Yager is running rough

[Shooter]

I mean really rough. Thought it was bad gas. It is not. When riding it bucks and jerks anytime I try to accelerate quickly.  Last time I rode it it got really bad.  Rode last 10 miles home at about 25 mph. Any time I tried to go faster, It would start jerking and felt like it would just shut down. It never did and now I need to have someone look at it.  Any ideas what could be wrong.  Belt? It only has 3100 mile on it.  I have changed the gas and put in a new spark plug so far.  Need help.

[Yager200i]

Can you more fully describe what the problem is?

Is the engine bogging or bucking?

FYI, mine is starting to do that, as well. I believe it's the ignition coil starting to go, as it only happens under hard acceleration with the new Pulstar spark plug, which stresses the ignition coil more to get a hotter spark.

Try reducing your spark plug gap down to 0.4 to 0.5 mm and let us know if it starts running OK. If so, it's an ignition coil problem, it can't generate enough voltage anymore to jump the usual 0.9 mm gap.

If you've still got problems after that, we'll try something else to narrow it down.

[CROSSBOLT]

Have you drained the puke tube? Have you initialized?

Karl

[Yager200i]

Here's a new one for you... I found the cause of my stumble. The spark plug wire goes through the frame member before it curves over to the spark plug... and it'd worn the insulation. Not a lot, but it was enough that when I put that new Pulstar HE1HT9 plug, which works the coil harder to get a hotter spark, it blew a tiny, tiny hole through the insulation and it was intermittently sparking to the frame.

Not sure why it would only do it at 6000 or so RPM under heavy load, though, and not higher or lower RPMs. I'd surmised that it was due to cylinder pressure increasing spark gap breakdown voltage just enough, but it's just a guess.

5 closely-wrapped layers of electrical tape (which is equivalent to 10 layers, since each layer is half-overlapped) on the entire length of the spark plug wire fixed it right up. No more stumble.

[Shooter]

 If I start to excelerate to much the bike seems to bog down for a second and then lunges forward. If I back off it usually settles down. Yesterday It  got really bad and I couldn't really go much faster than about 25 mph.   Bogs down then tries to lung forward. It happens every I try to go a little faster.  That's the only way I know how to describe the situation.

I have no idea what the puke tube is??  I am not real mechanical. I usually only do the basics, like oil change, spark plug and air filter. Once I get into the engine I am pretty much lost. All help is greatly appreciated.

[Yager200i]

Yeah, sounds exactly like what mine was doing, only worse.

Ok, first, pop the spark plug wire off the spark plug and off the ignition coil. You'll have to take out the Met-In box (the helmet box under the seat), but you don't have to remove the seat to take that out. You'll find four bolts (one at each corner of the Met-In box), I think they're 10 mm, and a large Phillips-head screw just beneath the seat hinge. Take those out, then lift out the Met-In box part way. You'll see an electrical plug for the Met-In box light on the left-hand side of the bike. Unplug that. I leave mine unplugged. Then lift out the Met-In box and set it aside.

On the left-hand side, you'll see the spark plug wire. As you're taking it off the spark plug, you can twist it back and forth a bit to get it loose, but don't twist it around and around like you're unscrewing it from the top of the spark plug, you'll break the wire internally.

The other end, on the ignition coil, just use your thumbs to push down on the boot evenly all the way around until it pops loose. There's some paint / glue / whatever on there that you'll need to crack first, so it's a bit hard at first, but comes off with firm pushes after that.

Then thread the spark plug wire down through the gap in the frame and pull it out, holding the other hoses out of the way to provide clearance.

Inspect it very carefully... you'll likely find a wear spot right where it goes through the frame. If so, you'll likely find a microscopic hole in that wear spot. If so, wrap that spot and a few inches to either side of it with about 10 layers of electrical tape to insulate it.

Get out your digital multimeter and check the resistance of the spark plug lead... it should read about 13 KOhms.

Then check the resistance of the primary side of your ignition coil. On the coil, you'll find a plug. Unplug it and test the resistance on the pins on the coil. It should read about 0.6 Ohms. (Yes, only 0.6 Ohms, not KOhms.)

Then take out your spark plug and check the center electrode resistance. It should read about 5 KOhms.

Then plug the spark plug wire back into the ignition coil, plug the 12 volt electrical back into the coil, plug the spark plug into its boot, rest the shell of the spark plug against the engine, turn on the key, turn on the kill switch, and crank the engine. You should see a purplish-blue spark.

