90cc Minarelli Quad

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DanielO.
Posts: 180
Joined: Fri Sep 07, 2012 1:19 am
Location: Efland NC

90cc Minarelli Quad

Postby DanielO. » Sat Aug 27, 2016 11:39 pm

So let me start out by saying that this past Friday, I tried really hard to take the ZX and the scootie kart to the track... It wasn't meant to be... but I will try again this week and there will be pics and Video!
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Since that adventure was thwarted, I decided to tear apart my little Dinli Helix 90cc kiddie quad I've been beating on for the past year or two.... I bought it for $40 bucks out of the boneyard of a shop that was downsizing. the transmission has a High and Low range and reverse, High range had teeth stripped off the gear so I pulled the counter shaft gear off and have been running it in low range... I de-restricted the throttle and the top speed was about 21 mph..
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I expected to destroy the thing in short order but it kept on and on.. pretty much the most fun I've had for 40 bucks... the bodywork did take some abuse, I mean really.... who's Idea was it to make ATV bodies from rigid plastic? Don't they know whats going to happen?
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Last winter I decided to make a pipe for it, and put on a bigger carb... I knocked up the exhaust using the headpipe from another mina quad I had laying around and a broken technigas rs2 that I got from Josh... it works pretty good... the carb was a YSN 28mm that also came from The Scooter Garage, you'll start to see a pattern here...
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Those mods, along with some 4.5 gram roller weights and random red clutch springs from guess where, brought the top speed up to 29 mph and improved acceleration considerably.. Then the clutch decided it didn't like all the abuse my 220 lb mass and relatively technical woods trail were providing so it kind of got sidelined for most of 2016... I had some health problems in February that have kind of lingered which got me behind in all other aspects of life... but I'm getting caught up and feeling much better so shenanigans may be more frequent in the coming months...
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DanielO.
Posts: 180
Joined: Fri Sep 07, 2012 1:19 am
Location: Efland NC

Re: 90cc Minarelli Quad

Postby DanielO. » Sun Aug 28, 2016 12:03 am

That gets us up to date with what has transpired with this thing, so now for what I'm up to currently.... I stopped by my good buddy Joshs like I do fairly weekly, and mentioned the aforementioned clutch issue... to which he replied, "I've got one" and proceeded to dig it out of a box of parts. I asked about a carb, because I had to put the 28mm back on the ZX where it belongs. "oh yeah, its only a 21 mm but its a PWK style carb so all your jets should work" so after a brief business transaction I had a bunch of new goodies to put on the quad... it was at that point I decided it was time to go nuts on this thing, and the engine had to come off... The goofy transmission had to go, and there needed to be some porting done..
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The bore actually looked really good, as did all the rest of the engine internals
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DanielO.
Posts: 180
Joined: Fri Sep 07, 2012 1:19 am
Location: Efland NC

Re: 90cc Minarelli Quad

Postby DanielO. » Sun Aug 28, 2016 12:39 am

Now the fun part begins, I came up with about 130 degrees transfer timing and 180 degrees exhaust...
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Lets make it 140/195ish and widen up those ports some, I only took one pic mid process... lots of chips! The porting setup Josh has really makes this kind of work easy, I'm thankful he lets me use it! I have a cheap chinese flex shaft tool but it's a toy compared to the professional tools at TSG
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Lets make a squish band head while we're at it....first the mandrel I made using an old spark plug and a bit of steel...
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and the donor 50cc head mounted up...
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and cut with a 12 degree angle to match the piston crown
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Finally, the bowl...No idea of the chamber volume, don't really care...
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one last pic for tonight and I'll post more as the engine goes back together...
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Areomyst
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Re: 90cc Minarelli Quad

Postby Areomyst » Mon Aug 29, 2016 6:24 am

AWESOME! I look forward to seeing the outcome.

Was 140/195 a typo? That's pretty high on the transfers. I figured you'd set them around 130, but I was busy when you were here an didn't pay as much attention to your project as I'd like to have. I'm glad you shared it here on the board! That thing is going to be a VERY fun quad to whip around the woods!!!

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

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Areomyst
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Re: 90cc Minarelli Quad

Postby Areomyst » Mon Aug 29, 2016 6:25 am

PS: The cylinder head looks far superior to the original one! I be there's a lot of torque and power to be found with the head modifications alone, not to mention cooler CHT!

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

DanielO.
Posts: 180
Joined: Fri Sep 07, 2012 1:19 am
Location: Efland NC

Re: 90cc Minarelli Quad

Postby DanielO. » Mon Aug 29, 2016 8:08 am

The transfer timing was already pretty much 130 degrees... I raised the transfers about 1 mm, and widened the B ports towards the C port...which I also raised... never re-checked with the degree wheel, I was being extremely sloppy about the whole thing... The exhaust port was the one I really hogged out, 70 percent of bore and reshaped the top edge considerably.. I'll put the degree wheel back on it when I reassemble and I'm checking squish clearance...

