1993 Jawa 210 No power with rider?

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1993 Jawa 210 No power with rider?

Postby rgp717 » Sat Sep 08, 2007 8:29 am

Hi, I'm glad I found you all. Just purchased a 1993 Jawa 210 for my 14 year old son to take to school. It starts up (though it takes effort to get it going), and it runs like crazy on its center-stand. But the minute my son tries to ride it, there is no power (we're talking 3 mph tops). The motor just won't get any rpms.

I checked gas, and gas lines, and I'm pretty sure it's ok. It's my strong belief that the carb is ok (could be better, but ok). I pulled off the exhaust pipe but that made no difference (though the noise was deafening). Compression is 110.

Some hints: The previous owner bragged about replacing the clutch plate (is there such a thing on a moped). Could he have screwed something up there? If it were a car, it feels like there is no spark advance to me? Finally, I noticed during while my son was cranking it over, that puffs of air/gas were coming out of the carb, and then once it started, no puffs coming out anymore. Any help would be very much appreciated. Thanks.
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re: 1993 Jawa 210 No power with rider?

Postby pehuskey » Sat Sep 08, 2007 10:07 am

How do you choke that model?
It sounds like the choke could still be engaged
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re: 1993 Jawa 210 No power with rider?

Postby steamboat » Sat Sep 08, 2007 10:35 am

Here is the link to a Jawa 210 workshop manual in our repair section. Hope this helps. Jim
http://www.mopedriders.org/article_view ... fldAuto=17
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re: 1993 Jawa 210 No power with rider?

Postby rgp717 » Sat Sep 08, 2007 12:34 pm

pehusky and steamboat -- thanks for the replies. I already found the links to the various manuals, and I'm a good wrench, but my diagnostic skills are not so strong. So, I'm hoping for some educated guesses from the members here.

Choke - there's a push button located on the carb; push it and the choke engages. Reving the throttle releases the choke. The choke is wide open (no choke), motor is warmed up, and we still have the problem.

New hint: My son and I cleaned the carb (again) and exhaust this morning. No improvement. However, I was checking to make sure the cylinder bolts were tightly secured to the cylinder, and I'm pretty sure one of them is stripped. Contrary to the picture in the manual (http://www.mopedriders.org/article_view ... fldAuto=17), my head only has 3 bolts? Two on the bottom corners and one in the middle (just below the sparkplug).
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re: 1993 Jawa 210 No power with rider?

Postby steamboat » Sat Sep 08, 2007 12:41 pm

Check your compression and let us know. Jim
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re: 1993 Jawa 210 No power with rider?

Postby rgp717 » Sat Sep 08, 2007 2:22 pm

Compression is 110, which doesn't sound too bad to me. Especially, since it's just me kicking the pedal (throttle wide open). Also, we started the motor (starts easier thanks to the carb cleanings), and while the motor was idling, I sprayed some starter-fluid around the seal of the cylinder. No change is speed or rpms, which I think seems to indicate the compression is OK and the seal is decent.

Still puzzled. Is there a spark advance system on a moped?
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re: 1993 Jawa 210 No power with rider?

Postby steamboat » Sat Sep 08, 2007 3:10 pm

2-stroke mopeds operate with fixed timing but it must be set correctly. Some if not all Jawas have an electronic ignition system which I know nothing about. Jim
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re: 1993 Jawa 210 No power with rider?

Postby Houdini » Sat Sep 08, 2007 4:11 pm

My ped had this same exact problem, because it was getting too much gas, and not enough air. Down jet, or clean/ replace your airfilter.
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re: 1993 Jawa 210 No power with rider?

Postby niss » Mon Sep 10, 2007 3:04 pm

Pull the clutch cover off, I had a problem like that with my jawa (one of many) when i finally parted out the engine, just clutch shoes with no meat.
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re: 1993 Jawa 210 No power with rider?

Postby rgp717 » Wed Sep 12, 2007 7:45 am

Houdini, good idea. In fact, my float wasn't doing it's job properly and gas was leaking in the carb. Took the dang carb off, cleaned it and fixed the float problem. And it seemed a little (very little) better, but still no guts.

