Moby giving issues with no resolutions?

So here's what I got, my moby 50v '78 was running great for the past two months after a mild port job, new high comp head installed, dellorto 15.15 sha with intake to match. It starts up, it runs on the stand and idles, it revs all the way up while riding but sometimes will just die. I know what you thinking condensor. Nope changed that put a new one on. Ground wire seems fine. New plug. Replaced the rings when i did the port job so compression is also fine.. Not really sure whats going on? Any ideas? Oh and it never loses spark through this whole process and the gas is clean.

Re: Moby giving issues with no resolutions?

Any help is appreciated!

Re: Moby giving issues with no resolutions?

Resistor cap can fail that way if you have a new externally mounted condenser and the bonding strap goes from a intake stud to a external coil stud. Also if you have the kill switch hooked up that can be problematic.

Re: Moby giving issues with no resolutions?

I have tried a different resistor cap to no avail. Does the headlight kill switch count as the kill switch from hell? Also you think this problem is electrical and not like an air leak or gas flow problem? It idles and rides but will die at stops then a little bit harder to get started and have to work the throttle some. but then cruises back up to speed.. not really sure. its killing me!

Re: Moby giving issues with no resolutions?

Dies and a bitch to start is usually condenser, timing or air leak.

Re: Moby giving issues with no resolutions?

set timing, changed condenser, I will have to try and look for an air leak when i get the time... It's not that that hard, just a little bit harder to start.. anybody else have a problem similar?

Re: Moby giving issues with no resolutions?

starts, runs choked with not much power, let off choke to get to top speed, gets there, but when letting off gas letting it go back to idle starts to die and then does die, but leaving it choked seems to idle... is that fuel related? Crank seals haven;t been replaced as far as i know? Does that sound like a leaking crank or leaky seals in general or is it jetted improperly?

Re: Moby giving issues with no resolutions?

Give it a leak down test to check the carter sealing (spi seals, base gasket, carter halfs, intake).

What is the event timing for your 'mild port job'?

SHA15:15 have issues with low vacuum signal on Mobys so you need to retard the ignition timing to 1,5mm BTDC.

Re: Moby giving issues with no resolutions?

Hey Roger,

I have a 76' Mobylette and I replaced the carb to a 15.15 SHA with intake to match as well and I have the same issue. Initially, when I start it up it runs like a dream, idles perfect, runs smoothly no issuse. However after about 30 min or so, if I press the rear brake it slowly goes to idle and just dies on me making it a pain in the ass to start back up again. Also, sometimes when im at WOT, it will just randomly slowly rev down until it shuts off all together. If you do find a solution please let me know. I thought maybe tickering around with the idle would do the trick, however I have had no such luck.

Re: Moby giving issues with no resolutions?

Jimbo Grand Daddy /

Maybe your timing slipped.

Re: Moby giving issues with no resolutions?

Greg, have you replace your condensor yet? Its like a ten dollar part you can go to the auto store and tell them you have a car from the 70s or older... I had similar problems to what you have and it was the condensor... I have a sick feeling that mine is timing related..

Re: Moby giving issues with no resolutions?

I have not, I will give that a try. Thanks for the tip

Re: Moby giving issues with no resolutions?

So I purchased a 12V condenser, and now my issue is how do I go about installing it? do I have to take the flywheel off, and if so whats the cheapest way in doing so.

Re: Moby giving issues with no resolutions?

take the magneto cover off. It's reverse threaded so remember that. If you have a strap wrench to hold the other side that is the most ideal method. the lead is attached with the other two wires on the points. make sure you try and mount it externally if it is not already. It gets too hot when its inside the genny and thats what gives it problems.

Re: Moby giving issues with no resolutions?

Re: Moby giving issues with no resolutions?

If you have a bad or failing internal condenser that fuel tank mounted external is the easiest check. Can just plug it in and leave the bad stock one in place. I had to do this when my condenser died out on a ride a few years back and it worked like a charm - got all the parts at Pep Boys.

I'd double check your SHA is well sealed to the intake - for some reason this sounds like a vacuum leak popping up every now and again to me. Have you already got an O-ring in between the end of the intake and the carb body? Makes for the best seal for sure.

Re: Moby giving issues with no resolutions?

If your carb has sealing or clamping problems then check here - http://mabecanemobylette.freeforums.org/dellorto-oring-sealing-t1769.html

Also - if you are putting an external condenser always disconnect the old one.

Re: Moby giving issues with no resolutions?

Ya know...this might be silly or unrelated, but my SHA 1515 had leaky threads on the main jet that were causing issues...maybe it's pulling extra fuel at higher vacuum though the threads? and flooding out the bowl or something? I teflon taped mine and it's been good to go.

Re: Moby giving issues with no resolutions?

Gromosaurus Rex - Brad Pitt /

Greg Z Wrote:

-------------------------------------------------------

> Hey Roger,

> I have a 76' Mobylette and I replaced the carb to

> a 15.15 SHA with intake to match as well and I

> have the same issue. Initially, when I start it up

> it runs like a dream, idles perfect, runs smoothly

> no issuse. However after about 30 min or so, if I

> press the rear brake it slowly goes to idle and

> just dies on me making it a pain in the ass to

> start back up again. Also, sometimes when im at

> WOT, it will just randomly slowly rev down until

> it shuts off all together. If you do find a

> solution please let me know. I thought maybe

> tickering around with the idle would do the trick,

> however I have had no such luck.

I had nearly the same experience after hooking up my 15.15 SHA on thrusday night. I thought i was imaging the connection between pressing the rear brake and it dropping down to idle and dieing. I let off the brake and floor it and almost save it but it konks out. 15 mins later its ready to start. Let me know what you figure out.

Re: Moby giving issues with no resolutions?

♣Slew Foot♣ /

the condensor wire runs under the point set. my VLX that was basicly factory fresh had the condensor wire pinched by the flywheel leaving a bare wire that would ground if it was close enough to the stator or coils at WOT it would arc and kill the bike it may be worth a looky lou.

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