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What piston kit?

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Doing a top end on my 98 RM 125. What is everyones opinion on which piston kit to get? Also, does the cylinder need to be honed or is this a nickel plated one? Is there a way to tell?

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Your cylinder is nickel plated in stock form. It could be a steel sleeve if someone chose to go this route for a repair. Take a picture, post it & we can tell you if it is sleeved or nickel. Take the picture from the underside (base gasket side) of the cylinder.

As far as pistons. I would go with oem or proX. Both are made in the same factory & are identical pieces. A high quality part.

The cylinder can be honed or scrubbed with a scotch brite pad. If you choose to have it honed, all that is required is a few passes of the hone. It doesn't need to be honked on over & over. After honing, use a rag & thouroghly wash the cylinder with dish soap & water. The idea is to get the abrasive hone material out of the cylinder bore.

Edited by KPRacing

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Honing will NOT hurt the bore. Over the yeats, I have literally honed hundreds of (nickel) cylinders with ZERO problems. It is absolutely normal procedure to hone any cylinder. Just a light hone to deglaze the cylinder. A few passes in & out. Then a thorough clean job with dish soap, water, & a rag.

When I build engines, I prefer cast pistons like stock or proX. Any piston is going to work so pick what you want. I personally would choose a cast piston.

Edited by KPRacing

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I use a precision hone. It has 4 stones. It is not one of those spring hones. A spring or ball hone are fine to deglaze a cylinder. To finish out a cylinder after boring (steel sleeves), you need a precision hone.

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Hi Ryan,

 

OEM pistons are a good way to go. 

 

Looks like the casting goes all the way to the cylinder wall so it is safe to say that there is no sleeve. That means your cylinder has a nikasil plating and should never ever ever ever be honed. For proper cylinder care, please watch this video:

 

 

If your cylinder is worn out, it is best to have it replated again. 

Edited by ManBearPig.

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Call U.S. Chrome & ask about honing. ;)

Do you NEED to hone? No. Is it okay to hone the cylinder? Absolutely.

The pictures are very good. Your cylinder is a plated cylinder.

In that YouTube video, slaves mentions that the plating companies use a diamond hone to finish the bore to size after plating...they do. They use a diamond hone because a standard "stone" hone won't hardly touch it. They would be at it for a MUCH longer time & consume ALOT of stone hone plates.

Slavens is a terd by the way. :lol: If anyone knows anything on how to build a REAL engine. Watch his video on "how to port a ktm" or whatever it's titled. Laughable. He goes rite to the transfer port entry & works that. That is were 100% of ALL rookies go & there is basically ZERO power to be had from that spot. He then gives some talk of why you want to work that spot & what it does & if he told you anymore he would have to kill you. He simply can't tell anyone anymore so his speech on modding ends there. He's a poser. He puts up YouTube videos as a net to snag lesser informed bike owners & to generate business.

Edited by KPRacing

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A little off topic but I also noticed when I drained my oil that a few ounces of antifreeze came out first. This means that the base gasket on the cylinder was bad right? Only reason i'm asking is bc the gasket appeared to be in good condition. 

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The cylinder needs to be checked with a dial bore gauge. Then a micrometer on the piston. Compare the differences between the sizes & that is your clearance. Having a bore that is round & straight is important. When checking the bore, make sure it is both round & straight.

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Yes, you can & should hone a nickel cylinder.

 

Well that article was something i did not come across before. I started to do some more research on whether or not nikasil plating should be honed and discovered lots of conflicting results. What I got from all the research was this:

 

Special tools are required to hone a nikasil cylinder and can be done by most plating companies for about $50. However, this might take your past the service limit.  If the cylinder is heavily glazed and or "scratched" then a very light use of an aluminum oxide ball hone (>240 grit) is acceptable. If the cylinder is in good shape, then scotch bright and soapy water can be used to deglaze it. Ball hones do damage the plating and you have to be careful around the ports. The Suzuki manuals do not mention the use of a hone. New rings will still seat even if the cylinder is left untouched. 

 

Here are the articles:

http://bmwmotorcycletech.info/cylinders.htm

http://www.electrosil.com.au/news3.htm

http://www.electrosil.com.au/pdf/ElectrosilRobArticle.pdf

http://www.eric-gorr.com/images/documents/2-StrokeTopEndAndPerformance.pdf

Edited by ManBearPig.

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A little off topic but I also noticed when I drained my oil that a few ounces of antifreeze came out first. This means that the base gasket on the cylinder was bad right? Only reason i'm asking is bc the gasket appeared to be in good condition. 

 

Coolant can also leak past the water pump seal. Did you drain the oil after the cylinder was removed? Some water could of splashed into the case when you removed the cylinder.

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Both the oil and coolant were drained prior to removing the cylinder. I'll have to see about changing the water pump seal. The coolant level was low as some of it was in the oil. My clutch wasn't operating smoothly at all so I also removed that and took measurements on the friction plates and springs and everything checked out good. I wonder if the water in the oil had anything to do with this? It is also possible that the thrust bearing on the end of the push rod was previously installed backwards. I checked the manual for proper installation when reassembling but couldn't remember how it was when I removed it.

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