The endless saga of the troublesome Motobecane...

Matthew Westberg /

Okay, still haven't gotten it running. It comes close to turning over, even firing once or twice, but does not run.

When it died, it had a big drop in performance (from 30 mph to 10) right away and then it felt like it was only firing on a few strokes, less and less over a period of maybe 20 minutes, until it died completely.

The following has been done checked:

- Spark is a lovely fat blue-white, with a new plug. Timing has been properly set. Twice!

- Fuel flows freely to the carb and all carb ports/pipes are clean and free of blockage and the float moves freely.

- Compression is excellent, the testing gauge I borrowed gave me readings ranging from 80 - 150, (it was just a basic gauge, over the several times I tested it, it was usually in the neighbourhood of 120)

- Piston head and cylinder look fine through the ports and the rings are in very good shape.

- Air filter is clean and free from any obstruction.

- Exhaust and exhaust port are free from carbon and any obstructions.

- Clutch engages well.

I'm seriously confused at this point.

I thin the problem MIGHT still be in the carb, but to all appearances it should be fine - if ONLY because I know for SURE that the spark is good and well timed and the compression is good. The throttle and choke do not feel loose at all and pulls well on the throttle slide moves well, as does the choke.

Earlier, after I cleaned out the carb (for a second time) it ran for about one-two seconds (NO more) before dying. but each time I tried to run it after it wouldn't even get going other than a fire or two. Someone suggested it might be flooding and admittedly, there is an amount of blackened, gas-oil mix that comes out as I try to run it, but I don't know if it's flooding or that's just the unburnt gas from when I crank the throttle to try and start it.

It will not run when I squirt gas or lighter fluid in the cylinder, but it's a messy process and it's hard to funnel gas in there (it's not very accessible, for instance the fins and decompressor mechanism prevented me from doing a basic compression test with my thumb, even though that's way inaccurate), so I'm fairly certain that's only me and not the cylinder.

I really have no idea what the problem could be at this point. I COULD just buy another carb, but that will wind up costing me at least $130 or so ($90 carb + $30 intake manifold + at least $10 to have the manifold shaped to fit). That's $130 I really don't have right now. I'll spend that money if I HAVE to, but I don't want to blow all that only to find it STILL doesn't work, or that there was some much simpler, smaller, cheaper thing I could have done.

I really would appreciate some help or ideas with this. Thanks.

Re: The endless saga of the troublesome Motobecane

Mike Scouty McScoutington /

I would suggest checking/changing the points. I know you say that you have good spark. My buddy has a puch magnum that "has good spark". That is it has good spark till he runs the bike. his points are worn and when the bike is running they don't line up right, therfore giving him shit for spark when he rides, in turn killing his bike. It sounds like you have checked everything else. Do you have the stock carb on your bike? I replaced mine on my 50v with a dellorto 15:15 and it only ran me $65. You can find intakes that will fit in your bike nice and snug for like $10 and the carb itself was somewhere around $60. If you would like I can talk to the guy who sold me the intake and find out where he got it. Good luck, and I hope you get it to run.

Re: The endless saga of the troublesome Motobecane

Dear Bjerg,

it might be the thingy on the picture. They tend to not give up suddenly, but over a space of time. It'll start with the occasional hikup and get worse over an x amount of kilometres. Can even be a few days. I had it one day when my moby ran worse and worse and on a beautiful day finally gave up on me. 20 km from home! Luckily i was on my way home from visiting a colleague of mine, from whom i'd just bought three moby engines for spare parts and had also brought the tools i needed to open the flywheel to check the donor engines i wanted to buy. I replaced the condenser with one from one of the other engines and was saved a long walk. Otherwise it might be the coil under your petrol tank ( don't know the english term for it, in dutch it's called a "bobine").My moby doesn't have one, it uses only the condenser behind the flywheel. Your engine might not even have one of those, because of the "bobine", they roughly serve the same purpose. It might be a good idea to get that one checked out.Good luck

1100192611_condenser.jpg

Re: The endless saga of the troublesome Motobecane

Matthew Westberg /

My condenser should be working just fine. I retightened it a while ago and it improved performance (it was loose - bad contact). It's also external (not within the flywheel). My understanding is that the in-flywheel condensers used to break down, but I've never heard of problems with the late-model external ones like I've got.

