Mobylette 50V Starting Issues

Nicholas Conte /

Hey everyone, I'm a new member and also a bit dumbfounded by my "new" mobylette 50V.

I got this thing from a guy down the shore about a month ago, and it's beautiful. Guy said it hasn't started since he garage kept it 2 years prior, which I was expecting. Fast forward to now, and I've got a new petcock, new fuel line, Dellorto SHA 15.15, new throttle and choke cables, new gas in the tank, etc. I cannot for the LIFE of me get this thing started.

I put a new sparkplug in there last week before installing the dellorto and tested it with the plug out of the block, saw the spark myself and I'm getting power to the lights. Put the new carb on this weekend, including new cables, and now I'm not getting a spark at all. I think it might have to do with the fact that my choke cable might not be getting enough slack, and not enough air is getting into the engine, making me flood it every time I start.

So my questions are:

Will the choke cable not having enough slack affect startup?

Could my brand new plug really have fouled from too rich an air/fuel mix?

If you can't tell, I'm new to small engine stuff. Appreciate your help all!

-N

Re: Mobylette 50V Starting Issues

Richard Eberline /

need more info the year, and etc.

Re: Mobylette 50V Starting Issues

Nicholas Conte /

It's got an AV7, 1977, it's a 50V with variator

Re: Mobylette 50V Starting Issues

I'd definitely go back to getting spark first. Especially if you had it already. Double check that the kill switch is in the on position, or bypass it.

I would temporarily disconnect the choke. If you have spark and fuel, you should be able to get it to fire. Once you do, you can go back getting the choke working right.

I just got my 50V a month ago and it took every ounce of energy I had to get it to start by pedaling on the stand. Once I tore everything apart to install new bearings and seals, I discovered the starter clutch and drive clutch were a rusted mess. After seeing how bad it was, I was amazed I was able to get it to run before addressing.

You can also run a drill on your magneto to make troubleshooting and getting it started a lot easier. I'd stay away from an impact gun though. Use a drill, start slow, and use the decomp lever/valve. Begin with the decomp lever engaged to make it easier to turn the engine and once it feels like it wants to fire, let it go.

In my case, I needed to choke the Gurtner carb with my thumb while spinning the engine with the drill. It took cleaning and setting the float to get it idle and run decently. I did end up getting a Dellorto clone though, which has been better. (edited)

Re: Mobylette 50V Starting Issues

Nicholas Conte /

Yeah I'm not sure exactly how to get everything running right so getting a spark is the best lead I have at the moment! Killswitch is turned to the on position, and hasn't been giving me trouble since it clicks into the correct position.

Question - I can get an impact on my magneto, but how can I get a drill on there? I don't know if I have a bit that will fit it.

Going to try this out tomorrow, you're saying it should start even if the choke is open?

Re: Mobylette 50V Starting Issues

Yes, you should still be able to get it to fire with the choke open. It may not idle well cold, but it should still fire. What worked for me was holding the throttle open just a bit, spinning up with the drill, the choking the carb with my thumb. I used my right hand on the drill, left hand on throttle and decomp until it was up to speed, then moved my left hand to choke the carb when I felt it wanting to start, then right hand to the throttle to keep it running. Once I got it to run for a bit, I switched to pedal start, which I got on the 1,000,342nd try.

I used the 3/8" bit driver that fits my impact and just chucked it in my electric drill. I gradually built up speed with the drill as to do as little damage to the Novi nut as possible.

Re: Mobylette 50V Starting Issues

So did you just get the 15.15 and toss it on? Did you look and even see if it had a jet in it? I'm sure it had one in it but did you even look? Just because you purchased the carb and intake from treats or other company does not mean the jetting is correct. Been awhile since I messed with a moby and can not help you wit jetting but I'm sure you can find a good starting point with a little search on here (edited)

Re: Mobylette 50V Starting Issues

No spark, replace the dang condenser with a external one. Use a Delco 6 cyl from 1960s or a Bosch one from similar vintage, disconnect the old one (blue wire with black stripe) Disconnect the 6v terminal on the back of the magneto and make a jumper to the engine, disconnect the wire going from the grey coil wire to the master switch from hell (use the decompressor to also stop the engine) . Replace the bonding strap with one going from a intake stud to the lower external coil mounting stud. Clean points with a metal points(or nail) file and chase it out with brake cleaner (NOT sandpaper and carb cleaner).

It should then spark...

Re: Mobylette 50V Starting Issues

Nicholas Conte /

That's right, got the new intake pipe and shim and all. Wasn't sure about jetting or how it works besides vague speculation, also new to carburated engines. Not really sure what to look for in terms of jet or where it is, but I'm going to do some digging to find out.

