quick ? for you 2 stroke gurus

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frit91

frit91

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I have a 300cc air cooled 2 stroke engine that starts right up when cold but is a bitch to start after it warms up. My ? is will a blown or leaking head gasket cause this problem? I have exhausted all other culprits and am left pondering about the head gasket. There is an oily residue around the front of the head and at first I thought maybe it was just from an exhaust leak but I really don't think there is a leak. Any thoughts or opinions on this?
 
Rings are bad, thats why its harder to start when its not cold anymore. As for the oily residue at the front of the head if its coming from the exhaust area then that is normal since the gas has oil mixed in. You can replace the gasket between the exhaust and cylinder head to slow down this oily mess but the only real way to avoid that is to ride the piss out of it at all times like 2strokes are meant to be riden.
 
D'oh! That's why I asked a question. I checked the compression when motor was cold and it was a little low but acceptable. I never thought to check it once the engine was hot. Thanks for the info, I feel like an idiot but I get that feeling often, so it's really nothing new for me.
 
Dont worr about it, you gotta learn somehow and somewhere. I know 2strokes really well. When i had my kx125 i had my rebuilds down to a science, every 6months was a topend and every year to year and half was bottom end unless it blew before i got around to rebuilding it.
 
THORrider05 said:
Rings are bad, thats why its harder to start when its not cold anymore. As for the oily residue at the front of the head if its coming from the exhaust area then that is normal since the gas has oil mixed in. You can replace the gasket between the exhaust and cylinder head to slow down this oily mess but the only real way to avoid that is to ride the piss out of it at all times like 2strokes are meant to be riden.
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Uh, no. More like a bad head gasket or base gasket.
 
alex456123 said:
Uh, no. More like a bad head gasket or base gasket.
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If gaskets are blown it has the same compression no matter hot or cold. Aslo if it was the base gasket you should replace the rings cause you removed the cyl. Also if you replace the rings then you get both new head and base gaskets.
 
Well either way,
Step 1: do a compression test
Step 2: Do a leak down test
Step 3: ?
Step 4: profit
 
2strokes are very finicky, its really hard to tell what the issue is unless you ride it. Looking at it and trouble shooting like a 4stroke wont give you exact results of what the issue really is. Ive dealt with this when i raced 125's and 80's.
 
If you can't fix a 2 stroke you have a problem. There the easiest to work on a simple to figure out its not rocket science.

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jeffsyfm350x said:
If you can't fix a 2 stroke you have a problem. There the easiest to work on a simple to figure out its not rocket science.

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No ****. I had a brain fart and did check compression cold but never did check it after it was warmed up. It had a float issue and would suck the bowl dry if you kept going at wot. I fixed that and still had carb issues, that's why I fixated on the carb. I noticed the oily residue and thought head gasket but I figured I was missing something simple and decided to ask a question, you know get a fresh perspective on things. I had looked at it for about 2 hours on and off while working on other ****. Checked comp and it was 115, after riding it and checking it was 95. So I agree it was a dumb move on my part but maybe you don't make mistakes so I am sorry if I am not a rocket scientist like you, lol.
 
^^ The above comment wasn't to piss you off Jeff, I was actually laughing when I typed the last sentence. I just reread it and wanted to make sure you don't take it that way. I simply was asking advice. Now that I think about it I had an old IT 175 that did the same thing and it was a head gasket, or at least that helped it out until I sold it. But that was 20 years ago and I forgot about it. I guess basically I was being lazy and seeing if someone else had the same problem somewhere along the line. Gaskets make sense and so do rings so I am just going to change both. Thanks for the ideas and the possible insult.
 
Bad news is the rings are shot. Good news is the cylinder is fine and new rings and gaskets all together cost me a whopping $28. As long as it lives for another year or so I will be happy. Btw I did do a leak down test to confirm before someone else decides to chime in and yes I cleaned, inspected, measured with a snap gauge to confirm bore size and roundness, and honed the cylinder. Thanks fellas.
 
frit91 said:
No ****. I had a brain fart and did check compression cold but never did check it after it was warmed up. It had a float issue and would suck the bowl dry if you kept going at wot. I fixed that and still had carb issues, that's why I fixated on the carb. I noticed the oily residue and thought head gasket but I figured I was missing something simple and decided to ask a question, you know get a fresh perspective on things. I had looked at it for about 2 hours on and off while working on other ****. Checked comp and it was 115, after riding it and checking it was 95. So I agree it was a dumb move on my part but maybe you don't make mistakes so I am sorry if I am not a rocket scientist like you, lol.
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Lmao! Wasn't directed to you. Posts saying they are finicky and isn't that way at all. 2 strokes are cut and dry to build and figure out I was rebuilding them at 10 years old.


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frit91 said:
^^ The above comment wasn't to piss you off Jeff, I was actually laughing when I typed the last sentence. I just reread it and wanted to make sure you don't take it that way. I simply was asking advice. Now that I think about it I had an old IT 175 that did the same thing and it was a head gasket, or at least that helped it out until I sold it. But that was 20 years ago and I forgot about it. I guess basically I was being lazy and seeing if someone else had the same problem somewhere along the line. Gaskets make sense and so do rings so I am just going to change both. Thanks for the ideas and the possible insult.
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No offense taken lol. 9 times out of 10 it will be the rings. Gaskets rarely go but the seals will which will allow it to suck more air and which will make it run super lean and then will blow. But as far as gaskets going the head one will go rarely the base and depending on what kinda 2 stroke ya have either air or liquid cooled its easy to figure out and the air cooled you will hear the leak and liquid cooled you will foul your plug and you will see antifreeze on the plug. And if you don't see it you will smell it.

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jeffsyfm350x said:
Lmao! Wasn't directed to you. Posts saying they are finicky and isn't that way at all. 2 strokes are cut and dry to build and figure out I was rebuilding them at 10 years old.


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I take it as your talking about me cause i said they are finicky? Obviously you dont know **** about 2strokes. When i said finicky i was referring to them as finicky when riding, IE alot of them dont like to be ridden like a 4stroke all the time. If you still have a problem with me then send me a PM and settle it like a man.
 
Yeah let's talk about this over the Internet. That's settling it "like a man"
Just take your damn ego, get the **** up, then drag your ass out of here.
 
THORrider05 said:
I take it as your talking about me cause i said they are finicky? Obviously you dont know **** about 2strokes. When i said finicky i was referring to them as finicky when riding, IE alot of them dont like to be ridden like a 4stroke all the time. If you still have a problem with me then send me a PM and settle it like a man.
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Yup your the a hole I was talking about and don't know ****! I've built them for 29 years so longer than you have been around! I also own 3 yz 490s, RM 250 , CR 250 and a Tri Z 250. So don't get me started there bud. Just like your 500 frame and your over priced tires trying to screw members that know no better your a cool guy! You should really think before ya post. If ya have a problem talk to admin I'm sure he will help ya lmao.

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