Suzuki 2 Strokes

I have just recently purchased a restored GT550 1974
Question is, the bike runs really well, but under hard acceleration there is alot of smoke, also at 80- 90 km/h there is no visable smoke, but when 100 km/h is reached there is smoke from all exhausts.

I have checked and set up the oil pump exactly to the manual.

Inspection of the spark plugs shows them to be ok. ( the bike has electronic ignition which I have checked and all set up OK.)

Is it normal for these bikes to smoke constantly at 100 km/h or over? I wouldnt have thought so?

Hi and welcome.

The big clue is that you've just recently bought the bike. If the previous owner only rode the bike gently, a LOT of oily crud will have built up in the exhausts, and as the bike gets used a little harder, that stuff starts burning off causing the excess smoke.

The best thing to do is give the bike an Italian tune-up: top up your 2-stroke oil tank, fill her with petrol and take her for a long ride out to quiet roads with no cops or speed-traps, and give her a good workout. If you're able to, hold her at 6,000rpm or so in top gear for a few miles. You'll make smoke like a crop-duster initially, but it will help clear out the pipes and afterwards it will smoke less.

As for the 2-stroke oil itself, any brand-name 2-stroke injector oil that meets the JASO FC standard is ideal.

+1 with Craig on the above. Also have you been starting the bike in the garage without riding it afterwards. Some owners do this and it causes condensation to form on the inside of the pipes which will collect at the lowest point .thus then turns into steam when the bike is ridden. At the end of the day these 2 strokes like to be ridden and ridden hard occasionally to clear out otherwise they choke up.
One last thing to check is your transmission oil level as when crank seals fail it can be sucked into the cylinders and burnt during combustion.