Modern Buddy

I need a little help. My 2008 Roughhouse died on me while I was out riding the other day. It seemed to be running fine, the engine sounded good, it felt like it had plenty of power, it had over a half tank of fuel, and without warning it just stopped running. The battery and spark plug are both new. What should I be checking?

I would check for spark first, to be sure the ignition is working (or not).

You need air, spark, and fuel. Air is pretty much guaranteed unless your automatic choke suddenly decided to goof up. Will it start, later, when cold? If so, could be choke. If not, concentrate first on ignition.

With the plug pulled, you'll want to check for a bright blue-white spark on the plug, not orange, which is weak.

If you get any spark then you can eliminate a lot of electrical things. But the ignition module/coil, or spark plug, would be my first guesses.

As for fuel, as long as you really have fuel, it should fire at least somewhat. Unless the carb got plugged up with gunk and isn't passing any. Another culprit is the vacuum operated valve which allows fuel to flow from the tank when there is vacuum (when the engine is turning and creating a vacuum).

Of course the question has to be asked. Are you sure you didn't hit the kill switch accidentally?

Yep Im sure

Thanks. I'll check the spark and let ya know how that turns out.

Update: I checked it last night; I have a good blue-white spark.

Keck wrote:I need a little help. My 2008 Roughhouse died on me while I was out riding the other day. It seemed to be running fine, the engine sounded good, it felt like it had plenty of power, it had over a half tank of fuel, and without warning it just stopped running. The battery and spark plug are both new. When I try to start it now the engine doesn't turn over. What should I be checking?

Got fuel? Vacuum petcock opening? Is it flooded?

I have plenty of fuel, and it's not flooded. I will need to look at the petcock.

Guess I should have asked do you have fuel to the carb?

I just tested the petcock and it's working well; the carb has fuel. Since that seemed to be ok, I checked the compression and it's sitting at about 60 psi, which is low. (It's supposed to be around 100 right?) Is 60 psi low enough to cause the bike not to start? I'll continue reading up on small engines and using the garage manual but if you guys have any more suggestions, I'm all ears.

60 psi does seem low, but I don't know if the motor would start with 60 or not. I have a feeling it would, but maybe lack power.

I am guessing, but I think you should get a reading closer to 100. But I have never checked mine. However, the RH50 compression ratio is something like 6.5 : 1, so psi reading won't be too high even on a known good engine.

Make sure you hold the throttle wide open when you do the test, or your results will not be accurate. And kick it over several times (or use the starter) to be sure you get a peak reading.

How did you verify that you get fuel to the carb? Have you considered putting just a few of drops of fuel in the sparkplug hole, reinstalling/connecting the plug, then trying to start it?

If you do this, use very little fuel. A half teaspoon full is more than plenty. Then, turn the motor over briefly without the plug (too eliminate possibility of bending the rod if you got too much fuel in). Then reinstall the plug, connect the plug wire, and try to start. If it fires a few times then quits, I suspect you still have a fuel flow problem. Or maybe a choke problem.

If it still won't fire at all then perhaps compression is too low, or ignition is still an issue. As long as it is getting air...

By the way, does anyone know if this is a reed valve engine? If it is, could the reed have become damaged?

Been following this for some time now. 2008 my initial thought was rings. Now I am still thinking rings. 2T have 2 rings at the top of the piston, they take lots of abuse and eventually wear out. And unless they are broken or you have some thing to measure them you can't tell by looking at 'em. With 5 years on yours there due to be checked/replaced. From your description it sounds like ring failure, gas'es are blowing by the rings, kills the compression.

OldGuy wrote: How did you verify that you get fuel to the carb?

I checked the auto cock by applying a small amount of vacuum to the line to make sure fuel was flowing through both it and the fuel filter -- it was. I then loosened the carburetor draining screw to make sure there was fuel in the carb. That also looked good. I've since taken the carb off and disassembled it for cleaning, but it doesn't look like it needs much work. I'll spary some cleaner in it, blow it out, put it back together and try putting a little fuel in the spark plug and see how that goes.

If that doesn't work I guess I'll be taking a look at the rings.

This is the carb before cleaning

The carb is clean and back on the bike. I put about half a tsp of fuel in before I screwed the spark plug back in but no luck. I guess it's time to read up on how to check the piston and rings.

It turns out that one of the piston pin snaps found it's way between the piston and the cylinder.

Bummer; but glad you found the issue.

Seems like a good excuse for a performance increase using a larger cylinder kit...

Whoa that's a definite cylinder replacement issue. Was hoping it was just the rings, lot cheaper and easier to replace than the whole kit.

I guess I am too late to chime with...."your compression reading is WAY low, dude."

I recently checked my 2009 RH50 compression. She has 10k miles on her, and the compression reads 130.

Good luck with the fix!

You were spot on in saying my compression was low. I've since fixed the scoot (twice now because I soft seized the engine by running to lean oops) and my roughhouse is running like a dream.

Since I started this thread I have replaced the top end with a 70cc kit, installed a 19mm dellorto carb using 96 main and a 38 idle jets, modded the stock air box a bit, repacked my prima pipe, made an air scoop for the engine shroud intake (I need to install a temp gauge to see if that mod is actually making a difference), and I have the 50cc NCY transmission kit on it's way. Once this thing shifts properly it's going to be a beast.

After the clutch and variator have been replaced I'm going to start in on the handle bars and controls. I'm looking to do something similar to the 110 rattler.