Can't tell if my cylinder needs replating

[Yz250JdT250]

What grit of emery cloth should i use for the gasket surfaces? Coarse, medium, or fine?

 

[whenfoxforks-ruled]

You should not sand or file machined surfaces,EVER.They make sprays to help when adhesives or sealants are used,but basically need to be scraped off without effecting the sealing surfaces.Your cylinder should be cleaned with oven cleaner or if you have experience a muriatic solution,the acids will discolor the aluminum if left on more than 20 minutes,and is a dangerous substance!Honing should be left for the professionals,over 30 years (some off for good behavior!)of racing,machine shop in school(1000 hours) and some 8-10 years in shops,I will send it to Eric Gorr before I mess with it myself,money and security well invested!

 

[2strokerfun]

I haven't figured out exactly what it was yet, but I think it had something to do with me jokingly saying I cut corners for beer money.

Is he against cutting corners or against beer?

For the record, I've never sent a cylinder off for reworking and all my bikes still ran well when I sold them (well, OK, maybe the transmission in that Mini Enduro was a little suspect, but hey, I was just a kid!). I'm sure these people do Great Work, but I'm not convinced every cylinder ever cast needs reworking.

 

[Yz250JdT250]

Hey foxforks, how can you say that whoever honed the cylinder last did not know what they were doing? I bought this bike 3 years ago. I rode the piss out of it for 2 good seasons. It always started up first or 2nd kick. Took it apart and its surprisingly good. Does eric gorr have a new website?

 

[76GMC1500]

Personally, I don't think the pictures are clear enough to make a proper judgement about the hone job. Honing, with a flex hone, is no that hard for an amature to do and pretty hard to really screw up. Spending $200+ on a replate that doesn't need to be done isn't money well invested. If you're really worried about, take it to your favorite shop mechanic and ask him what he thinks. If he's a good mechanic, he'll even mic it for you and hone it(maybe at a small charge).

 

[02rm250]

http://www.eric-gorr.com/

 

[Yz250JdT250]

Yeah the pictures are a little blurry, i had to focus far away and then go close. I am going to use a flex hone. What grit flex hone should be used?

 

[76GMC1500]

Aluminum oxide, 240 grit, 10% smaller than bore size, according to Eric Gorr's book.

 

[whenfoxforks-ruled]

When it is honed correctly you will see x marks,hence crosshatch.The crosshatch REMAINS on the cylinder,the piston and rings wear off and is called flashing. Flashing needs to be removed,chemically is the ticket,honing is also an option. You need to determine the bore size. If oem will still fit,great,otherwise you may be able to get an oversize aftermarket,or its time to bore it and replate. What is your price on a new cylinder?325 is retail.A hone WILL remove plating,who ever honed that cylinder before does not have a clue,but he has a hone! The horizontal swirl pattern at the bottom side in your pic was a dead give away.I do not know the exact thickness of your plating,it was not put on there to hone everytime you change a topend,a couple of thousandths thick would be my guess!US Chrome says theirs is .02,yours might be as thin as .001!Replating may run 150 to 200.Eric Gorr can put some voodoo in it,check him out if you need machining,plating or mo power!The last time I honed a cylinder I think it was 2 maybe 3 strokes,who ever honed that cylinder thought they were mixing a cake!(what is the chances that is a iron liner?)

 

[IndyMX]

A hone WILL remove plating,who ever honed that cylinder before does not have a clue,but he has a hone! The horizontal swirl pattern at the bottom side in your pic was a dead give away.

I'm with you.. It's pretty obvious that there is a horizontal pattern on that bore..

 

[Yz250JdT250]

Would this be a good micrometer for measuring the ID of the bore?

http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO=5789532&PMT4NO=22405839

 

[Yz250JdT250]

or the mechanical type

http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO=1653386&PMT4NO=0

 

[IndyMX]

This looks like it might be a better tool for measuring the bore..


http://www.brandsonsale.com/ht-001410.html

 

[76GMC1500]

This is the kind of inside micrometer you would want. This type allows you to measure deep inside the cylinder. If doing clearances, make sure you calibrate it against your caliper/micrometer.

However, if you already have a caliper/micrometer, snap gauges/telescoping gauges work quite well for measuring cylinder clearances and are much less expensive. Calipers can be accurate enough. A good Vernier caliper is accurate to .001" and if you have really amazing eye-sight, you can make reasonable judgements within .0005". You can olnly do this with the highest of high quality calipers, though. The jaw deflections on the cheap ones really throw things off.

 

[Yz250JdT250]

I'll have to get one of those bore gauges. But is there a way for me to tell how much nikasil is left? Or is that another tool??

 

[Yz250JdT250]

would you recommend a digital or mechanical bore gauge?