Can't tell if my cylinder needs replating

Yz250JdT250

Member
Apr 26, 2004
142
0
My 1998 yz125 cylinder looks pretty good but the bottom half seems like it might be low on the nikasil plating. I am not sure though. Can anyone with experience in evaluating this tell me if it needs replating?

HPIM1856.jpg


HPIM1857.jpg


HPIM1858.jpg
 
Last edited:

Yz250JdT250

Member
Apr 26, 2004
142
0
I know the two pictures of the bottom are kind of blurry but thats where the minor scoring is. Also, that scoring is on the sides, could that mean the crank rod bearing (not wristpin bearing) is worn out?
 
Last edited:

76GMC1500

Uhhh...
Oct 19, 2006
2,142
1
You've got to upload them somewhere like www.photobucket.com first. The bottom half of the cylinder usually barely wears at all. That's what you should judge the rest of the cylinder by. To accurately gauge whether or not the cylinder needs to be plated, you need to mic it.
 

Yz250JdT250

Member
Apr 26, 2004
142
0
Alright the pics are up. Mine has wear on the bottom half though.. Is a mic a micrometer? or can i use some calipers?

Oh yeah, spectro 100% synthetic is excellent, i have no carbon deposits in my exhaust port! Nothing caked on!
 

Yz250JdT250

Member
Apr 26, 2004
142
0
Actually, after looking at it again, it looks like theres a tiny bit of horizontal scoring on the intake side on the bottom.
 

Yz250JdT250

Member
Apr 26, 2004
142
0
So by a mic do you mean calipers? My brother knows a lot about motors and said it just needs to be honed. I was skeptical but now im starting to think thats all it needs.
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
Sorry GM,that is what a cylinder looks like when a fool with tools has at it!Like gm said,bottom is a low wear area.Check your clearances with a feeler gauge where the rings ride.An inside micrometer or bore gauge is handy.Other than fools with tools the finish is damn near indestructible,and when it fails it flakes,just like a chrome bumper,go figure!The material behind the plating will move and distort the bore.
 

76GMC1500

Uhhh...
Oct 19, 2006
2,142
1
2-strokes don't really need to be honed. Calipers don't really work for this measurement because there is a ridge at the top of the cylinder that doesn't wear and stays at the original diameter no matter how worn the rest of the cylinder. You need a set of snap gauges and an outside mic, an outside mic and inside mic, or an outside mic and a dial bore indicator to measure the piston to cylinder wall clearance. If the cylinder tp piston clearance exceeds .004" or the cyilnder wall taper exceeds .002", it's time for a replate. Like Fox said, they're pretty much good until they wear through the plating. You should be ok to toss another piston in there, but it's always good to measure.
 

Rich Rohrich

Moderator / BioHazard
LIFETIME SPONSOR
Jul 27, 1999
22,820
16,889
Chicago
76GMC1500 said:
2-strokes don't really need to be honed.

Does your butt ever get sore from all the time you spend out here talking out of your ass?
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
1.that's crosshatching.(wrong)2.To accurately gauge whether or not the cylinder needs to be plated, you need to mic it.(wrong)3.That's what a new cylinder should look like.(wrong)4. 2-strokes don't really need to be honed.(wrong)5.You need a set of snap gauges and an outside mic(wrong)6.You should be ok to toss another piston in there(GUESS AGAIN!)That is about that!Yz,a wild guess is that bore is screwed up,you need to determine the bore size and or the piston to cylinder clearance,if it is good then have a professional hone it,chamfer the ports and CHECK THE RELIEF ON THE BRIDGING,good luck.
 

