As some of you know, I have a passion for motorcycles in addition to Z's. I have owned the bike below since college and have spent years restoring it to its current condition.

This has been a real challenge for me because I am not that mechanical inclined. I can bolt on parts with the best of them but when it comes down to more complicated mechanics - such as points, timing, syncing carbs, etc. I need a lot of help.

I will be installing two new aftermarket carburetors on this bike this weekend. Before I do so, I need to time the ignition at idle and full advance.

I have a conductive strobe light and all the tools. All I am missing is the brainpower to get it done.

Anyone out there that has good knowledge of using a timing light and setting ignition timing?

The process is pretty similar to that of a car.

If so, do you want to stop by and help me either tomorrow or Sunday?

I'll buy lunch, beer or whatever your preference is!

Please call me at 203-722-3961 if interested.

Ross

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Ross Williams
1978 280Z Black Pearl Edition 38k Original Miles

I owned that same engine on an 1981 (1980?) Yamaha I had back in '85. No matter how I tried, I couldn't time it myself, and I have three years of auto mechanics school and more than 40yrs of "meaningful motorcycle experience" (mistakes and skinned knuckles) . I took it to the Yamaha dealership in Cheshire and let them do it.
Plus, I could no longer kneel down that low for that long!

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1970 240Z

The problem is that the folks that work at these shops are all used to electronic ignition and fuel injection. The last shop I brought it to had it for a week and had to look up how to do it in the manual.

When I got it back it ran no better.

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Ross Williams
1978 280Z Black Pearl Edition 38k Original Miles

Ahhh......admittedly, when I took mine in for service, they were still accustomed to working on bikes with dual-point ignitions.

There are many small motorcycle shops around the state which are fully qualified to work on your older machine. In fact, the last one I visited was working on a dozen bikes with upright engines, drum brakes and spoked wheels. Call Steve at CT Cycle Works up in North Haven. He's older than most of the bikes he works on and, like Vinny, he's a perfectionist. He rides daily and is a Yamaha specialist.

Steve 203-234-7000

See my incoming PM.

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1970 240Z

Thanks Frank. That's a great reference.

Valves adjusted
Cam chain adjusted
New irdium spark plugs installed
Old carbs removed
Old airboxes removed
New carbs installed
New filters oiled
Gas lines connected with new inline filters

And then the moment of truth....

Started filling the tank with gas and it came pouring out one of the petcocks!!!
Tried everything to diagnose the leak and have decided to give up for the day.

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Ross Williams
1978 280Z Black Pearl Edition 38k Original Miles

Are you sure you installed both fuel filters properly? Some of them are one-directional. If you installed one upside down, it could block fuel flow from the tank.....
just a guess....
Obviously the one which is not leaking is put on properly. Compare the two and zee if there is an obvious difference....

Further....if there's a spark source in your garage (water heaters are most common), move the bike away from it. Gasoline vapors hug the floor so if they are allowed to build up inside the garage, they can eventually "swim" their way over to the heater. Since it's warm enough outside, you might consider venting the garage with a window or slightly open door.

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1970 240Z

Well the fuel filters are downstream from the petcocks. So if the petcocks are leaking it's not due to the fuel filters.

The one smart thing I did was to bring the bike well out onto the driveway before gassing it up. So at least the spill occurred outside.

Gas is all enclosed in the garage with no equipment that may spark. After the Tommy Sullivan tragedy I am very diligent in keeping any flammable liquids under safe conditions.

I think I unfortunately have a bad petcock, even though it is brand-new.

Really disappointed because I spent about five hours getting all the work done and was inches away from hearing those new carbs operate.

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Ross Williams
1978 280Z Black Pearl Edition 38k Original Miles

"...The one smart thing I did ..." It sounds as if you've accomplished a lot of smart things already today. That's an honorable list of achievements to have done single-handedly in one afternoon.

OK, I'm picturing two petcocks feeding two carburetors thru two fuel lines, one on either side of the tank.

Yes, the filters are downstream from the petcocks, but if one filter is acting as a block and the fuel line isn't completely tight on the petcock stem, the fuel could leave the tank but, having "no place to go" (because the filter won't let it pass), it could back up and leak out at a bad connection of the fuel line and the petcock stem.

