Bmonk

Is the distance(measurement) from the piston pin hole to the piston crown the same for both pistons?

Looks like a YZ piston...what are the numbers on the piston crown?

. Now MT you can't be messing with the free market economy..

If in doubt you can purchase a antifreeze tester at any auto parts store pretty cheap.

Or the slightly more personal "hey Buddy".

No

If it leaks for just a short time it is just some air escaping from the space between the tube and rim.If it leaks enough for the pressure to drop in the tube you have punctured the tube.

The numbers on the float valve assy( often referred to as the needle and seat Assy) refer to the actual size of the hole .So if you reduced the size of the hole from 2.5 mm to 2 mm that is a 25 percent reduction in the fuel flow . what you describe is a engine running lean so before trying to tune for this condition check to make certain the correct float valve Assy is in the carb.

Yes it's the classic o ring around the main jet holder

Pistons and cylinders for Japanese MC are also classed at one hundreth of a millimetre.

Replace the needle and seat assy

Can't imagine you can swap the ignition source coil for the lighting coil and expect the motor to run properly.Most condensers are .22 mf and can be mounted external from the points plate.Contact breakers are pretty specific and usually set at .012-.016 " or .3-.4 mm

Thanks for the info...

On another site someone has done some research and posted that numbers 525-000102 to 525-002751 are for 1975 models and 525-100107 to 525-102650 is for 1976 models. Can anyone confirm that this is correct?

Most of what you will need for parts is available at the Yamaha dealer ...lots of TY parts are common with other models I get a few things at rpm cycle and I order some from fortnine..

If you have to screw the pilot air screw all the way in to make the engine run correctly and the engine,intake/exhaust/carb specs are stock,then you need to figure out why.Logically if you have to shut off the air flow in the carb to make it run right ,where is the air coming from .? It would follow that there is an air leak somewhere....base gasket,intake manifold or a leaking crank seal are the most likely. Trying to adjust the carb jetting to accomadate a air leak will be a impossible task.

my oil can holds about 250mils ,so use at least 1/2 of that ,put the piston at the bottom of the stroke so the oil flows down the ports to the bottom end and turn the motor over the get everything coated....get everything good and wet with oil ,you can't use too much. It will smoke like a stack when you start it up and will probably foul a plug.

Looks like a fun project I have had good luck cleaning tanks by filling them with a container of evaporust and a handful of old nuts and bolts....then over at few days of soaking and shaking things look pretty good.then flush with a solvent.I used to line tanks but no more. For the exhaust,no Chrome to damage ,get the pipe and silencer hot enough to start the carbon burning(propane torch) and leave it outside.....smokes and stinks and not neighbour friendly

I understand that here are tons of people that have had good luck with fogging oil,but I am not one of them.If the fogging oil can only contained oil,that's one thing,but it's the agent that makes it an aerosol ,often alcohol based that can be a problem.I disagree that introducing oil into the spark plug hole does not lube the crank and rod bearings.....liberal amounts and turning the motor over to distribute the oil is the key.In the winter months when things are cold all the time it maters little if the fuel tank is full or empty.But in the early spring when the nights are below freezing and the days are above freezing,in a shed ,the probability is high that condensation will happen inside the empty(lined) tank.....so it is a trade off ....which is the least harmful scenario water in the empty tank or a full tank that is treated.and the possibility that the gas stabilizer is not working 100 percent.? The fact that something gets done and the bike is prepared for winter is usually a signal for success.Most problems are from just parking the bike and not doing anything.. The reason I recommend non synthetic oil for storage is the same as using an aerosol fogging oil ....sythethic oil ester based is by its nature thinned with as evaporative agent ,in storage this often evaporates leaving the heavy deposits in the base and in the process of evaporating absorbs moisture...in my experience sythethic oil is great for lubrication but no so good for storage. ..?..

If the garden shed is not sitting on a insulated pad,then condensation can be a problem.In this case I would fill the tank with fuel and treat the fuel with stabilizer ,start the bike and warm it up so the fuel in the carb is also treated.Next,remove the spark plug,with a oil can squirt a liberal amount on non synthetic 2 stroke oil in the spark plug hole and turn the motor over to be assured that the crank and piston are coated in this oil.Replace the spark plug.Coat any exposed metal surfaces with Vaseline ,ie fork tubes,shock shaft...anything not painted that you do not want to rust/corrode.If you have a stand for the bike,use it to elevate the tires off the ground,if not put some cardboard or plywood under the tires.Put a cover ,anything but plastic,and old bed sheet works good, over the bike and its a good idea to tape over the exhaust and air filter intake to keep out moisture and rodents.Set a mouse trap or two under the bike.

It's a 78 ?....is there a manufacture date on it? Looks like a 75....not that it maters.

The carb o ring is available from Yamaha,I found one in my tool box that worked.there are two o rings in the carb replace them both. the rear sprocket is dished ,it is the same as the one used on the tw200 ,only tw is steel not alum ...you can get them aftermarket in 51t, cheap Front sprocket is 12 teeth Same as xt/dt Allot of different models and brands use that spline size 428 chain ..just service the forks New seals and oil they are soft anyway dont worry too much about tires now ,new tubes and if they hold air ....get some time on it ..then get tires common issues are the kick start ratchet mech and worn shift lever cover plate /forks and difficult shifting. your bike looks good ,you have fenders,nice tank,silencer...even both lights....do you have both switches and is your oil pump still there? think you would have a difficult time getting a plate and would be strange to ride on the road.... my opinion.....most aftermarket throttle cables do not have a oil pump cable...so you know model code is 525 They are super easy to work on

Steve, That is awesome,where did you find that? Exactly same as mine... Is that the one J George had years ago? Ya know, I think there is enough these coming out of the woodwork to have a twin shock trials meeting. you up for it?