1974 Kawasaki F7

Inspired by Kurt's work / thread, I though I just had to play along. So, bought me a bike that's older than I and here we go!





Pretty interesting bike:

• Oil injected 2-stroke. No pre-mix (as long as the injection system works).
• Vacuum-operated petcock, so no "off" position. Only Run and Reserve. (again, cool, if it's reliable, but no way to fully drain the carb by turning off the fuel and letting it run dry...)
• CDI - no points. (again, well, you get the idea)
• Rotary inlet valve which I'd never heard of before
• "Hatta" forks that allow three different choices of trail / rake.
• Quoted 21.5 bhp and 253 lbs curb weight

Current state of the bike:

• 760 miles on the clock
• Starts on first kick (usually) but idles poorly and it in a bad state of tune. So, we've got compression and spark, and fuel and air - at least some times!
• Electrics seem to work. Battery is new but stays dead, as it never runs long enough to charge up. Signals, lights, horn, idiot lights all work.
• After a bit, the engine races and hitting the kill switch won't even kill 'er.
• OEM everything, and several pieces (turn signals, mirror, rear rack) had been removed and stored separately, so these are pristine.
• A fair amount of superficial rust, scratches on the tank and a couple small dents

So, I'm going to focus on the functional bits first, then will proceed to the cosmetic, then to the legal (getting her titled, plated, insured, etc).

So, here we go!

No fair restoring an already restored bike! JK! That bike is beautiful! please excuse the momentary threadjack, Guys these Bikes are our heritage and if we don't save them, one day( already here) these things will be extinct. Not just buying and restoring but maintaining and riding them! Congratulations on a beautiful Bike!

SRADkneedragger said:

No fair restoring an already restored bike! JK! That bike is beautiful! please excuse the momentary threadjack, Guys these Bikes are our heritage and if we don't save them, one day( already here) these things will be extinct. Not just buying and restoring but maintaining and riding them! Congratulations on a beautiful Bike!

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What he said. Started out with a '76 KE 100 myself. Great little bikes. Never any problems with the oil injection on mine. Just keep an full and your set. Glad that you bought it before I took out a second mortgage.

That bike is exactly my age.

SRADkneedragger said:

No fair restoring an already restored bike! JK! That bike is beautiful!

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It IS beautiful from 6 feet away. But step closer, and you'll see the need for some love and attention. To be sure - this isn't a restoration project. Rather, i'll start with just getting her to run decently and then go from there.

And that's how it starts....

So, I opened her up today to see what's what:

The carb in behind a cover, and looks pretty good from the outside:



Not bad inside, either:



But, there is some crud in there, and since it won't run without opening the choke all the way, I gotta think the pilot jet at least is plugged up. So, all those little jets, brass fitting, etc are in a nice warm solvent bath.

I can't seem to figure out how to get this float off. I'd like to remove and clean the fuel valve under it, but can't get at it at the moment.

Besides not idling without choke, the other big problem is that once warn, the engine will rev to 6 or 7k and the kill switch won't even stop it. I have to stall her out. I guess this is just really bad dieseling?



This isn't the stock plug and doesn't cross reference to a suitable plug. Looks terrible and won't live to spark again.

The head doesn't seem to look terrible:



But the piston head is a mess. Is this expected for a 41 year old bike?



My shop manual said to scrape the carbon off with a flat-head screwdriver. Sounds a little severe, so I started with a hard plastic wedge. Then went got the screwdriver out.

The cylinder walls were in good shape - except for a rectangular patch on one side - probably right where the piston pin cavity sat for a decade. At this spot, it was a bit rough and rusty. I think good enough for now.

So; questions for those smarter that I:

1) Is the engine racing and inability to kill it really dieseling? Does that carbon muck and probably way to rich mixture sound like the culprit?

2) the bike starts on the first kick (with the choke all the way open) but won't idle without full choke, even once fairly warn (before the racing starts). Pilot jet problem? Anything I need to think about other than the full carb cleaning, and then fuel filter / petcock / tank cleaning?

3) What's the obvious third question I can't think of?

