What did you do to your Yamaha YZ 2 stroke today?

[TwoFiddyYZ]

On 4/25/2020 at 2:03 AM, Justn1k said:

I bought it.

Pics or it didnt happrn 

[2strokeYardSale]

On 4/26/2020 at 11:48 AM, 2strokeYardSale said:

Rode some hills, mostly. Decided the crank and/or bearings are done after hearing a new sound and feeling a new vibration. Or maybe it's all in my head.

@numroe you have claimed to hear crank noise in a previous video. Check this out. I first heard the noise cresting the hill and getting off the gas (2m 40s), but I don't hear it in the video. I don't hear it anywhere else in the video, either. Regardless, it was always under very light or no load, often backing off the throttle. It got worse, or I noticed it more, as the day wore on and I decided not to ride the second day. But it was very rare.

Well, it's a moot point now. I ordered the tools and began the tear down.

 

[2strokeYardSale]

Anybody seen reeds darkened like this? They started out as Boyesen fiberglass a long time ago.

[Motox367]

7 hours ago, 2strokeYardSale said:

Anybody seen reeds darkened like this? They started out as Boyesen fiberglass a long time ago.

Normal looking used boyesen.  Why did you use stoppers with them tho? Just curious 

[vossman23]

Switched over to the NEDJ Suzuki needle from the OEM needle, seems to rev cleaner. Will ride it soon.

 

[2strokeYardSale]

On 4/28/2020 at 6:06 AM, Motox367 said:

Why did you use stoppers with them tho?

Because I RTFM.

[numroe]

On 4/28/2020 at 11:04 AM, 2strokeYardSale said:

you have claimed to hear crank noise in a previous video. Check this out. I first heard the noise cresting the hill and getting off the gas (2m 40s), but I don't hear it in the video. I don't hear it anywhere else in the video, either. Regardless, it was always under very light or no load, often backing off the throttle. It got worse, or I noticed it more, as the day wore on and I decided not to ride the second day. But it was very rare.

It sounds ok, but not great. Nothing too bad but it's a rattly motor. It would annoy me a little. Or perhaps your camera picks up the sound too well.

What I try to listen for is a drop in the mechanical knocking/rattle/tapping sound when you are on throttle vs off. In your motor I think that happens, suggesting some freeplay somewhere. But not real bad.

If you find the main and big end bearings are ok, and also the main bearings are nice and tight on the crank ends, then check how true the crank is.  I found that a true crank can make a huge difference to the vibration in the YZ250, and I'm not sure if it'd effect noise, but it's something to consider.

Your jetting sounds really good. To save me searching your old posts, what's your jetting (incl slide assuming it's the PWK), pipe, squish clearance, altitude and typical air temp?

Why do you have the idle speed set so high?

I once had  Boyesen fiberglass reeds and they looked just like yours. No problem I think.

Nice scenery there. The dryness of the terrain really strikes me.

[2strokeYardSale]

The bike was running excellent that day; I was very happy with how smooth and controllable it was down low and how plentiful the power was up top for the hills. 172/42/N3CK-2/8-slide/40-pwr for the high desert.

The flywheel doesn't have any play in it whatsoever, measured by grabbing and attempting to wiggle.

Regardless, I'll soon have a rebuilt crank with new main bearings and seals.

[Motox367]

2 hours ago, 2strokeYardSale said:

Because I RTFM.

Not sure what you mean there ? but ok whatever ?

[The Rock Enduro]

New rear tire, ghetto folding saw holder, new lock on grips and sat there debating if I should try the PV/governor mod 

 

 

[2strokeYardSale]

21 hours ago, Motox367 said:

Not sure what you mean there ? but ok whatever ?

I Read The &%$#@!ing Manual (instructions), which said to use the stock stoppers. The fiberglass Super Stock reeds didn't come with retainer plates of their own anyway.

[EmpireofDerp]

On 4/4/2020 at 3:28 PM, Scralatchtica824 said:

Rode 5 hours today in very tight technical rocky, rooty, hilly off camber terrain in West Virginia and going to 13/50 was a bad idea. 1st gear is so low the rear just spins even with clutch work going into 2nd is good the bike has gobs of traction and will loft the front effortlessly. I’ll be switching back to 14/50.

Yup, my experience as well. 14/50 for me. 

[LSHD]

Pulled the engine. She blew up real good. A little brass embedded in the head. Not a good sign. ?

[Tahoe Gator]

4 hours ago, LSHD said:

Pulled the engine. She blew up real good. A little brass embedded in the head. Not a good sign. ?

Inquiring minds need to know: What happened?

[LSHD]

9 hours ago, Tahoe Gator said:

Inquiring minds need to know: Whati  happened?

My fault, or maybe just a coincidence. I swapped back to summer jetting on Monday (42/170/NEDJ-2/#8 Slide/0.046" squish). Had the bike on the stand with an industrial fan blowing on it. Got it up to temp to set idle and I noticed it started to buck a little bit each time I gave it some throttle. Braaap, braaap, braaap, bzzzzzzzzzzzmmmmmpppp - locked up tight. I've done the stand thing forever and never had issues. A three foot industrial fan puts out huge amounts of airflow. Needle was at 1 turn out during warm up and the bike sounded fantastic before the disaster. So thinking maybe it was a coincidence. Rather it happen on the stand than way down at the bottom of a Parson's Mountain trail (which I rode last week).

