Moped won't go

Idles great. Runs, dosent stall when I come to a stop, etc. Takes off from a stop fine. as I drive it, and apply more throttle the bike bucks and does not want to accelrate, it will try to go faster, but it's as if somehting is holding it back.

Does the same thing on the stand, if I open it all the way up, it seems to hit a poin ttoward the middle where it's not getting something that it wants, gas maybe? Float needs to be adjusted?

So far I've -

Cleaned the carb well (multiple times)

Added a new fuel line and fuel filter

Removed and cleaned petcock.

Changed tranny fluid twice

New Spark plug

Clutch looks ok upon visual inspection (nothing broken, rattling around and pads look OK, no grease or oil)

Back brake is not dragging, etc.

Chain is adjusted properly.

All suggestions welcome.

Re: Moped won't go

You don't mention the gas tank, so first, I'd make sure there's no crap in there and that you have good fuel flow.

Next, see if it runs better with the choke on. If it does, this means that it's either getting too much air or not enough fuel--probably due to either the wrong or no air filter, or a fuel delivery problem.

If that doesn't solve anything, take off the air filter (assuming there is one) and see if it runs better. If it does, it's either getting too much fuel or not enough air--you may need a smaller carb jet, or your air filter may be clogged.

Hope this helps!

Re: Moped won't go

Thanks Gabe, Gas tank is not rusty, I'd had the petcock off and flushed the tank with some old gas. there was rust built up in the petcock screen but I cleaned that out. Flow to the carb from the tank is OK.

I did try engaging the choke while it was running and that acually caused it to bog 'worse', no accleration at all.

There is no air filter on this bike. I was running it on the stand and covered the intake with my thumb to restrict the air comming in but that also made it run worse.

Re: Moped won't go

Try lowering the clip on the needle valve one slot and see if it helps. It may be starving for fuel when you get into the secondary circuit of the carburetor.

Re: Moped won't go

im not a pro but it almost sounds like your timing is off

Re: Moped won't go

no, don't you raise the clip to make it leaner? that lowers the needle more into the needle jet, restricting a little more gas flow.

Re: Moped won't go

Patrick Mattison /

before you do that, check your exhaust. make sure it's not clogged

Re: Moped won't go

my jawa used to do this, what i did was,

adjust the timing

put in a hotter plug

it seems to run great now...

give that a try!

good luck,

colin

Re: Moped won't go

I agree with Patfark

Check the exhaust pipe it may be plugged . At one time this bike ran the way it was setup. So I doubt the carb setting was off. Check usual basic wear items points plugs and a carboned up exhaust port.

Re: Moped won't go

What plug are you using? I have the standard Champion L86C - Idles really well with that.

I thought there was no timing adjustment for the Jawa, there is a big warning sign when you take off the cover that says, no servicable parts, do not touch anything in here (or something like that) I think the Owners manual says the same thing, I'll check it when I get home.

Re: Moped won't go

I thinkthe original post was saying basicly to raise the needle up/lower the clip one notch, this would increase fuel flow.

The vertical lines represent the needle -

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- <clip is here now

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change it so it looks like this

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- <move clip down/neddle up

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Do I have the concept right? The second position would cause the needle to seat higher allowing more fuel in.

Re: Moped won't go

Hmm, browser messed up my drawing, one more time

Before

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..... clip is here

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after

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..... move clip to here

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.... this raises fuel content

Re: Moped won't go

would this show up at higher revs? It dosent seem clogged intha tit runs great at lower speed (idling on the stand). I did try to pull out the sleeve fromthe exhaust but couldnt get it out. I guess I can try it again, if the needle thing doesn't help.

Re: Moped won't go

One other thing, when I replaced the fuel line I left the new line a little long. The line dosent run straight down, it kind of lays over so there is a flat spot. would this slow the flow to the carb or does suction come into play when it's running? I can shorten it up a bit, but I didnt think it would matter. Let me know if it does.

Re: Moped won't go

I think he needs the airbox opened up. It sounds like 4-stroking to me. Try letting more air in. don-ohio

Re: Moped won't go

Try restricting the carb intake a little more. Cover half of it with your hand and see if that helps or gets worse. My Puch has a similar problem and covering up half the intake helped. And since I just moved up from a 48 to a 50 jet, it's a little worse now.

Chas

Re: Moped won't go

With no air filter it is probably running too lean at the top end.

Can you put the original air filter back on?