DanielO.
Posts: 180
Joined: Fri Sep 07, 2012 1:19 am
Location: Efland NC

Re: 90cc Minarelli Quad

Postby DanielO. » Fri Oct 07, 2016 12:15 am

Ok, time for an update... Still have not gotten to the track, if Its not the weather its something else... next Wednesday is looking promising.. On to the build... After looking back over my previous posts, I noticed that I incorrectly stated the transfer port timing was 130, and the pictures clearly show it's only 125... I put the degree wheel back on during assembly and the final numbers came out to 132/190 but somehow failed to take pics of that... bore and stroke is 52 mm x 45 mm ..actual displacement is 96cc

I spent a bit of time looking over the "lets see your porting thread" and seriously considered some heavy porting of the case.. Then, while actually looking at how the parts fit together, It seemed to me the first major choke point is where the reed stop nearly touches the cylinder skirt, and isn't that far away from the crank... So I made a reed spacer... Oh, and also cut away a fair portion of the rear of the cylinder skirt so the boost port windows in the piston actually had path to the boost port

without spacer
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with spacer
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Next was to actually assemble the bottom end, which was boring and I won't waste bandwidth on.. Then It was time to install the piston and cylinder and check the squish clearance.. It was a bit wide at first so I had to do a bit more machining on my cylinder head. I thought I had calculated it out perfectly but when I bolted it together the first time something was making contact...
I had not taken into account the arrow cast onto the piston, if you look close you can see a little mark on the bottom of the head where it was touching...I had to scrape it off
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I set it pretty tight .023"=.584 mm
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I wound up replacing all the bearings and seals in the transmission, which was also boring but necessary... Its worth mentioning though because Josh had all the parts in stock, and an awesome set of blind bearing pullers that made it so easy it took longer to take the pics than it did to pull the bearings...
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awesome seal driver too
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DanielO.
Posts: 180
Joined: Fri Sep 07, 2012 1:19 am
Location: Efland NC

Re: 90cc Minarelli Quad

Postby DanielO. » Fri Oct 07, 2016 12:50 am

On to the install.. I had to modify the engine mounts because the cases I used are more like the ones used on scooters than the weirdo Dinli cases...

no es bueno
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also, the whole engine had to move back about an inch and over about the same to get the sprocket to line up... I raised the front of the engine up about an inch to get some clearance between the right front wheel and the fan shroud... this required cutting the whole rear crossmember out and replacing it, and making a spacer for the front mount...

mucho mejor
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Relocating the engine meant that my carefully crafted exhaust no longer fit... I started to just cut an inch or so out of the header and re-weld it, but looking at the size of the pipe, and the new bigness of my exhaust port, I decided it would be more better to make a new header... It wound up being at least 2 inches shorter than before, which means MOAR RPMs!!!

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DanielO.
Posts: 180
Joined: Fri Sep 07, 2012 1:19 am
Location: Efland NC

Re: 90cc Minarelli Quad

Postby DanielO. » Fri Oct 07, 2016 1:05 am

last couple pics for tonight... I cleaned the carb I got from TSG, and installed the clutch and variator.. carb is an OKO 21 mm and it is a power jet model.. haven't played with power jet carbs much so I'll have to keep you posted on how it goes... I DID manage to fire the thing up today and after going from a 135 main jet down to a 122, it revs pretty clean with no load... much higher than before, I don't have a tachometer around but it definately sounds over 11k... I'm thinking 12.5k but I'll have to check it with someone who has more sophisticated equipment than I do...

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DanielO.
Posts: 180
Joined: Fri Sep 07, 2012 1:19 am
Location: Efland NC

Re: 90cc Minarelli Quad

Postby DanielO. » Mon Oct 17, 2016 4:49 am

After much swearing and gnashing of teeth, a video for your viewing pleasure!
https://www.youtube.com/watch?v=Vo_Egz_ ... e=youtu.be

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Areomyst
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Re: 90cc Minarelli Quad

Postby Areomyst » Sat Oct 22, 2016 12:28 pm

Man, that engine seems to really haul compared to before - and it was plenty of fun even then! I can't wait to get over there and ride it around some. Even with the heavy weights/light spring it seems like it's doing much better than before. :D

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

DanielO.
Posts: 180
Joined: Fri Sep 07, 2012 1:19 am
Location: Efland NC

Re: 90cc Minarelli Quad

Postby DanielO. » Mon Jan 09, 2017 12:32 am

Another video, a bit shorter this time... with some work done on the variator to get the rpms up a bit more and a slightly more aggressive clutch setup... still could use lighter weights... top speed is up to about 35, starting to get scary...

https://www.youtube.com/watch?v=4SYK5iE10HY


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