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82 YZ250 dumb questions
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Posted by: stepman
I am used to working on cars and this 2-stroke thing is new to me but, I am willing to learn. I have this bike that I would like to get running so that I can go riding with my son but, can't seem to get it to fire. I picked it up cheap due to the forks leaking. When I got it home, I tried it out to see if it would fire. I got it to fire 2 or 3 times but, didn't let it run because of the coolant leak.
Now I've fixed the coolant leak but, it don't want to fire now. It appears to get fuel as the plug is wet. It has spark, although it appears to be kind of weak. I figured that I would look at compression so I plugged in a guage and I get 70lbs....which is where I get lost as I understand that there is more to a comp test on these. Should I look farther into the comp, or change the 70 dollar coil? 
Any help would be appreciated.
I should also add that this was said to "run when parked 5 years ago"
Posted by: jmics19067
70 lbs of cranking compresion will make it very difficult to start. If the bike sat for 5 years there is the possibility of it only being a stuck /frozen ring which could be a relatively easy / cheap repair. being a 1982 bike and not a 2000 bike makes me think the motor will be worn out and need a good overhaul though.
is the spark blue or orange if the spark is blue you might not need a coil an ohm tester and the right values to check against will tell you
Posted by: originaldirt
Yeah, you're going to need well over 100psi compression to get it to fire. Make sure you did the comp test with the throttle WIDE opem , otherwise you'll get a bad reading on a 2 stroke. Also, try shooting some WD-40 ( my favorite starting fluid) in the plug hole to help the rings get some traction andthen in the intake tract while slammin the kicker to add some flammable jooce to the shebang.
OD
Posted by: stepman
Thanks for the help. I kind of figured the compression was on the low side. My spark is blue and just real weak looking but, I think that I'm going to see if I can get the comp up some before I spring for a new coil. Can't remember if I had it wide open when I checked it or not, guess I'll check it again. (I should know that from working on cars ) Squirted some WD in it last night to see if I can loosen it up some. I'll get out in the next day or 2 and look at it again.
Posted by: handywork
Sitting round for a while will give you fuel probs.Oil accumulates in carb as the fuel evaporates and will give you an oily mix when you go to start again.CDI is good ignition and I haven`t had one fail yet,not saying they don`t but you probably got more chance winning the lottery.Plug I`d guess or maybe cap isn`t biting into lead or corrosion or loose cap on plug.Have you seen it run?Fuel/oil mix should be at least 40/1 thats 4litres gas 100ml oil and will have starting difficulties and performance woes if you used your lawnmower 25/1 or similar mix.Two strokes have lower compression than four strokes hence the lack of torque,as they have a smaller effective compression stroke because of ports in barrell where a four stroke has a full barrell.That`s why they are easier to kick
Posted by: stepman
O.K....let me get more specific. When I got the bike, it had some problems but, I was told that it ran when it was parked 5 years ago. ( I know that doesn't mean a lot when someone is trying to sell something) The "boot" between the carb and the cylinder was cracked so, I replaced that and cleaned out the carb which looked like it ate the air cleaner. It also had a broken needle in it so that was replaced also. Once I got it back together, I wanted to see if it would fire so, I kicked it a few times and indeed it fired. It ran for a second or two and I kicked it again and it fired again for a second or two. Not wanting to let it actually run with no coolant in it, I quit there.
I had a coolant leak in the forks so, I tore into that and repaired the leak. Now, all ready to go ( I thought), I tried to fire it up. Nothin' doing now. Thinking it may be bad gas, I went and got some more gas and some oil and tried again. Still nothing. That's where I am now.
It's been a good while since I have last rode ( about 25 years) so I guess I have to relearn everything. I was thinking that I used to mix about 30/1 but, my book says 20/1. If you say 40/1 than maybe that is my whole problem, huh? ( I could only hope) I'm going to go out in a little to look at it some more but, first I'm doing a long over-due cleaning of the fish tank. I think I'll go get another 2 gal's and bring the mix more in line.
Got a lot to do this week-end....better get busy.
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