You can see the pin holding the float in. It should push out without too much effort. The piston top really does not look all that bad--the carbon is normal, but it is a good idea to clean it all up. The engine racing is more likely a lean condition either related to your carb issues or an air leak.

The pilot jet is tiny and very hard to clean right. Easier to just replace with a new one assuming it is readily available. The other jets have big enough air passages to clean effectively.

Johnf3 said:

You can see the pin holding the float in. It should push out without too much effort. The piston top really does not look all that bad--the carbon is normal, but it is a good idea to clean it all up. The engine racing is more likely a lean condition either related to your carb issues or an air leak.

The pilot jet is tiny and very hard to clean right. Easier to just replace with a new one assuming it is readily available. The other jets have big enough air passages to clean effectively.

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Thanks for the tips, John. I tried pushing out the float pin, but quit before it came loose. I'll put a little more oomph behind it tomorrow.

I'll see if I can find a carb rebuild kit for this fella.

Jeff S said:

Thanks for the tips, John. I tried pushing out the float pin, but quit before it came loose. I'll put a little more oomph behind it tomorrow.

I'll see if I can find a carb rebuild kit for this fella.

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Should tap out with a drift punch. I have only worked on one rotary valve two stroke and it was a long time ago. It is cool how they work though. I think I worked on a Suzuki but I remember it had a slotted disc that turned off the end of the crank and that is what controlled the charge into the cylinder.

Awesome project and Johnf3 as always has good advise. That is what I love about TWTEX. Just a few thoughts.

To get the pin out I like to take a block of wood and drill a hole close to the edge for the pin to go into. Then lay the carb on its side so the block is supporting the offside casting. Then gently tap, once it starts to move it should go easy.

The lean or choke must be on condition could be a fuel delivery issue. You mentioned cleaning the tank and petcock, this is a good start. The carb can't draw fuel if not in the bowl. Once you are satisfied with the flow out of the petcock reassemble every thing and open the bowl drain on the carb and ensure constant flow all the way through the needle valve on the inlet.

The spark plug is important. Be sure you get the correct plug. Heat range is important so that you don't get pre-ignition due to heat in the plug. This could be part of the runaway along with the lean condition. More on heat range and the effects if you want more. http://www.ngk.com.au/spark-plugs/technical-information/heat-range-explanation

If you do all of this and still have issues, I would suspect crank seals on a bike of this age.

Plus one on the air leak. Most likely a dried out main seal on the crank or where the carb attaches to the engine.

Yes - amazing resource that is TWT! And - like most things - the more you use it, the more valuable it is!

I got the float pin out - was just nervous to push hard enough before I got some encouragement that I would break it. A little tap tap tap was all it took.

The radial value in this thing has a seal keeping it separate from the rest of the crankcase. That seal is rumored to go bad, which then leaks oil and air from the crankcase into the intake, after the carb. That would cause the my lean condition - but totally outside carb. Bummer, as the carb is easy to get to. Might that extra/wrong oil also be causing the fouled spark plug?

The boot that attaches the carb to the intake is in perfect condition.

So: as advised, I'm going to continue to clean the carb, re-assemble, then test with a direct fuel line to the carb, then with the vacuum-operated petcock. If I'm still lean, then I'll see what the radial valve crank seal looks like.

For carbon build up use a small tooth brush sized wire brush. Harbor freight and all part stores have them. Way easier on the parts than a screw driver. Less chance of damaging them.

I have the big brother to that bike ,a silver and black 1975 350 Bighorn.
In High School I bought a 175 just like Yours. I stripped it down , put unbreakable Preston Petty fenders on it and cut down the rotary valve.
That bike would start on the first kick evey time and it was unbreakable.

Back to Your bike, I bet the crank sea is bad. My bighorn needs a crank seal, and I have too many projects......

Have fun!

Here is is My 75 Bighorn.

Very cool Jeff!

I like old enduros. I saw a bunch at the Barber Vintage Festival last fall. Lots of Yamahas and only a few Kawasakis. You got a lucky find.

