250 The 1999 YZ250

Mihylo33

Mihylo33

Trfsrfr:
Me and my buddy Dan have been working on his 83 CR480 and we finally got it running this week, so this morning we took the YZ and the CR out for a ride, and put about 15 miles on. It was my first real test drive of the YZ.
The YZ runs okay/good I think (with my limited experience), but it feels slightly boggy before it hits the powerband. But when it hits, it goes like a raped ape.
When I got it home there was some spooge coming out the muff. So I am assuming I am still running rich.
Now that I am back in the garage and have some football on I am going to mess with it. I think I might drop the jet needle one position, recheck the float level, and run it again tomorrow. I will also double check the compression.
If anyone wants to add their .02 I am all ears open.

Interesting note; we switched bikes near the end of the ride, and I would have to say that his 480 is comparable to the YZ in power and speed, but his rise to power feels a bit more linear, like a 4-stroke, unlike the sudden burst that the YZ has. It also has a very cushy seat and feels like a racy Cadillac, just my initial thoughts. Also thought the YZ could use another gear, and disc brakes are awesome.
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The 480 doesn't have a power valve so it rolls up to the power. It also is a bit more tractor like with the coffee can piston and heavier flywheel.
 
Trfsrfr

Trfsrfr

It was my first time on both bikes. They seemed fairly comparable.
Got the YZ apart in the garage right now, like the 480, I really appreciate the removable subframe, it makes access to the carb so much easier, unlike the KLX...
I'll report back later with accurate numbers, and will rip the exhaust off and take a look at the pistion/rings as Andy mentioned.

Quick update - New compression reading is 190PSI.
 
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O

ossagp

you may look at the compression readings and say "cool, it has some more life". and then look at the piston and think that it seems worn. then you are second guessing and losing sleep.
 
PALMER84ONE

PALMER84ONE

190 is good, piston/rings might show wear. With the piston at TDB, get a good look at the cylinder for any score marks on the intake side. You are more than likely going to see that there is some wear through the exhaust. Just keep in mind, if it drops off more, you are getting closer to lifes end.
 
Mihylo33

Mihylo33

Trfsrfr:
Umm,...please explain that comment. I haven't looked at the piston/rings yet.
Click to expand...
ossagp:
you may look at the compression readings and say "cool, it has some more life". and then look at the piston and think that it seems worn. then you are second guessing and losing sleep.
Click to expand...
PALMER84ONE:
190 is good, piston/rings might show wear. With the piston at TDB, get a good look at the cylinder for any score marks on the intake side. You are more than likely going to see that there is some wear through the exhaust. Just keep in mind, if it drops off more, you are getting closer to lifes end.
Click to expand...



Cheap insurance.

https://www.ebay.com/itm/391126655917
 
Trfsrfr

Trfsrfr

Carb questions:
I am still trying to get it dialed in and yesterday I dropped the needle clip to the top position. I took it around the block, and it may have made a difference, but haven't brought it out to the dirt wind it up. I'll do that when I'm done typing here.
But I am having issues identifying what I have;
According to Palmer, I may have a RM carb on it??? as the idle speed is controlled by turning the choke knob.
And this is where my problems start - see, I have a manual for a 1999 250 M model, that says I should have a PWK on it.
Then I also have a manual for a 1998 L model that says PWM.

According to the data I have, I have a 1999 YZ250 L1, model code 5CU1, G engine, and the 10th vin digit is an X, which from what I have read means it is a competition model, and it has a PWM carb, with a 172s MJ, and 50 PJ. I did not write down the needle number...

One manual (the 99 M with PWK) calls for a 175 MJ, with an N3CW-3 needle/pos
And the other (the 98 L with PWM) calls for a 172 MJ, with a N3VF-2 needle/pos.


It seems to run okay, currently it wont idle, although I am sure I will get it dialed, but it would be nice to know where to start looking for accurate info and I haven't found a manual yet that exactly matches what I have, or to tell me what the stock settings and part numbers should be.
I'm gonna go load it up and bring it out the desert now, be back later.
 
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Trfsrfr

Trfsrfr

ossagp:
show the carburetor. hondas had a carburetor that set using the enrichenor knob too. total junk.
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Will do.
Did some test runs out in the desert today like I said, with Gopro vids, and took some pics.
Trying to upload the vids to my Youtube channel now so I can attach links, but it takes awhile.
My next post should have links and pics.
The GoPro vids should at least give y'all the opportunity to hear the bike as I ran it.
Did a plug-chop at the end and will attach links to video, and the pics of the plug.
Waiting for the uploads now...
 
Trfsrfr

Trfsrfr

Okay, below is a link to the Youtube vid so you guys can listen to the bike;
https://youtu.be/yYbKWBQsh2g
I was able to turn the choke knob counter-clockwise and get it to idle, although it was kinda choppy sounding. Also, I was able to turn the air screw all the way in, and a full 3 turns out and it didn't make a difference in the way it ran.

Below is a photo of the plug after doing the plug chop;
100_2744.JPG
Here is a photo of the carb;
100_2747.JPG
 
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Mihylo33

Mihylo33

Trfsrfr:
Okay, below is a link to the Youtube vid so you guys can listen to the bike;
https://youtu.be/yYbKWBQsh2g
I was able to turn the choke knob counter-clockwise and get it to idle, although it was kinda choppy sounding. Also, I was able to turn the air screw all the way in, and a full 3 turns out and it didn't make a difference in the way it ran.

Below is a photo of the plug after doing the plug chop;
View attachment 30035
Here is a photo of the carb;
View attachment 30036
Click to expand...


It's lean.
 
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