'78 Batavus Regency, Laura M56 sounds like a Pterodactyl

Soooo......got my '78 Bat finally running awesome. Swapped the crappy Encarwi out with a new Delortto 15.15 carb and MLM intake. It was running amazing. My son took it out for its first long-ish ride. Came back completely devastated.

Said it began to bog. Then made a really bad screeching sound coming from the engine. He had to walk it all the way home. I turned it over when he got it home and it started but, there is an AWFUL rattling sound coming from what seems to be the lower end. I'm assuming maybe main bearing(s). Or maybe threw a tooth of a gear.

Either way, he is of course devistated as we have been working on this for weeks. We finally got it running beautifully and now this happens.

Does anyone have any experience with this particular thing. I'm pretty savvy with this moped. Basically, the only thing I haven't done yet is split the crank case. Any help is appreciated!!!


Devastated father and son

Re: '78 Batavus Regency, Laura M56 sounds like a Pterodactyl

Sounds like it could have seized up. With the carb swap you went through tuning it to get the proper air and gas mix for the bike? A lean bike feels like a beas up until it does not have enough lubrication and heats up the cyl until the piston gets swelled and sticks to the cyl walls. Usually it is the rings that bloat into a port. Remove the head and see what the walls of the cyl looks like. If you "soft seized" the piston should still move. If the cylinder is still smooth then you could still run it. If it feels gouged then you will need to hone the cy and get a new piston. Or a new whole top end. If it is hard seized you will need to replace the whole top end as all the pieces are probably not salvageable.

Re: '78 Batavus Regency, Laura M56 sounds like a Pterodactyl

I hadn't even got to doing a plug chop yet. This was it's first voyage with the new carb. I did let it get up to temp before letting him take it for a spin. Did not seem to be running to hot and the exhaust seemed fairly rich. So I wasn't too worried about seizing her up. I'm hoping it is only top end. I'll pull the head once I've allotted myself the appropriate grieving time and quit being angry about it. From the sound of it, if the rings are shot, it certainly sounds like pieces of them may have made it down into the crank.

Re: '78 Batavus Regency, Laura M56 sounds like a Pterodactyl

Should be noted, that I do NOT have a cylinder kit. The head, piston and rings are all stock. The new carb does NOT have air/fuel mixture adjustment. Only thing that can be changed is up jet/down jet. I did NOT advance or retard the timing. It seemed to be "four stroking" without the silencer on the exhaust. It seemed to stop "four stroking" once the silencer was put back on. I'll start tearing into her once I'm not mad anymore....lol.

Re: '78 Batavus Regency, Laura M56 sounds like a Pterodactyl

The piston still moves but, feels VERY rough when carefully cranking her over. I dare not crank her over anymore until I pull the head and see whats going on. How do I determine if she is in fact running too lean if there are now adjustments on this carb? I should probably be running a temp gauge. But like I said she didn't smell or feel too hot and the exhaust had what I consider an appropriate amount of smoke.

Re: '78 Batavus Regency, Laura M56 sounds like a Pterodactyl

What kind of carb is on there. I thought they had some kind of sha on there. There is only an idle mix, but a few different slides that can be used for better mid range. The air/fuel mix is going to come from the ret and then the air flow through your filter. You can restrict or de restrict the airflow in your airbox. And those carbs have a big difference between idle and WOT. Idle will always be too rich if you have the top end jetted correctly. Always get a few plug chops in around the block before taking it out on a longer ride. Grab a 4 pk of plugs as you will want a new plug for each chop.

Re: '78 Batavus Regency, Laura M56 sounds like a Pterodactyl

The stock was an Encarwi H12. I could never get that thing to run right. The new carb is a Delortto SHA 15.15. No air/fuel adjustment. Only a main jet. It has a lever-style choke and only one main throttle slide. I bought an array of jets to go with it. However, the one that came with it ( I believe is a 62 or 65) seemed to be operating pretty well.

Re: '78 Batavus Regency, Laura M56 sounds like a Pterodactyl

What jet were you running? Please don't say the one the carb came with......

