Moped Mountain motor

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Has anyone done this? Is there a build thread?

Re: Moped Mountain motor

> Charlie Dorius Wrote:

> -------------------------------------------------------

> Has anyone done this? Is there a build thread?

Do you have a Honda MB80/MT80/MTX80? What're you trying to put this on?

Re: Moped Mountain motor

Tomos!

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Re: Moped Mountain motor

🇮🇹💦 Of the Loin /

The reviewer is correct too

Stock MB5 does really well with a VM22 and better reeds

I can only imagine this would probably use a 28 no problem

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Well the description lists the bore as 57mm, not including the skirt diameter. Measure your Tomos cases. Also what's the stud spacing, is it the same? I'm not saying it can't be done I'm saying it's going to be a real hell of a time trying to do that, looking in the background of your pic it seems like you have a background in machining/fabrication so go for it if you know what you're doing

Re: Moped Mountain motor

Emil Kniemel /

Similar stroke lengths and difficulty sourcing a piston? Also fins pointed the wrong way or are you gonna liquid cool it? Seems like a lot of work but would make for an awesome build thread no doubt.

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I don’t think mounting the cylinder is going to be a problem. Will the case volume support a displacement of this size? Is that a thing?

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Sander Mulder /

What are you going to do about the stroke difference?

Re: Moped Mountain motor

I believe an MB80 has a stroke of 44mm?

The Tomos has a stroke of 43mm. So that sounds like a spacer.

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Or milling the mating surface down on the case? Or decking the cylinder?

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Dirty30 Dillon /

I appreciate the thought, but there are so many better cylinders that you could have used.

The Tomos trans will never withstand this. I doubt you'll even be able to open it up enough to use it.

Also, this is for 50.8mm stroke, if the wiki is correct.

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Interesting. I haven’t purchased a cylinder. What would be a better choice?

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57mm bore and 44mm stroke = 112cc. It’s advertised as 115cc. So I’m thinking it’s for a short stroke, over square engine.

Re: Moped Mountain motor

> Charlie Dorius Wrote:

> -------------------------------------------------------

> Interesting. I haven’t purchased a cylinder. What would be a better

> choice?

Any of the numerous kits made for a Tomos

Re: Moped Mountain motor

Where is the challenge in that

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Sander Mulder /

> Charlie Dorius Wrote:

> -------------------------------------------------------

> I believe an MB80 has a stroke of 44mm?

>

> The Tomos has a stroke of 43mm. So that sounds like a spacer.

Our mb8’s have a 49mm stroke

Re: Moped Mountain motor

Does anyone know of a 110mm connecting rod that uses a 14mm pin? I think the little end would have to be 18mm for roller bearings? In a perfect world the big end would be 21mm for the crank pin I already have, but it’s not critical. Any leads? Vespas? Motorized bike parts?

Re: Moped Mountain motor

most of the 80cc dirtbikes use a 14 small end rod but the big end is usually a lot bigger than a moped, and wider. You can use this chart or email pro-x with your desired dimensions and they might have something close. you'll probably have to shim or machine down the cases to get the deck height perfect-o

https://krakowparts.pl/original-connecting-rods-jasil-en

you might be able to find another piston to fit the kit, otherwise you can bush the piston pin bosses by pressing in an aluminum slug and boring it out to fit.

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Your Tomos guts are going to turn to dust

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Such negativity!

Maybe they will, maybe they won’t. I’ll cross the driveline bridge when I arrive there

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Thank You!

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But They will

Better to put the kit on something that could possibly hold up like an e50 or a m1 or hobbit or something without balsa wood internals.

Look up the Tomos Gila. It was nothing but problems.

If you insist on doing this, I will bathe in your tears. I’m due for cleaning

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I am doing this as an exercise. I’m certain there are better engine architecture choices, but this is what I have. And whatever scraps are left after it’s inevitable destruction can go to my kid for his bike.

What do you think will be destroyed first? Clutches? Chain? Gears?

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Clutches for sure

Then it’s a tossup. Shafts, gears, bearings

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usually first gear clutch explodes first, then second gear clutch, then if you get those two to hold the one-way clutch in the countershaft fucks up and cracks the housing, so you replace that then the soft cast iron gears get chewed up and your transmission gets obliterated by the grey paste of doom which means all new trans internals and all new bearings, plus a new side cover because invariably those exploding clutches trashed it. usually sometime around the second set of internals you give up because all you ever do is feed it parts and all it gives you is pain and crushing disappointment.

you can only gear them up to like 30x22 due to the physical limitations of the hub and the front sprocket, so there is really no point to go to a bigger kit that will be way oversquare and not rev correctly and throw off the balance and just break clutches. the puch polini is probably, practically speaking, the fastest kit you can put on a tomos and have it live. you can do 70 mph on that if you do it right, so i don't see any reason to go through all these crazy hoops for a bike that will, ultimately, be slower and less reliable than something thats bolt-on.

BUT HEY YOU DO YOU, SAVE SOME BATH TEARS FOR ME! Sometimes you gotta just wreck some shit and find out. Maybe you'll figure out how to do the open dry CVT belt setup or something wild and crazy. Whatever man its mopeds do it up.

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Thank you, I appreciate the insight! I have no expectation of it being fast. And I’m dead certain it will fail. But I’m having fun and it’s keeping me occupied and out the bars. Sorta.

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♣Slew Foot♣ /

Clutch materials and slip...

If you get it down to 180 gear transfer oil and get the fluid ramping effect going Tomos transmission will hold up. But even a WOP hero kit needs case welds...

An open port batavus with a tomar...?

Re: Moped Mountain motor

Vintage scooter con rods are likely in the range your looking for if you can fine one where the pins match then you can always add spacer and deck to get where you need on length. Dream team tuning must still be in the game cause the made some wild am6/tomos case recently as a one off. I'd get ahold of them for clutches. And if the gears become an issue start looking on dutch forums cause there are a few strait cut gears floating around albeit custom and likely pricey, but you knew this wouldn't be easy.

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