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New rings on Wiseco piston, New gaskets?

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Hi all, I have a 01 yz125 it has 24 hours since last rebuild ( Top end rebuild only), I can feel what I think is a little less compression then it had. I believe rings should fix that and wondering if I should get all new gaskets also?

If you could say what gaskets that would be nice!

Thanks!

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I would go ahead and replace the gaskets. There not really that expensive and it would suck if one of them failed.

If you want to replace everything, there should be an oem top end gasket kit for about 30 bucks. This will have everything you need(base, cylinder head, expansion chamber, reed, powevalve, etc.)

That's what I would do, although you certainly could replace less of them if you wanted.

Edit: I can't find a complete oem kit on rocky mountain, but I'm sure if you shop around you'll find one. There's a bunch of aftermarket ones that are around 30 bucks also.

Edited by chris88

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All you really need is the base gasket for a re-ring.  You can just leave the head on unless you are doing a full cleaning/decarbonizing job.  Then again that's how it is with my Honda.  Haven't done a Yamaha 125.  If you are going to take everything apart and clean it all up etc you might as well get a new piston and do the whole job at once.

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All you really need is the base gasket for a re-ring. You can just leave the head on unless you are doing a full cleaning/decarbonizing job. Then again that's how it is with my Honda. Haven't done a Yamaha 125. If you are going to take everything apart and clean it all up etc you might as well get a new piston and do the whole job at once.

I've heard people say after you put a new piston after 20 hours replace the rings then after another 20 hours replace the piston. Then repeat.

Why spend $100 when you can spend $15 on rings?

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I seriously doubt you need a new ring at 25 hours.   Here is a thread I started that shows some pics of a high hour wiseco from a yz 125:

https://thumpertalk.com/topic/1128226-955-hour-yz-125-piston/?hl=%2B95+%2Bhour+%2Bpiston#entry12278658

 

I find that compression does not tell you a lot, as there is a lot of variability from test to test, and you need to have established a baseline to make any inferences.

 

As noted above, you can replace the ring by sliding the barrel off, so all you need is a base gasket.  I would not reuse a base gasket as they are so cheap to begin with.  Why risk the headache of having to pull it apart again?

 

You can easily inspect the ring for blow-by by simply removing the pipe.  Use a flashlight and inspect through the exhaust port.

 

Don't believe all this 20 hour piston replacement silliness you hear unless you are James Stewart fast, especially if you are using a forged piston.  If you run 32:1 with fresh gas and keep your air filter clean, a piston will last a lot longer than 20 hours.

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I seriously doubt you need a new ring at 25 hours.   Here is a thread I started that shows some pics of a high hour wiseco from a yz 125:

https://thumpertalk.com/topic/1128226-955-hour-yz-125-piston/?hl=%2B95+%2Bhour+%2Bpiston#entry12278658

 

I find that compression does not tell you a lot, as there is a lot of variability from test to test, and you need to have established a baseline to make any inferences.

 

As noted above, you can replace the ring by sliding the barrel off, so all you need is a base gasket.  I would not reuse a base gasket as they are so cheap to begin with.  Why risk the headache of having to pull it apart again?

 

You can easily inspect the ring for blow-by by simply removing the pipe.  Use a flashlight and inspect through the exhaust port.

 

Don't believe all this 20 hour piston replacement silliness you hear unless you are James Stewart fast, especially if you are using a forged piston.  If you run 32:1 with fresh gas and keep your air filter clean, a piston will last a lot longer than 20 hours.

+1 on the compression test.  Without a baseline test to go off of, a compression test now will tell you nothing.  You can't compare your numbers to someone elses and expect any value from it.

 

With a little dirt or dust ingestion and borderline lean jetting I could see rings beginning to wear at this point even with just some wide open riding.  The piston should be fine though.

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+1 on the compression test. Without a baseline test to go off of, a compression test now will tell you nothing. You can't compare your numbers to someone elses and expect any value from it.

With a little dirt or dust ingestion and borderline lean jetting I could see rings beginning to wear at this point even with just some wide open riding. The piston should be fine though.

I will run a compression test and report back!

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I will run a compression test and report back!

 

Lol...

 

You completely misunderstood.  Unless you did a compression test immediately after a good break in ride there is no point to doing a compression test now...

 

Your numbers will be meaningless.  The only numbers that matter in a standard compression test are if you have experienced more than a 10% drop in compression since new.  If you don't have the numbers for what your bike was with new, broken in rings, then don't waste your time.

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I seriously doubt you need a new ring at 25 hours.

I'm sure you meant to say "piston" instead of "ring"? If so I'm in total agreement as most will be.

Here is the problem with not pulling the head when you do this job...you can't really measure the ring end gap. Which is really what you should be measuring to establish your trends for hours between re-ring and re-piston, etc.

I'm surprised someone hasn't brought this up yet. The big problem with running rings too long is not compression falling off. It's that when the ring end gap gets too large the ring can jump the alignment pin and hook a port and break itself and all kinds of stuff in the process. I have seen good compression on rings with too large a gap. And yes I have fallen victim to the "I'll just get one more ride in and then put new rings in" self justification. Cost me 500 for new piston kit, gasket kit, and a replate on my cylinder.

Measure the gap. Keep a log book. You will see the trends and learn how far you can safely push it. And changing the piston every other ring set is very common. On my 250 I most times get 3 ring sets on a piston.

My 2 cents any way.

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Lol...

You completely misunderstood. Unless you did a compression test immediately after a good break in ride there is no point to doing a compression test now...

Your numbers will be meaningless. The only numbers that matter in a standard compression test are if you have experienced more than a 10% drop in compression since new. If you don't have the numbers for what your bike was with new, broken in rings, then don't waste your time.

Lol I'm not stupid I do all my bike work, I 100% know there has been a compression loss since I put the Wiseco in 24.5 hours ago. So why wouldn't you put new rings in? I will take a compression test before I install the rings and after and see the difference.

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I'm not 100% sure what you mean, I plan on carb cleaning the cylinder jug but don't know how to properly "Hone" the cylinder.

So use a scotch bright and Carb clean the cylinder jug, another one said use scotch bright and atf fluid to clean the cylinder? I'm thinking scotch bright and hot water and then carb clean and clean with paper towels?

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scotch brite should do it. afterwards clean it with hot water, not sure how much carb cleaner you plan to use and how they react to the oil seal in the cylinder. Atf is not aggressive though  

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scotch brite should do it. afterwards clean it with hot water, not sure how much carb cleaner you plan to use and how they react to the oil seal in the cylinder. Atf is not aggressive though

So just scrub the cylinder with the scotch bright then use hot water. Or should I use scotch bright and atf fluid to scrub the cylinder ?

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