Honestly I don't think it's a problem with the electrical sytem at all. If there's SOME kind of spark it should at least run - perhaps horribly - but it should still run. Replacing all my electrical components just to see if it'll do anything doen't sound like such a good idea to me. And no, I have no coil under my gas tank. And my points are actually fixed very well -it's a good design on these models to prevent them from coming out of alignment (it's the timing cam on the cranshaft that comes out of alignment - but that's fixed). My spark is regular, well-timed and beautiful, I can't see why it would stop just because I screwed in the spark plug fully.

This thing only has about 3000 miles on it, so I dunno. Although I just noticed yesterday that the carb is older (like a 75).

If you know where I could buy a new manifold for a dellorto for $10 that will fit a moby (and leaves room for the variator to swing the engine fully, without smashing the carb on the frame) please, let me know. I'd appreciate it.

Re: The endless saga of the troublesome Motobecane

Mike Scouty McScoutington /

i will talk to the guy i got mine from and get back to you on the manifold. this manifold puts my carb almost centered on the bike. it is a little bit off to the left. the only trouble i have had with this setup is making sure that the fuel line isnt kinked or hitting the pedal sprocket.

Re: The endless saga of the troublesome Motobecane

Matthew Westberg /

That's okay, I have an inline filter so I already have to worry about that problem anyway... LOL!

Re: The endless saga of the troublesome Motobecane

gurtner carbs apear on ebay often, I even saw this one today

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=4503423908&category=35620

Re: The endless saga of the troublesome Motobecane

Hayden Stevens /

I only skimmed the first post here......

This probably isn't your problem.....but make sure your engine case is completely sealed with gasket and make sure all bolts are where they should be and tightened...

That was the problem I had once, The place where the carb support connects to the engine wasn't there, so I put a nut and bolt where it would have been and then It ran....it didn't have enough pressure in the case to pull fuel through the carb...

just check it out....

Re: The endless saga of the troublesome Motobecane

Matthew Westberg /

If you mean my manifold, it's fine.

Other wise I'm not sure what you're saying. I know the problem isn't with a cylinder seal, since my compression is good.

Re: The endless saga of the troublesome Motobecane

Hayden Stevens /

what I am talking about is below the cylinder.....the crank case..(the shaft goes through it, magnito on one end, clutch on the other,) ...

what happened to me was...I would try to star the thing and it would kind of fire, but it would never run...I took the motor off to inspect it....when I spun the shaft by hand slowly, I would hear like an air leak sound that was wet (like it was foaming or something) ...

I got a general idea where the leak was coming from (I think it was neer the bottom) and noticed that there was a bolt missing (one of the bolts that holds the crank case together).... on one of my other Motobecanes, that missing bolt held the support that goes to the Carb.....the leaking engine didn't have that support when I got it, which doesn't really matter except that the bolt holds more than just the support arm, it also helps hold the crank case together....

So just check to see if all the bolts that hold the case together are there and tight.

Look at the picture to see what I'm talking about...

1100292316_motobecane_crank_case.jpg

Re: The endless saga of the troublesome Motobecane

Hayden Stevens /

here is a picture pointing out the support arm I was talking about

1100292399_motobmotor.jpg

Re: The endless saga of the troublesome Motobecane

Matthew Westberg /

I have a different carb... my intake manifold is much shorter and doesn't have a support arm.

I have all my crankcase bolts, with no visible loosening or gaps and the seal looks good, besides which, I have full compression. Thanks for the tip though, something else to keep an eye out for.

Re: The endless saga of the troublesome Motobecane

See Ya Moped Army /

Honestly, unless you want to have a stroke and/or go broke in the process, I would set this moped aside and get yourself a Puch. You can always come back to the Moby later. I've been in your position and have been close to taking a sledge hammer to some of my Motobecanes. Luckily, I never did and I was able to eventually figure out what ailed my bikes. A Priest and Holy Water may be what's required to exorcise the demons from your Moby.

Seriously, Motobecanes are good bikes but I would not recommend one as your primary moped. While I enjoy working on my mopeds, I enjoy riding them more.

Take my advice, or you'll end up hating this great hobby.

Re: The endless saga of the troublesome Motobecane

I know it sounds stupid, but i reccomend you go throught the troubleshooting list in the motobecane repair manual. I suggest things, like, the decompression valve not seating, that a non motobecane repair person would not know.

