YT125 with a weak spark

[generallee2005]

I think I'm dealing with a weak spark on the Stud Duck. Here's the deal, I cleaned the carb & have been thru it 3 times, everything this is good, gas is pumping thru & floats are the best they have ever been. I found a piece of trash in the reeds, so I took them out, cleaned them & rubbed them slightly with the brass brush. I boiled the intake & tube from the air filter to the carb, they are as tight as ever. I've tried using a brand new spark plug, the plug I've been running for about 6 months, & a hotter plug, I think its an 8, I can't get the little guy to start with any one. I got some starting fluid, still nothing. I pull the plugs out & the spark just doesn't look as strong as it has been before. I've tried push starting, it'll turn over good, but it won't pick up & start going. I've got the manual & plan on going thru each electrical check tomorrow or Monday, but from experience is there a simple fix, or something that goes wrong more times than not? I tried to take the ignition coil off the frame to clean the ground, but the screws are rust welded to the frame now, so they're soaking in P'Blaster. I've triple checked all, let the plug stay out for a few hours for the cylinder to dry out, just in case of flooding, the plugs come out wet, but not soaked like a flooded cylinder. Everything was perfect the last ride, & just a quick check list-the gas is fresh 93 octane, kill switch is on, & I'm standing in the superstitious stud duck starting position every time! Drop some knowledge on me guys!

[just ben]

I can't remember if it was my 125 or my 175 but it ran fine one day and the next day I got nothing. It ended up being the cdi. I don't know enough about these bikes to know if it's a common issue or not it's just what I experienced.

[El Camexican]

I've tried using a brand new spark plug, the plug I've been running for about 6 months, & a hotter plug, I think its an 8, I can't get the little guy to start with any one. I got some starting fluid, still nothing. I pull the plugs out & the spark just doesn't look as strong as it has been before.

Get the correct plug for your trike. I think it is an NGK BP6ES, but check that with a manual, an 8 is a colder plug and will not run as well as the 6 (if that is what your stock plug is). Set the gap, make sure the coil wire is screwed firmly into the plug cap. In a dark room (or at night) ground the plug to the frame and pull the engine over. If the spark is blue and crisp I doubt anything is wrong with the spark, try starting the trike again. If is is yellow and weak looking then you are right, something is wrong. Start testing parts.

[generallee2005]

Thanks Ben & El, I've got two of the 6's, I thought the 8 was hotter. I'll toss it since its not, it had to have been in there when I got the trike.

[El Camexican]

Thanks Ben & El, I've got two of the 6's, I thought the 8 was hotter. I'll toss it since its not, it had to have been in there when I got the trike.

I sure hope that's all it takes to get the mighty Stud Duck up and going.

[generallee2005]

Well, I tried pull starting the duck again today with no luck. Its raining so I really only wanted to see if the spark was good since it was darker outside. I believe the spark to be good after all. I did notice the spark plug boot was loose, I didn't know they screwed on/off until I saw it in the manual, so that likely was the cause of what I saw as weak spark.

Yesterday while looking at the carb good, I did notice this:
The carb valve stop caused this, it was not like this when I opened the carb up last year, thoughts on this? I don't like it.

Even more disturbing to me, today I noticed this:
The head looks to be leaking, its hard to see in the pictures. I've got a new head gasket, I guess I'll throw it in. Last year my compression was around 110, I guess I'll go borrow a compression gauge from the local Advanced Auto Parts & check it again. I just really don't want to open the motor, that's a can of worms I'd love to open, but not right now!

When I put the duck away last night I did forget to turn the gas off at the petcock, so today I had a puddle of gas in the floor of the shed, but I assume that is normal? I've never not forgotten to turn the gas off before. After I try to crank the trike, the plugs always come out wet, but not what I would consider soaked. I guess when it comes down to it, the carb is a little box of mystery for me, that is assembled right according to the manual, but I know I've not got any finesse in it. It never sounds to be flooded anyway.

[El Camexican]

Ok, as short and sweet as I can.

Great news on the spark. You can trim off a 1/4" or 1/2" of the wire if there is still some extra lenght. That will expose some nice clean copper wire for you to thread the cap into.

That shiny spot on the ramp of your slide (if that is what you are concerned about) is normal wear and tear from letting the throttle close, no worry

Your may have found your problem thanks to the leak. It is NOT normal. It means that your needle/seat assembly is not working correctly. You should always shut your fuel off to be safe, but because yours is not working it means that your fuel flow is not stopping when the floats get to their pre-set height. Float height is critical to your engine running good. You leak means that when you are driving there is too much fuel in your float bowl. Clean it or change it, set your float height and try starting the trike again

Why are you taking your slide needle out of the throttle slide in the photo? That carb is a PITA when it comes to removing that needle. Put the clip in the middle grove and put it together, It and the cable can stay together when you screw the cap off the carb.