Re: Moped won't go

It dosent seem to have an original air filter, the jawa has this weird thing (see photo) where it has a rectangular box that sucks air in, then thru the frame, thru a rubber tube and into a plastic cover and into the carb. There dosent seem to be a place to put a filter. I'd thought about trying to stuff a sponge into the rectangular bit but I've seen a couple of posts here saying they didnt think the jawa has an air filter.

I did try covering the air filter with my hand and choking the carb while it was running but that made it bog worse, no accelration at all.

I moved the clip on the throttel needle down on notch but now I'm having trouble starting it. I'll update when i get it running again.

1159195771_foto04.jpg

Re: Moped won't go

I found that this made it worse. I tried covering it while it was running on the stand and that almost stalled it. I'm having a problem now (after moving the the throttel needle up/clip down one notch) where it wont start and I'm thinking it's a fuel flow problem. there's a big air bubble in my fuel line and the bike wont start. I'll check it more this weekend. Could be petcock clogged, float valve stuck closed, etc, etc... I'll work thru it, get it started again and see if moving the clip helped (or wether it was a fuel flow problem to begin with) and update.

Re: Moped won't go

The air bubble in the fuel line does not mean anything and will not effect the operation of the carb as it is a gravity flow system and fuel will just flow past the bubble.

Have you checked the carb float bowl vent? It needs to be clear and open for fuel to flow to the float jet.

Have you cleaned the muffler yet? Have you removed the head and checked the exhaust port? They could both be plugged up if the previous owners were using dino oil.

Re: Moped won't go

Bleck. Now the thing wont run at all. Cant start it. It sparks when I hold the plug against the engine, if I remove the fuel line at the carb, fuel flows thru it. I just added a new fuel filter (and fuel line) so no rust or gunk should have made it's way into the carb but it wont fire up.

Whaaaaaaaaaaa! This isn't any fun any more. I'm thinking stuck float needle but why? I thought the filter would clear up all those bullshit problems.

: (

Re: Moped won't go

Have you tried a little starting fluid in the carb? If it runs after you shoot some stuff in it you'll need to clean the carb again.

Something could have gotten in the carb before you added the filter.

If it doesn't start after you shoot it with starting fluid you could have a coil with a weak spark.

Chas

Re: Moped won't go

Actually I did try the starting fluid in the carb, and it did not start, but I was thinking that maybe the fluid has gone bad, I've had that can around for probably ten years. I'll pull the carb apart (again) and flush it.

I'll keep the 'weak spark' in mind. My biggest nightmare is trying to scrounge up parts for this bike so I hope it's not the coil.

Re: Moped won't go

I had a Babetta , I had a similar problem when I accidentally overdrilled my jet - grabbed the wrong wire size. You are running too fat or your exhaust is plugged with carbon . You may have a weak spark under compression just for grins close the gap a few thousandths if this helps you have a weak spark. Of course check the timing and coil connections etc The coil is strange but fixable - but you have to cut it apart.

Re: Moped won't go

would the exaust being plugged cause more of a problem at higher RPM than at lower (idle). When it was running, it was idling very nicely. I've tried to pull the sleeve out but coudn't get it. I'll try and have another crack at it after I get it started again. We'll see what happens with the coil etc.

Funny, if I'm going to have this much trouble with a moped I may consider scrapping it and getting my self an old Harley to work on. I figured this would be 1,2,3 and I'd have something to putz around on. What a headache.

Re: Moped won't go

Just disconnect the pipe from the engine and see if it'll start.

When I got my Jawa it ran great for 2 days, then 30 seconds after I started it it died. I took apart the carb several times thinking something was in the carb. I was finally able to start it after pedaling my ass off for 15 seconds, but it didn't have any power and I could only keep it running at high rpm and as soon I let off the throttle it would die. Then it eventually wouldn't start at all even though I had spark at the coil. When I found a coil for it and put it in the spark was way brighter than the old coil.

Are coils that hard to find for Jawas?? I was able to find one in a week or so from someone on here a few months ago.

Chas

Re: Moped won't go

Make sure the jet isn't plugged. Clean the carb.

Re: Moped won't go

I was wondering is your coil the cylinder type or is it square shaped?

I have the square type which has the electronic ignition.

The cylinder type has points??

How about checking timing??

Chas

Re: Moped won't go

will do. Tks.

Re: Moped won't go

I'll post some snappies. I'm pretty sure the coil is a cylinder. I'm shit scared to mess with the timing. Never adjusted points before and I dont want to try it. I still havent gotten the carb back off for another cleaning so I dont have any kind of a progress report. I'll think about timing/coil etc after I clean it again.

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