Hellooo.  Looking to double check the float height on the 1977 DT100 with the Mikuni IT9 - 60 carb.

This is the second carb as the original had some essential threads stripped out in the body.

I have the official DT100 manual from the tech library and in the 1977 appendix it says the float height is 26mm + - 1mm.
It says this both at the setting description and in the specifications.  The same specifications do list the IT9 carb as for the 1977 model only.  Later ones are 2F5 iirc.

Problem being both the original carb and the replacement had floats set considerably lower than 26mm and required the tang bending by maybe 20 degrees to get the specified setting. 
Also, my rule of thumb normally says at close to the setting, the tang and float arms should be roughly parralel to the gasket face.
At 26mm they have quite a droop going on.  Too much so, esp the tang.

This has set alarm bells clanging.  A quick look at the later models gave 21.5mm height - a more reasonable figure.

If anyone has an alternate source of info re the 77 DT100, IT9 - 60 carb setting, I would be most grateful for a double check.  My spider senses are tingling.  Every nerve in my body is screaming that the book has a misprint.

 

There are a lot of Yamaha misprints on float level...  some manuals have conflicting float level specs right in the same book!

Also some confusion as the spec was sometimes given as a measurement from the end of the needle jet casting protrusion down (carb inverted) to the float arm instead of up from the float bowl gasket surface to the float arm.  

I've long wondered if the discrepancy in specs was due to the different measurement methods?  ...but have never tested that theory..  mostly because I gave up measuring and simply check/set the floats so the arms are parallel or nearly parallel to the gasket surface. 

The Yamaha Technical Bulletin M6-056 also states 26mm +/- 1.0mm for the 1977 Dt100D 1T9.  But as I said above, I stopped using the specs years ago because of the errors/inconsistencies.  I use the "parallel" method now and it has always worked for me. 

Pic of alternative method of float level measurement that was sometimes used below

I recently needed to set the float height on my DT1E after replacing an old needle valve and found two different float height in the same manual! They both were "close enough" IMO because in either case the two arm bellcrank levers were more or less parallel with the bowl mating surface. I love my DT1E, it is my favorite ride until i get on the others!

I am am just about complete rebuilding a 77 DT100. I have done the carb clean and rebuild and I vaguely remember this. .I will go throuch and look through my notes, but off the top of my head, I believe I used the 26+/- number. From what I remember, you need to pay attention to where the measurement was specified to be made from. It is not the same model to model carb to carb.

Go back through the information you have and look for something that gives you a reference of where the 26+/- number is measured from.

The servide manual says

"Measure the distance from the bottom of the float to the float bowl gasket surface. Bend the tang on the float arm if any float hight adjustment is necessary. Both floats must be at the same height. If the float height is too high, a lean air/fuel mixture will occur. If too low, a rich mixture will result."


There is also a picture in the service manual that shows a diagram of the carg/float and shows where the measurement is made.

From what I remember, mine was spot on and did not need any real adjustment. In the picture, it shows the tang almost, but not quite parrallel to the bloat bowl surface. Note However that the measurement is not made tothe surface of the metal. There is a little indentation in the surface. If I could post a picture I would. But yous should be able to see this in the service manual. It is on page 35.

Thanks for your input Johnste1960 and the others.  Much appreciated.

Carb has had its ultrasound bath, all passages have been scrubbed out by fine bottle brushes, all jets checked for correct fitment and no blockages.
Pleased to note that the pilot is correct size and also main jet is as specified.  The main also has the square within a square logo, so genuine Mikuni.  Thats about £15 saved.

Set float arms back to parallel with the gasket line, tang parallel with the arms and double checked that the arms themselves were not bent by ensuring a convenient moulding line on the float itself was also in line with the arm and parallel with the gasket face.

Once it was all reset, I measured the resulting float height....

21mm and small change.  This correlates to the float heights specified on the later models.  The 26mm specified in the 1977 appendix is almost certainly a misprint or mistake.