i purchesed my first ys engines the two lines at front of engines go where?

Care to tell us WHICH YS engine model you have? Makes it easier to help.

Didn't then engine come with an instruction sheet? It is explained pretty well there.

Basically one lin eis fuel supply from the tank and one is pressure to the tank. It is also very important to make sure the check valve is in the right line and facing the right directions.

Any leaks in you fuel tank or lines will cause issues too.

Once the engine is plumbed correctly though it will run very well and be very reliable.

Since you didn't say, I will assume that you have YS 4-cycle engines. The line on the same side of the engine as the needle valve is the pressure line to the fuel tank. It MUST have a check valve in it,the enginewon't run without one. The other line is the fuel supply line from the fuel tank and should have a filter in it. If you have neverrun a YSengine before, look here for a primer on tuning them. They don't tune the same as other engines you may be used to.
http://www.patternflyer.com/troy/?page_id=13
Paul

+1 for reading the above link, in it's entirety, before trying to start your engine. I followed everything on that page to a 'T' and have been very successful in running my first YS. If you take the time to do things properly you will be greatly rewarded =)

<span style="font-size: larger;"><span style="font-family: Comic Sans MS;">Remember to read the instructions on tuning, it gets you almost there, If you start to mess about it will only cause heart ache and hell for you. They are lovely engines but many have problems with them because they do not read the tuning instructions and take the fittings etc for granted, they do a shoddy job.

We went to Spore for a F3A meet recently and one of the guys had a dead stick on his 170 during the first heat. I told him to change the plug but he decided not to and tuned the engine up 'nicely'. Heat 2 was a failure ... he got nothing for 2 heats. He changed the plug and then she was sweet. Leave nothing to change with the YS. Its not forgiving when you take her for granted. Other than that, its easy to run.
</span></span>