horizontal Minarelli Differences

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radioflyer
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horizontal Minarelli Differences

Postby radioflyer » Sat Mar 09, 2013 3:33 pm

Hello I was wondering what the differences in these engines in the U.S. are?


Do all the US motors take the same parts? Do the aftermarket gears for a jog fit the zuma too?
Do they all come with a 10mm wrist pin or do some have the 12mm pin?

Is there a post or link that explains compatibility that you could share?

Thank You

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Areomyst
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Re: horizontal Minarelli Differences

Postby Areomyst » Sat Mar 09, 2013 4:17 pm

radioflyer wrote:Hello I was wondering what the differences in these engines in the U.S. are?


Do all the US motors take the same parts? Do the aftermarket gears for a jog fit the zuma too?
Do they all come with a 10mm wrist pin or do some have the 12mm pin?

Is there a post or link that explains compatibility that you could share?

Thank You


There are several different types of Minarelli engines, as you may suspect. I've taken some photos today showing the difference between some of them, and I will get them posted up later on tonight.

Most in the US have a 10mm pin, but many also have 12, depending on where it came from. I will let the photos clarify, but won't be off work till later on. :)

Best,

~Josh
"The more a man learns, the more he realizes how little he knows."

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Areomyst
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Postby Areomyst » Sat Mar 09, 2013 11:42 pm

If you have a Yamaha Zuma, Yamaha Jog, etc, you can rest assured that your cylinder and piston are the standard Minarelli type. This is a 40mm piston with a 10mm pin. However, if the scooter you're sourcing parts for may have been modified, or perhaps it's a Chinese bike with a Minarelli clone, a CPI, or other type of Mina engine, then you may want to have a close look at your cylinder before ordering parts.

There are a couple of key things to pay attention to with the Minarelli cylinders/pistons. Probably one of the easiest things to spot, is your piston pin size. They're usually 10mm or 12mm.
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If you're not sure what size the pin is, you can remove the pin and measure the OD of it. The coating on the piston in the above photo is irrelevant to the focus of this post - some of the new kits come with coated pistons.

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So, the piston pin is easy enough, but what about the rest? In the above picture, the middle cylinder is the typical Minarelli cylinder found on the Yamaha Zuma, Jog, Vino, Eton Beamer, Malaguti air-cooled engines, etc.

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The above two photos are of what I call the "standard" Minarelli cylinder. If you put the cylinder on the table with the exhaust flange flat, you can see that the angle of the exhaust flange causes the cylinder to tilt towards the left a bit.

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The above two photos, show the CPI style cylinders. Notice how the cylinder is laid on the table with the exhaust flange flat on the table. From the front view, this cylinder is not tilted to one side or the other as the standard Minarelli is. The angle of the exhaust flange is different. Also notice the boost port! The boost port is smaller on these CPI cylinders. They typically come with a 12mm piston pin, but I have seen them before with a 10mm pin also, so you really need to check first to be certain.

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Finally, there is this type of cylinder that's seen a bit less frequently than the other two. It has the same style transfers as the standard Minarelli, but the exhaust flange is the same angle as the CPI! This cylinder came with a 10mm pin, but again, measure to be sure when you're ready to order a replacement cylinder for your Minarelli engine.

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Finally, in closing, a lot of Minarelli cylinders come with this "D" shaped exhaust port. Oftentimes, it's worthwhile to cut the port to match the exhaust better. In the above photo I outlined where I would cut with a marker. There can be a small performance gain to be had here. I have not yet measured the difference on the dyno, but that is a modification that I feel pretty confident about anyway. :)

Ciao!

~Josh
"The more a man learns, the more he realizes how little he knows."

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2strokd
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Postby 2strokd » Sun Mar 10, 2013 1:42 am

This is informative.. Good to see all those different cylinder lined up.
I have found my CPI and other mina,s to be different than what you have explained Josh. Not that your wrong, i like what you have come up with.
However, on all my Mina,s barring the FM style, or anything over 49cc from the factory. CPI or not, all i have seen cylinder wise are the standard style mina cylinders you have shown. Never a straight flange, or smaller boost ports.
I have seen these kits on forums. One was ordered as a factory replacement for a Vento and had those small boost and trans tunnels.

Do get allot, almost all of them with the D cut ex port tho.

Most all CPI, or Chinarelli,s (China based Horizontal Minarelli,s) before 2003 have 13mm crank shaft vari splines, and a 10mm piston pin..
After 2003 and you have a 12mm piston pin and a 16mm crank shaft.

Here is were it gets even more complicating. 2003 was a mixed year. I have seen this year engine with a 16mm crank (vari) shaft and a 10mm piston pin rod end. After research and seeing others with the same combo on the 2003,s only, i think this is the only "mix" year.

Overall, to be sure. Like Josh said, its best to look yourself. Your scoot might have had an engine swap at some point, who knows?
The CVT is seriously underestimated by some!
01 CPI Misketo MZ49cc to70 to103cc-Drag scooter
03 Kymco Cobra (SF10)49cc- Daily driver

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Areomyst
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Postby Areomyst » Sun Mar 10, 2013 7:49 am

I've messed with a lot of CPI Olivers, Oliver Sports, and Oliver City scooters, along with the GTR, etc and they've all got the flat exhaust port. (I haven't worked on any older than 2005 though, I don't think!)

