Yes. When I jet I start with a hot motor and I start with the idle circuit, but only after I'm sure the float is set properly. From pilot to mid to main in that order. I haven't had to do plug chops in about 8yrs but when I did I started with about 20 new plugs and I started with 1/8 throttle increments marked out on the throttle assembly. Now I break into quarters since I won't be doing any nationals or serious racing anymore.
250 The 1999 YZ250
- Thread starter Trfsrfr
- Start date
Yes. When I jet I start with a hot motor and I start with the idle circuit, but only after I'm sure the float is set properly. From pilot to mid to main in that order. I haven't had to do plug chops in about 8yrs but when I did I started with about 20 new plugs and I started with 1/8 throttle increments marked out on the throttle assembly. Now I break into quarters since I won't be doing any nationals or serious racing anymore.
Okay cool. And since I ain't doing anything near racing I am going to move forward with my plan.
I wont be buying 20 plugs though, maybe one.
As far as float height, they give me a 2mm range from 5.5 to 7.5, but I would prefer just one number.
And why the range? How much different will it run at 5.5 compared to 7.5?
Whatever.
Right now I believe I am at about 7mm, so I'm going to leave it and run it.
Gonna be lots of mud out there after today...
I wont be buying 20 plugs though, maybe one.
As far as float height, they give me a 2mm range from 5.5 to 7.5, but I would prefer just one number.
And why the range? How much different will it run at 5.5 compared to 7.5?
Whatever.
Right now I believe I am at about 7mm, so I'm going to leave it and run it.
Gonna be lots of mud out there after today...
New update:
Zach and I took the bikes to ACP today. My main objective was to make it to work on Monday, have fun, and hopefully find some help with the way it runs.
There was a dude from a motorsports company there that offered to check it out for free, removed the exhaust and gave it a once-over.
He said that I have a visible groove in the piston, (last time I checked compression it was (Sorry for late edit, it was/is 211 psi). He pulled the plug, and recommended to drop the needle one position, and go to the next size smaller jet to fix the sputtering on run up problem.
Then he also said that there is an unusual noise from the engine, which I have heard since I've owned it, and said that it might be piston slap, or a bad bearing.
What does that sound like?
I took it back to the truck (ignoring the noise, like when you roll your tongue to pronounce some Spanish words) , dropped the needle to the top position, and it ran better, didn't sputter as as much, accelerated faster, but still misses on run up in the mid-section. But definitely better.
We're moving into off-riding season here soon, so I'm good with a tear-down, but I am on a mission to learn as much about this thing as possible beforehand. I need to understand first.
Thoughts?
Zach and I took the bikes to ACP today. My main objective was to make it to work on Monday, have fun, and hopefully find some help with the way it runs.
There was a dude from a motorsports company there that offered to check it out for free, removed the exhaust and gave it a once-over.
He said that I have a visible groove in the piston, (last time I checked compression it was (Sorry for late edit, it was/is 211 psi). He pulled the plug, and recommended to drop the needle one position, and go to the next size smaller jet to fix the sputtering on run up problem.
Then he also said that there is an unusual noise from the engine, which I have heard since I've owned it, and said that it might be piston slap, or a bad bearing.
What does that sound like?
I took it back to the truck (ignoring the noise, like when you roll your tongue to pronounce some Spanish words) , dropped the needle to the top position, and it ran better, didn't sputter as as much, accelerated faster, but still misses on run up in the mid-section. But definitely better.
We're moving into off-riding season here soon, so I'm good with a tear-down, but I am on a mission to learn as much about this thing as possible beforehand. I need to understand first.
Thoughts?
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Piston to cylinder clearance. It is something I can never get anyone to post their specs on, when building an engine. Even when specifically recommended. I assume it's because they aren't taking the measurement, which makes it hard to report as correct. Funny, it's a big step in every service manual I've ever read.
Typically you get the cylinder worked and honed to a new piston kit. Send in the new piston with the cylinder. And then double check prior to assembly! -BIG DAN
Typically you get the cylinder worked and honed to a new piston kit. Send in the new piston with the cylinder. And then double check prior to assembly! -BIG DAN
Okay, good info, thank you Mike and Big Dan.Piston to cylinder clearance. It is something I can never get anyone to post their specs on, when building an engine. Even when specifically recommended. I assume it's because they aren't taking the measurement, which makes it hard to report as correct. Funny, it's a big step in every service manual I've ever read.
Typically you get the cylinder worked and honed to a new piston kit. Send in the new piston with the cylinder. And then double check prior to assembly! -BIG DAN
I dont recall this noise being there when I initially bought the bike, but honestly, I probably wouldn't have known or noticed it at that time since this is the first real performance 2T that I have owned and monkeyed around with.
I have a bunch of experience with 2T construction equipment (chainsaws, concrete cutters, weed-eaters, etc), but they are very different in their carbs (Tillotson, etc), and certainly no power-valves.
But so I can understand further, would this issue cause all of the problems I have been having with this bike in this thread since day one?
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Yes. That's why you needed to jet so lean to get it close to running decently.
A total rebuild will cost you around $400 max. A little More if your cylinder needs replating. Cherry picking your parts will bring a total rebuild down to about 200. FYI. Always go oem with crank bearings or at the very least make sure they are koyo brand.
Something's not right here. Not at all.
211psi with a skirt rattle. Yammi does this thing with a,b and c Pistons. I'm not really sure about it though. You'll have to ask Palmer or Ossa.
If it were me this thing would have been torn down a long time ago but with a 211 psi reading I can see why you didn't.