Re: The endless saga of the troublesome Motobecane

Matthew Westberg /

Enh.

I'm too flat broke to consider anything else. Mopeds are often stupidly expensive for piles of junk in and around Toronto and southern Ontario. Some dude tried to ask $700 for a rusty honda Express and wouldn't even allow test drives... Yeah... I _don't_ think so (and $1100 for one of those horrible horrible horrible old Harley Davidson mopeds! HA!).

That was about par for the course, sadly. My friend James had to drive for three hours, to rural nowhereland just to get a fair-priced Puch, and even then that thing has it's share of problems. I got mine - in very good working order - for a very fair price of $400 Canadian, so I'm not complaining there. This was after we spent about 3 months looking.

I'll probably buy a Dellorto, because at the very worst I will now have a much more reliable carb on my machine, even if that's not the problem.

Of course I like riding my ped more than I like working on it, and yes, for every week its run since I bought it, it's sat for about three. But I just don't have any other options. I don't have $2000 for a new Tomos (I'm _thinking_ about getting one with some modifications done when I'm able to work again next year, but I may not get my finances in shape enough to afford that until middle or late summer), and people want almost half that for something in poor shape that's 30 years old. I really would like a ped I didn't have to ride listening to every tiny noise waiting for it to fail, but it looks like that's just the way it is.

Besides, I've already had about three strokes anyway from this thing failing and biking it for hours. Might as well push my luck even further. ;)

The funniest part is that the local shop only deals in Tomos, but this one guy talked them into fixing an old Moby, and it's been sitting there for months. Hahahaha!

Re: The endless saga of the troublesome Motobecane

Matthew Westberg /

Well, according to the troubleshooting guide, I've checked everything that could be the culprit and then some.

In theory my carb should be fine, it certainly LOOKS okay, but I dunno. When I cleaned it out, the engine came SLIGHTLY closer to running (actually fired a couple of times, without fully turning over) so there was a noticeable _change_, but the problem wasn't solved.

I wish I had a _known_ working carb to substitute in it's place, but I don't, so I'm shit outta luck for finding a cheaper way to do this. At least money spent on a new Dellorto carb won't be WASTED - strictly speaking.

Re: The endless saga of the troublesome Motobecane

See Ya Moped Army /

Have you checked to see wheher the choke is operating correctly? If not, the engine would flood out and you would have a no start condition.

Re: The endless saga of the troublesome Motobecane

Matthew Westberg /

As far as I can tell it is. The choke valve is clearly moving in its jacket and springs back well.

Do you know what the stock jet is on the Gurtner? I want to get a range of jets if I get a new carb, but the manual doesn't list the stock jet on the Gurtner and I want to know what number to range from.

Re: The endless saga of the troublesome Motobecane

See Ya Moped Army /

The jet size depends on the size of the carb and intake, and the speed rating of the moped.

Re: The endless saga of the troublesome Motobecane

Matthew Westberg /

15 mm carb, 30 mph

The 15 mm Dellorto I might pick up comes with a 68 jet, but I wanted to get a few extras, going for top speed mostly.

Re: The endless saga of the troublesome Motobecane

Matthew Westberg /

Extra jets I mean.

Re: The endless saga of the troublesome Motobecane

I think you maybe getting yourself into an even bigger headache trying to attach a delorto.

from what I hear, they work great, but the actual attaching to the moby intake I have heard is trouble (search the archive for peoples stories)

I beleive if you measure the gurtner on your bike you will find that it does not come close to measuring 15mm any way you dice it. so you may have to modify porting, exhaust, jets, airintake, etc. and that is assuming the problem is even carb related.

It is not that I am oppessed to the idea of adding a delorto carb, I would just not try to do it untill the bike is running. Once you put on the delorto and it still doesn't run, then you really won't know where to look.

Gurtner carbs are listed inexpensivly on ebay often.

Re: The endless saga of the troublesome Motobecane

Also- have you tried to remove the muffler, and then pedal your ass off.

if should spit a little gas out of the exhaust hole. if it does, then you at least know gas is flowing through the carb, and into the cylinder.

Re: The endless saga of the troublesome Motobecane

Matthew Westberg /

Yeah, tried that, it does.

It was one of the shop guys who suggested it might be flooding. I mean if not, what am I supposed to do with this thing? It's my only lead, and a tenuous one at that.

Is there anything that could say... disrupt the vacuum of the venturi so that it won't draw fuel?

