prices.

Man, I am used to riding my 400ex.... switching to the 2 stroke side thinking so few moving parts maybe it would be cheaper.. I guess I am wrong lol. Either way I can't wait to ride again. But damn a new top end every 15 hours, thats a month of riding for me. I don't ride hard.

Ok so now I know what needs to be done, where can I get a flywheel puller for a KX 125? Any online websites??

 

[whenfoxforks-ruled]

Rotor puller, everywhere has them, some local shops carry them. I like Service Honda. Nearly one size fits all mx bikes. Tired of the 125 maintenance schedules, get a bigger bore, a 500 lasts longer! But, you go through more tires and chains. IMO, running long on servicing the top end, ovals the cylinder.

 

[Brandon H.]

Care to take a minute and find a pic of one for me? There seem to be a lot of different kinds.

I have tried 2 different sized ones of this kind (btw this is not my motor in the pic)
http://www.greenflag.net/images/tut_disassem6.jpg
I tried 2 different sized tools, none fit.

 

[whenfoxforks-ruled]

THATS NOT IT! STOP NOW! DANGER!!! That is a 2 jaw puller, that pulls the back of the rotor, if it breaks loose at all. it will shoot off at a very high speed! No pic, but there are for others, and manuals, http://www.bikebandit.com/product/9331, http://www.bikebandit.com/assets/product_images/06K&NFlywheelPullLG.gif, http://www.bikebandit.com/manuals/c/a642315?mg=4875&t=1

 

[Brandon H.]

Well crap, I am glad they didn't fit or I could have hurt myself. Mine was actualy a 3 jaw puller.

I really like the deal on
http://www.bikebandit.com/product/9331

I looked at the specs and it says it fits KX 125, so hopefully it fits my model. I will order it tomorrow night.

 

[whenfoxforks-ruled]

And the manual? It may have showed the proper tool. An oem is preferable over the aftermarket. Compare Service Honda's prices, they are usually cheaper!

 

[Brandon H.]

Aww yes, a manual. I forgot about that too. Looks like I will be ordering one of those with my flywheel puller tonight.