Period test of the 604

I found an interesting test of the ATK 604 in the August 1990 issue of Dirt Bike, seems they liked it quite a lot.

http://tinyurl.com/dirtbikeaug90atk604

 

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“Eating an elephant, one bite at a time”

That’s how a friend describes what I’m doing here and it’s an apt anology. Big job, done little bits at a time. Doesn’t help when you have to make parts for the elephant though! ūüôā

Yesterday, I finished machining the other three swingarm spacers. Held my breath when I first tried fitting the swingarm with them. Would they fit? Will I have to make them all over again? Yes and no. They fit perfectly the first try, I guess all of the time I spent measuring and calculating paid off.

All four swingarm spacers finally finished.

All four swingarm spacers finally finished.

Next task was to see how much clearance there was between the head of the swingarm pivot bolt and the brake disc. Mounted up the brake disc. Turns out, only about a hairs width – too close. So, I removed approx. 1mm from the head of the bolt and now it’s fine.

Just enough clearance between the brake disc and the head of the swingarm pivot bolt.

Just enough clearance between the brake disc and the head of the swingarm pivot bolt.

I didn’t have much more time to work, so played around cleaning the footpeg assemblies, installing them and test fitting some related bits. I mounted up the brake caliper and right footpeg loosely. It all fits like it should, though I may need a shim or two behind the caliper to center it on the brake disc. The disc guard fits nicely and looks pretty cool. Think I’ll paint the “ATK” in red.

Test fiting a few parts

Test fiting a few parts

Fresh hardware and the pegs go on.

Right footpeg installed

Right footpeg installed

Left footpeg installed, test fitting the shift lever

Left footpeg installed, test fitting the shift lever

Back to paying work tomorrow for sure.

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In the “swing” of things…

Still no parts for paying work! Not making any money, so I may as well get something done on the ATK…

Cleaned the swingarm with Purple Power and then gave it a quick polishing with Autosol. Looks pretty nice except for the chips in the plating. Installed the new pivot bearings and spiral retaining rings. I carefully measured the position of the old bearings before removal and made sure the new ones were in exactly the same depth from the edge of the swingarm.

Time for some fun: putting on some parts to see how it looks and more importantly, how it feels. Swingarm, rear shock and rear wheel go on easily.

Right view

Right view

Left side

Left side

Stand back for a look.

Swingarm, shock and wheel in place.

Swingarm, shock and wheel in place.

Putting some rear fenders and side panels on.

"Enduro" fender

“Enduro” fender

"DOT" rear fender

“DOT” rear fender

"DOT" rear fender with sidepanels

“DOT” rear fender with sidepanels

The only difference between the two fenders is the taillight. The DOT taillight is larger, mounted lower and illuminates the license plate. The Enduro unit is smaller, higher with no means of lighting the plate. One big consideration for me is that the DOT lens (made by CEV) is very difficult to find, even in Europe. The Enduro lens is an Acerbis part and easy to find. So, for a bike that may suffer a cracked lens, the choice is obvious. The black plastic fender extension will be installed on the new fender whichever taillight I use.

While¬†all of the bits were on the bike, I climbed aboard¬†to see how it feels. Without having the¬†footpegs installed, there’s only so much I can tell for sure, but the handlebar position and height fits me well and the seat-to-bar distance is right. I was able to manipulate the lift controls with my right foot while on the bike, so lowered it down onto the wheels. With the spare (stock 406) suspension on the bike, I¬†can just get the¬†tips of my toes down. Still too tall. I’ll be assembling the original suspension with the lowering bushings installed and see where that puts me. I’d like to at least be able to get the ball of feet firmly on the ground.

After all of that fun, it was back to work. Took some careful measurements swingarm-to-frame and swingarm-to-engine and calculated the thickness of the spacers needed. I have eight original spacers and none of them were¬†correct.¬†After skimming a little over .020″ off of one, the right-side swingarm-to-engine spacer was done.

Working on the spacers for the swingarm spindle.

Working on the spacers for the swingarm spindle.

I used a laser attached to the rear sprocket to check alignment with the front sprocket and it’s dead on. Good deal. Now to make the other three.

 

 

 

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Happy New Year!

Spent the morning trying to figure out to use Microsoft Expression Studio 4 to update my website. Managed to get as far as making changes to the website pages in the program, but not how to publish them. I was getting a headache from staring at the computer screen, so after lunch I gave up for the time being and went out to the shop.

