2 Stroke 1998 CR80R

[ossagp]

Okay, moving right along;

What do you guys recommend for piston ring endgap?
Service manual says .011 to .017.
Right now it's at .0125 so I assume I should just leave it at that...

And then I have heard different theories on installing the piston;
I heard dry, and then the manual says to lubricate all sliding surfaces.
What do y'all recommend?

Cleaning it is more important to me that lubing it if I had to choose one over the other. Though lots of us have probably put some on trackside with no cylinder prep and no more than cleaning with gasoline or premixed fuel. When in the shop I clean the cylinder with a paper towel and automatic transmission fluid, until the subesquent towels are clean. then I rub it until the towel isn't picking up any more atf. fire it up and bring it to temp and you can hit the starting line without any adverse affects.

I have put at least 200 cylinders from two strokes to four stroke diesels (two stroke diesels too) together completely dry with great results on them all. Someone convinced me to try the aft method described and it yielded the same great results. But now I don't feel so much like I am building something that is oil deprived.

your ring gap will be fine the way you have it. my rule of thumb is at least .012 on a single or top ring on a two stroke.

 

[Trfsrfr]

It sounds like I'm on the right path then.
The kiddo got all into it last night when he saw that the piston was next to be installed and stuck around to help out. He didn't care too much for re-assemblying the trans and the cases too much, but I let him choose how to install the piston.
He opted to go for coating everything "with sliding surfaces" with 2T oil, like it says in the manual.
I'm going to go out and add some more parts this afternoon after it warms up out there, maybe even have it running by tonight.

 

[Trfsrfr]

Is it possible to put the shift drum mis-aligned, or in the wrong way?
I probably should have asked this a long time ago...

 

[Mihylo33]

Is it possible to put the shift drum mis-aligned, or in the wrong way?
I probably should have asked this a long time ago...

It's possible to sign it wrong and bind it. Shifting is the 2nd thing I check after torquing down the case bolts.

 

[Trfsrfr]

It's all good.
It went together well with a few hammer blows and is super tight.
It's sitting in the frame now.
Just gotta put the rest of the stuff back on (carb, magneto, etc.) and give it a kick or two.

 

[Trfsrfr]

Update;
After taking two steps back and one forward we fired up the CR80 today.
It runs.
Not sure how well it runs, but is fires up and seems to idle good, although the idle speed screw is turned all the way in...
Sounds like it has a "tinking" sort of noise near the front of the engine. I put my stethoscope on it and it sounds like it's near the cylinder, or the water pump area.
I thought maybe it was running lean so I screwed in the air screw and it sounds like it may have lessened a bit, but not sure.
I never really revved it too high, just fired it up and let it heat up at idle a couple times. It probably has 10-12 minutes run time on it now.

Also, before we fired it up I put the compression tester on it, and it has 150 psi.
Thoughts?

 

[Mihylo33]

Update;
After taking two steps back and one forward we fired up the CR80 today.
It runs.
Not sure how well it runs, but is fires up and seems to idle good, although the idle speed screw is turned all the way in...
Sounds like it has a "tinking" sort of noise near the front of the engine. I put my stethoscope on it and it sounds like it's near the cylinder, or the water pump area.
I thought maybe it was running lean so I screwed in the air screw and it sounds like it may have lessened a bit, but not sure.
I never really revved it too high, just fired it up and let it heat up at idle a couple times. It probably has 10-12 minutes run time on it now.

Also, before we fired it up I put the compression tester on it, and it has 150 psi.
Thoughts?

Sounds good. That idle screw has me worried and so does that air screw. It should have died when the air screw was all the way in.

 

[Trfsrfr]

My bad, I didn't screw the air screw all the way in. I just screwed it in more. It was at 2-1/2 turns out, and I screwed it in to 2 turns out, which is what the manual suggests.
I'll play with it more tomorrow.
FMF recommends the air screw at 1.5 turns, and the MJ at 122.
I forget what's in it now...

 

[Mihylo33]

My bad, I didn't screw the air screw all the way in. I just screwed it in more. It was at 2-1/2 turns out, and I screwed it in to 2 turns out, which is what the manual suggests.
I'll play with it more tomorrow.
FMF recommends the air screw at 1.5 turns, and the MJ at 122.
I forget what's in it now...

That idle screw has me concerned. Matchbit up with a picture online

 

[Trfsrfr]

Matchbit up with a picture online

I dont understand what you're requesting here?

I just went out and fired it up for the 2nd time today. Put the air screw at 1.5 like FMF suggests. I plug chopped it in the garage and it's running very rich, plug was wet.
In my head it makes sense that the slide should need to be up more to allow it to idle...
I'm sure I'll get the carb figured out, and it's been sitting about 6 weeks since I went through it.
I'm gonna worry about that tomorrow though cuz it's Superbowl time.

But it still has this ticking/tinking noise near the front of the engine though...I am more concerned about that at the moment.

 

[Mihylo33]

I dont understand what you're requesting here?

I just went out and fired it up for the 2nd time today. Put the air screw at 1.5 like FMF suggests. I plug chopped it in the garage and it's running very rich, plug was wet.
In my head it makes sense that the slide should need to be up more to allow it to idle...
I'm sure I'll get the carb figured out, and it's been sitting about 6 weeks since I went through it.
I'm gonna worry about that tomorrow though cuz it's Superbowl time.

But it still has this ticking/tinking noise near the front of the engine though...I am more concerned about that at the moment.

If the idle screw is screwed all the way in there could be an issue.
Maybe it's the power valve assembly.

 

[PALMER84ONE]

Typical ticking/tinking sound for a 250. Almost sounds like slap but not as loud. It's the PV system, levers, side pistons, main, ticking loose in the exhaust cycle.

 

[ossagp]

I dont understand what you're requesting here?

I just went out and fired it up for the 2nd time today. Put the air screw at 1.5 like FMF suggests. I plug chopped it in the garage and it's running very rich, plug was wet.
In my head it makes sense that the slide should need to be up more to allow it to idle...
I'm sure I'll get the carb figured out, and it's been sitting about 6 weeks since I went through it.
I'm gonna worry about that tomorrow though cuz it's Superbowl time.

But it still has this ticking/tinking noise near the front of the engine though...I am more concerned about that at the moment.

Keep idling it rich like that and you are going to end up with a glazed up cylinder that never really seats. When I put one back together I want JUST enough idle time to see that nothing leaks or is falling off and then it gets a load put on it to warm it, then it gets up to full cylinder pressure before it reaches 5 minutes of run time.

 

[ossagp]

If the idle screw is screwed all the way in there could be an issue.
Maybe it's the power valve assembly.

Yeah, I'll bet that power valve is missing.

 

[Mihylo33]

Yeah, I'll bet that power valve is missing.

Wasn't sure if that yr had one or not. I guess I could have gone back a few pages to see the pics again.