85 Aero 50 project

[colvinry]

hey guys new to the forum. Picked up A project bike.going through it right now. Piston and ring gaps are out of spec. I would like to build is close to stock as possible. What do you recommend I do? Aftermarket big bore kit or stock oversize pistons? I don't want to mess with sourcing a new carb and would like to have something that works with stock components. Do you have a source for the stock oversize piston's?

I found some on partzilla but they seem to be overpriced a tad and I can't seem to find a full rebuild kit with the rings and gaskets. Does anything like this exist?

does anyone on the forum do any machine work
? Mainly I would just like to have the cylinder board to match the oversize piston. I'm thinking I'll probably source this locally but I figured I would check.

Thanks for the suggestions, and I look forward to putting this scoot back on the road!

[Wheelman-111]

Greetings:

If you're going to all that trouble, I recommend a Polini or Malossi 47mm cylinder kit. The stock carb and airbox and pipe work just fine, and there's a real boost in performance. No loss of reliability if you jet the stock carb up to 90 or so with stock airbox.

[benji]

I would also suggest this, but doesn't have to be malossi or polini those are the favorites here tho. It is possible to get a used or nos bore and piston, but if your going to pull off the jug you might want to go bigger anyway, it's nice being able to have some power when you need it.

[colvinry]

Do you know anyone who is trying to sell either of those kits? or a reliable source for them?

So will any 47mm and 10mm wrist pin kit work in the 85 aero?

[benji]

Graphite9 aka scooter swap shop

[kuromi]

So will any 47mm and 10mm wrist pin kit work in the 85 aero?

You'll need to make sure the ports on the base of the barrel match up with the crankcase, or at least cover each other up with enough meat to make alterations.

Also the barrel needs to be the right height so when the piston is at top dead centre it isn't so high it smashes into the head, or too low so you lose compression.
In the case of too high you can add extra base gaskets to the cylinder to lift it.

There's plenty of tuners on here who'll tell you what will and won't work and I think there's a lot of options for Aero's.

[colvinry]

I went with the malossi 70cc kit. I ordered it from the Malossi USA website. I hope they are reliable, I would of went with the forum member but I found it and ordered before I check for any replies. I hope Malossi USA is a decent vendor.

I was researching the #90 jet for the PA04G Keihin carb. The only one I found was on CMSL and it was overseas. Have you guys had any luck with drilling the stock jet? Do you think this is a viable option? It sounds easy in theory but I haven't tried drilling jets before, I imagine it is a finicky task to do correctly.

Since I am going with the 70cc kit and upping the power a bit, where is the bottle neck on this setup going to be? (carb, air intake or exhaust). Will the stock rollers work okay for general around town use? Not trying to do wheelies but I would like to keep up with traffic as much as possible.

I am going to need new tires, does anyone have any recommendations? Looks like the stockers are 2.75 x 10. Do you guys put more rubber on for a plusher ride or do the stock tires do the job?

[Wheelman-111]

Greetings:

Daytona brand manufactures the only kit for the popular PA series carbs that I have owned. DayWot, JiangWayne, sold them at one time. Drilling is fine, I have done several. Hold the bit, spin the jet. Don't wobble.

Stock rollers are 10g. Get 7s-8s and experiment. The stock pipe is a bigger performance impediment than the intake side. Graphie made an attractive alternative, and there's a LeoVince #4447 and the Malossi Wild Lion if you can find one.

3.00 tires fit fine on stock rims. Pirelli SL is an affordable choice at MotorcycleSuperstore.com.

[colvinry]

I received my Malossi 70cc BBK yesterday and was looking over the manual and the compression ratio was in the 13's to 1 range, I believe. I will have to double check. The compression ratio got me thinking about the fuel octane. What octane fuel should I run in the kit to avoid detonation?

If the kit requires higher than 93 or so (readily available pump gas) can I use additional gaskets to raise the cylinder and drop the compression ratio?

Any advice or experience with the kit is welcomed.

Ryan

So I did a little math and a 13 to 1 is way high. Based on increasing the piston to 47mm diameter with the same stroke and head the compression ratio should be about 8.4:1 , I will look at the Malossi manual and confirm. Answering my own questions over here, helps to write it down and think about it.