1982 Yamaha Seca 750 Carborator rebuild

Seca 750 carbs.
Make sure you have plenty of table space with good light

My 1982 Yamaha Seca 750 Carbs were completely sludged up. The previous owner didn’t take care of the bike at all and it sat for what I can only guess was many years outside. The gas tank was full of rusty gas. I wish I had thought to take a picture of the gas as I poured it out it was brown rusty with chunks of flaky rust. It was beyond bad and it all flowed into these carbs and packed the jets with rusty paste. It then was allowed to dry and become so varnished up that a person could not twist the throttle. I figured the cable was rusted up from the winter(s) it sat outside. That was not the case the cable was free.

As I took the carbs apart I noticed that someone else had taken them out and managed to strip out the screw heads and loose the little lock washers and other ‘un-needed parts’. The guy I purchased the bike swore it ran only 6 short months ago. It only needed a new starter switch on the handle bar. I am pegging the guy and an absolute liar. I probably should have really thought twice at attempting to clean these carbs.

So here are my tips for this project.

1. Buy and read the Haynes owners workshop manual.Seca Owners manual

Wear gloves the solvents are not good for your skin. I liked the white ones in the following images. They were tighter fitting and allowed me to pick up little parts easier, however the green ones held up much better. It also helps to lotion your hands, it fills the pores in your skin with lotion rather than oil and solvent. It washes off much easier.

Wear some safety glasses. I hate them but every time I take them off I flick some solvent in my eyes or when using the air compressor to blow something off I get a faceful

These float bowl drain screws are not a bolt you can pick up at Menards

cutting a new slot
Use a Dremmel tool to cut a new slot. You may want to get these out later.
Removing a brass carb jet
Use the right size screw driver. It should fit snugly across the entire radius of of the jet.

Use the right size screw driver on the jets. Use a clean screw driver with a good sharp tip. Buy yourself a new one or grind it flat. These brass jets will take some force to remove and easily strip out if you are careless.





Cleaning tools
some handy items

Don’t use wire to clean out the jets. The brass and aluminum scratch easily.

If you feel you must poke – and I usually do. Use a nylon bristle from a scrub brush. Use an air compressor, it works 99% of the time.

Cleaning with safe tools
The plastic bristle won't be likely to scratch your brass jet




Here is a picture of the green gloves that hold up much better to the solvents and work.

When you are blowing out the jets with an air compressor watch your eyes. The jets sometimes blow back in unexpected ways.




The manual recommends you take the carbs apart one at a time. I agree. You will use one assembled carb as a guide to where the jets in the disassembled carb will go back. The book is only so good as it is black and white. However you may want to remove the larger rubber/plastic parts so you can dip the whole set of carbs as a unit. I found it impossible to get one carb at a time clean. So I took the big obvious parts apart and kept them separate. Use the float bowl – fill it with carb cleaner and place the parts (the parts you KNOW the location of) in it to soak.  Things like the diaphragm/piston shouldn’t be soaked in the solvent. I once left a tooth brush in the solvent overnight, it kind of partially melted. Once all the vulnerable plastic parts are removed you can get that carb cleaner all over it and avoid the whole dirty carb getting the clean one dirty. It goes much faster if you don’t have to do one at a time.

The book says not to touch the pilot jet. I felt I just had to. The trick is putting it back the way it was. Screw it in as far as it goes while counting the turns. Mine was 3.5 turns before it hit bottom. Unscrew it all the way – clean it out. Then screw it all the way in again and back it off 3.5 turns.