1982 Seca XJ750, ZRX1200 has company now.

[Bonz]

Rebuilt from the frame up 15 yrs ago by my uncle, 322 miles after he finished it, sat since then. He used NOS parts to replace parts that weren't "perfect" in his words. Carbs are now off, full unrack and clean. Front brakes next, then it'll be a looker and a runner. He has a 2010 Gen 2 VMax, 2015 CB1100 and a Road Glide as well as a 1977 Trans Am he took down to the therefore the Seca didn't get much riding time. Lots of similarities to the XS in general with respect to maintenance, how parts come off, etc.

[Socer4m]

Bonz, Hope it fits your xxl frame,,,it should be a fun fast scoot for around the area,,,also hoping we get a Colo. rally next year, Keep us informed on the seca progression. I had a number of xs750 and xj750 maxims....quick, fun up to around 75, but hard to beat the smoothness of the 1100 after that........cya, Mike in San DIego and PA

[JeffH]

Nice to get a Yama back in your garage.
That is a beautiful machine. As Mike said, keep us updated on progress.
Hopefully you have time to get it on those Colorado roads before the snow builds up (too much) in the twisty areas west of you.

Jeff

[Bonz]

Thanks fellas, looking forward to getting out on the road! Hope you all are well.

[Bonz]

The carbs are off, apart and cleaned. The hack at the dealership that cleaned the carbs for my uncle 15 years ago did a poor job. My uncle said it never ran like the one he had bought new when he was a lot younger. Anyway, below explains why, IMO...

Need some confirmation/help with a jetting question and request for parts guys that read this thread may have gathering cobwebs.

The Hitachi carbs call for 120 mains, 40 pilots on the fuel side. Good to go on all 4 with what the carbs have in them, and have 118 and 116 mains along with 38 pilots to play with from JetsRus. My elevation is 7200'.

On the air jet side under the diaphragm, calls for 220 main air jets and 80 pilot air jets. One carb had a 195 air jet and another had a 50 pilot air jet. Scarcer than hens teeth to find Hitachi air jets. JoeRDMCguy has a set of the same carbs from an XJ650 and is sending me the 210 main air jets and 70 pilot air jets. Very kind of him!

Hopefully that sets the scene for what I am working with.

My plan is to put 210 main air jets and 70 pilot air jets in the middle cylinders. Keeping the main fuel and pilot fuel jets the same (dropping down one or two sizes on mains, one on pilots for elevation). As air jets do the opposite of mains, the smaller they are, the richer the mixture, which would richen up the middle cylinders. Seems like a workable solution to run the middles slightly richer even though stock was the same across all 4 carbs.

Given the pilot and main air jets are at work at lower throttle openings to help with fuel atomization before airflow picks up, the fuel mains will work the same for mid range and above with little or no influence from the air jets.

What does the collective have to say about the above? Anything I am missing with respect to the overall plan?

Next, if someone has a single 220 Hitachi main air jet and an 80 pilot air jet, I would like to hear from you and work out getting those. I'd rather get the air jets all the same and use the fuel main and pilots for tuning in the best case scenario.

[Bonz]

Disregard the need for air jets. I found a box of parts that got put under a shelf in the garage in the hustle and bustle of unloading the bike from the trailer. Multiple spare carb bodies in the box, pulled the air jets and they are in carb cleaner soaking.

[oldyam80sg]

Bonz-Didn't they make a Seca turbo 750?

[Bonz]

Yamaha had the Seca 650 turbo. The only one that was carbureted as a bit of trivia. Honda and Suzuki had 650 turbos as well, Kawasaki was a 750. Honda, Suzuki, Kawasaki all used fuel injection.

As another aside, the master cylinder on this bike is unique and quite honestly Yamaha's stupidest engineering move ever. MC mounts under the headlight. A short cable goes from the lever to the master cylinder and then the hydraulics go to the calipers. The Piston is stuck solid as can be in the master cylinder. What are tricks y'all have used to loosen them up? I need to try and Salvage as many parts as possible.

Finding an MC is even scarcer than hens teeth, and no rebuild kits that I can find.

[bikerphil]

The Piston is stuck solid as can be in the master cylinder. What are tricks y'all have used to loosen them up?

Probably soak with penetrating oil and tap/pry if necessary and hope for the best.

the master cylinder on this bike is unique and quite honestly Yamaha's stupidest engineering move ever.

