Abarth

Those side covers look mint man, I'm keen to do this on my K0. Are you going to spray them with matt clear coat to keep them crisp?

The tires on it also looked about the same age as the shocks so they were binned for new ones, I liked the ribbed vintage look so I got some new Chen Sheng and Maxxis tires.

Then had a massive day at the workshop;

Installed new rear shocks

New tires, inner tubes and rim tape

Stripped and rebuilt the front forks, new genuine Honda seals and fork oil.

New brake shoes, lubed the brake drum mechanisms.

Tided up some rough as guts wiring around the points.

Rides well now, handles solid round corners and the brakes actually work. Stoked!

Next mission was to upgrade the way it went round corners, with blown front seals weeping milky fork oil and shocks on the rear which looked like the factory ones it was lose in the corners. Offered a lush ride over bumps but thats about it. 

Got some new rear shocks and painted the tops black to blend into the bike better.

This graph is for a Vespa 50cc 2 stroke but should be similar to the Honda 50cc 2 stroke. 

Handy for guessing peak power with different exhausts.

7.5 grams would be good to start with. Factory ET2 and LX50 vespas ran these weights and could hit 70kph on the flat. 

Yeah that port is effectively a breather, filtered through a carbon canister for emissions etc. Apparently people plumb it to the air filter?

With the idle mixture screw, generally its clockwise lean, anticlockwise rich. There will be a manual or something which specifies that the screw should be 2  to turns out from close. Set it 2 turns out,start the motor and warm it up, then screw the idle mixture screw slowly in till the motor starts to stumble, this will make it run too lean. Then slowly like quarter turns screw it anti clock wise to let more fuel in, you should hear the engine speed pick up a bit and smooth out. Too far antilock wise and it'll start to run poor again as it'll be rich. Should land somewhere close 2 turns out.

I used a glass spark plug to set this up on my motorbike thread, makes it an easy job but you should be able to get it reasonable good by ear.

Man this car is sweet, I've enjoyed watching it's progress.

That's a port to the carbon canister.

How does it run rough? Just Idle?

These motors respond well to side draft carbs. I had 40mm Solex's on my Fiat (same motor) and it was good for 130hp in standard tune.

Been riding this as my daily, everything was running good except the battery kept going flat.

Found these specs on the net: 

CB250 = 110W output (~8A)
1156 bulb draw - 27.3 watts EACH (1.93A)
1157 bulb draw - 26.9 watts full (1.92A), 8.3 watts running (.6A)
Headlight - OEM - 25W/35W (1.7A/2.5A)
coil charging (assuming 5 ohm primary resistance, 14.5 volts) - 42 watts (2.9A)
neutral/indicator bulbs - 3 watts (.2A)

So the charging system wasn't up to the task of keeping the battery charged while riding round with the headlights on 100% of the time. To fix this I upgraded to LED bulbs which use about 1/8 the power; brake light, park lights and gauge lights. Way brighter now and the battery stays topped up.

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This is interesting. My CL175 never ran right even at the factory settings. Think I might give this a go. How does the carb balancer work? 

Seedy's right it uses the vacuum from the carb to raise a little ball to a number. In this case the little ball is more of a peg shape sitting inside the orange plastic case, in the photo is hanging round the 1 on the gauge. When both carbs we in sync the gauge read about 2.5 for both carbs, do one at a time. 

These are the tools:

https://www.machinemart.co.uk/p/gunson-g4053-carbalancer/?da=1&TC=GS-052114053&gclid=CIfA4peDz9ACFQoB0wodavkDSA

https://www.machinemart.co.uk/p/gunson-g4074-colortune-single-plug-kit/

On 28/11/2016 at 08:29, Seedy Al said:

I have seen these two tools before from ye old days style.

Had never actually considered just how useful they would be for a motor bike tune. Much approve!

Yeah they work mint, I set it all up initially by ear and following workshop manuals like the pilot screw should be approx 1.5 turns out etc. But I was way out, running rich with the left cylinder doing all the work. Looking forward to using this on the Fiat's DCOE's when I get back to NZ. 

Clutch springs will help with launching it at every set of traffic lights.

Keep the factory air box if you're keen to keep the noise down.

With the pipe it's important to find which RPMs it makes the most power. Then attach cheap tachometer and tune the CVT gearbox to run at peak power RPM using different roller weights.

Off with the seat, duct tape fix wasn't cutting it anymore so I ordered a new seat cover and set about recovering it.

The foam underneath was actually pretty good, also drowned the metal seat pan in rust killer to tidy the underside up a bit. 

While waiting for the tank to cure I hit the engine with a brass wire brush to tidy up the oxidation on the engine. Worked surprisingly well.

Before

After: Other side of the engine but yeah it tidied up good.

Inside of the fuel tank was very rusty and kept dropping bits of rust into the fuel so I got a POR15 tank kit to fix this. First I stared with the degreaser:

Then added the Metal Ready rust converted for 2 hours turning every 30mins:

So far so good, have to wait for it to dry out completely before adding the final seal paint to the tank. After that it's a four day wait to let it cure before filling up.

Added the sealant paint, came out a bit lumpy, but coverage is good.

Earlier in the week I cleaned the inside of the carbs but reused the all the old parts to get it running. Which it did but not well, wasn't making any power. I decided to give them a proper rebuild with a Keyster carb kit:

 

 

After riding the Honda home the right cylinder started smoking like crazy in traffic, bellowing a white smoke screen behind, which is great from high speed escapes but not so much oil consumption.

I assume what's happening is that once the oil heats up it runs past seal and into the combustion chamber.

Question is - is there an easy way to change them without having to take the head off? It looks like a generic collet that holds the valve spring. Need a valve spring compressor that bolts to the head?

Got stuck into the bike as soon as we got it home, side walk mechanic style complete with the necessary G&T.   

This bike hadn't run properly for 8 years so I started off with the basics, gave it a good clean and degrease. 

Rust stains on everything, use the tinfoil and lemon trick on the chrome which brought it back to life. Cut the paint too which actually came up not too bad in low light

Removed the rear chrome parcel carrier which I'll hang onto if I ever decide to do some long distance rides.

The carbs on the other hand; dang time has been unkind to these. I pulled them apart and soaked them in carb cleaner over night. After this they actually came up alright, I still need to put a proper rebuild kit in as the O rings are toast and one leaks from the float valve not shutting properly. 

Loads of performance parts available for those GY6 / QMB139 engines. Best upgrade for those engines I found was swapping in 5 gram rollers.

Looks cool with the decals.

http://www.pedparts.co.uk/blog/sports-exhaust-testing-50cc-and-70cc-sports-mopeds-part-one

Read this blog mate is base upon the Piaggio 50cc 2 stroke but its got some wicked insights into what rpms the engine should be running at make decent power with the expansion chamber.