Puch MV50S - spark plug fouling and bogs in 2nd.

Hey everyone,

I've been trying to sort out some issues with my Puch MV50S (2 speed). Still new-ish to me, haven't had it running well yet. It keeps fouling the spark plug (dry fouling mostly), and bogs down like crazy in 2nd. Seems to run alright in 1st. It also seems be make a bit of a "clunky click" when running, doesn't matter which gear. Idles well.

I thought maybe it was an air/fuel ratio as I had the airbox off for awhile. Put it back on, no significant change...runs maybe a wee bit better.

What would you suggest as the next step(s) to try?

Thanks!

Re: Puch MV50S - spark plug fouling and bogs in 2nd.

kim jensen /

So this would be a Sears Allstate I assume? Standard 12mm old fashioned Bing carb?

Probably the 62 jet in it. First make sure the jet and other internal orifices of the carb are clean. These were designed to run with the filter screen pack full of screens, otherwise you will be too lean. RBO Puch in Austria has many parts for these but 62 is the largest they have. They make some kind of jet adapter that apparently you can put modern bing jets in to accommodate Increased airflow from removing some of the screens. Haven't tried it yet.

Obviously there are a mlion things that could be going on, it's a moped. Airleaks paramount among them. Put all the filter screens back in and set the needle at 2nd notch and see what you have. Try pulling the manual choke up slightly and see if it improves. If so, you are lean bogging. Let us know what progress you make!

Re: Puch MV50S - spark plug fouling and bogs in 2nd.

Close to a Sears Allstate, but it's a European bike that was brought over, so it seems to have a couple differences from the Allstate. I've attached a pic of the bike, plus some of the carb/air box connection.

Yes, Bing carb. Carb is clean. Can't remember off the top of my head what the jet looked like, so that could be something to switch out. If getting a new one...this should work --> https://www.treatland.tv/bing-jets-for-puch-mopeds-p/bing-jets-puch-mopeds.htm ?

With regards to the filter...I've got a goofy airbox thing that doesn't *really* line up with the carb. Maybe switching from the airbox to a different filter system would be better?

Thanks!

Keely.

DSC04677 smaller.jpg
DSC04674 smaller.jpg
DSC04675 smaller.jpg

Re: Puch MV50S - spark plug fouling and bogs in 2nd.

kim jensen /

NICE! Envious of the full size front hub for sure! That top of the carb doesn't look like the gasket is sealing real well, though I don't think you would introduce excess air in through the float bowl. That is a goofy airbox setup all right. And I see it has a click choke though the entrance for the cable choke is there as well. Try plugging the cable choke hole on top. You will just have to play with it and see if you are way lean or rich when you give it throttle and solve from there. The jet is unique on these as it unscrews from the outside. Also can adjust the airscrew next to it.

Re: Puch MV50S - spark plug fouling and bogs in 2nd.

Jeremy Homser /

if you end up ditching the air box let me know.I need one bad for a project

Re: Puch MV50S - spark plug fouling and bogs in 2nd.

Thanks!

That gasket was the shits, and I've since replaced it.

Any recommendations on a good filter set-up? Or just try to find one of those clip-in stock ones like the Allstate? If I remove the black rubbery piece that goes from the carb to the airbox, I should have some room for a different air filter.

Since the jet is different, do the Treatland ones work, or where do you get yours? Maybe the current one just needs some attention.

-Keely.

Re: Puch MV50S - spark plug fouling and bogs in 2nd.

Jeremy - probably going to leave the air box in place, more for the look than anything, and just piece in a different air filter where the black rubbery connector piece goes. If I change my mind though, I'll let you know. I have seen some of the air boxes sold online (almost all in Europe), so at least you know they do show up.

Cheers,

Keely.

Re: Puch MV50S - spark plug fouling and bogs in 2nd.

The clunky click could just be the transmission, maybe sort of out of gear, but slightly catching, if your shift cables are out of adjustment. The transmissions do a lot of clunking while shifting, etc, but they are STRONG.

I would imagine your main seals are about ready to quit doing their job. Possibly dried up, and leaking a little. You might also test your compression. if you are hearing a higher pitched clacking, you may have lost a ring. I don't think that jet from treats will fit your carburetor. Try calling Matt, at Motorwest. He probably has every jet option there. It's best to call them, and they have more than their website shows listed.

You can also ask him questions, as he's very keen on these bikes. I too love your large brake hubs! I think you can get replacement connections for those airboxes at Rinky Toys, but he's overseas.

That airbox, etc, shouldn't be your problem though. It's even possible you are getting an vacuum lock in your fuel line. If your cap isn't breathing well, it will starve it for fuel. My wife's bike had that issue for 3 years before I finally figured it out.

