MOPED ARMY

Where'd you move from? What's the elevation difference silly goose? Sounds like you went from sea level to mountain level or something. You're gonna need to downjet, there's not enough oxygen in the air compared to wherever you moved from for how much fuel delivery you have currently

Down jetting means putting smaller jets in the carb for less fuel delivery

If the only variable changed was the altitude and climate then it's 100% the jetting. Put a smaller jet in the carb and blast.

Thanks for the input guys.

@PD. This afternoon I will give the bike a closer inspection. I don't know what the carb is supposed to look like, so I'll need to do a bit of research to know if anything is out of place from the normal position.

@Nick and Papa. Okay thanks. Sounds like I'll need to look into that. Is it something I could do on my own provided I get all the parts and have a repair manual in front of me?

And, Papa, I just looked up what four stroking is. Let me run another test later today and get back to you about that.

@Kilian. Thank you.

Haha great, I'll listen for it. And would it be all the time? Just while I'm throttling hard? Just while I'm idling?

Now that I think about it I was actually recording a video while I took it riding (or tried to) yesterday, so I assume that should be enough to show if it's four stroking or not.

You're four-stroking like crazy. Downjet

You might try raising the slide needle clip to the top notch .

Here's a manual :

https://drive.google.com/drive/folders/1xzSqebrL4bLYS5pPZlUlB_Hta2bLoNWC

page 16-1 shows the slide needle ...

Awesome, thank you both very much. I will look into this when I get off work today.

And I believe I have the stock carb, the only major thing that's not stock is the 65cc.

Update:

I have figured out that I actually do have a replaced carb. A Dellorto SHA. Looks like it should be likewise pretty easy to change the jet. I'm going to get a flathead today and open it up and see what size the current jet is and then order a smaller one.

Once I've got that done I'll report back with results.

Thanks again a lot to everyone who responded so far.

before u downjet,make sure your choke is working, that your float needle is sealing off gas flow and your throttle cable is outside the spring, all which would make it run rich.

Good call on switching to the Dellorto. Did it on my buddy’s and he went from 20mph to 30mph. Also, try taking the exhaust off the moped, and take the nut off the end of the exhaust and pull it apart. Then, take a plumbing pipe cleaner(or a coat hanger) and go to town on that fucker. Sometimes they get clogged up with carbon and it ends up pushing some air out of the intake, making it almost impossible to pull in fuel.

Update: talked to Sabatino in portland (love that shop) who initially installed the new parts a few years ago and saw the moped as recently as a month ago. He likewise suggested downjetting due to the elevation change.

So, I got the carb out, got a look at the jet (78), and ordered various other jets from Treatland (70, 72, 74, 76). Going to try the 74 first, as per Sabatino's recommendation. All in all, feeling somewhat accomplished so far considering I have zero prior mechanical experience.

@rebel. It's the dellorto 15. And I'm sorry to say that I don't know the answers to your other questions since I'm not well versed in mechanics. But you can see the moby and some info here: https://www.sabatinomopeds.com/product-page/1978-motobecane-50v

@dillon and @pat: I appreciate the recommendations. I'm gonna downjet first, since Sabatino seconded that idea and because I want to limit how many variables I'm messing with at any one time, especially because this is all new to me. Will report back and, if downjetting doesn't do the trick, begin considering other possible options.

@PD thanks! I'll check'em out.

BAD NEWS: fractured my hand in a bicycle accident yesterday. Definitely going to impede progress on both the project and riding for a bit :(

Just wanted to report back that a few weeks ago I finally got the chance to get to work on this. Downjetted to a 74 (as per Sabatino's recommendation). It was my first time doing any real work on a vehicle, but with a combo of Sabatino/MopedArmy/Youtube, I got through it smoothly. I feel pretty proud, even though it was only a minor mechanical operation.

Anyway, all is well now! The motobécane runs as good as it did up in Portland. Back up to 33ish MPH on flatground. I went for a 10 mile or so ride today, with a pitstop to pick up some pizza along the way. Great fun!

Thanks for the help everyone. Mopedarmy rocks!

Huzzah!

Excellent news