Yamaha Starting Update

I recently posted about my 1980 Yamaha Champ (VERY similar to QT50 Yamahopper) and my problems starting/running.I received it recently after being dormant for 2 years. Did all of the cleaning and flushing and adjusting of fuel delivey, carburetor, and spark plug. Did not however drain and refil oil in tank (its injected) can this go bad too? Anyways after stumbling off of starting fluid and carb cleaner a number of times I found that clearing out the small idle jet did the trick and off I went!

This worked for about 3hrs of riding before sputtering out. I get it home (after LONG walk) to see what appeared to be a fouled plug (no spark) so after purchasing new ones and seeing spark on them prior to installing and attempting to start, it still would not even sputter at all. In fact after just a few kicks I would pull the plug to find it wet with gas and no longer seeing a spark when grounded. I repeated this process several times.

Then suddenly just as it did before, I put in yet another (about 5th) plug and it fired up first kick! Again ran for a couple hours and a good distance with normal engine and transmission behavior, running very strong with decent accelleration reaching 30-33 mph no problem, no excessive smoke, easy restaring after shutting off and just all out FUN! Then of course the same thing happened again! While going at a decent speed it sputtered out to nothing and would not restart even after changing to a fresh plug, I learned my lesson to carry an extra in my little basket. The plug that was merely a couple hours old looked good and clean, not overly dark and rich nor white and hot, just a good gray.

Now I am back to square one with it having gas, compression, air, and clear exhaust, and a visible SPARK before installing, yet, NOTHING! It is NOT the carburetor, it IS getting gas. I have researched and have read about a spark just not being strong enough and once the fuel hits it it is not strong enough to create combustion and is fouling out. Is this possible. It is CDI so no points to check for. Coil and spark plug wire are all one piece but I hear it is rarely the coil. Do either of these tend to fail? Why does it go so good when it goes, and then die out to NOTHING?! I am stumped. YES I have done all of Freds checklist to get it running, which is why I have it narrowed down to the ignition. I have been suggested everything from vapor lock (not it), to dirty points (dont have em), to broken flywheel key (what is it? do I have one with the CDI?) to bad plug (changed it 10 times) bad gas or mix (drained fuel several times, injection works) to bad coil/wire, to bad CDI box, to recently engine gets hot, head gasket changes shape thus losing compression, but this would not account for sparking issue after sitting a long time. But could I use a liquid high heat gasket in place of paper thin metal one? I am going crazy and have no clue! I just want to ride!

HELP!!!!!!!!!!!!!!!!!

Re: Yamaha Starting Update

Josh,I just don't know! From what you just wrote,it could even be a sticking carburetor float or needle valve.Too much gas will drown it out,that's for sure.It only takes a little piece of foreign material to keep your float and needle valve from working properly.And your absolutely positive there's no water in the gas,right?So the carb flooding you out is my best guess.I'm sure the Gurus will answer you now that you've re-posted,and you'll get better advice.BYE!

Re: Yamaha Starting Update

Chris Robertson /

Hi Josh:

<ol>

<li>Are these spark plugs you are using <i>brand new</i>? Are you using the right kind?</li>

<li>You said that cleaning your carburetor fixed the problem the first time and then after 3 hours it stopped working again. Have you cleaned the carburetor again? If your tank is dirty/rusty, it can clog your carburetor up very quickly.</li>

<li>Is it possible your petcock is bad? I've seen them go intermittent where fuel will flow fine for a few hours, then barely come through, and then flow correctly again... The next time your moped dies on you, disconnect the fuel line from the carburetor and verify you are getting a decent fuel flow.

<li>If you've ever removed your flywheel you'll know what the key is: it's a little notch on the crankshaft that fits into a little groove on the flywheel that prevents the flywheel from getting "out of sync" with the engine.</li>

</ol>

Good luck!

Chris.

Re: Yamaha Starting Update

Josh:

The one item you didn't mention was the spark plug boot. These have a resistor inside and can go bad. But as far as I know, they will last a long time and seldom give trouble.

That would be the only other item to check, other than the ignition switch circuit.

Jim

Re: Yamaha Starting Update

It could be the carburator is adjusted wrong.

Deja Vu

It sounds like you are getting too much fuel.

Are you sure the choke is in the correct position ??... (as in ..OFF.. after it warms up?)

Next...

You MUST install an inline fuel filter.

You MUST carefully inspect the float needle valve (in the carb) for wear on its tip and bits of crud letting in too much gas...