No, off the shelf comes jetted anywhere near what a moped needs. They are sold as generic replacements and it's expected that you will know the general jetting range. If I remember correctly, sha15's come with a jet in the low 60's? Range. Too lean

Are you running the correct size dellorto intake shim? Did you put an o-ring into the carb mounting clamp throat before mounting the carb?

I'm betting airleak or improper jetting... :( (edited)

Re: '78 Batavus Regency, Laura M56 sounds like a Pterodactyl

The jet that came with it is either a 62 or 64. My intake at the head has reeds and a factory spacer which I left intact. The carb side has the correct shim. I pulled the one out that came with the carb. Was a bitch to get out. I did NOT put an O-ring in there. But, I did test with carb cleaner for air leaks. There was no change in RPMs.

Re: '78 Batavus Regency, Laura M56 sounds like a Pterodactyl

Whoopsie, diddnt see that last post.... yeah, probably improper jetting

I believe I was running a 70 on my Batavus when I had it. That was years ago tho. Could be wrong.

Re: '78 Batavus Regency, Laura M56 sounds like a Pterodactyl

Regardless, pretty simple engines. Pull the cylinder and feel the crank directly for slop and roughness. You might have gotten lucky and just seized your top end in which case it won't be a huge deal. But if you did seize the crank. It's a bit more work to rebuild but not a hard job.

Re: '78 Batavus Regency, Laura M56 sounds like a Pterodactyl

Welp, most likely my fault she seized up. This sucks! I was going to ask, what size jet SHOULD I be running. I bought up to a 68 I believe. Now to tear the head apart and see how bad the damage is. Hopefully the head and piston is salvageable and I'm just looking at rings and a good cleaning. But, knowing my luck....probably not.

Pieces of rings can make it down into the lower end, right? Am I looking at a guaranteed case split now?

Re: '78 Batavus Regency, Laura M56 sounds like a Pterodactyl

Most likely you seized the bottom end bearings, that sound your describing points in that direction. Soo yeah, spliity time.

If you seized your top end, it doesn't necessarily mean you broke the rings.

You will know once you pull the head and cylinder. If it's the bottom end, spinning the crank manually will feel chunky, gritty...etc..should be buttery smoothe. If it's the top end...well you won't overlook it.lol

Like I said I think I was running at 70. .there's probably an entry in the wiki with jetting info though.

Re: '78 Batavus Regency, Laura M56 sounds like a Pterodactyl

Thanks man! I'll try and keep you all posted. Grrrrr!!!!

Re: '78 Batavus Regency, Laura M56 sounds like a Pterodactyl

Yes I feel like 68 or low 70's is going to be the jet for that carb on a stock setup.

Get an o-ting in there. The cab has to have it. I respect that you had checked for an air leak and did not detect one, but I am still going to advise putting one in. I bought a little o-ring kit from harbor freight for like $5. It comes with all kinds of o-ring, one of which is perfect fit for the sha intake area. They sell a specific formed o-ring for sha, which I have had included in the two 16:16 sha that I have purchased.

Dont be discouraged even if it is something that could have been your fault. Just a learning experience. It is just a moped after all.

Let me tell you how much my immediate neighbors hate me because of all the tuning runs in front of my house.

Re: '78 Batavus Regency, Laura M56 sounds like a Pterodactyl

So this o-ring should go in after the shim. So it is between the shim that is already installed in the carb and intake pipe?

Re: '78 Batavus Regency, Laura M56 sounds like a Pterodactyl

No, put the shim into the carb. The press the o-ring into the shim. It gives a rubber mating surface fully around the circumference of the intake manifold, so the whole round end is sealed to the carb

The shim fill the space around the intake so it can clamp on, the o-ring is smooshed between the intake and carb throut.

Wouldn't worry about it untill you diagnose your problem tho...it could also be a Piston pin clip that flew out and trashed the cylinder.

Re: '78 Batavus Regency, Laura M56 sounds like a Pterodactyl

Werd! Yeah, right now I have much bigger problems...lol. As I'm sure you're aware, these old Bats are pretty hard to find parts for. I'll try and snap some pics of my face wincing as I open her up for ya!