Pretty sure the lower end gave way, throwing brass and steel up past the ports and causing the piston to break and seize. Shipping it to YZDOC today and installing my original 2005 that he rebuilt and converted into a YZ250X transmission for me a couple years ago. It's been sitting in the crate, ready to go. While he was rebuilding it, I bought a new crate 2017 engine, and that is the one that blew. Only had about 50 hours on it. Can't wait to try that transmission in the 2005.

If you ever need someone you can trust to rebuild a YZ engine, or an entire YZ (and many other brands), you can trust YZDOC to do it correctly and at a fair price. Gary is a good man. He is also shockingly fast compared to many shops. Can't find the words to recommend him highly enough.

[indy rider]

14 hours ago, LSHD said:

Pulled the engine. She blew up real good. A little brass embedded in the head. Not a good sign. ?

Sorry for you loss

 

 

...of seat time. Hopefully you're back up running soon.  

[indy rider]

4 minutes ago, LSHD said:

My fault, or maybe just a coincidence. I swapped back to summer jetting on Monday (42/170/NEDJ-2/#8 Slide/0.046" squish). Had the bike on the stand with an industrial fan blowing on it. Got it up to temp to set idle and I noticed it started to buck a little bit each time I gave it some throttle. Braaap, braaap, braaap, bzzzzzzzzzzzmmmmmpppp - locked up tight. I've done the stand thing forever and never had issues. A three foot industrial fan puts out huge amounts of airflow. Needle was at 1 turn out during warm up and the bike sounded fantastic before the disaster. So thinking maybe it was a coincidence. Rather it happen on the stand than way down at the bottom of a Parson's Mountain trail (which I rode last week).

Pretty sure the lower end gave way, throwing brass and steel up past the ports and causing the piston to break and seize. Shipping it to YZDOC today and installing my original 2005 that he rebuilt and converted into a YZ250X transmission for me a couple years ago. It's been sitting in the crate, ready to go. While he was rebuilding it, I bought a new crate 2017 engine, and that is the one that blew. Only had about 50 hours on it. Can't wait to try that transmission in the 2005.

If you ever need someone you can trust to rebuild a YZ engine, or an entire YZ (and many other brands), you can trust YZDOC to do it correctly and at a fair price. Gary is a good man. He is also shockingly fast compared to many shops. Can't find the words to recommend him highly enough.

Yea, the fan should have been adequate airflow, it is for dyno runs...and I don't see the jetting change being big enough to being the culprit.

[LSHD]

1 minute ago, indy rider said:

Yea, the fan should have been adequate airflow, it is for dyno runs...and I don't see the jetting change being big enough to being the culprit.

Agreed. That is my standard summer jetting and is used by many of us here that have had squish done and NEXJ-series needles. 42 might be slightly lean, but if so, just barely.

[Motox367]

Rebuilt 2 125s and few other things to them. 16'and19'. Both had brandnew cylinders last summer use 32:1 927. Top 2 pics are the 16 next 2 the 19' both vertex pistons.  New oem brakes, chain sprockets on both and tires. These two bikes are raced hard and i see them alot lol both are rippers and run clean that's for sure ? no black goo here 

Edited May 1, 2020 by Motox367

[Motox367]

56 minutes ago, LSHD said:

My fault, or maybe just a coincidence. I swapped back to summer jetting on Monday (42/170/NEDJ-2/#8 Slide/0.046" squish). Had the bike on the stand with an industrial fan blowing on it. Got it up to temp to set idle and I noticed it started to buck a little bit each time I gave it some throttle. Braaap, braaap, braaap, bzzzzzzzzzzzmmmmmpppp - locked up tight. I've done the stand thing forever and never had issues. A three foot industrial fan puts out huge amounts of airflow. Needle was at 1 turn out during warm up and the bike sounded fantastic before the disaster. So thinking maybe it was a coincidence. Rather it happen on the stand than way down at the bottom of a Parson's Mountain trail (which I rode last week).

Pretty sure the lower end gave way, throwing brass and steel up past the ports and causing the piston to break and seize. Shipping it to YZDOC today and installing my original 2005 that he rebuilt and converted into a YZ250X transmission for me a couple years ago. It's been sitting in the crate, ready to go. While he was rebuilding it, I bought a new crate 2017 engine, and that is the one that blew. Only had about 50 hours on it. Can't wait to try that transmission in the 2005.

If you ever need someone you can trust to rebuild a YZ engine, or an entire YZ (and many other brands), you can trust YZDOC to do it correctly and at a fair price. Gary is a good man. He is also shockingly fast compared to many shops. Can't find the words to recommend him highly enough.

Been doing this long enough to see things just happen.  Looks like big end bearing took a shit id say is what started it anyway.  The 19' in post i just did the ring broke and hit port ruined cylinder.  Bike had 5hrs on it. Sometimes it just happens no matter what . Keep a spare top end around for them and others if need in pinch. Comes in handy its got a few threw the weekend . Have bearings and cranks too lol . 

Edited May 1, 2020 by Motox367
Found pic of it