yoda

You need to bed new pads in by using them.

Even if you did use 12v you still have the same problem. You need to clean all the earths and contacts.

Your trying to rev it from to low in the power band.

You must go and see the bike, don't buy it on pictures. Look for normal wear and tare, clutch, sprockets, chain, brakes, tires, lights, head bearings, swing arm bearings, battery and so on. Not sure about something, then take an expert.

Good point. has he connected it round the right way?

Looks like a rich cut. The carbs are overfueling on opening.

Well for my two pennyworth, I would say that a tappet has come loose or is sticking.

Several things influence mpg, the biggest one being load. 1, Ensure that the tyre pressures are correct and kept on the high side for best economy 2, Make sure the chain/belt drive is not too tight 3, Don't drive on the choke 4, Keep the bike weight to the minimum 5, Keep your speed down unless you have a full fairing, aerodynamic drag causes high fuel consumption, not high speed 6, Do not accelerate hard, it's a waste of fuel 7, Do not fit a low back pressure exhaust system, as this will allow unburnt fuel into the exhaust 8, Drive smoothly, brake gently and think ahead, as this will increase your mpg

The crankcase breathers need to be checked as well. If these are at all blocked, you will get the same result.

I think Drewpy is right about the rings. If the ring groves have gummed up or coked, then there could be a problem. Also if the rings line up which does happen, there will be a reduction of compression until they spin around again. Cannot fault the expression of running the engine to maintain it.

This is a case of over-fuelling causing a rich cut type of problem. When you are opening the throttle, it is overfuelling so you need to find the cause of that.

Your battery is to all intents and purposes dead.

The man with no brain had medical insurance, but no helmet. He didn't need medical insurance to pay out anything when his brain came out.

Ok sweety!

Well done Goff, saves me from giving that American twit a few pages of grounding lessons.

Welcome to the forum. Always worth getting any bike or car checked for outstanding loans. You need to check or have checked all of the usual things. If you are not sure, pay for an engineer to check it. I think the RAC will do it.

The severe lack of aerodynamics on your Yamaha model which is characterised by the severe bufferting is the cause of the gas milage. Fit a full fairing and get better milage!!!

Why don't you ask the manufactureers for their advice as they were the ones who were supposed to check these sort of things.

Do you get it out of second gear before accidentally leaving the island?

When you took the engine apart, you didn't look at the cams did you? If one is soft and has worn, it might give a clue to what is going on. Have you overhauled the cylinder head? I think you need to look deeper. Ususally I would put this type of problem down to cam timing, that is the lobe action caused by bad engineering design. In this case I doubt that but usually with peaky engines, this cam problem can be overcome using the fuel mapping. Another problem could be the exhaust gas scavenging. If the exhaust is damaged ie partially blocked or is not standard for that engine, this can cause the problem. If this bike has an ex up valve, is it all working? Assuming that you have fully overhauled the carbs, has the fuel system been checked to ensure full flow from the tank at all revs? Does the flat spot happen in all gears at the same revs?

How many sheats?

Hi and welcome to the forum. You might need to put some bar weights in to change the vibration frequency to stop the above problem.

Welcome and good luck with the project. You could make a new electrical harness by taking the old one off and just copy it. The other bit you can find in MCN or on ebay. Good hunting!

Sounds very much that the carbs are getting hot and when shutting down the engine the fuel is vapourising in the carbs causing a lock. Essentially, keep the carbs cool. Dont let the bike idle before stopping the engine and dont rev it then shut down.