I like spark plugs: NGK B6HS or B7HS. also I run Amsoil Injector 2 stroke synthetic oil in my fuel at 3 oz. per gallon. (Yes, amsoil suggests other types of their oil for mopeds, but I have used most all of them, and the Injector just seems to run the best. I think it has to do with it's thickness somewhat.) Anyway, i also use that oil straight, in my transmission. Quieter shifting, cooler running, and just all around better than 30wt or whatever.

Re: Puch MV50S - spark plug fouling and bogs in 2nd.

Jet seems to be a 48. Could that be the issue, since 62 is recommended?

Tinkered with the air screw. No matter which way I went, she ran poorly. She now is bogging in first and second, and I can hardly get any power. Yet, she doesn't seem to be fouling the spark plug as much. If that makes any sense at all.

Pulling the choke makes everything worse.

Deezy, what do you mean about vacuum lock in the fuel line, and the cap breathing well?

And I'm using NGK B6HS spark plugs. New ones, so they can't really be the problem.

Re: Puch MV50S - spark plug fouling and bogs in 2nd.

Carb seems to be leaking again too... Is it possible it's something stupidly simple like the carb float?

Re: Puch MV50S - spark plug fouling and bogs in 2nd.

Sorry for all the posts... Positive update though. Switched out the gasket on the carb, cus I realized that she hadn't run this badly before I cleaned the carb and replaced the gasket. (Not back to the shitty one in the pics, it was one from before that). She's running the best she has in awhile. Not perfect, but a HUGE improvement. Now she dribbles some gas out of where the carb connects to the air box (I can see it because of the poor connection there). What's the cause of that, and/or what's the fix?

Appreciate all the help, guys! This seems to by my fussy moped...my Maxi's been nothing but easy so far (knock on wood). ;)

-Keely.

Re: Puch MV50S - spark plug fouling and bogs in 2nd.

kim jensen /

So it is a 12mm bing with the large jet that screw's out of the side of the carb from the outside? #48 sounds small. What altitude are you at? If you are lean, choking it slight should improve it a little. The carb will spit gas out the front, but if it dribbles out while off, your float needle isn't sealing properly and may need cleaning. Also make sure the float bowl is clean. Dremel with a nylon or wire brush works well. Gasket could also affect this.

All states normally came with #58-62 jets see if Matt at Motorwest has those.

They make a click class k when shifting, but as DZ said adjust your cables to make sure it is shifting fully.

Re: Puch MV50S - spark plug fouling and bogs in 2nd.

Yep, 12mm Bing I'm pretty sure, with the jet that sticks out of the side. Pretty sure it's 48...that's the only number on it. It's on the head part where you'd put your screwdriver to remove it.

Altitude...maybe 50m above sea level. I'm in the Annapolis Valley in Nova Scotia.

Float bowl is clean. Float seems ok. It's one of the ones that's on a needed...like this: http://www.motorwestmotorcycles.com/shop/index.php?main_page=product_info&cPath=10&products_id=52 Unless it only *seems* fine but is actually a bit off. Appears to be the original, so if it wasn't working, it wouldn't be a huge surprise...

I guess maybe the gasket and float are the best guesses right now?

Good lesson for me as a new mopeder --> can be lots of different things. Be thorough, check different options!

Re: Puch MV50S - spark plug fouling and bogs in 2nd.

kim jensen /

It would seem that jet is way too small for sea level. I'm in Minneapolis at about 1500 ft and run a 62. You need a much bigger jet for starters and more restrictive filter than me. If I take screens out of my air filter, I get lean quickly. But 62 is a big a jet as there is unless you get that adapter from RBO Puch.

Re: Puch MV50S - spark plug fouling and bogs in 2nd.

Thanks Kim, worth a shot to up the jet and try different filter stuff. Appreciate all the help! :)

Re: Puch MV50S - spark plug fouling and bogs in 2nd.

I'm just wondering if your carburetor is slightly different than the older Allstates. Ours don't adjust for air mix, they merely change out. There's the needle jet, and the jet on the side. Sometimes those side jets have the number on the side of it too, and it may be different. Yours looks like my carbs, but I can't see every bit of it enough to know for sure... weird they cheapened up on a choke cable, and just have that finger flippy thing on the side for yours though.

The vacuum leak I spoke of is when the tank is being drained while running, it may not be letting air in through the gas cap, which after a bit of running will make it act like it's running out of gas, and quit. It can also happen if it was warm outside, and it recently cooled off, such a s a rain. Just like the plastic gas cans react in sunlight and shade. If the gas cap isn't breathing enough, this will happen. I sort of doubt this is your issue though. I think it could be a float issue, jetting size or air leak.

