2 Stroke 1998 CR80R

Trfsrfr

Trfsrfr

I think the cooling system is probably working and that I just messed up.

Here is some of the info I have been working with;
So according to many, the pilot jet only affects idle to 1/4 throttle, right? I have heard many people say this.
But according to the article that Mike posted here,
https://www.dirtbikeaddicts.com/content/threads/dirt-bike-jetting-101.5692/,
"the pilot circuit affects the entire throttle range. When you are at full throttle, the main jet is the primary fuel metering device, but the pilot is still delivering fuel as well"
So those are 2 conflicting thoughts.

Below is what I get from the service manual;
Screenshot from 2017-02-26 10:45:10.png
Notice it doesn't give a specific recommendation for my 1998 PJ like it does for everything else.
And here is what I have from FMF, (which BTW I just noticed that the expansion pipe say Calif on it);
Screenshot from 2017-02-26 10:43:09.png
If you remember I said I was gonna drop the PJ to a 48, and I did. It didn't seem to really make a difference, so while out in the desert that day I decided to drop the jet needle from the 3rd position to the 2nd, and when Zach rode it he said it felt better. That was when I decided to ride it and burned it up.
It melted down with a 48PJ, 122MJ, and 2nd needle clip position.

I'm going to chalk it up to operator error, and spend the $400.00 to get it fixed.
 
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Mihylo33

Mihylo33

Trfsrfr:
I think the cooling system is probably working and that I just messed up.

Here is some of the info I have been working with;
So according to many, the pilot jet only affects idle to 1/4 throttle, right? I have heard many people say this.
But according to the article that Mike posted here,
https://www.dirtbikeaddicts.com/content/threads/dirt-bike-jetting-101.5692/,
"the pilot circuit affects the entire throttle range. When you are at full throttle, the main jet is the primary fuel metering device, but the pilot is still delivering fuel as well"
So those are 2 conflicting thoughts.

Below is what I get from the service manual;
View attachment 30619
Notice it doesn't give a specific recommendation for my 1998 PJ like it does for everything else.
And here is what I have from FMF, (which BTW I just noticed that the expansion pipe say Calif on it);
View attachment 30620
If you remember I said I was gonna drop the PJ to a 48, and I did. It didn't seem to really make a difference, so while out in the desert that day I decided to drop the jet needle from the 3rd position to the 2nd, and when Zach rode it he said it felt better. That was when I decided to ride it and burned it up.
It melted down with a 48PJ, 122MJ, and 2nd needle clip position.

I'm going to chalk it up to operator error, and spend the $400.00 to get it fixed.
Click to expand...



Yes. The pilot will effect how well the main works which is why I always start with the pilot of the pilotnisnt right it will give false readings through out. Now keep in mind they are running 50/50 mix of race and pump premium and premix of 32:1. Race gas runs a little richer and a little cooler showing for a leaner jet.
 
Trfsrfr

Trfsrfr

I'm starting to get a more well-rounded and balanced feel of engines now. This latest melt-down was not wanted, but I think necessary.
On one hand I really like (and am comfortable with) 4 strokes for their ease of diagnosis, but I appreciate the lack of complexity in 2 strokes.
So I am going to start searching for a happy medium, a 3 stroke.
If anyone sees one for sale, let me know, I'll buy it ASAP.

I'm also in the market for unicorns, any age.
 
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Mihylo33

Mihylo33

Trfsrfr:
I'm starting to get a more well-rounded and balanced feel of engines now. This latest melt-down was not wanted, but I think necessary.
On one hand I really like (and am comfortable with) 4 strokes for their ease of diagnosis, but I appreciate the lack of complexity in 2 strokes.
So I am going to start searching for a happy medium, a 3 stroke.
If anyone sees one for sale, let me know, I'll buy it ASAP.

I'm also in the market for unicorns, any age.
Click to expand...



 
Trfsrfr

Trfsrfr

Mihylo33:
Click to expand...
I should have known someone here would call me out...
Emily:
I see your current 2 stroke woah and I raise you my current 2 stroke woah.
2000 CR125
Click to expand...
Ah, I see how it's gonna be.
I see your current CR125 piston and cylinder that looks like it has been flogged a bit and maybe had some debris sucked into it, and raise you one damn near brand new (7? hours desert time) melted piston that still has very readable markings...100_2873r.JPG 100_2874r.JPG
 
PALMER84ONE

PALMER84ONE

If I could only post photos easy. I have about 6 pistons of various bikes. Best one is a melted hole in the dome. Guy said he lost compression during a ride. Hahaha, yah let me JB weld that for yah.
 
Emily

Emily

Trfsrfr:
I should have known someone here would call me out...