Of course, sitting here, I don't know exactly where you're describing it leaking from. Maybe your petcock just needs to be screwed a little tighter into the tank or needs another gasket. Or the petcock is somehow defective, itself. I assume you can turn the fuel OFF so the petcock doesn't leak in the OFF position? That's what leads me to wonder if there's just a poor connection or bad seal someplace, rather than a bad petcock. Since you mentioned it was brand-new, I would think maybe it hasn't been screwed in fully or a gasket/ring/seal wasn't seated properly, or a fuel line wasn't fit snugly onto the petcock stem. Maybe one of the hoses got split or cracked during installation. If you have new petcocks and new carburetors, you should have new fuel lines, as well. It's easy to crack or split an old fuel line which has sat on a bike for a few years. You pull it off the petcock stem and it stretches and splits and you won't even see the tiny pinhole leak until you flow fuel thru it. Another possibility is that the new petcock stem and the old (or new?) fuel hoses are different diameters, so they no longer form a tight seal.

I think the first step would be to determine exactly where the leak was coming from; ABOVE the petcock, BELOW the petcock, or FROM the petcock itself.

And it's important to know if the petcock leaks in any position (Off, On or Reserve) or only in some positions.

Just trying to picture what you're describing.

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1970 240Z

Thanks Frank. The petcock was leaking in all positions. The leak was coming from where the petcock seats to the tank. I made a rubber gasket from an old gas tank flapper from my Z and installed it between the tank and the petcock base. Leak is now totally gone. I know some rubber degrades with gasoline but I'll keep an eye on it.

So once I resolved the petcock leak, I turned the petcocks to the on position to check the flow into the in-line filters and to make sure all of my many fuel line hose clamps were holding. In-line filters filled with gas and no leaks!

Checked to make sure I still had a full crankcase of oil.

The moment of truth (part two).....

Drum roll....

After a few seconds of cranking, the bike fired up, but immediately went into a very high rev - 5-6k

I adjusted the idle mixture screw but that did not bring down the revs.

I now have a feeling that the throttle cable is stuck, crimped, or otherwise causing the high revs. Or, I might have done something wrong when I fed the throttle cable through the top of the carb and connected it to the plunger inside.

I have now decided to retire for the day from my mechanical adventures. Fixed one problem only to encounter a new one.

I am pretty close to rolling the bike into the truck and driving up to see your friend in North Haven. In fact I plan to call him tomorrow.

On the bright side, I used the beautiful weather as an excuse to get the Triumph out and go for a ride.

The Triumph runs perfectly because I have never worked on it

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Ross Williams
1978 280Z Black Pearl Edition 38k Original Miles

["The Triumph runs perfectly because I have never worked on it"]

Yeah, the world is full of cars which run perfectly because I can't get at them!

Reach your finger into each carb and see if you find an open throttle on one of them. Any difference btwn the two indicates exactly what you suspected.
If there's no difference inside the carb throat, suspect a major air leak somewhere around the carb/manifold junction.

To determine which is the offending carb, stick your hand over one at a time, blocking the airflow. When the rpm fall off, you've found the carb which has a problem.

Good work on making a petcock gasket Pretty clever.

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1970 240Z

I have to say that every time I work on my Z or my Yamaha, I get a newfound respect for those with mechanical abilities. People like Bryan Little, Dave Cerutti, Clive Bogle and countless others in our club. Mechanics are often looked down upon by those with advanced degrees and professions. But you've got to be pretty darn smart to understand all of the electrical systems, fuel delivery methods, engine rebuilding steps, etc. of an engine.

My Dad taught physics at Columbia University yet I struggle to understand the basics of how electrical systems work.

I do not plan on quitting my day job any time soon.

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Ross Williams
1978 280Z Black Pearl Edition 38k Original Miles

It used to be a LOT easier. Back in the days before "computer" cars, kids could work on their own engines and gearboxes. That's one of the greatest attractions of the early S30 cars; simplicity. Today's 360s and 370s and the 300zx cars are incredibly complex. I too look at the RDZ guys with amaZement and respect.
I still consider my AutoMechanics shop teacher to be one of the most-influential people in my life, and that was at least 100 years ago.

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1970 240Z