If that all checks out, then turn off the key, unplug the spark plug from the wire, put a light coat of copper antiseize spark plug compound on the spark plug threads, thread the spark plug back into its hole by hand then snug it to about 12 Ft-Lbs torque, unplug the spark plug wire from the ignition coil and thread it back up through the frame, in reverse of how you pulled it out (it's the only way it'll go back in), connect it again to the ignition coil and push the boot onto the coil hard, hook the spark plug wire back to the spark plug, and reply to this post letting us know what you found.

[Yager200i]

As for the puke tube, if you look on the left-hand side of the bike, just ahead of the variator casing, you'll see a clearish plastic tube with a black knob on the end of it. Get an oil drain pan, slide the clip back a bit, then pop that black knob out of the end of the tube. A bunch of water and white gunk should drain out. Let it drain for a while, then put the plug back in and slide the clip back in place.

I actually put a small bottle at the end of the plastic tube, so I didn't have to drain it so often. Works really well.

[Shooter]

Yager, I appreciate your input, but I will have to have someone with more experience tackle this job. It may sound simple to you, but it is something I would probably cause more damage if I tackle this.
 I may have to ride the scoot 17 miles or so to get someone to help me with this.  Will I cause any more damage if I ride slowly to my mechanical friend? 

[Yager200i]

Without knowing more about what's wrong with it, it's hard to tell, but most likely not. Just take it slow and easy, don't try to rev beyond what the engine's comfortable with.

[disccop75]

I was having the exact same problem!! I will try to wrap the spark plug wire and see if that helps.  The other problem I know I'll have is that my scoot has been sitting for well over a year.  How can I drain the fuel to put fresh in?

[Yager200i]

When I got a bad batch of fuel from Costco (had tiny particles in it that were smaller than 12 microns, thus they got through my 12 micron fuel filter and coated the intake and partially plugged the fuel injector), I stripped the bike from the air cleaner to the intake valve, from the fuel tank to the fuel injector, and cleaned everything.

To drain the tank, I'd previously created a suction device for single-person brake fluid changeout. It's a reversible aquarium air pump. I use it to create a suction in a glass container, which then sucks the fluid out of whatever I'm working on (brake system, fuel tank, etc.).

That's what I used to suck the fuel out of the tank. Then I cleaned the tank, and reversed the aquarium pump to blow air into the glass container, which pushed the fuel out. I strained it through a doubled-over coffee filter and back into the tank.

An aside... you shouldn't need to drain the fuel tank... there are a couple things you can do. Put about 2 ounces of acetone per gallon of gasoline. That'll re-liquify any varnish in the tank that's settled out and clean out the tank. Put a 12 micron fuel filter in the fuel line before running the bike, to filter out any chunks. I use Wix 33031 / Napa 3031 filters, they're metal bodied and can withstand 60 psi pressure.

Then get a Fitch Fuel Catalyst and put it in the tank (don't put it in through the fuel filler hose, it'll get stuck. Take the floor of the scooter off, take the fuel pump cover off, and drop the Fitch Fuel Catalyst directly into the tank). That'll help to keep the fuel fresh for long periods of storage, and will help to improve your fuel mileage when you do ride it.

[ScooterWolf]

Don't think I can add anything that hasn't be brought up as a possible answer or cause of the problem. Some of what you describe sounds like a problem I had with my  old Yager's roller weights. They were somehow deformed in shape and had to be replaced.

Hope you're able to fix the problem.

-Wolf

[Louder North]

If I start to excelerate to much the bike seems to bog down for a second and then lunges forward. If I back off it usually settles down. Yesterday It  got really bad and I couldn't really go much faster than about 25 mph.   Bogs down then tries to lung forward. It happens every I try to go a little faster.  That's the only way I know how to describe the situation.

I have no idea what the puke tube is??  I am not real mechanical. I usually only do the basics, like oil change, spark plug and air filter. Once I get into the engine I am pretty much lost. All help is greatly appreciated.

Shooter, did you ever solve this problem?  It sounds a lot like a problem I am having and I now suspect a malfunctioning fuel pump.  A very simple test is to use a multi-meter to measure the resistance across the two leads from the fuel pump - it should measure 1 ohm only.  Mine came out to 2.7 so I think it is too weak to supply the necessary fuel pressure when under load.  Thats my theory anyway. 

[JJJoseph]

It sounds a lot like a problem I am having

Count me in - now there's three of us.  I'm getting the feeling that there's something wrong with the Yager 200i!  I've been through all the systems like you have.  This Yager has only 5,000 miles and runs so rought. Unfortunately, for these machines, there's no diagnostic tools.

[CROSSBOLT]

Well, sounds to me like the vacuum vent valve is stuck closed. Open gas cap. Then if that lets it run, vent the gas cap. Had the same problem on my Yager in 2009 or so. Removed valve and re-plumbed to rear by tail light. Even stuck a filter on the hose!