1997 Honda Dio SR AF18

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bainer1290
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1997 Honda Dio SR AF18

Post by bainer1290 »

Hi there,
I am re-building a Canadian Dio SR AF18, has 12,500 km on the odometer, in great overall shape, runs but has low compression. Thinking of putting a 70cc BBK kit and trying to decide between the:
-Polini Contesa 70cc Sport kit
-Malossi 70cc Sport kit

Planning to leave the stock crank in it as the bearings are good and I will replace all the engine seals/gaskets upon rebuild. Would like to use the stock carb and exhaust as well, might get an aftermarket pipe down the road but this will be used often for both commuting and fun so its needs to have drivability and reliability.

What do you recommend?
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NZHonda
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Re: 1997 Honda Dio SR AF18

Post by NZHonda »

Welcome to the forum. Please upload pictures. We love pictures! As for your question. I can only speak to the Malossi cast BBK.

I have an AF28 JDM Dio ZX. AF18. Years and years and years ago installed a Cast 72cc Malossi BBK.

My brief was the same as yours. I wanted a reliable but faster scooter. I would rate the malossi BBK up there with factory Honda quality.

My original spec was stock carb, exhaust & crankshaft. The Dio went really well with this combo. The beauty of this setup is the scooter instantly gets better in every respect. Acceleration and top speed improve but it can also climb hills/mountains. I regularly ride mine on an event in New Zealand across a mountain range. The cast malossi is a fantastic BBK.

At the very least you'll want to add the BBK (of your choice), Malossi Variator and Belt, re-jet your stock carb, TTO temp gauge, fuel/oil mix.

If you're going to replace the crank shaft seals and split the cases then you may as well throw in a new set of OEM Honda bearings. The BBK went straight onto my AF18 without changing the bearings. I didn't even get the cylinder run in before the bearings shat themselves. I should have done them from the start. The BBK puts a lot more pressure/force/effort on those bearings.

The cast malossi BBK is an excellent upgrade. It is streetable and reliable. It will run on the standard carb and exhaust but will also respond well to any future upgrades.

Good you've done some research and we're comparing apples with apples - the 2 street big bores not the racing big bores from Malossi and Polini.

Looking at scooter swap shop website the price is the same so it's up to you.

https://scooterswapshop.com/products/ma ... linder-kit

https://scooterswapshop.com/collections ... g-bore-kit

http://hondaspree.net/phpBB3/viewtopic.php?f=4&t=30265

http://hondaspree.net/phpBB3/viewtopic.php?f=4&t=28820
Honda AF28 Dio ZX - Malossi 72cc
Honda DJ1R project
bainer1290
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Re: 1997 Honda Dio SR AF18

Post by bainer1290 »

Thats great info thanks for the reply! I will have to share some pics as we start to put it back together since its in pieces right now haha

The scooter came with 2 belts, an old maybe original Honda Bando 23100-GZ5-0130 and the one on the engine was a Versah 634 15.5 30. The Versah looks to be in good shape but is 634 too short? The oem Honda belt listed for it is 641 15.5 30, but then I see on some Scooter sites they list Polini and Malossi belts that are 649-652 long but slightly narrower 15.3-15.4. I assume the length/width has an impact on speed, so what do you recommend for my build?

For the Variator I may buy a better one down the road but for now just plan to replace the roller weights. The ones in there have some flat spots and I weighed them and I think they were 9 grams, with the Polini or Malossi BBK and the rest of the bike being stock what weights would be good for street drivability and fun?

Thanks again!
bainer1290
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Re: 1997 Honda Dio SR AF18

Post by bainer1290 »

Anyone with more info on belt sizes and its effect?
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Re: 1997 Honda Dio SR AF18

Post by bainer1290 »

A box of fun arrived today!
Polini Contessa top end
Athena Crank
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bainer1290
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Re: 1997 Honda Dio SR AF18

Post by bainer1290 »

I was checking out the Athena crank wrist bearing that it came with and its 12.7mm wide. The Polini piston has an opening of 15.3mm, so about 2.6mm of space. The oem piston measured 15.1mm and the oem wrist bearing is 14mm, so leaving only 1.1mm space. No thrust washers were included so am I good to run it with this spacing?
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ntonar
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Re: 1997 Honda Dio SR AF18

Post by ntonar »

Yes, the cylinder will keep the piston centered once installed.
bainer1290
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Re: 1997 Honda Dio SR AF18

Post by bainer1290 »

Yes I was more concerned about the pin bearing, the piston and rod should stay centered but the bearing can move freely. However it would still have 85-90% coverage on the rod bore even if it was all the way to one side or the other so I assume that is a non issue?
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Re: 1997 Honda Dio SR AF18

Post by Meatball »

Get a wider bearing. The ones I run are like 15.7mm or so. The small end bearing that Athena provides must be for a different slug. The bearing cage can hang out either end a bit, thats fine. Even the rod on the Malossi MHR is 12.5mm or something so the width of the Athena rod is spot on. SSS has good small end bearings on hand.
I need to find some new haters...the ones I have are starting to like me.
bainer1290
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Re: 1997 Honda Dio SR AF18

Post by bainer1290 »

Ok I figured that might be a bit too much free space, I might just order an oem Honda one in as they are a decent price $10
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