The engine itself basically sounds like it's running when I have it going with the pedals, and it makes engine noises when I give it throttle but it dies down immediately, hence my confusion.

I'm going to start with spark then try jet.

Thanks!

Re: Mobylette 50V Starting Issues

Nicholas Conte /

Ah, came with a #68 main jet.

Re: Mobylette 50V Starting Issues

Richard Eberline /

first get spark,

Re: Mobylette 50V Starting Issues

You need to jet your carb correctly. No carb comes set up. They are universal. You need to find what jet people run on a stock av7 with your intake and carb. Too lean=too little oil=kaboom...

It's been 10 years or so since my last Moby but I don't think you are too far off although, my last dellorto came with a 58, not a 68..make sure

I think I ran a little bigger than that...regardless, two strokes have lubrication in the fuel so you don't want fuck that up...

Clean the points and bypass that wierd twisty horn/kill switch. Then see if you get sparky. I had alotta trouble with mine.

Re: Mobylette 50V Starting Issues

Richard Eberline /

The Moby is metric and the novi nut is a 10mm square and not 3/8.

Use a drill on the variator nut 14mm and put the drill in the reverse mode.

Re: Mobylette 50V Starting Issues

Richard Eberline /
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Re: Mobylette 50V Starting Issues

Nicholas Conte /

Okay so I may have found an issue - I have an unshielded wire running along the bottom of the gas tank that may have been exposed when I redid the throttle and choke cables. It seems like it could be a ground wire. Will shielding this possibly solve my issue? I'll try when I get home.

I'm going to try and run the magneto with my drill later on to test it, but I replaced the spark plug and have no spark still at the moment.

Re: Mobylette 50V Starting Issues

If it's a ground it wouldn't matter. A ground is a ground. If it shorts to the frame who cares. Still ground.

Post a picture

Re: Mobylette 50V Starting Issues

It is a ground wire, it was not shielded from factory, it should attach to the pivot bolt, but relocate it to a head stud. There is wiki info re this under Rebel Moby. The ground is necessary as the engine is isolated from the frame by the rubber silent blocs or engine mounts. It is also know as a "bonding strap" may help with the search on this site, Rebel discusses this at length.

Re: Mobylette 50V Starting Issues

^^please reread and do what rebel moby wrote, and report back.

Re: Mobylette 50V Starting Issues

Nicholas Conte /

Hey guys, was busy for a couple days. Definitely going to read up on Rebel Moby. Was also told to replace the ignition coil and create a new ground, so that's my first step.

Thanks!

Re: Mobylette 50V Starting Issues

Do the ground first, unless the coil is visibly cracked, or has a chalky appearance.

Re: Mobylette 50V Starting Issues

Rebel Moby’s posts are great, you will resolve this if you keep at it—but for the love of God, get yourself some proper jets since the clones come with one big enough for a Harley. 56 is a good size to start with if you don’t have air leaks.

Re: Mobylette 50V Starting Issues

Nicholas Conte /

Well guys, good news is that it's running and started. Got some help from a friend to get this thing going. I've got it running like a top now, just got to get the right fuel/oil ratio. I've looked around and everyone is saying 50:1 or 40:1. Can you guys confirm?

I had it running really well with my last batch but I used lawnmower oil (I know, bad bad), but now this time it's running rougher. I'm going to invest in some good 2 stroke motorcycle oil and a mixing cup this time around.

Re: Mobylette 50V Starting Issues

Nicholas Conte /

Hey guys, NOT SO FAST!

Now my magneto seems to be seized and won't budge. Already asked Richard (on the thread) about this and he gave me some advice. Has anyone else had a problem like this? I can usually turn it by hand. Usually it frees itself, but unfortunately the novi nut is stripped so I'm working on getting that off now too.

So stuck magneto, anyone know?

Re: Mobylette 50V Starting Issues

Do you mean your flywheel won't come of the shaft ?

Re: Mobylette 50V Starting Issues

Nicholas Conte /

Not quite, I mean the flywheel won't turn. The nut is stripped so I'm working on that issue, but as of right now it won't spin

Re: Mobylette 50V Starting Issues

You were jetted incorrectly and seized your engine. Rebuild time.

Re: Mobylette 50V Starting Issues

Nicholas Conte /

Oh that's great. I was definitely running rich for a little but I didn't realize that would seize my engine, never had that problem before. I downjet to a proper size and it was running perfectly not 2 days ago. Oh well 🤷‍♂️ rebuild time it is!

Re: Mobylette 50V Starting Issues

Cut a notch in the Novi nut to get it off, they are reverse thread... 32:1 is the stock mix from the factory, I've always used that and never had any problems, lawn mower oil will not hurt anything, all modern 2 stroke oil is better than what was avail when the bike was new. My Motobecane's have always liked Castrol 2T.

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