89 cr250 - plated or steel lined cylinder?

[Steve St.Laurent]

I'm new to the off road world and just recently bought this 89 cr250. I just changed the air filter for the first time and found that the previous owner had assembled the airbox/carb boot incorrectly and it's been sucking in unfiltered air and there was a good bit of dirt in the intake. I did a compression check and I'm only getting 100 psi so it looks like it's top end time. Never done one before so I'm researching what I need to do. I've done a lot of research on here, reading my service manual, and Eric Gorr's twotopweb write up. I'm not real clear on whether I have a plated or steel lined cylinder. The service manual talks about reboring for an oversized piston if it's outside the service limit and makes no mention of replating so I'm assuming that it must be steel lined - anyone know for sure? If that's the case and I do need to have it bored out can any automotive machine shop handle that or are there special considerations for the ports? Thanks in advance.

 

[TimberPig]

It's Nikasil plated stock, but could have been sleeved. A magnet will tell you for sure.
If it's worn out, replating is the preferred option, although steel sleeving is used by some. Some automotive machine shops are capable of handling a 2 stroke bore job if it has been sleeved, although many have no clue that the ports need to be chamfered to prevent ring snagging.
Thats about all I can tell you until you get that top end torn down.

 

[dirtcurtis]

Wash your cylinder out with muratic acid and use a metal brush.

 

[Steve St.Laurent]

I pulled the head tonight to take a look at the bore. It does have a steel sleeve (PO must have had it sleeved). The cross hatch is still all there. The bore measured all within specs (2.6125-2.614 and .0015 out of round). There is one score on the cylinder wall at the 9 o'clock position (as your sitting on the bike). My plan is to hone the cylinder and drop a new piston and rings in it so I know where I'm starting from and see where it goes from there.

 

[TimberPig]

Wash your cylinder out with muratic acid and use a metal brush.

Muriatic acid is only used for removing stuck on aluminum from the bore. Oil glazing can be removed with oven cleaner and a Scotchbrite pad. A wire brush is needlessly abrasive, and likely to cause more damage than anything. A flex hone is the preferred tool for honing, if the bore needs more than the glaze broke with a Scotchbrite and oven cleaner.

 

[Steve St.Laurent]

I'm planning on using a 240 grit aluminum oxide flex hone as suggested by Eric Gorr. I'm trying to find one now and so far I haven't found anyone that carries them other than contacting Brush Research directly - any suggestions?