Been watching this thread for a bit.

I have run some rattly pistons, and wrung them through their paces without issue. Your video's sound (and like others have mentioned, the mic amplifies the rattle) isn't that bad. If you aren't familiar with how these engines sound, you may be worried about normal sounds. 4 stroke quietness is simply not possible. A fresh properly bored cylinder & piston set is quiet "ter" but the expectation of keeping that quietness on a bike that is used and ridden is not reasonable.

I had a CT2 whose piston rattled pretty good (Rick C and others at California based Gorman Enduro rides heard it), and never did the piston let me down. In fact, on long uphill single track rides in Coeur d'Alene when I lived there, the piston would quiet up to NO rattle. It was amazing...then on cool down, downhill stretches the familiar piston rattle would come back. In fact, if that didn't happen, I was worried!! I put over 2000 miles on that rattly piston, without an issue. It's the character, the "A B C's" of our beloved little 2 stroke Yamaha's.

Grumbling sounds are worrisome. That's crank bearings letting go. Detonation is a worrying sound, something that must be solved to prevent impending doom. A sharply rattling piston is usually the result of lots of miles, no air filter and extended use, or some other impending doom (big end con rod bearing failure, pin bearing failure).

A slightly rattly piston is a worn in happy piston. My 2 cents.

^ thanks for posting.

You and a few others have mentioned It sounding normal. Which I’m glad to hear.

I’m glad that experienced folks are willing to help with the issue. I’ve decided to just clean everything up and put it back together as it was.
I will also be replacing the left and right crank seals for good measure.

This bike shows about 2800 miles on it. Surprising its already had a top en change for some reason.

As you mentioned I wasn’t too familiar with the sound and the rattling sound startled me.

Use 77-79 IT175 crank seals.

And you did a great job going through and checking everything out instead of just "guessing" and ending up replacing a bunch of stuff and not fixing anything.

Dang, I already ordered the dt175 seals.
Can you school me on why you recommend the it175 seals?

Clutch side is the same... dual lip seal. Probably the same part number even.

Stock ignition side for the 125 and 175 "Enduros" is a single lip seal... designed to seal best in only one direction... but has to seal both vacuum and pressure.

I've had vacuum leaks with the stock seal while it seals pressure perfectly... Worst case was I bought a very nice DT175 cheap because it had a bad air leak (actually would "run away" and rev to the moon by itself and ignition would not shut it down. Scary!) and the previous owner spent a small fortune a dealer trying to fix it. He had receipts showing it passed a pressure test.. I thought they probably didn't actually test it... But they did. I had a bad feeling in my stomach when I pressure tested it and it held perfectly. Then I vacuum tested and it wouldn't hold at all... On other bikes when the ignition side leaks a little under pressure (but still acceptable) I often find they leak much worse (unacceptable) under vacuum.

The YZ's and IT's came with a proper SW type dual lip seal on the ignition side. Same size, fits perfectly and is just a better seal. Stock single lip seal will work. Dual lip seal is just much better.







.

wow, again appreciate the experience shared.

seems like worth the $12 bucks to get the SW type seal for the magneto side
for the IT175 I found part number 93103-25125-00 is that correct?

As you mentioned the clutch side on the DT175 indicated the SW type seal on the schematic but no on the ignition side.

You're welcome. Yes, that's the number.

GJVGC, I'm sure MarkT finds it a pleasure to help you because you listen to what he has to say, you trust him, you try exactly what he suggests you try, and then you say thanks when it works! From time to time, frustration grows when you try to help someone, they don't believe you, they question you, they don't do what you suggest, and then the problem does not go away for them, and they are dissatisfied with the help they're getting from the guys on the site.
So when someone like you comes along, it doesn't matter how many questions you ask. It's rewarding to help you. Or even just to watch MarkT work in helping you. We all learn something!

^ well said!

Definitely appreciate the help from everyone.
The learning part is one of the most fun of the hobby to me.

I made the mistake of just throwing new parts at projects and most times its been a waste of money and time not to say you really don't learn much about troubleshooting etc.
I'm planning to keep the bike for a long time so its a worthy investment to learn as much as I can.
This forum came up on all my searches so hopefully it does the same if someone comes up with the same issues I've had.

To you guys that have been dealing with these bikes for years. Who is your go to online website to order oem Yamaha parts from?

I don’t have a local Yamaha dealer and I ordered from yamahapartsmonster with long shipping time. I don’t see a parts section for older bikes on the Yamaha website.

The other parts I got were from yambits and got here in 2 days from U.K.! Yamahapartsmonster is 2 states away and it’s been over a week. Surely I’ll be ordering more parts in the future and looking for your recommendations.