some questions about my yt 125. Problems!

[90nut]

Ok I bought this thing this summer for 50 bucks because the piston was actually melted and broke apart in the cylinder. After a long while of looking at it I decided to get off the wallet and order the parts for it. So in the time it was sitting in my barn it must have got some condensation on the crank shaft and it kinda siezed up. So without reall thinking about the best way to fix that I poured a little bit of oil on the crank. About a 1/4 of a quart. Let it sit for a while and she freed right up. So I get it back out last night and clean some of the oil off the crank and start assembling the top end. I get it all together and it has good spark hella good compression and no start. I am going to clean the carb out today. Now the question is think it will start with this oil on the crankshaft? I mean it is way more than the risidual oil you get down there from the engine running. If I can't get it to fire how should I go about draining the oil out from the cank? I made kind of a goofy call doing what I did. So if anyone has any ides help meout. Thanks

[Unclediezel]

That oil should drain off during the normal compression cycle of the engine--But it will foul your plug in the process---Clean the plug(or replace it) and while it is out--rip the cord a few dozen times-------and watch for the oil to pump out the spark plug hole---Reinstall the plug--and that should be a done deal

[90nut]

Ok, I believe the oil is out of the crank case. Now I have an entire new set of problems. first off when I pull it over the pul rope will "kick back". Like if you are starting it and the rope jerks back. So basicall the engine is firing before the piston is at TDC correct? Does this have an adjustable timing plate? One other question, when I pull it over it sounds like there is an air leak but if I put my hand over the back side of the carb without the air filter on it it does not do it. I guess it is just the engine sucking in through the carb? Any help is great. Thanks

[Unclediezel]

no the timing isnt adjustable, but the plate can be put on wrong.check a manual for stator installation---Funny thing is---if you get it started like that---it will run BACKWARDS.

Compression??????---you may also have a reed stuck open?

[90nut]

all right, has excellent comp. Brand new piston, rings, bore job. To check and see if plate is put on wrong how/ what would I check for? Also is the nut that holds the fly wheel on right or left hand thread?

[90nut]

Also, if one of my reed petals were stuck open would that cause the recoil to "pull Back"?

[Unclediezel]

absolutely-----Explosion happens in the crankcase instead of the cylinder---

[Unclediezel]

RH thread on the crank nut----pick up coil towards the top.

[90nut]

Well, I am going to go out right now and have another look at her. Hopefully I will figure something out. Thanks, I will let you know what happens.

[Howdy]

This may sound like a stupid question, but is the pullstarter wound up properly? I only ask this because Yamaha 125/175 has the rode come out of the frount top verses the rear top. The rope is actually guided around by the one little puller inside. If the pullstarter is wound / wrapped wrong, then it would spin your motor backwards. This would cause the symptoms you have stated.
If your looking at the motor from the left ( pullstarter ) side, it should be turning over counter clockwise.
Howdy

[90nut]

Well I think I solved the pull back problems. I pulled the reeds out and I guess when the shop bored my cylinder the didn't remove the reed cage. Well that was all gumed up with metal shavings,oil, and what not. Cleaned all that out and the rope doesn't pull back anymore. So it still won't fire but there is still more oil coming out of the crankcase yet so I guess I just keep yanking until all of that is gone. When I pull the plug out there is oil and crap all over it but it still has great spark. I am thinking that there is so much oil getting in the cylinder that the engine won't fire. I am going to mess with it some more tomorrow aong with some other projects I've got going on.

[YTM200BOY]

this sounds like my problem on a ytm200EK there is oil all over plug and it wont start and also my pull start doesnt pull back were in the same boat together i cant figure this damn thing out! lol were both 15 - 16

[Rm250RF900R]

Well make sure you have some nice fresh brandnew plugs by your side. I bet that plug in it now is fouled. Too much oil on a plug will just kill it. Yank that sucker a lot until its clear, put in a nice new plug, and see what happens.

[Howdy]

Well I think I solved the pull back problems. I pulled the reeds out and I guess when the shop bored my cylinder the didn't remove the reed cage. Well that was all gumed up with metal shavings,oil, and what not. Cleaned all that out and the rope doesn't pull back anymore. So it still won't fire but there is still more oil coming out of the crankcase yet so I guess I just keep yanking until all of that is gone. When I pull the plug out there is oil and crap all over it but it still has great spark. I am thinking that there is so much oil getting in the cylinder that the engine won't fire. I am going to mess with it some more tomorrow aong with some other projects I've got going on.