You MUST blow high pressure compressed air through the fuel inlet to the carb .. both ways.. after removing the float and needle..

Is the main jet still in the carb? (nobody lost it before you got it?)

Then... clean the air filter in gas (don't oil the filter yet though).

All those checks and fixes are to make sure it isn't getting too much fuel.

Then put a new spark plug in and leave the air filter off temporarily and start it and ride it and pay attention to how it is running.. run it for a half an hour and check the plug color. .

(if you live on a dusty dirt road... make sure that dust isn't going into the carb.. if it is.. you should put the air filter on for the test)

Try all that.

Re: Yamaha Starting Update

Ron Brown /

Josh,

Good post.

You explain that when the ped died the first time, a new plug would show a good spark until you installed it, then get wet and quit sparking. This was almost certainly too rich. 2 cycles can foul a plug faster than you can change it when they are too rich. The second time it died, you mention that the plug was a nice grey color. Was it wet and did you then have the same symptoms you had after the first failure?

I think Fred is on the right track. If you have dirt traveling through the carb, when it sticks to the needle valve you run rich and if it travels to the main jet you run lean or stop.

Keep us posted,

Ron

Re: Deja Vu

If I have done all of the carburetor troubleshooting, and it still wont even stumble off of spraying starting fluid or carb cleaner into cylinder directly, how can it be carb and not ignition related? I will say however when I received it it showed al classic signs of running too rich, excessive dark (carbon?) buildup in cylinder as well as on plug, as well as in exhaust. But when it ran the last 2 times I did run it w/o the filter assembly in efforts to lean it out, and the removed plug was gray and not black (although this was only after a couple hours). Does any of this help diagnose further? Also no one replied to question regarding the head gasket and wether or not the paste stuff used for automobile gaskets. Thanks

Re: Deja Vu

Hi,Josh! Use a proper head gasket and not silicone sealer.Now I went back and read your top posting and the other guys posts and the answer has to be there somewhere.I'll tell you a problem I had with a nearly new ANKUR moped once.Every doggone time I hit a big bump that thing would quit on me.That was,of course,the CDI wire hitting the frame.So it looks like if you have eliminated what we said about it flooding out on you,you're gonna have to run the wiring for shorts or weak connections.If that spark is hot and you have any fuel present,it's gonna pop at the very least.Don't get too discouraged.Even the best mechanics get stumped sometimes and ask for a second opinion.That might be what you need;an ace mechanic to look it over or someone good at electrical troubleshooting.Believe me! From what I've seen of these guys that are trying to help you,it's just a matter of getting their hands on it for a little while.Hope for the best!

Re: Deja Vu

Thank you very much for the reply and encouragement, I must admit I am getting a bit discouraged, but it is so damn fun to ride when its working I just cant give up. There is no choke on the thing either, it is an "automatic" choke so it cant be that. I recently received the original service manual so hopefully that too will help me. I was never told however if 2cycle oil can go bad with age. And if indeed the CDI unit is shorting out somewhere or is bad all together would there be any spark at all? Does anyone think I should replace the plug wire/coil combination piece?

Re: Deja Vu

Hi,Josh! CDIs,like any electrical component,depend on a good connection to work right.That's why I said `weak connection' instead of a broken one.You wouldn't believe what a little rust in the wrong place can do.And any electrical connection can be poor.So,don't give up because you'll straighten it out pretty soon.I don't suppose you live close enough to one of the Gurus to take the bike to them?See ya later!

Re: Yamaha Starting Update

I live in Milwaukee WI. I do not know if it is close enough to anyone associated with this site that has more knowledge with thes than I do. If anyone is near..... HELP!!!!!!!!!!!!!!!

Re: Yamaha Starting Update

Josh! You're not that far from scootertherapy in Madison,WI. E-mail them with your problem if you don't fix it soon.They seem to know their stuff. Here it is: scootert@chorus.net BYE!

Re: Deja Vu

Ron Brown /

Josh,

You are losing me here on your questions and comments about head gasket stuff, starting fluid etc.

Give us a current status.

When you try to start it, does the plug get wet?

Do you have a good, fat blue spark?

Ron

Re: Deja Vu

Ron Brown /

Josh,

You are losing me here on your questions and comments about head gasket stuff, starting fluid etc.

Give us a current status.

When you try to start it, does the plug get wet?

Do you have a good, fat blue spark?

Ron

Re: Yamaha Starting Update

hey i have a yamaha champ too but it is older. i can't get a spark and it doesn't have any points. i got a new coil and it still don't have a spark any help will be nice

thanx

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