Niss, I did remove the cover (the guy I bought it from said he replaced the clutch (and I beleive him).

More description of my problem: The moped starts easy (one or two kicks and its running). If its on the center stand, then twisting the throttle produces great results (the motor revs and the back wheel turns like crazy). But if I take it off of the center stand, then twisting the throttle gets nothing (half the time, the engine konks out).

It is NOT the following: I twist the throttle, the motor increases rpm, but I don't go anywhere. If it were, then clutch would sound like the problem. But this is not what happens.

I can't get any power out of the motor when it's off of its center stand and under load.

By the way, thanks for everyone's help. I've been following up each suggestion with an evening in the garage and checking your suggestions on the moped. Any more ideas?
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re: 1993 Jawa 210 No power with rider?

Postby TowerTower » Wed Sep 12, 2007 2:17 pm

These symptoms are most often caused by either a) a stuck choke or restricted air supply and/or, less likely, b)a severely restricted fuel supply, or c) over grinding ports, jug, piston, etc

The most likely cause is a slide that has been reassembled in reverse, a scored choke, bent needle, or any number of assembly defects. The only way to know for sure is to take apart and reassemble ensuring all parts are OK and properly oriented.

Its fairly easy to verify the fuel flow, right up to the float needle. ensure the needle is cutting off and opening correctly. Visually inspect the needle to make sure the taper is perfectly flat and not worn to a dimpled point.

Timing would be a good guess also. By "timing" I mean in the broadest sense, especially if the PO had somehow messed with the generator/alternator, or with the jug or ports. Since I'm not at all familiar with Jawa, you'd have to see if changing clutch parts requires unfastening any electro-mechanical parts. If so, then make sure they have been bolted back correctly. Timing is also effected by the space between the jug and crankcase, so if this has been either reduced or increased, a defacto adjustment was made and perhaps hasn't been properly compensated. Finally, if the PO had done any head, jug or port grinding, that could have severe implications on timing.
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re: 1993 Jawa 210 No power with rider?

Postby bryanofmyrons » Wed Sep 12, 2007 11:56 pm

Might be a dumb question but can anything bigger than a pencil go through the exhaust port? Also the end of the "stinger" in the muffler is notorious for getting blocked off by a flake of carbon
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re: 1993 Jawa 210 No power with rider?

Postby TowerTower » Thu Sep 13, 2007 9:38 am

Almost forgot one more liklihood - the reed valve is also involved in "timing". If the reed material is cracked or not sealing properly, a key symptom will be lack of power under load.

Don't know if Jawa's have reeds, but if they do, unbolting the intake manifold would be the way to check the condition of the reed.
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re: 1993 Jawa 210 No power with rider?

Postby rgp717 » Thu Sep 13, 2007 4:47 pm

Thank you all for you many suggestions.

"A slide reassembled in reverse." Interesting. Is the slide the metalic cylinder at the top of the carb? The one that goes up and down when I twist the throttle? How should it go? I've always reassembled it the way I found it, with the large, angled slot in alignment with the carb adjustment screw.

The reed valve is a great idea (same symptoms happened on my waverunner, and it was the reed valves). But this thing does not have a reed valve (already checked).

I've removed the exhaust completely, tipped the bike and looked up the exhaust hole ... it looks fine from this point of view.

I'm about ready to pull the motor out, tear it down and build it up ... just to eliminate who-knows-what as a possibility. Keep the suggestions coming. I refuse to be beaten by a 50 cc motor.
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re: 1993 Jawa 210 No power with rider?

Postby TowerTower » Thu Sep 13, 2007 7:55 pm

Quote: "Is the slide the metalic cylinder at the top of the carb? The one that goes up and down when I twist the throttle? How should it go? I've always reassembled it the way I found it, with the large, angled slot in alignment with the carb adjustment screw."

Yes. The cut-away should be pointing forward to the air intake side and not to the manifold/engine side.
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