While you're going over things, inspect the oil injection system.

I blew up my old A7 because of a failed "injecto-lube". Engine locked up while I was going 80 MPH.
That was a both a terrifying and sad day.

As has been pointed out, your air leak is most likely a dried up seal. It could be a rotary valve seal, but I'm betting on the crank seal behind the flywheel. Also, it might be a problem with the vacuum petcock not supplying enough gas due to a bad diaphragm which would cause you to run lean as the carb slowly dries up and fails to keep up with demand.

Oh, the joy of fixing 40 year old issues

I opened up the vacuum-operated petcock. It was pretty nasty inside with a fair amount of rust from the tank behind the little in-line fuel filter, and also gumming up the main/res/primary selector valve. But, the two rubber diaphragms that make up the valve itself seemed in dern good shape.

So I hit everything with acetone and a toothbrush, and buttoned it back up. I'll give it a test, but I think I'll be keeping that goofy thing on the bike. OEM is good.

The tank isn't in too bad of shape, inside or out. One small dent where the triple-clamp impacted the tank, and a couple superficial scratches on the top. Inside, there's rust on the metal, but not too much and it's not loose; so I think a layer of this stuff should sort that out. Unless ya'll know of a better solution there. Got a new inline fuel filter, too.

That should sort out the fueling side of things. Weather permitting, I'm going to put the carb back together today and will hook up a aux fuel tank - bypassing the petcock and all that stuff. We'll see if that runs any better...

So: I haven't found anything yet that I think would cause the troubles the bike has. That means I get to open up the crankcase and look for those seals around the crank and rotary valve.

Jeff, I would urge You to NOT coat the inside of the tank. There are numerous rust removal products out there that will clean that tank.
I prefer RUSTECO, it is a organic product and so safe no eye or skin protection is needed.
If You line the tank, and just one problem occurs, You will be fighting it forever-
I have numerous old bikes, and I have a lot of experience in dealing with rusty tanks.
Here is a link to a thread I did usuing Rusteco on a Triumph tank.
http://www.motorcyclistcafe.com/forums/showthread.php?9906-Rusteco-Metal-Treatment&highlight=rusteco

There are always differences of opinions. I have coated a bunch of tanks over the years and the red kote stuff works good. You can get it at O"Reilly's Auto Parts.
Before you get too worried about a crank seal, clean the carb and spray contact cleaner or carb cleaner through the jet and carb body orifices. You must see liquid come out of the outlets in the venturi to verify that the body is clean.

Man, that thing is sweeeeeeet! Paging rogerlee; behold your bike's Doppelgänger.

Yes - I think I'll heed advice and not seal / coat the inside of the tank just yet. It's not in bad shape - a round of de-rusting should be all I need for now.

So, progress report:

I put the carb back together and used an aux fuel tank to bypass the petcock. Didn't run much differently. She still won't idle without a good amount of choke, but once she warms up a bit, it just wants to race. I didn't get the dieseling issue when I swapped out the plug, but I don't think it got as hot as it did during my first couple attempts.

So: into the rotary valve to look at his seal that's supposed to be problematic on these.

Step 1) remove side case cover screws. Done.
Step 2) remove the side case. Done:





I destroyed the gasket getting in there, so a new one's on order. But - now I see I need to pull the clutch and remove the primary drive gear:



That'll be a first for me, but then again, all of this is!

Now - I think before I jump into that, I'm going to pause a do what I was instructed to do earlier and to a compression / vacuum test on the crank case. I think I just need to big rubber stoppers (carb port and exhaust) and a hand pump with a gauge. Anyone have one of these lying around waiting for me to borrow it? If not - they don't look too pricey.

Jeff, if You want to send Me Your tank, I will do the rust removal no charge, just pay the shipping. I am in Canyon, Texas. There is not much to it, with the Rusteco.
I saw a video detailing the crank seal job recently, I will see if I can find and post it.

I found the site, I think it is under the F-9 project, probably episode 2.
This guy is the rotary valve Guru.
http://www.thejunkmanadv.com/kawasaki-f9-project.html