Hi chaps.

I have a friend who has just purchased a ys 91 four stroke. It looks similar to the 110 with the big air box on the back.
The problem is getting it started. It's a real pig to start taking quite a while, but when it does finally start it runs very well.
The plumbing is all ok and so is the fuel and plug. We know the motor is getting fuel as it drips from the carb once primed.
I have 2 YS 140's one is a pressurized tank sport and the other is a DZ. Both of which are a pleasure to operate and start.
As I am used to running and setting up these engines I am at a loss as to why this particular engine is so reluctant to start.
Please can anyone shed some light on this, am I doing something wrong but can't see it.

James.

switch the glow lines sounds like that are backwards...

would it even start if they were reversed? Even though it takes ages to start there is pressure in the tank. The reason I know this is because I took the engine fuel feed off just to check and fuel shot out. Would that happen if the fuel lines were back to front.

The fuel tamk would not pressurize if the lines were reversed. I have 3 of the 91ACs and they are as easy to run as te rest of my YS engines. If takes a lot to get it started but runs wonderfully after it is running I would look at the easy to eliminate suspects. Make sure it has a YS #5 or an OS #F plug in it and the glow driver is charged and not weak.

If your carb is dripping fuel you might want to take a peek in the regulator for debris and gelled fuel.

Sounds to me like it's just taking a long time to get fuel up to the carb. Once you do, it runs OK. Make sure the check valve is a YS valve, not one of the Tettra brands, or whatever that other brand is. The YS valves work on an entirely different principle than the others, so if you have a different brand it might be preventing the tank from pressurizing as quickly as it's supposed to. If you aren't sure, take one off an engine that's starting easily and try it, make sure you get it installled in the right direction.

There is no problem in getting the fuel upto the carb, the check valve is the original that came in the engine box and the plug is good, it's a model techincs super cat 4 stroke with a good strong glow driver.
Could there be any internal problems with the engine that would not allow the fuel to reach the combustion chamber.
The engine is brand new in the box and has only had 3 tanks of fuel through it, and it was a real pig to start for the first time too.
The last time we tried to start it it took 20 mins, when it did eventually start it was with one hell of a back fire.
Can we check anything internally????

I am not familair with that plug, but I can tell you that I had put a different four stroke plug in one of my YS engines and it gave me fits until I put a YS or OS #F plug back in it. The YS and OS plugs are supposedly the exact same plug and they are what you want.

If you are getting fuel to the carb the rest of it's journey is not easily blocked. It goes down to the crankcase and then up into the airbox and into the cylinder once the valve opens. New engines are good for contaminating plugs with microscopic bits of metal as the parts wear in. Change the plug and let us know if it help or if there is no change.

We changed the plug today for an OS F and re set the needle valves and regulator, It started better and ran more consistant. When I stripped out the original tank I found a leak and the bung wasn't holding pressure. I'll keep you posted on the performance, just needs some more running time. Just out of interest, do you have a list of modifications that have been carried out on the DZ 140's. It would be good to see what has been done to my motor and if there is anything outstanding.

Thanks for the help so far Pete.
Take care.

James.

Glad it's running better for you. Have a Boddingtons for me.