Re: Puch MV50S - spark plug fouling and bogs in 2nd.

kim jensen /

Agree with Dz. Loosen gas cap and run to check fuel flow though.

Re: Puch MV50S - spark plug fouling and bogs in 2nd.

In the manual, the screw near the jet (on the outside) is labelled "throttle slide stop screw". Lots of people were saying this is an air screw though, so I adjusted it. Would make sense if it wasn't an air screw, since it didn't make any positive changes one way or the other. Is that more similar to yours?

Also, I have no idea of the age of the bike...can't find anything to identify an age on it. Can only find the serial number. Can you find age, using that? It's European, so it doesn't line up exactly with the Allstate bikes, unfortunately.

Sorry if some of these questions sound silly - I'm still quite new to mopeds, and learning as I go!

Re: Puch MV50S - spark plug fouling and bogs in 2nd.

Yep, there's a throttle stop screw on the same side as the jet.

I have no idea how to find the year, but a few European people might.

I bet this guy knows: http://www.puchverkstan.se/?m=1&lang=en

Re: Puch MV50S - spark plug fouling and bogs in 2nd.

Ah, then I was adjusting the throttle stop screw yesterday, not an airscrew as I thought. Ha, no wonder it didn't help! ;)

I'll order in some different jet sizes to see if that helps, plus a new float just in case, and in the mean-time, I'll loosen the gas cap to see if that's what's up.

Thanks again for all the help!

Re: Puch MV50S - spark plug fouling and bogs in 2nd.

Loosening the gas cap was a huge help! Not bogging now, but it's not running perfectly. Likely a jet issue now I'm thinking. Or a spark plug boot issue -- I touched the boot to make sure it was secure while idling...it shocked me. She's not idling very well now either. Likely tied into the same issues.

You guys have been a great help. Too bad you're not closer to grab a beer and celebrate the improved running of the ole girl. :)

Re: Puch MV50S - spark plug fouling and bogs in 2nd.

It shocked you? You must have something grounding out somewhere.

It's always nice to finally get one of these gong.. and after you do, there is usually very little maintenance. Check that gas cap for a gasket.. if it's all the way across the inner top of your cap, poke some holes in it. If it's just a ring type, you may have some rust inside the tiny little hole that lets air in.

Yep, I bet your jetting could be it now.

Re: Puch MV50S - spark plug fouling and bogs in 2nd.

I could have a grounding issue. There's currently no tail light on the moped, and just one wire hanging out of her back fender. I haven't really touched any of the electrical so far.

There's no gasket in the cap as far as I can remember. But the cap screws on, and I had it on there pretty tight. As soon as I loosened it up, even a wee bit, huge improvement.

I've been trying to contact the guy at Motor West to order jets, but no luck getting him on the phone thus far. Anywhere else good to order these sorts of jets?

I'm pretty excited to have her all complete (when I eventually get there), and move from the repair stage to the maintenance stage. Poor moped was a bit beat up before I got her, so it's just taking the time now to get her set up.

Re: Puch MV50S - spark plug fouling and bogs in 2nd.

kim jensen /

Other than Motorwest or RBO Puch, not much available anywhere else. Motorwest has a plug wire that works for the internal coil models. If you have one of the old school plug wire caps, they are mind of an odd duck. The internal connector actually screws out of the cap and the wire is crimped by it. If you can get it out you can snip off some of the wire and get fresh material for the internal cap screw to make contact with. Provided the internal screw still is good. Otherwise replace it.you should have two wires out the back, one for tail and one for brake. I am assuming you have the brake light switch back by the rear brake as well.

I've got to get mine back up to speed, I miss riding the little stud!

Re: Puch MV50S - spark plug fouling and bogs in 2nd.

Is the Motorwest fella usually pretty good at returning calls? I've called 2 days in a row, no answer, no return of phone calls. I'm hoping to hear from him soon, because I'd love to pick up a few different jets to try.

I don't know what spark plug cap I've got. I think it's something that was pieced in. I potentially have the original too (came with the bike when I bought her). I picked up a new NGK one too. I've attached a couple pics of the cap that's on her now. First one I'm just holding it, 2nd one I'm pulling the rubber back a bit.

I thought one wire wasn't enough! I'll have to look and see if it's gone entirely, or where it's nipped off. I haven't tackled any moped electrical yet. If I need a new wire, where's the best source? Are there any differences in wires or is it all the same stuff just with different colours on it? The one wire I have is yellow. My diagrams don't mark that as a tail light colour. I don't think I have a tail light switch. If I did, where would I find it?

DSC04702 smaller.jpg
DSC04703 smaller.jpg
« Go to Topics — end of thread

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account