125-200cc Here is my 144cc husky

It starts as necessity - i seized my piston, carb fell out from connection so it goes very lean.




To save money i decide to go for iron sleeve, so cylinder was bored and head was modified for yz144 piston. PV was trimmed be myself.









It all cost me near 70$ + 92$ for piston with free shipping.
I run only once, and can't really tell how good or bed it is, only two things that i can notice for now:
1. good pull from start on second gear - old 125 dont like to start from second gear at all.
2. wery good response from idle to max rpm.
Also i got two plugs fouled real wet and oily - it running very rich from bottom, still have to mess with jetting.

View: https://youtu.be/F2fVxwgdkuI


View: https://youtu.be/UomconPwd1U

I want to thank all who answered me on forum, especially to Walt http://www.cafehusky.com/members/wallybean.586/ without you this wouldn't be possible!

Eeeeeend it's gone....
Obviously, it goes lean. It's first time i go up to 6th gear on the road, other time when i go wide open - up to 3rd gear - everything was OK.
I got some more vid of this ride, i can post... can anyone tell by the sound - am i right, that it running to rich from idle, but went so lean at WOT?
one thing that i noticed - radiators was cold, but before it they was warm, maybe even too hot for +2 celsius outside.

When it seizes in the four corners like that it usually meant not enough piston to wall clearance or it got too hot due to lean or not enough coolant. The pitting on the top of the piston is lean craters.

The marks on piston is more like paint, that scratches, its pretty smooth, i think i can run it after little of sanding. It was 3rd time i ride it, so if it was piston to wall clearance i should have much more damage. I believe it go a little lean. But the main reason - fail of coolant system, i dont know for now in what part, but now i remembering that i always has red light flashing of temperature - i was thinking that it bugs.

Buy a new piston mate!

The piston is oval when it's cold, almost round when up to operating temp but when it gets too hot it will get kinda square and begins to scuff on the corners like yours did. I like to set my clearance on the big side of the spec especially with a forged piston. (my yz125 with a forged Weisco is at .0045") That way when it is in extreme racing conditions it doesn't scuff.

That looks like it's a cold seize just a minor one, I've filed pistons that were worse but do replace the ring.
Iron sleeves heat up slower than nikasil hence why that they aren't that highly recommended.

I think your bike wasn't fully warmed up.
And looks slightly lean by the piston crown burn pattern.

Is your bike pre mix or oil pump ?
Either one you may need too correct for the 144 cc requirement
Plus raise your needle to open up more fuel that may be your issue.

Maybe i will, i this one will fail, it's really fine as for me.

Another new for me, thanks!

No, it's not a cold seize, for that moment i spent one hour in woods, and radiators was hot. But after it seized - they were cold. So i sure for 95% that it's fail of coolant system. Plus it was little lean at WTO, I think i should go for one size bigger main jet. So i will file piston, and maybe will be lucky to find ring. it's pre mix - 20-30 ml to 1 liter.

jet the main richer until it fours strokes then back off a size. dont piss around going up a size, down a size, up a size, down a size.

Sorry, I don't understand what do you mean

Spark plug burned out to

Your lean, justintendo is trying to say that if your main jet is 380 there is no point buying a 385 go for 400 and if that's better go 410.
Jetting gets expensive fast if your going up in .5 increments.

I understand. I got all the jets. I will increase the number.

Good spotage!

The little specs of aluminum on the plug and combustion chamber used to be the piston top and the craters are where it came from. You've taken some excellent pictures, in fact this one is good enough to put in a service manual to show what aluminum deposits look like after lean detonation occurs.

hi all
so i back in business
I want you to look at my video, and tell me what you think.
First of all i have to say that temperature +2 celsius, snow is wet and very heavy so it makes big rolling resistance. And is it to rich for now? It going up hill very good even at half throttle (125 was not able to do like this). I think it is to rich from bottom.

Sounds rich on the main or maybe the needle too. I can't tell what throttle opening you are at when it is sputtering. Remember it's not what RPM you're at it's what throttle position you are at that determines what carburetor circuit is delivering fuel to your engine.

Pilot jet idle to 1/8th
needle 1/8-3/4
Main3/4 - full throttle

There is some overlap so it helps to mark your grip so you can look down and see where you are at when it spudders

I read so many times about markin grip, but never attached no importance. And i understand finally that you mean - "it's not what RPM you're at it's what throttle position you are at ". So now i see that it sputtering up to 1\4 throttle.