Turbocharged XS1100!

[Bowtied]

I thought a turbo charger only forces more air in the intake system causing it to take in more gas with it. Hence the term "forced induction". Anybody?

[Ivan]

Carbs work on the pressure differential between the venturi and atmospheric pressure. If you start cramming air down the throat of the carb and the pressure in the venturi exceeds the pressure in the bowl, the fuel will go to the lowest pressure, meaning it will force the fuel back into the bowl of the carb. I have tried this on cars when I was a punk kid. My friends and I had a turbo rigged up on my mustang and when it would spool up the car would die. Sounded pretty coo up until then. We couldn't figure it out until we saw fuel shooting out the bowl vent. What let down...

[JustJeff]

Turbo

Looks like allot of the hardware I started with.

[Crazcnuk]

It sounds like a two-stroke dirtbike.

I am guessing a single carb. You can see the manifold going to the outer two cylinders, and a single aircleaner.

It likely uses a blow-through carb designed for turbo use.

The boost guage is there, but hard to see.

[DiverRay]

The Yamaha Seca 650 Turbo DID pressurize the carbs! You just have to make sure the "vent" is part of the pressure system. With the later XS carbs, that would be no problem.
The Seca WAS a blast to ride, but the turbo lag was about 1.5 seconds! It DID get me into trouble once, and took about a month to get all the repair parts in to fix the plastic that I scraped. It was a good machine, just too top heavy for mountain roads.

[Ivan]

So it just pressurized the bowls with the turbo?

What kept the fuel flowing into the pressurized bowls?

[DiverRay]

I'll need to find my manual for the bike to tell you. I DID buy the Yamaha repair manual for it, just have to locate it in my "storage", 10X30', full of stuff including 2 XS1100 and parts......

[Jerry]

The Yamaha Seca 650 Turbo DID pressurize the carbs!

Have not seen the Yamaha turbo 650, but my car versions did <B>not</B> pressurize the carbs. The turbo sat below the carb on the Corvair, the Audi was fuel injected. Turbo below the carbs eliminated 2 problems, pressurizing the carb and reducing the ambient air temp of the incoming air, which heats as it comes through the turbo. (Thats the reason newer high-perf cars have an intercooler; it reduces the heat of the incoming charge, resulting in a denser mix entering the combustion chamber.)

A turbo is fun to drive in the right conditions, but they are harder to work on, are expensive, and add complexity to your engine. I don't see them appearing on bikes in large numbers anytime soon. However, I would have liked to ride a turbo XS11 through a place like Deals Gap just for grins.

[DiverRay]

Jerry,
A turbo that has the carbs on the intake side needs special seals. When you pressurize with a turbo you DON'T need the seals. Cost difference is about $75 per unit for a manufacturer, and about $200 retail. The Corvair turbo DID have problems when the seals went out, as the gas mixture would "wash" the oil off the pressure side bearing and kill the turbo. With FI, you just increase the fuel pressure if you are boosting more than about 10 psi.

[rpgoerlich]

The Yamaha XJ650 Turbo also had an electric fuel pump with a bypass back to the tank when carb bowls were full, controlled by a fuel pressure regulator.
Stock was 7psi of boost. I later found a power up kit for it which slowed the waste gate from opening and brought up the boost just under 12psi. Some would disconnect the wastegate and let the popoff valve in the surge tank relieve at 15psi, It was a loud screeching when it did!
I didn't have mine long enough to get into trouble, but it was fun to ride!

[EricHa]

That's a piece of history there, an old RC Engineering kit. I had a KZ1000 back in the day and put an Americian Turbo Pak kit on it. The single carb made the bike rather anemic when off the boost. I only set it to 7 psi of boost with stock everything, but it was a completely different bike. When the impeller spooled up in 2nd, hang on baby! It would pull in 5th gear like a stocker in 3rd. I'll bet that XS is a STRONG runner if it's been taken care of. Be sure to run a rev limiter, or don't miss a shift!

[Hideki]

I've seen a few of those XS1100 turbo kits before, RayJay turbo and single carb. I almost had one too, one that desperately needed rebuilding sold for over a grand. Wouldv'e been nice though

[Yamanatic]

Look closely at my avatar, that's an ATP (American TurboPac) equipped 'E.' The compressor is a RaJay just like they use on cars and aircraft (and on that Midnight), and is capable of inducing over 1.7 atmospheres of pressure - 24 psi. The carb is a 1.5 inch Zenith pumper one barrel bolted to the other side of the turbo, and is not pressurized. In place of the stock carb bank is a log manifold. There is an adjustable waste gate, and right now I have it dialed to 15 psi which will make short order of rear tires and the competition. The motor is stock except for a 1/16" spacer plate to drop the compression, and an extra washer in the cush. The Turbo has been on since the early 1980's and has racked 35,000 miles without failure; it has not been apart since putting in the spacer plate, and I swear it keeps getting faster as it loosens up.

When starting cold, expect a puff of smoke because the RaJay has a plain bearing with a little piston ring looking thing to seal it, and they are known to seep oil into the intake when shut down; it is an amazingly simple system. Also, there is a remote fuel pump with the kit to keep up with the demand. To launch one of these things without any lag you just lean on the rear brake, load the motor using the clutch, and when the boost gauge starts to move, get off the brake, drop the clutch, and hang on - WoW!

That Midnight is a bargain; if you remove and sell the Turbo, you can buy everything to return the bike to stock, and still put a very healty wad of coin in yur pocket. A complete turbo system is easly worth a couple grand. Drop me a line if you buy the bike and want to sell the turbo, I have another XS just waiting :-) If you like LOTS of power though, you would keep it just as-is! I did get a chuckle about the mileage comment though; I Never get better than about 12mpg, but I drive it like it's stolen...


I also own a Yamaha Factory 650 Turbo Seca with the update mod. The Seca is slightly quicker than a bone stock 11, but not anywhere near as exciting as the compressor equipped Eleven, and a lot more complicated. I rev the 'E' to 10 grand all the time, but mostly because it is tough to shift fast enough. Redline in top gear is too easy, and with a slight over-rev it will do 150 mph in a big hurry. To keep the chassis under control there is a stout fork brace, and a pair of YZ80 monoshocks on the rear. Just be warned, beef up the drive cushion and make the 1st to 2nd shift very carefully or you will be replacing gears and shift forks.

Cheers,
Warren
aka Yamanatic

[DJinNH]

Wish I had a better photo to post. I have seen this bike in person as the owner, Mike, aka "Viper" is working on my SG.

It's an 1100 Special ('79 I think) bored out to 1500 and has a turbo. This photo totally lacks showing what a sweet bike it is. It has a drag tire on the back and the paint scheme is outstanding!



Don

[Winterhawk]

I had 5 different ones since 1982. My current one I ride several times a week. They are good bikes after the front brake is modified with a different master cylinder and braided brake lines. 47mpg as an average.