Ah, I see how it's gonna be.
I see your current CR125 piston and cylinder that looks like it has been flogged a bit and maybe had some debris sucked into it, and raise you one damn near brand new (7? hours desert time) melted piston that still has very readable markings...View attachment 30625 View attachment 30626
Click to expand...
Yeah, my brother took that bike out last. Never put a dime into it, nor did he assist in routine maintenance. Frikkin twat waffle.
 
Mihylo33

Mihylo33

Trfsrfr:
I should have known someone here would call me out...

Ah, I see how it's gonna be.
I see your current CR125 piston and cylinder that looks like it has been flogged a bit and maybe had some debris sucked into it, and raise you one damn near brand new (7? hours desert time) melted piston that still has very readable markings...View attachment 30625 View attachment 30626
Click to expand...


Looks too lean to me. There is zero carbon on the dome. It also looks like there is some detonation happening but that could just be my phone. What's the underside of the piston look like?
 
O

ossagp

Trfsrfr:
I should have known someone here would call me out...

Ah, I see how it's gonna be.
I see your current CR125 piston and cylinder that looks like it has been flogged a bit and maybe had some debris sucked into it, and raise you one damn near brand new (7? hours desert time) melted piston that still has very readable markings...View attachment 30625 View attachment 30626
Click to expand...

You could have a coolant leak on that one. Abused, maybe. When you get pieces breaking off of the front of the piston it can happen from liquid coming in from the head cylinder area. It is slower at moving than the fuel air mix, and it is something relatively cold hitting something that is very hot. It doesn't take much.

I would try to move the aluminum off of the cylinder without using acid on it first. leave any of it and it comes back to haunt you.

Mike was correct on the pilot jet affecting the entire range of throttle openings as far as jetting requirements go.

If I might criticize your approach a little: you can't jet one on the stand. (well anyway, I sure can't. )you pay less in the long run if you change one thing at a time. adding some "chemical wizardry" to a couple of changes just makes it harder.
 
Mihylo33

Mihylo33

ossagp:
You could have a coolant leak on that one. Abused, maybe. When you get pieces breaking off of the front of the piston it can happen from liquid coming in from the head cylinder area. It is slower at moving than the fuel air mix, and it is something relatively cold hitting something that is very hot. It doesn't take much.

I would try to move the aluminum off of the cylinder without using acid on it first. leave any of it and it comes back to haunt you.

Mike was correct on the pilot jet affecting the entire range of throttle openings as far as jetting requirements go.

If I might criticize your approach a little: you can't jet one on the stand. (well anyway, I sure can't. )you pay less in the long run if you change one thing at a time. adding some "chemical wizardry" to a couple of changes just makes it harder.
Click to expand...


Nice pick up on that one. :thumb:
 
Trfsrfr

Trfsrfr

This has been a somewhat painful (more my ego really, but I'm not made of money either) learning experience, but I try to be a glass half-full kind of guy, and I think I have learned a great deal from it.
I think it was an expensive,unwanted necessity.
ossagp:
If I might criticize your approach a little: you can't jet one on the stand.
Click to expand...
Andy, I am always open to yours, and the other senior members here's critique (you all know who you are). Most of what I know about performance 2-strokes comes from you guys and this site, and I very highly value all yours opinions.
On this point, lesson learned.
I think I am done with plug chops tests too, as you have previously stated you don't do.
Thanks for chiming in by the way, I was hoping you would :thumb:
Thanks for everyone else's responses too, those that have been following me on this 'disease' I seem to have caught lately.

I have spent the past few days wondering how to get it fixed and how to do it the least expensive way, but today I spoke with my buddy with the CR480 that we brought back from the dead, and he asked how much a new cylinder was.
I hadn't thought of checking because of my $12.56 Kawasaki main jet total rip-off experience, but it turns out, at Motosport, a new OE cylinder is $305.00, and a piston is like $46.00, and both are in stock.
So I think I am just going to get those coming, and start over.

So after the new parts arrive and get assembled, my new plan is this, and please please let me know if I am still not going in the right direction, cuz I still have a YZ250 that has the same symptoms that the CR had, and I like to learn from my mistakes...

My plan is to put the stock jets in (125, 50), and start the tuning process with the needle jet and it's position.
The bike ran noticeably better to my son, who has zero experience, and to me, when I dropped the needle one slot. It was better on the run-up to WFO, no sputtering.
Then I burned it up at WFO.

The coolant issue I am still considering, but am tending to believe it is a non- issue right now, only because we put 7 hours on the bike 2 weeks ago with no problems so...
But I'll monitor the situation closely and report back when I get some new parts installed.
 
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Trfsrfr

Trfsrfr

Sweet, thanks Palmer!
I've bookmarked that site.

Any chance my new HotRods wrist pin bearing is a different size than OEM?
 
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