My little brother has a YZ85. There is a black oil-like substance coming out of the exhaust pipe. The plugs always come out with this same oil-like stuff. This is our first 2-stroke so we are pretty much clueless. :dunno: Any help would be appreciated. Thanks!
it is getting too much oil or not burning it completely. try running race gas, it burns 10 fold better and doesnt leave as much oil on the silencer.
also your plug may be fouled so try changing that.
one last idea is that your jetting is way too rich, you could try to change the main jets.
hope this helps
Or your fuel/oil mixture ratio is off.
Quote from: alerbaughMy little brother has a YZ85. There is a black oil-like substance coming out of the exhaust pipe. The plugs always come out with this same oil-like stuff. This is our first 2-stroke so we are pretty much clueless. :dunno: Any help would be appreciated. Thanks!
Since you stated that you are "
pretty much clueless when it comes to two strokes hee goes:
First off a two-stroke is what we call a total loss oil system in that it does not have a wet or dry sump lubication system such as the GS500 which has a wet sump system so what does this mean? On the YZ85 you are adding the engine oil to the fuel by one of two means either by having to pre-mix the oil with the fuel or the bike might have an oil injection system that as it is called injects oil into the intake which will in turn mix with the fuel and lube all of the bearings, rings and the like and then the oil is either burned up in the combustion or forced out the exhaust thus the "
oil-like stuff" coming out of the exhaust.
If the bike is using pre-mixed fuel use the highest octance fuel from your local gas station. You do not need any special race fuel, avgas or the like just good old pump gas from your local gas station. Buy quality two-stroke oil such as Motul 800 or Motul 600 and read the bottle since you can not use Motul 800 in an injection system since it was designed for pre-mix only but you can use Motul 600 either way. If you dod not read the instruction you can destroy your motor.
On Pre-mix go with a 30-to-1 ratio or to break it down that is 4oz of oil to 1 gallon of fuel. Yamaha usually list 28-to-1 or 30-to-1 ratio for premix.
Warning!!!! Do not think that by adding more oil to the fuel it will be better when running pre-mix because this will in turn run the motor on the lean side and cook the motor. If you change the ratio of oil-to-fuel from the stock set-up you might have to rejet the carbs so it will run better.
If your bike uses an injection system then the oil pump might be out of adjustment and the pump is injecting to much oil into the motor and this would lead to non burned oil coming out of the exhaust.
Warning!!!! You can adjust the pump but if you do it wrong you will cook the motor!
The oil could also be coming from a oil seal leak between the crank and the transmission and the oil you are seeing is actually transmission oil. This can be checked by checking the level of oil in the transmission. If it is low top it off to the proper level and see if it goes down after you run the bike for a while if it does then it could be a seal.
There is the issue of the carb and is it adjusted to factory specs since if it is not then the bike might be running to rich which in turn will foul out plugs and cause the engine to not burn some of the two-stroke oil due to a rich combustion mixture.
The fuel is at 30:1. Could it just be he's running it to soft or could a hotter spark plug help this out as well?
And one more thing. How do you drain the tank. There is nothing in the manual about it.
I thought that an fuel/oil ratio of ~40:1 is normal for a 2-stroke. Does the manual say that it should be 30:1?? Maybe that is the cause of the fauled plugs and oil out of the exhaust.
The engine shouldn't be revved to low, you have to race it once in a while to blow out the carbon that has collected in the cylinder/exhaust port and to burn the sparkplug clean.
I went to the local shop and they looked at the plugs. They say we're not running it hard enough. For how hard we run it we should run it at ~45:1. We got the fuel out of the tank the suck on a hose and into a bucket way but I still ned to get the rest out of the carbs. Is there some screw I overlooked? Man I'm lost on 2 strokes :dunno:
I'm pretty sure the YZ will be similar to my CR-250. To drain the carb, turn the petcock to off and lay the bike on its side. Use a rag to catch the fuel that runs out of the carb vent. As for the full mix, I run 32:1 which gives me a little richer fuel/air mix than the 25:1 or 28:1 a lot of people run. A little less top-end power in exchange for a little longer span between top-end rebuilds. 40:1 is recommended for my weed wacker, but if you use that in your MX bike, you'll lose a lot of your overrev which is the whole point of a 2-stroke motor IMO. Hope this helps.
Rich
Thanks guys; the bike doesn't "bleed" any now. I guess he just wasn't running it hard enough for the fuel/oil ratio.
2 cycle engines like to be run hard/wide open, dont have to but more prone to foul plugs. try changing plug and running again. :dunno:
might even try a slightly Hotter plug, i had a 73 yamaha DT175 enduro, had that injection crud on it. one day very little oil, next its pumping oil like a feind. finnaly i pulled the control cable for it, drained the tank and blocked the feeder tube for the pump and mixed each tank. never had an issue after that.
so I'm safe to say he wasn't running it hard enough. I'll have him run it higher RPM and see if that helps but the oil-goo has slowed/nearly stopped.