new have some questions

manny gouveia /

1st off thanks to all replies in advance.

I jjust picked up a moby 1980 it doesnt start ,seller says no spark and supplied a new CDI I have not installed yet! Before I start tinkering with it I would like to find out what kind of shape the engine is in can someone tell me what compression I should have? Its a 50V I believe. I did a compression on it and only came up 25lbs.

The frame is in great shape and wouldnt have a problem putting some money into it.

I guess my ulitimate goal would be to have it cruise at around 35 mph

.I am totally new to this Motobecane thing but have twisted wrenches for some time. thanks

moped.jpg

Re: new have some questions

Moped Lar (OFMC) /

Compression should be In the 120 psi ballpark.

Re: new have some questions

Pushrod Fifty /

Your gauge must be leaking at the plug hole or your rings are stuck from sitting but worse case you have 90, anything less than that, the bike would have been a bitch to start. I would fix the stock ignition first, just because irs simple and you can go by the downloadable manual and good advice here from the Moby gurus, unless you have experience with electronics and engine timing...i.e. youve done it before.

Re: new have some questions

Hi manny and welcome to the forum.

I am having the same problem with a 77 Peugeot LVS-U3 that is only getting 60psi

I found a conversion formula if you know the compression ratio of your moby.

I is on the moped army wiki page basically it is multiplying the compression ratio by atmospheric pressure. and as far as the lack of pressure on the cyl, it could be a number things like head gasket, worn piston rings, decompression valve leaking (if you have one) worn cylinder all the things i mentioned i had except the decompression valve. And i still have the problem with the low compression.

Hope this helps.

Re: new have some questions

@ manny,

Oh and by the way nice looking moby!

Re: new have some questions

Is the decomp stuck open? BEAUTIFUL bike. Have you tested for spark? (edited)

Re: new have some questions

manny gouveia /

thanks for the quick replys folks!

so 120 is where I should be! correct?

Re: new have some questions

manny gouveia /

> Pushrod Fifty Wrote:

> -------------------------------------------------------

> Your gauge must be leaking at the plug hole or your rings are stuck from

> sitting but worse case you have 90, anything less than that, the bike

> would have been a bitch to start. I would fix the stock ignition first,

> just because irs simple and you can go by the downloadable manual and

> good advice here from the Moby gurus, unless you have experience with

> electronics and engine timing...i.e. youve done it before.

where can I find this downloadable manual?

Re: new have some questions

manny gouveia /

> rob res Wrote:

> -------------------------------------------------------

> @ manny,

>

> Oh and by the way nice looking moby!

thanks

Re: new have some questions

manny gouveia /

> Stephen Keller Wrote:

> -------------------------------------------------------

> Is the decomp stuck open? BEAUTIFUL bike. Have you tested for spark?

thanks NO I have not, It doesn't make sense to me to do the ignition yet without knowing if the compression is ok 1st.

I will check on the decompression tab make sure it is closeing correctly and report back... I have a feeling I am going to sepend alot of time here.:)

thanks guys .

O

Re: new have some questions

120 should have you in good company .

Manuals :

https://drive.google.com/drive/folders/1XZIGaODutDY-NlVuGu-7WwoZTPyHWxPk

Re: new have some questions

manny gouveia /

> P D Wrote:

> -------------------------------------------------------

> 120 should have you in good company .

>

> Manuals :

>

> https://drive.google.com/drive/folders/1XZIGaODutDY-NlVuGu-7WwoZTPyHWxPk

wow thank you!

OK no foolin around here! (edited)

Re: new have some questions

> manny gouveia Wrote:

> -------------------------------------------------------

> > Stephen Keller Wrote:

>

> > -------------------------------------------------------

>

> > Is the decomp stuck open? BEAUTIFUL bike. Have you tested for spark?

>

> thanks NO I have not, It doesn't make sense to me to do the ignition

> yet without knowing if the compression is ok 1st.

>

> I will check on the decompression tab make sure it is closeing

> correctly and report back... I have a feeling I am going to sepend alot

> of time here.:)

>

> thanks guys .

>

> O

I would test for spark anyway, that way you may not have to mess with the cdi, as nice as that bike is it may only need a cleaning of the points. I can't imagine why a machine so clean would not have compression, have you tried to start it at all?

Re: new have some questions

@manny,

Check to make sure that you know what the compression should be for your moby.

I agree on checking first the compression problem.

Let us know if you find the problem and what it was.

Looks like you will be spending some $$$

Re: new have some questions

manny gouveia /

it has 6500 miles on the clock!

Re: new have some questions

manny gouveia /

can some one educate me the AV7 and AV10 differences?

Re: new have some questions

Av7 is a Piston port engine, meani g the intake attaches to the cylinder and the Piston acts as the intake charge valve.. av10 is a case inducted reed valve engine, meaning the carb attaches to the cases and has a reed one way valve to contain the fuel air charge. Av10's were never imported to the us.