Re: '78 Batavus Regency, Laura M56 sounds like a Pterodactyl

No on aaron with the oring. If you have tour carb off. The oring goes in to the intake mou ting area first. The shim I never remove from my intake so I never consider it a part of the carb. I consider the shim part of the intake. So basically the oring is sandwiched between the carb body and the plastic shim. The oring will seal off the clamp gap on the carb body.

Re: '78 Batavus Regency, Laura M56 sounds like a Pterodactyl

Doesn't sound like a seize since you were able to re-start it. Sounds more like bottom end. Probably due for bearings/seals anyway. I have a set that I have been planning to put in my M56 this winter, just haven't got to it yet. Here's the list of bearings/seals you'll need: https://vintagemopeds.net/batavus-laura-m56-engine-bearing-seals-rings/

If you have trouble finding them, check with a local bearing shop. They can usually source them, if not let me know and I can probably find you some.

They also have a lot of manuals and stuff there for M56: https://vintagemopeds.net/manuals/

Make sure it has gear oil when you rebuild it (be interesting to see if it had any in it right now). Also, as suggested, you should probably check your jetting on that SHA. I doubt the stock jet is correct.

Re: '78 Batavus Regency, Laura M56 sounds like a Pterodactyl

I was wondering the same thing, if it was just time for the bearings to fail. The moped sat (with the previous owner) for approximately 7 years with no fluids in it. I, of course, checked it before running. I'm currently running ATF Type F in there right now. I'm not 100% sure if that is correct.

I've seen this list from Vintage Mopeds. Thanks so much for providing the link. I have a buddy who works in sourcing bearing so, hopefully it is relatively easy to find them all. I've done pretty much everything to this bike except for the breaks and splitting the bottom half. I'm a little apprehensive about it to be honest...lol. I've read up on it some. Is heating the case to over 200 degrees paramount? Or is that just to facilitate removal of pressed bearing, etc.?

And yes, definitely going to start high on the jetting and work my way down with ample amount of plug chops. Thanks for the input!!! I'm going to pull the cylinder this week and check out the top end. If she looks okay, I'll start tearing into the lower end. Do you think my gears are okay?

Re: '78 Batavus Regency, Laura M56 sounds like a Pterodactyl

Per the M56 tech tips pdf in the link above: "Hold the engine at a 45 degree angle, filling it with oil to the bottom side of the fill and drain opening. By doing this, the gearbox will be filled with approximately 80 cc's of oil. Use motor oil SAE 50 or gearbox oil SAE 80. After the break-in period of 500 miles, the oil should be drained, refilled with fresh oil, and then should never require another change."

I haven't ever cracked an M56 open yet, but I don't imagine you should have to heat it to do so. Probably need to for removing the old bearings and possibly installing the new ones. Again, haven't taken this motor apart so I can't even visually think of what it looks like inside.

Gears are probably fine. Hard to say for sure though without looking at them.

Re: '78 Batavus Regency, Laura M56 sounds like a Pterodactyl

if its crunchy when u turn it by hand you gonna have to forget about the jetting stuff and do a full rebuild.

Re: '78 Batavus Regency, Laura M56 sounds like a Pterodactyl

Bearings failed I’d guess.

I’ve never had an o ring in my sha on the regency or any other bike and never had a problem.

My 14.12 sha on stock regency with a biturbo hacked on (hasn’t changed in over 10 years) is running a 56 Pacco jet (much to my surprise just now when I popped it open to check).

Anyone know if pacco jet sizing is...different? Because that seems v small. Haha

Re: '78 Batavus Regency, Laura M56 sounds like a Pterodactyl

My bearings could have very well just been ready to shit the bed. The ped sat with the previous owner for 7 years dry as a bone with no fluids in it. I checked everything as best I could before running her (without splitting the case of course). The plug chop (post incident) actually looks great. Nice dark tan/milk chocolate. So, I'm not so sure she was running too lean. I also performed air leak checks after installing the new carb. The air leak check was good. I'm certainly not opposed to the o-ring thang. I'll give it a shot when I rebuild her (in the cooler months because its too damn hot here). For now, I got an '08 Tomos running pretty well for the kid.

« 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