Return to dirt = CR125

[tigertim20]

Pulled the top off today.
Have a few questions if people can help me out here.
Two pictures, one of the bore, the other the piston.
Most of it looked fairly clean, but there was a scratch in the piston, but not the ring.
There was aslo a mark on the bore, the one on the bore however, I cant feel when I run my finger over it, so Im not sure if its necessary to get it honed out?
pics are here:


Dunno if the pics are enough to see, if they arent, Ill have the wife take it into the local shop and have them take a gander.

One other question too.
On the inside of the piston the only markings I could find were

ART
L
3

Can anyone decipher this? - Im hoping that the absence of anything like .020 etc means that it is still a standard size and hasnt yet been taken out larger.
any help here appreciated folks!

[barty5]

clean the top of the piston they normally stamp the top of them.
hone depends if its plated or not if not id spend the 80 odd bucks an go up one size in piston when you replace it then you know the bore is mint.

[tigertim20]

took it to the local bike shop, they said that the bore looks fine, but it wouldnt hurt to do a very light hone.
if I geta very light hone will I be able to use the same sized piston, or go up a size?

[noobi]

took it to the local bike shop, they said that the bore looks fine, but it wouldnt hurt to do a very light hone.
if I geta very light hone will I be able to use the same sized piston, or go up a size?

Depending on what size the piston in it now is, it probably wouldn't hurt to go up a size. Although in reality the difference between the sizes is 0.01mm, which is pretty much immeasurable by most people, so it doesn't really make a difference.

[ktm84mxc]

If it's just getting a light hone you'd be ok fitting the same size piston, if you desire while it's apart get the barrel checked by an engine builder to see if its square eg not oval, most wear occurs above the exhaust ports.

[tigertim20]

ok thanks for that, Ill take it to the local engine reconditioner and get another opinion - the bike shop commented that it was in pretty good nick for its age.

I just cleaned the top of the piston with a dremmel, and there is nothing that I can see stamped on top of the piston, just a big flat surface, so I guess I need an accurate vernier caliper to measure it and figure out what size the current piston is?

[Crasherfromwayback]

ok thanks for that, Ill take it to the local engine reconditioner and get another opinion - the bike shop commented that it was in pretty good nick for its age.

I just cleaned the top of the piston with a dremmel, and there is nothing that I can see stamped on top of the piston, just a big flat surface, so I guess I need an accurate vernier caliper to measure it and figure out what size the current piston is?

Is it not a nikasil bore mate? I would've thought it was. Worn rings won't make a two stroke smoke...just a cunt to start and it'll have no power.

[noobi]

so I guess I need an accurate vernier caliper to measure it and figure out what size the current piston is?

The accuracy you are trying to get is smaller than the accuracy of even the best verniers. The only thing it will tell you is whether the piston is oversize or not. The bore should be 54mm, and the piston should be slightly smaller, you wont be able to determine the spec of the piston with a vernier. A good engine shop should be able to give you an accurate measurement of the bore though.

[tigertim20]

Is it not a nikasil bore mate? I would've thought it was. Worn rings won't make a two stroke smoke...just a cunt to start and it'll have no power.

i have no idea, im still trying to track down a manual so i can get the info i need, i did notice though that the piston had quite a bit of blackening around a third of its circumference below the ring.
The bike shop confirmed it needs ring, but it was my intention from the moment i bought it to put in a new piston and ring anyway - you never know what you have been given eh?

It does have what I can only presume to be carbon fibre reeds though, is this common? looked very clean like they may well be quite new.

The accuracy you are trying to get is smaller than the accuracy of even the best verniers. The only thing it will tell you is whether the piston is oversize or not. The bore should be 54mm, and the piston should be slightly smaller, you wont be able to determine the spec of the piston with a vernier. A good engine shop should be able to give you an accurate measurement of the bore though.

ok, will try get that sorted out on monday then, plenty of stuff I can be doing like cleaning for now anyway - Im considering getting teh frame powdercoated, it isnt very expensive, but if I do that, I will feel like I should do something with the bodywork as well, and I dunno if I can be bothered with that to be honest!

[Crasherfromwayback]

i have no idea, im still trying to track down a manual so i can get the info i need, i did notice though that the piston had quite a bit of blackening around a third of its circumference below the ring.
The bike shop confirmed it needs ring, but it was my intention from the moment i bought it to put in a new piston and ring anyway - you never know what you have been given eh?

It does have what I can only presume to be carbon fibre reeds though, is this common? looked very clean like they may well be quite new.


!

Yeah that's just blow by. Carbon reeds are the norm now. Way back when...they used to be metal!!! No good when your engine munched one!!!

[nzspokes]

ok, will try get that sorted out on monday then, plenty of stuff I can be doing like cleaning for now anyway - Im considering getting teh frame powdercoated, it isnt very expensive, but if I do that, I will feel like I should do something with the bodywork as well, and I dunno if I can be bothered with that to be honest!

I guess it comes back to what you want from it. I looked at powder coating mine and getting plastics painted. Then all I would do would be scared to drop it out riding. So as I fall off a lot(ask anybody thats ridden off road with me) I decided its not worth it.

But you may well be more skilled.

[tigertim20]

I guess it comes back to what you want from it. I looked at powder coating mine and getting plastics painted. Then all I would do would be scared to drop it out riding. So as I fall off a lot(ask anybody thats ridden off road with me) I decided its not worth it.

But you may well be more skilled.

heh, in my experience dirt bikes fair better than sportsbikes in a bin haha.

The frame im thinking of doing as the paint is work and chipped in several places, and it has that very light surface rust - I would do it to prevent any future deterioration more than anything else. - Its just that Id feel like a half arsed cunt if i did the frame and didnt tidy up the bodywork. Full bodywork kits can be had for a couple hundy, but im interested in spedning coin of having a mechanically sound dirt toy - not overly concerned with cosmetics as long as it rides well.

-thanks for that crasher

[tigertim20]

Pulled the HPP apart today, fuck mee was it filthy! The slides were so caked up with carbon that I couldnt remove the slide from it's sleeve without quite a bit of force - I dont think theyve been looked at in a long time.
Spent ages attacking the parts with petrol and a steelo type pad thingy and they are a big improvement, moving freely now and no sticking anymore, unlike before.

Hope to get the barrel down to the engine reconditioner tomorrow to get checked, and then hopefully i can order some parts by the end of the week.

Had a second look at the frame, and I think I might get it powdercoated, the underside is looking pretty ugly.

[cheese]

If you're talking about the power valve being gummed up that will stop it reving out.

[tigertim20]

If you're talking about the power valve being gummed up that will stop it reving out.

yup, on this particular model its called the HPP = Honda Power Port. same thing, different name.
There was some general grunge, but where it stuck was just at, or after, the full open position - i.e. it didnt get stuck in normal operation, it just wasnt particularly free moving. I didnt have the stuck problem until i had detached the slides from the part that actuates them so I could remove them completely.
does that make sense? - it does to me!

Either way its a bit of maintenance that needed done thats IS done now.

Hopefully tomorrow I will have some better answers about the cylinder, then I can order bits, slap her back together, clean out the carb/tank/aircleaner/fuel line throw in a new plug and see if she runs right. hopefully it does.
then its wheel bearings, bushes for the ass end, and about 200 other tiny little things to do before it can be ridden.