The a 10 is more efficient and powerful, too much hp and top speed over 35 made it too fast for most us states moped laws.

Just pull the head off and inspect the bore man. Its a ten Minute job to pull the whole engine! (edited)

Re: new have some questions

Bruce Zapper /

I have owned many moby's that is the highest mileage I have ever seen! Are you sure its not 650.0 Looks to be great condition. Nice to know someone really enjoyed that moby

Re: new have some questions

manny gouveia /

ok thanks for that.

ok so I was messing around this morning trying to check my compression noticed that the crank wasnt not spinning useing the peddel method. I than set my compressor to 30 lbs and blew air into the chamber and turned the crank by hand and it held he air pumped into it very well.

am I not peddeling fast enough or is there an issuse with the clutch not engageing and locking in?

Re: new have some questions

manny gouveia /

6941 to be eact :)

Re: new have some questions

manny gouveia /

The belt is on its turning the inside pulley on the crank but not engageing the outer chrome ring that ,when I turn it by hand does turn the crank.....

Re: new have some questions

Pushrod Fifty /

Did you use the decomp on the right handlebar side to intiate turning it over? It wont start to crank without it, the belt will just slip. The lever says KILL, thats slightly misleading, but you need to pull the decomp toward the bar until the engine starts to turn and then let go. I wouldnt blow air into the engine, you could be blowing carbon into the crankcase and ruin your seals, and that doesnt tell you anything. I wouldnt worry about compression numbers until you get spark, which you need to make it run. First thing I do is replace the plug on a non runner just to be sure. With a clean carb, ignition sorted out, and clean exhaust it should do 35mph.

Re: new have some questions

Yeah you gotta pedal fast enough to engage the starter clutch and get the engine turning over.

I don't think you have a compression problem, I've never seen a moby with bad piston/cylinder, they are chrome bore and even with 6,000 miles it's probably got life left in it.

Do you actually know how to start it? Hold the decompressor lever on the right, hold the choke, ride it preferably down a slight hill and get going fast enough for the engine to start turning over, then let go of decomp it should fire up.

Re: new have some questions

The older AV7 was a higher speed and hp engine in stock configuration, according to the homologation documents,:

the AV10 powered 51v had 1,85hp and maximum 5400rpm giving up 44,7km/h (27.7mph) as a top speed;

the AV7 powered 50v had 1,95hp and maximum 5900rpm giving up 48km/h (29.8mph) as a top speed.

North America was being invaded by the more affordable asian machines so only the old US style of the Frenchie was imported into USA.

> Aaron Blair Wrote:

> -------------------------------------------------------

> Av7 is a Piston port engine, meani g the intake attaches to the cylinder

> and the Piston acts as the intake charge valve.. av10 is a case inducted

> reed valve engine, meaning the carb attaches to the cases and has a reed

> one way valve to contain the fuel air charge. Av10's were never imported

> to the us.

>

> The a 10 is more efficient and powerful, too much hp and top speed over

> 35 made it too fast for most us states moped laws.

>

> Just pull the head off and inspect the bore man. Its a ten Minute job to

> pull the whole engine!

Re: new have some questions

@manny,

I don't know if it has been mentioned but do you have the drive knob (rectangular looking thing that is on the Plastic pulley) in the out position? (out position is away from the pedal crank) In position is for driving it in bicycle form.

If it is in bicycle configuration it will not crank the engine over.

If i am mistaken someone let me know.

Re: new have some questions

@manny,

You can do a goggle search and find the manual also you can find it here on moped army.

I found a Clymer peugeot manual for the 103, a factory manual and a general repair manual called the moped repair handbook by Paul Dempsey and the Peugeot 103 Owners manual. Another good place to find information about your moped is Myronsmopeds lots of info there too.

Hope this helps

Re: new have some questions

manny gouveia /

1st major hickup with this moped I tried every method to get this crank 2 turn it wouldnt.

heard some rattling inside the clutch looked in there and found a couple of bearing I am pretty sure they shouldnt have been where they where ,so I decided to disassemble the variator for closer inspection and ended up stripping the nut,,,,,,

I am going out tomorrow to try to find a 14mm nut easy out.

any thoughts?

I also need to purchase a new nut

this nut is a left loose correct?

chit ruined my day

thanks

20201012_142216.jpg

Re: new have some questions

@manny,

Sorry about my confusion i thought you had a Peugeot even though some of the info in those manuals might apply to yours.

That's a bummer man, sorry about that nut being damaged.

As far as being a regular threaded nut i don't know. On my Peugeot it is normal thread

meaning lefty loosy righty tighty.

Someone should chime in letting you know.

Good luck and i know the feeling i am stuck right not with a new cylinder kit with low compression.

Cheers

Re: new have some questions

Soak that nut with wd-40 and some blaster solvent overnight maybe that will help.

Look in youtube for ideas on how to remove stripped nuts.

Re: new have some questions

manny gouveia /

got it off thank you welded a bolt to it .

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