Why not just go with a handlebar mounted unit?

[Bonz]

I ran it through the ultrasonic cleaner this morning along with another soak with penetrating oil. I was able to get it to move a little bit. Soaking it again now that it's moved a bit and going to put it in ultrasonic cleaner again.The goal is to keep the bike as original as possible. It's in pristine shape. I bet there aren't five in the country that are in this good of shape having been rebuilt with all NOS parts.

If this master cylinder is not viable once I get it loosened up, then a bar mount is potentially in the cards. It's possible internal parts on the master cylinder match other bikes. In the grand scheme it's a funky arrangement that a specific kit is not listed for this bike. A bar mounted master cylinder would necessitate different bars, master cylinder with lever, custom lines etc.

Yamaha has a funky bar on this bike in order to mount the plastic shrouds around the bars that give it a sleek look. Switchgear may be challenging to find when swapping the bar, I've been reading up on it and seeing what the options are.

Edit: After another soak in penetrant and ultrasonic cleaning, along with a couple shots of high psi from the compressor, I tapped down on the plunger with a small socket on an extension and everything freed up and popped out. Bore is good, rubber cup/seal is good, spring looks brand new and the piston is in good shape. Everything is apart that needs to be apart now with the brakes and carbs, waiting on the caliper seal kits to arrive and getting the carbs reassembled hopefully today yet. Next weekend is hopefully getting things back on the bike.

[bikerphil]

Well I'm glad you got it free and it's useable. I understand wanting to keep it all original.

Just a reminder, some solvents will swell the rubber and make it unusable. Brake fluid is 100% safe and works well as a cleaner.

[Bonz]

A trick my friend Vincent Hill who used to race Superbike back in the 80s as a privateer shared with me is that brake cleaner works real well on all brake parts. He said think about it, it's meant to be used on brakes with rubber components. Also works good for shooting through carburetors to clean out pilot jets, not harmful to the O-rings on the pilot screws, needle seats, etc. Carburetor cleaner, specifically the spray kind or the soak kind is no bueno in most of my experience and probably others as well especially if left to sit on rubber parts for any length of time.

Using a brass bristle brush (on a Dremel) of different sizes/shapes to remove the corrosion/smeg in the calipers and master cylinder. The rings for seals/circlip are clean as the day they were new and the bores shiny,

[DiverRay]

I had a Seca 650 Turbo in '83. The dealer put in the "boost kit", as I had it broken in within a week. Turbo lag was FUN! 55mph in third, full throttle, and 1.5 seconds later the front end was in the air and you were at 90mph.
Yamaha DID experiment with the production bikes in the '80's. They tried a lot of "unusual" solutions to problems nobody had.

[Bonz]

I've always felt they could have fuel injected the 650 Seca Turbo like all the rest of the big 4. What did the "Boost Kit" do in terms of turbo psi vs stock?

Blow through carbs are are real crap-shoot and so much more to go "wrong", IMO, but they made it work on the Seca 650. I'd like a Honda CX650 turbo, period tests had it stronger than a GPZ 1100 in roll-on. I like mid-range, one of the reasons my ZRX 1200 has ZZR1200 cams, ZZR1200 carbs adapted on to it (Vincent Hill and I created as a mod that many used on the ZRX forum)), JE 12.5:1 pistons. It is strong. Beats an FJR 1300 in 3rd gear roll-on to the ton and stays close to a flashed Concours 14 to the ton when aero takes over.

Getting the Seca 750 up and running is a labor of love, the Uncle who gifted it to me has early Parkinson's and it'll be great to get him on it next summer when he visits Colorado again. His garage has a Gen 2 V-Max (most insane acceleration I have ever felt. Period.), 2015 Honda CB1100, 2015 Road Glide and 1977 Pontiac Trans Am he also took down to the frame and put a built motor in that makes almost 600 lbs/ft and 540 hp. He's a first-class gear head and getting this 750 Seca back to original running order will mean a lot to me and a whole lot more to him.

[DiverRay]

IIRC, boost was 6psi stock, and 12psi with the kit. The problem was there was no pop-off valve, so you could over-pressure if you chopped the throttle too quickly. I didn't have mine long enough to find out. Some idiot entered the freeway too fast on wet roads and took out two cars and my bike.
The Honda turbo would walk away from the Yamaha! That I DO know from experience.