Cody, If your getting that much oil in the crank case, then you may have bad crank seals. Bad Crank seals will allow your tranny oil to get into the crank case. I hope this isn't the problem, but it is another possability.
Howdy

[MTS]

If you still have oil in there from when you dumped it in, i would just take the plug out, drain the motor oil and flip the motor upside down let it sit like that overnight let it all drain out...Also,,, if the shop you took it to left the reed cage in there, Get a new shop to do work, that is Pathetic...haha

[42F67N]

my yt125 has bad crank seals sadly so it sits in a lonely corner of my garage.

[90nut]

Howdy, I am 98% sure that the crank seals are OK. It is just the oil I put on the crank to keep it from rusting and freezing up when I had the top end off. So today I am going to go out and pull off the top end, drain the oil and gas and flip her over so the oil around the crank will drain off. Hopefully that will fix it.

42F67N- It is my understanding that you can replace the crank seals in these witout splitting the cases. not 100% sure if thats true or not though.

[90nut]

Howdy- I think your onto something here! I pulled the top end off and the cylinder and crank case was just full of un burnt gas oil crap. So flipped her upside down and drained all that off. Put it back together and still nothing. So I took off the pull starter and seperated it from the case a little ways and pulled it. Guess what, rotates clock wise if you are standing on the left hand/ pull starter side. Fly wheel turns up towards the handle bars. So if you are correct, which most likely you are because you know your stuff, my engine is spinning the wrong way. This is spining the wrong way it won't fire correct?

[Unclediezel]

Yes --Howdy is exactly correct---I thought about that after I mentioned your plate being backwards.Your plate isnt backwards--your flywheel spins the wrong way.Your spark fires at the bottom of the stroke instead of the top. since your reeds only understand how to "Suck in" and "HOLD", (Unlike Intake and exhaust valves, Which each have a function) your fuel charge is already in the exhaust by the time your spark fires.Double check compression one more time after fixing your starter---to make sure nothing has been botched up by a backfire---

[Howdy]

Yep, spinning the motor the wrong way can / will cause it it not fire correctly and or fire on the up swing. This would give you your "Kick Back" feeling.
Howdy

[Howdy]

Yes --Howdy is exactly correct---I thought about that after I mentioned your plate being backwards.Your plate isnt backwards--your flywheel spins the wrong way.Your spark fires at the bottom of the stroke instead of the top. since your reeds only understand how to "Suck in" and "HOLD", (Unlike Intake and exhaust valves, Which each have a function) your fuel charge is already in the exhaust by the time your spark fires.Double check compression one more time after fixing your starter---to make sure nothing has been botched up by a backfire---


Actually you would fire at the bottom of the stroke at all. Example: If it is set to fire 12 degrees before TDC then when you spin it backwards it would fire 12 degrees after TDC. The only way you can get it to fire at the bottom of the stroke would be to have a sheered / missing keyway.

I have to dissagree with the fuel charge being already in the exhaust because of it spinning backwards. The design of a 2 stroke wouldn't allow this. I know because I had a 87 Tecate that the flywheel was put together wrong ( magnets were glued in 1/4 turn wrong ) and it ran backwards. This was discussed in detail on the 3WW forums a few years ago.
Howdy

[90nut]

Well I am going to wrap a rope around the flywheel and pull it that way to make sure it will run. Then I will tackle re-winding the pull starter, can hardly wait for that. I hate pull starters.

[Howdy]

Well I am going to wrap a rope around the flywheel and pull it that way to make sure it will run. Then I will tackle re-winding the pull starter, can hardly wait for that. I hate pull starters.

While the 125 / 175 pullstarters are harder to rewind than a Honda, they still aren't too bad. If you use the method of rewinding them like I have mentioned here on the forums before you should have much of a problem. As in my PM: Do you have a picture of the inside of yours? If you can get a picture showing the rope as it goes into the inner pulley. This way we can confirm or rule out a problem. ;)

Below is a hand sketch on how the rope should be routed. I sketched it as if you have it off and are looking at the inside of it. Note: The Red line is the rope.
Howdy

[90nut]

Howdy, just read this after I sent you that PM. Mine is definatley wound wrong. My rope goes in and then straight down. So I guess that means the rope is wrapped clockwise around the pulley. I will still get you a pic of it just be sure.

[90nut]

Ok, got a couple of pics fr you guys, Let see if I can get them to work. Ok, i quit who can I e-mail them to to post them for me?

[Kintore]

pmed ya! 90nut

[Kintore]

Here ya go 90nut!:pics: I didnt feel like uploading them to my site. So this works just as good but people need to click them to go to full size thats all.

[90nut]

Ok, re-wound the pull starter the way it is supposed to go. As you guys can see it looks nothing like any other 125/175 pullstart I have seen. Now since I have wound it the correct way the rope will not recoil back in because it gets pinched in the top where it bends around the housing. I guess I am going to have to get a pullstarter off of e-bay cause this one sure isn't working.