Yz85 help

[Daniel Hamilton]

So I got a kick start for my yz 85 sounds weird when I kick it it almost sounds dry but I have checked the oil and help would be great as I'm not sure what it is although I do think it's the bottom end 

[Zack Brappp44]

since your bike is a 2 stroke, the transmission oil that you put in your bike is not the lubricating oil that is actually used for operating the bike. Oil that is used in the gas is what lubricates the cylinder of the bike. Its hard to tell what is exactly going on with your bike through your description. Is the bike easy to kick over? Does it make a knocking sound when you start it? does it bog down bad? need some more info to help you out. 

[Daniel Hamilton]

1 minute ago, Zack Brappp44 said:

since your bike is a 2 stroke, the transmission oil that you put in your bike is not the lubricating oil that is actually used for operating the bike. Oil that is used in the gas is what lubricates the cylinder of the bike. Its hard to tell what is exactly going on with your bike through your description. Is the bike easy to kick over? Does it make a knocking sound when you start it? does it bog down bad? need some more info to help you out. 

I've not seen he bike run mate and it's got compression although not a lot and the sound I'm trying g to describe is when I kick the bike it sounds like the gearbox is dry if you know what I mean? A bit like grinding but not bad just doesn't sound right I've tried looking for videos can't seem to see any with same problem I know it had a rebuild in June as I know the dealership the boy got bike from but still unsure what's going on I've cleaned carburettor it new spark plug checked trans oil it did backfire that's about it won't bump start either

[Daniel Hamilton]

I have attached pic of piston and ring think that might be my problem

[Zack Brappp44]

Looks like you have a bit of scoring on the piston but nothing major. How does the cylinder look. Also what would the bike do when you kick it over?

[Daniel Hamilton]

It sounds like air there's no much sound when I kick it and wasn't a lot of compression the barrels actually not to bad to be honest the ring was stuck at exhaust side and loose that loose I could just pop it off

[Zack Brappp44]

Maybe check ring gap, it could have been not holding psi on the compression stroke.

[Daniel Hamilton]

Thats what I think it quite a gap tried to get that in picture but I couldn't 

[Zack Brappp44]

Simply put the ring In the cylinder about a inch the take a feeler gauge set and find out what size gauge barely fits into the gap and then report back here with the measurements. You have to put the ring in the cylinder to see ring gap, look up a vid on how to do a top end rebuild and then it will show you how to take off the piston.

[Daniel Hamilton]

1 minute ago, Zack Brappp44 said:

Simply put the ring In the cylinder about a inch the take a feeler gauge set and find out what size gauge barely fits into the gap and then report back here with the measurements. You have to put the ring in the cylinder to see ring gap, look up a vid on how to do a top end rebuild and then it will show you how to take off the piston.

I've got piston off mate il attach couple pics I looked up it ahould be 47mm and mine is 48.5mm must have had rebore I looked up and it same size as cr85 could I use that piston? Or where would I get one to fit?

[Zack Brappp44]

You need to make sure that the gap between the piston and the cylinder is within spec and if it is not then you either need to get the cylinder repaired if crosshatching is not visible or if the cylinder is good, go order a piston according to the bore size. Someone correct me if I’m wrong.

[Daniel Hamilton]

Just now, Zack Brappp44 said:

You need to make sure that the gap between the piston and the cylinder is within spec and if it is not then you either need to get the cylinder repaired if crosshatching is not visible or if the cylinder is good, go order a piston according to the bore size. Someone correct me if I’m wrong.

I seen a cr85 piston that is 48.5mm would I be able to put hat in the yz as long as piston same size?

[Zack Brappp44]

I seen a cr85 piston that is 48.5mm would I be able to put hat in the yz as long as piston same size?

It all depends on the bore size, here is a good thread to reference for help

http://www.allthingsmoto.com/forums/f-30/yz85-ring-gap-56677/

[Zack Brappp44]

I seen a cr85 piston that is 48.5mm would I be able to put hat in the yz as long as piston same size?

You really need to know the exact size of the bore before you know what size of piston you need. Lots of shops will probably just take it and measure it for you for cheap or free. You just need to know the bore size before anything.