01 YZ 125 Top End Job now beginning

[deuscent]

Ok thanks everybody for your helpful contributions thus far.



i now have the Wiseco piston kit ready to install.

what tool is used for the piston pin clip??? any special technique, like a twist with needle nose pliers?

also, do i have to, or do i want to remove the cylinder head or can i just take apart the cylinder?

before i start, i just want to review the other tools and supplies i have to get the job done, please contribute if you think i am missing something useful;

- fresh white sheet for ground and rags to cover bottom end
- old fluid container
- carb cleaner
- engine degreaser
- correct metric sockets and torque wrench with 0 to 100 ft lbs measure
- pipe spring puller
- gaskets and gasket sealer if needed
- dull butter knife for scraping
- ???

THANK YOU

oh wait one more thing, how can i get notified by email when people reply to the post? then ill really be set!

[Aus_Rider_22]

Originally Posted by deuscent

Ok thanks everybody for your helpful contributions thus far.



i now have the Wiseco piston kit ready to install.

what tool is used for the piston pin clip??? any special technique, like a twist with needle nose pliers?

also, do i have to, or do i want to remove the cylinder head or can i just take apart the cylinder?

Fine needle nose pliers will be very handy. Does the top-end come with new clips? If not be careful when you pull the clip out. If it flicks out and is lost it could be a big pain searching your area for a 1c piece of metal!

You don't have to remove the head from the cylinder. If you do you should get a new set of o-rings. Black outter one and red inner one from memory. Don't quote me on that.

The first time I did it on my own I didn't think about it when I ordered the parts and ordered the o-ring gasket/rubbers as well. It was interesting to pull the head off and clearly inspect the head surface and "squish band" area. It's up to you. Just get fresh o-rings and take note of the torque needed on the head nuts.

Originally Posted by deuscent

before i start, i just want to review the other tools and supplies i have to get the job done, please contribute if you think i am missing something useful;

- fresh white sheet for ground and rags to cover bottom end
- old fluid container
- carb cleaner
- engine degreaser
- correct metric sockets and torque wrench with 0 to 100 ft lbs measure
- pipe spring puller
- gaskets and gasket sealer if needed
- dull butter knife for scraping
- ???

THANK YOU

oh wait one more thing, how can i get notified by email when people reply to the post? then ill really be set!

You've got alot of organisation going on I wish I was organised as you were when I tackled my old YZ125! Having these things prepared and in close reach will make things alot easier and less stressful.

For getting emails to your inbox about this thread, try this.

Go to your UserCP (link top left of page)
Go to Settings and Options
Go down to Default Thread Subscription Mode and click subscribe.
That should do it I think.

Another mod should see this and be able to correct me if it's different.

Have fun and don't be scared to take photos and ask questions!

[MXtras]

Sounds like you have everything pretty much under control.

Just ensure everything is spotless and oiled when you go back together. Also - if it's your first time, it's helpful to have a second set of hands to help putting the jug back on if you are going to do so with the head in place. There is no real need to pull the head but with the head on and the engine in the frame, it's a bit tight to slide the jug back on. No big deal but for a first time, I can imagine it might be a tad frustrating to do by your lonesome.

Scott

[Aus_Rider_22]

Originally Posted by MXtras

Sounds like you have everything pretty much under control.

Just ensure everything is spotless and oiled when you go back together. Also - if it's your first time, it's helpful to have a second set of hands to help putting the jug back on if you are going to do so with the head in place. There is no real need to pull the head but with the head on and the engine in the frame, it's a bit tight to slide the jug back on. No big deal but for a first time, I can imagine it might be a tad frustrating to do by your lonesome.

Scott

Good call.

Trying to squeeze the rings into the piston while maintaining the end gap can be very hard with the other hand positioning the cylinder.

You can do it but be prepared to not get it easily.

[fordmugg]

make sure coat the piston with 2 stroke oil and the cylinder

[deuscent]

I have new pin clips, how do you put them in? That seems like a tricky part

Also, i have new O Rings for the head, would it be better to take off the head, and as da kine Aussie22 said, to inspect and clean the head? is it easier to reinstall the cylinder if the head is off???

by the way i do have a manual as well for torque specs etc

Cheers MaTeys!!! and Aloha!!!

[MXtras]

I locate the open end of the clip into the groove, then push the rest of the clip in. This way the ends of the clip don't score the pin bore. The chamfer on the bore helps close the clip. You can put one clip in beforehand on the bench.

Scott

[deuscent]

is it easier to put cylinder back on with the head off?

[deuscent]

head is off!!!

