'72 Yamaha R5 Mikuni Carburetor cleaning

'72 Yamaha 350 Carburetor Cleaning for 2 cylinder, 2 cycle, engine that does not pick-up the load properly, making it difficult to drive at low speeds.
Video describes cleaning the idle passages in Mikuni VM28SC carburetor.
Needle = 4
Pilot = 30
Main = 120
Air adjustment bleed screw 1 1/4 turn open
Yamaha DS7 250 may use VM26SC that are the same.

[@stevenedwards2162]

I recently a yds7 250, i have to turn my petrol tap to the off position every time i stop or my carbs will eventually start to over fill and leak through the overflow pipes, if this happens i have to bump start the bike to get to start, as long as remember to turn the p cock i have no trouble starting the bike on the kick start, what would you think the problem might be.

[@Adventurepilot70]

Welcome to the world of old bikes Mr. Edwards. In the old days it was very common to shut the fuel tap off when parking the bike for over-night or lengths of time more than a hour or two. They did not have vacuum taps back then.
I would suggest you replace the rubber disk that seals the lever of the fuel tap, and clean the filter screen. The rubber can get hard with age and the holes sometimes tear. I got mine on e-bay. Grease will make the fuel tap rubber run very smoothly.
I have a workshop manual here, and it says to prevent flooding, always use the center stand. The side stand leans the bike too much of an angle.
I would suggest you shake the floats to see if they contain any gasoline. If they do, place them held submerged in very hot water and watch for bubbles to find the leak or crack and get the gasoline out of the float. Solder to repair. Plastic floats can be dipped in fuel tank sealer.
Be sure needles and seats are not leaking and the seat is tight. Check your float levels and needle for sealing with a bucket of water as shown in the link. Use ONLY a GROUND steel ball if you cannot get the leaking stopped.
Be sure floats are not rubbing or hanging up on anything, and that plastic floats are not swollen from ethanol in the gas. LINK to you-tube video: Carburetor Float Needle and Seat Rep
ALWAYS TEST FOR LEAKS IN BUCKET OF WATER.
Good luck with the machine...😊

[@stevenedwards2162]

Thanks for your reply for some of the causes that I might have with my carburettors, I'm an old helmet now being 69, this bike was one of my first bikes as a 16 year old same gold and black colour as well, I just had to buy it, takes me back to my youth, anyhow thanks again 👌👍

[@Adventurepilot70]

@@stevenedwards2162 I am an old helmet also, being 74 years old. I have had my Yamaha R5C for many years now. still runs great at 35,000 miles. I have had the leaking carbs, same as you. I am too old now to push start the bike very well. I always shut my fuel off and let the carbs run dry when I put the bike away to prevent the varnish build-up.
I don't ride much anymore.😞

[@stevenedwards2162]

@@Adventurepilot70 Nice to here from you and your R5, yes I will take your advice and keep turning the petrol off for time being, us older one's have got keep going, I always say no one knows how old we are when we put our helmets on 🤣 thanks again from an old helmet from Wales Great Britain.