Re: The endless saga of the troublesome Motobecane

Have you checked your carb. float?

With the float bowl off does the float move correctly on its hinge? Is the float needle in good shape. If the float needle does not seal then the carb will flood.

Another hint: With the carb off and the float bowl removed, hook up the fuel line, then turn the fuel on. It should run out of the carb. By hand, raise the float. The fuel should quit running out. If it continues to run, then the needle is bad.

If this all works properly, remove the float from the carb and check it for leaks. The float itself should be empty, tha is with no fuel in it. Next, try submerging the float in a container of warm water. If it is bad you will get a slow stream of bubbles out of it.

If this all checks out OK, put the carb back together and shake it gently. You should be able to hear the float move up and down. If the float does not move, check to see that the bowl is on properly. Some float bowls will mount in reverse but then trap the float and prevent it from moving allowing the float to not work properly.

If all is ok, put the carb back on the bike (I assume that you are setting the idle mixture screw to the proper number of turns out. Try one and one-half turns out if you do not know the proper setting).

Do not turn the fuel on.

Take the spark plug out and crank the engine like crazy. This is to see if the crankcase is flooded and will pump any excess fuel out of the engine. Clean the spark plug.

Squirt a little fuel in the air filter and give her a try. If it fires and then quits, turn the fuel on and try it again.

Good luck.

Mike

Re: The endless saga of the troublesome Motobecane

Matthew Westberg /

I searched for the old thread on replacing the carb, but the only thread recent enough to come up on the search was a thread that said to search for the older thread!

:(

I know that the Mr. Moped shop can do up a manifold for me, or maybe a shim, but I still need to know what the right jet to use would be (or close enough). Mine was the 30 mph Moby.

Suggestions?

Re: The endless saga of the troublesome Motobecane

See Ya Moped Army /

To get the right size jet, you're gonna have to do plug chops.

Re: The endless saga of the troublesome Motobecane

Matthew Westberg /

Can't do that unless it actually runs. Hahahah!

Tried another couple of things... Bummed.

Matthew Westberg /

Anyway, I went over it again a little tonight. Reset the timing with a different measure, looked over the electricals. The spark seemed odd this time. Sometimes it would fire and then it seemed to be okay... now I'm back to having multiple doubts.

I don't know, for an engine with only 3000 miles on it it sure is a peice of shit, I may simply concede defeat and buy an entirely new engine. Of course with my luck it still wouldn't run. And that feels like a bit of a cop-out, y'know? (Not that I'm really in a position to complain). That's sort of the way I feel about buying something brand new - it's all well and good to have a more reliable moped with parts and service for the longer rides I like taking, but it feels like a failure to give up on this thing.

I really wish I had someone else to help here, some parts I could swap to see if they'd work. Geez I dunno, anything. I sunk a lot of hopes and all the money I had to spare into this thing, but I really do feel like I've failed at putting together an accomplishment out of this or promoting the hobby or the MA in any way. The Moped Army is great, but distant text messages guessing at potential problems is not the same as actual mechanical help.

I don't even mind having to fix up a lemon - even if it had problem after problem - but when the fault could be anything, ANYWHERE, you just have zero ideas and no way of getting out of the hole it's daunting. There's just nowhere to begin. If I knew what to fix or to buy I could just get to work, but without knowing what the problem truly is, I could go on buuying and buying and buying until the cows came home always wondering if maybe I bought another faulty part (I mean this stuff is all old, and usually used) or if the problem is something else entirely.

I have a few good memories. When I got this thing it was one of the weirdest sensations ever, sitting around realizing that I'd actually DONE one of those silly things I'd always wanted to do as a kid... but I just keep thinking of all the times I made a laughingstock of moped riders everywhere, as I pedalled my sorry ass home.

The longer my moped sits in the garage and the more things I do that don't work, the harder it is to go back to it. I worry so much this'll become some 'might have been' money pit non-hobby. But I do want to say I really do appreciate all the help and I'm not giving up on this stupid thing yet, without the army I don't know that I'd have ever even got to own this thing (although I could joke that might have been a good thing ;) Heheh.) .

Re: The endless saga of the troublesome Motobecane

Matthew Westberg /

That's pretty detailed actually. I'll go through those tomorrow if I get the time - who knows? Maybe I can figure it out this time.

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

Login or Create Account