[kwmotocrosspunk]

Originally Posted by deuscent

Uggghhh!!!

The engine bracket bolts are too tight and broke 2 of my 1/2 inch sockets!!!

bracket bolts....as in pulling out the engine?!?! dont have to do that for a top end!!!

or do you mean the head bolt caps? if thats it they are either wayyyyy too tight or are siezed on there, get your self some good liquid wrench! and let it soak! or get a bigger wrench!

[2strkyz]

I think he is referring to the bracket that connects the cylinder head to the frame.

[deuscent]

ok thats all good, the head brackets were real tight but budged after 2 broken sockets, im on my way to take the cylinder off now...



thanks!

i have a video...

[Only registered and activated users can see links. ]

[scooter842]

please please please.... dont forget to put a rag around the connecting rod to cover up the crankcase when putting in the circlip! Let the thing fly away... in the dirt... in your dinner... your dogs water bowl... in the rocks...... ANYHING other than the crankcase! Not sure if your piston is a single compression ring or double.. but be sure to have the end gap 90 degrees from the intake and exhaust ports.. and if it is a 2 ringer... be sure the two are 180 degrees out from each other... install rings with part numbers UP ^. Use lots of 2 stroke oil during assembly.. Once the rings are installed on the piston... coat the rings/piston and the cylinder wall well. Be gentle.. dont force things. Careful when compressing the rings and sliding the cylinder on. You dont want to snap a ring! And pay attention to your ring gap position... it does matter! And of course... use proper break in... seat the ring/s to the cylinder and it/they should not move after break in. I could keep going and going.. but i will stop there for now.

[deuscent]

how do you describe proper break-in?

just now got the cylinder off - cylinder walls have light scoring - i will use #600 wet sand paper to smooth it out and clean it with carb cleaner... is that ok?

NO IDEA how to get clip into new piston, clip seems WAY TOO BIG for piston and grooves are DEEP in the wall (much deeper than current one) and will take considerable bending and i already lightly scratched the new piston!!!



video

THANKS!!!

[Only registered and activated users can see links. ]

[deuscent]

With 2 stroke oil all over the place, it sure is a hard task to even get one circlip in before its even on the arm!!!

[Only registered and activated users can see links. ]

[wamxp1mp]

Oil the cylinder wall after you have the cir clips installed first. I don't bother oiling the piston n rings but I do oil the wirst pin and top end bearing.

[deuscent]

Ok thanks everybody!!!

rings are in, smooth functioning, etc

cant wait to fire it up!!!

[scooter842]

Question.... Does your new piston have the pins in the ring groove? If so... thats where your ring end gap will be... those pins hold the ring in place. I was thinking you had a full floating ring piston. That circlip looks fine and will/should fit in the groove.

[deuscent]

Ok, breaking it in now.

I think it went pretty smoothly overall. No excessive scratching to piston, only one light one near piston pin entry hole...

I had to remove head cover again because i forgot to put grease around o-rings - why do you do that anyway?

seems to run much better, i havent tried anything in the higher rpms yet or powerband so i dont know everything yet

not sure if i actually got the end gap on the ring exactly right, what are the consequences of error???

piston operated smoothly with head on...

[scooter842]

Congrats on finishing up! Sounds like it went smoothly.

Grease on the o-rings... Not real sure why you would need that on your head o-rings. My best guess would be to keep the o-rings in position while putting the head on, and maybe to help aid in sealing...? But typically, the o-ring does a fine job at that!

ring gap... here is why i always preach the importance of ring gap... For starters, i am an aircraft mechanic... and we often do cylinder maintenance on piston engines. After a few complete engine overhauls, and several upon several cylinder changes... I have found that when fresh rings are installed, an improper break in causes rings to "float" and when this happens... sometimes the end gap will line up... which then allows air to escape by the piston during the compression stroke... thus indicating a false compression check during inspection. Thats why break-in is important, to allow the rings to "fit" the cylinder. This will then prevent them to float.

In dirtbike terms... Some pistons have a "key", which is just basically a dowel pin that is pressed into the ring grove, prevents the ring from "floating". You set your ring gap in between the dowel. Otherwise your piston and ring wont fit into the cylinder. On pistons that do not have the key, it is important to position the rings correctly.... If it has two rings, and the gaps are lined up, you will allow blow-by and have a loss of compression and ring seal. If you set them "180 degrees out", it will prevent this from happening. It is also not a good idea to have the ring gaps set in the path of the exhaust and intake ports because they can clip the ports, causing scoring and in some cases break a ring.

Hope that makes sense.