Perhaps the MZ Muskito is different? Even the CPI GTR is the same of course, the difference being that it's liquid cooled. :) This was at the CPI dealer I used to work at. Oddly enough, we did not carry the MZ scooters, so I haven't gotten to mess with many of them, but I've rebuilt a few. I don't recall from memory, but I think you're right - standard cylinder, 12mm pin, 16mm splines and the "bigger" taper on the flywheel for those ones?

I think that different China bikes are popular in different areas of the country. Most of the China bikes I have messed with are the standard Minarelli cylinder, with the standard 10mm pin. Some of them had the 12mm pin and larger splines on the crank though, as you mentioned.

Here's some more, from 2007:
Areomyst wrote:The 2007 and 2006 Marshin cylinders are different. The 2007 Engines have the carters that fit the Yamaha Jog 90 cylinder! No machine work is required to fit it either. I was quite surprised to discover this. Here are some photos showing the differences. Keep in mind, that it also has longer stroke, but the same bore as previous engines. When the engine is back together, I will measure bore and stroke to get exact displacement.

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Note the longer deck height on the new cylinder on the right. Also, the cylinder barrel is wide at the base... it is the same width of the 90cc cylinder that I recently installed on an 06 Marshin! I could have just used one of these engine blocks and not had to do any machine work. Now I know. :)


Image


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Old cylinder is on the left, and new on the right. Notice the wider transfer tunnels.


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Another comparison in deck height. You can plainly see that this cylinder would require a longer stroke crankshaft.


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Here is the small end of the connecting rod. It looks like it was cast to be bored to 12mm, but I guess they decided to keep it at 10mm.


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The difference in crankshaft splines. The 16mm is the new one. On the 90cc project, I used the stock variator off of a new 2007 Marshin Predator.


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The new crankshaft provides better lubrication to the big end bearing.


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The flywheel/magneto ends are different as well. Seems like the engines used in the new Marshins are basically the 90 engines turned into 50cc engines by using a smaller cylinder and 10mm crank. I think it's quite interesting, and I'll have to keep this in mind if I decide to do another 90cc project. I'll certainly keep my tooling in better order if I use these cases. :P

Regards,

~Josh
"The more a man learns, the more he realizes how little he knows."

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Areomyst
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Postby Areomyst » Mon Mar 11, 2013 8:08 am

In hindsight, I think I wrote wrong in the quote in the above post. I can't remember because it's been a long long time ago, but I think that oddball cylinder had a 39mm bore, and a 41.4mm stroke. In the above post, I wrote that it had the same bore, but in hindsight I'm pretty sure it didn't.

Cheers!

~Josh
"The more a man learns, the more he realizes how little he knows."

dan v
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Postby dan v » Mon Mar 11, 2013 5:16 pm

I found this interesting - http://www.minarelli.com/rseng.html

It may help in describing what engine one is working with if it is a real Minarelli :?

Spent way too much time reading the posts on 49cc scoot about the jog 90 china cases - AIRC the engines have a 52 in the number stamped on the case if it will take the 90 cc cylinders.

Don't forget about the 80cc two stroke China minaclones that were sold a few years back. as 50cc........
How many scoots is too many?

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2strokd
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Postby 2strokd » Mon Mar 11, 2013 8:15 pm

Great points!!!

Come to think of it, i dont think any of the CPI Oliver,s, Hussar, Popcorn, MZ,s, etc were newer than 05? Wait, i take that back, i did work on a newer (2011 i believe) Oliver Sport that was very nice. But i didnt get into the cylinder/ex port flange, etc. This one was missing the CVT cover support bearing from the factory and had a bad bearing in the trans.
The CVT is seriously underestimated by some!

01 CPI Misketo MZ49cc to70 to103cc-Drag scooter

03 Kymco Cobra (SF10)49cc- Daily driver

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Areomyst
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Re: horizontal Minarelli Differences

Postby Areomyst » Fri Dec 09, 2016 5:10 pm

I'm digging up an old thread here, because it's relevant. I was discussing drive belt compatability issues with one of my buddies from Greensboro, and wanted to mention some of what we talked about.

There are many more varieties of Minarelli style engines than what we discussed above. For instance, some of the Adly and Silver Fox scooters with the Herchee engines used a left side crankcase with a Vino-style gearbox, but they still have longer cases for the larger wheels. This ends up making those engines have a much longer drive belt than usual Minarelli engines - 878mm if I recall correctly.

The Yamaha Vino 2-strokes have some really nice crank cases as far as induction from the inlet tract goes - the reed block is wider and the cases have more volume - but because of this, normal Minarelli reed blocks don't fit. See the photos:
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IMG_2688.JPG (460.97 KiB) Viewed 5182 times

IMG_2689.JPG
IMG_2689.JPG (453.66 KiB) Viewed 5182 times


~Josh
"The more a man learns, the more he realizes how little he knows."


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