76GMC1500

Uhhh...
Oct 19, 2006
2,142
1
Ok, I see nothing wrong with that cylinder. The only scratches I can see from the pictures appear to be cross-hatching. Cross-hatching like a new cyliner. Snap gauges and an outside mic are the best way to measure piston to cylinder clearances because it eliminates the bias error of the micrometer. I listed all of the other possible tools that would work, but a caliper won't because you can't measure deeper into the cylinder where most of the wear occurs. Visually, I see no reason he can't put a new piston in and reassemble. For honing, cross-hatching does give the piston rings a little something to wear into. It's not really necessary to hold oil like a 4-stroke, though. The most important reason for honing new 2-stroke cylinders at the factory is to fine tune the bore diameter. Instead of saying WRONG all of the time, lets discuss these things. You don't seem to be right all of the time, either, Fox. It seems that some shops hone and some shops don't. I know it's not a very wide demographic, but the 2 Honda dealerships I have been to don't hone. The third party shops all do.
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
Define cross and you will see what has happened to that jug.Calipers was asked and you have ranted long enough.A $3.00 feeler gauge will work to determine weather what is usable or not.The cylinder glaze is from FLASHING and should be removed.What in the hell difference does a 2t or 4t make?If some shops are idiots you keep going back?
 

76GMC1500

Uhhh...
Oct 19, 2006
2,142
1
I guess I couldn't see the flashing. And, I don't go to shops anymore after they blew up my transmission twice. Feeler gauges can give a reasonable accurate measurement of piston to cylinder clearance, in the hands of a competent user. But, they don't really work for the bridge relief.
 

Yz250JdT250

Member
Apr 26, 2004
142
0
Sorry GM,that is what a cylinder looks like when a fool with tools has at it!

whats that supposed to mean? I did not damage the cylinder in disassembly. So what are you trying to say, foxforks?
 

Yz250JdT250

Member
Apr 26, 2004
142
0
I know i didnt mess up the cylinder taking it off the crankcase, so I'd appreciate it if you wouldnt indirectly call me a "fool with tools".

Whats the relief on the bridging?
 

Yz250JdT250

Member
Apr 26, 2004
142
0
The bike was running for 3 years and ive submerged it and it stopped running a couple times, but i was able to start it back up when all the water was out. It was still running well when i decided to rebuild. It had about 150 psi cold (I live in NH).
 

76GMC1500

Uhhh...
Oct 19, 2006
2,142
1
Don't take the fool with tools comment as a personal attack against yourself. I believe it was a personal attack against me. Fox used to be cool, but I think I said something a few weeks ago that turned him bitter. 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.
 

02rm250

Uhhh...
Sep 25, 2006
81
0
If you have a few hundred extra bucks, sent it to Eric Gorr. He can tell you from a PROFESSIONAL pespective what needs done. If it needs plated he works with U.S. chrome, so you wont have to send it somewhere else. He can also port it for you, or do a 144 kit for less than 500 bucks. Hes a super nice guy, lots of people on here will tell you.
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
YZ,whoever honed that cylinder did not know what they were doing.You need to find out how the bore is.I do know who can fix it correctly,like mentioned before Eric Gorr.The rings ride up high and the skirt goes into the abused area,premature wear on a skirt can be very bad.The upper part of the bore and the lower are too different to just throw a piston and ring in,the bore is probably not true also.
 

Bunya

Member
Apr 26, 2007
147
0
Yz250JdT250 said:
So by a mic do you mean calipers?

NO! Besides the problem with the geometry that GMC mentioned, calipers simply aren't accurate enough for this type of work. Quality calipers such as Brown & Sharpe, Mitutoyo, and Starrett are typically only accurate to .002", digital or dial. The cheap Chicom ones are even worse. Anytime you need an accurate measurement, a micrometer is the prefered tool. Bore gages are good, but they are expensive and because they can only read the ID of the bore, a micrometer is still needed to check the OD of the piston. For accuracy, both the Bore gage and the Mic need to be checked against known standards before using them to determine clearances. A single micrometer and a snap gage are relatively inexpensive and will yield a sufficiently accurate number when properly used.

Marc -
 

Yz250JdT250

Member
Apr 26, 2004
142
0
Yeah i actually have a micrometer, after seeing a picture of one now i remember what it is. I dont have a whole lot of money, and i am rebuilding the transmission (everything but the gears & shafts is going to be new) and putting a new crank and shifter shaft in. So I'm just going to hone the cylinder, What grit hone should be used?
 
Top Bottom