I didn’t work yesterday, so the shop was cold, a fire in the barrel stove was the first order of business. Started work on the A-Track idler sprockets – removed the bearings and cleaned the sprockets. Pressed one new bearing that I had laying around¬†into the sprocket after applying a little Loctite bearing retainer, cleaned up the spacer and collected all of the pertinent hardware together. Not much progress there, once the rest of the bearings arrive, I can finish the job.

Moved on to mounting the handlebars. It’s taken me quite a while to decide what switches to use, but I think this is the “keeper” setup. I tried to use a K&S on/off-start switch on the right, but no matter how I tried, it interfered with either the Magura throttle, Brembo master cylinder or both. It was just too wide for the space it needed to fit into. So, unless I change my mind (again), I’m using a K&S push-button kill switch as the starter button.

Right-side controls

Right-side controls

On the left, I’m using a Domino lever assembly (from a Moto Guzzi Strada) and a K&S headlight/horn/signal switch. The lever assembly has a choke on top that I’ll modifiy slightly to use as¬†a compression release.

Left-side controls

Left-side controls

I’m getting anxious to see this thing down on it’s tires, so I installed my spare forks on it. Spares forks? Oh yeah. Forgot.¬†A pair of WP forks and a WP rear shock were on eBay cheap ($105 shipped) so I bought them. The shock is actually better than the one I had originally planned to use. The forks are a little scuffed, but don’t leak. However, they’re lacking the¬†external adjusters for damping like the others. Both are off of a 406, so the spring rates are a bit softer, giving me another set of springs to choose from. They went on without a fuss as did the front wheel. I wanted to see how the headlight surround and fenders looked on it too, so I put those on.

Front forks are fully extended

Front forks are fully extended

Stood back and had a look at it from the side. Wondered how close to unladen height (no suspension sack) it was, so I stuck the seat on and grabbed a tape measure. Seat height was exactly 37″, 13″ of ground clearance¬†– right on the money.

Mocking up with the spare set of forks, old fenders and narrow seat

Mocking up with the spare set of forks, old fenders and narrow seat

Once I get the swingarm cleaned, the new bearings installed and the pivot spacers made, I can stick my spare shock and the rear wheel on.

Swingarm awaiting a thorough cleaning before the new bearings and spiral lock rings are installed.

Swingarm awaiting a thorough cleaning before the new bearings and spiral lock rings are installed.

At that point I’ll play around with the spring choices and preload to decide exactly how to proceed suspension-wise. The swingarm shows just how rough of a life this bike had before it was parted out and I bought the rolling chassis. There’s still Florida sand all over it¬†and the chain must have broke at some point as there are scars to prove it. Some of the nickel plating is chipped off in places, so it won’t look quite as nice as the frame. But, I’m not building¬†a show bike here!

Sometime in the bike's past the chain must have been very loose or perhaps broke. Otherwise there couldn't have been damage here.

Sometime in the bike’s past the chain must have been very loose or perhaps broke. Otherwise there couldn’t have been damage here.

More signs that a chain broke at some point.

More signs that a chain broke at some point.

Parts for paying work should be arriving tomorrow, so I’m not sure how much I’ll get done for a while.

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A-Track musings

The one feature of the early (’93 and before) ATKs that I have the most misgivings about is the “A-Track” system. For those of you not familiar with this, it’s basically two idler sprockets positioned near the swingarm pivot, with the purpose of keeping constant tension on the drive chain at all times. The goal being to allow the rear suspension to move as it should,¬†totally uneffected by the forces imparted by the powertrain (no squat under acceleration or¬†rise during braking). Sounds like a brilliant idea, right? Well, yes it is a great idea. However, the execution of that idea is what worries me.¬†

Early idler sprockets¬†rolled on¬†a single¬†6002 ball bearing and were by all accounts rather short lived. The redesigned¬†idlers roll on a pair of 6202 ball¬†bearings and from what I’ve heard last longer. Trouble is, nobody¬†seems to be able to¬†tell me how long. It’s one thing if you’re a racer and only run a couple of motos a weekend before the bike gets torn down for service. It’s quite another if the bike is used as I intend to – long dual-sport trips into remote areas. A shagged idler sprocket bearing could be a serious issue out in the middle of nowhere. I plan to carry a complete spare idler sprocket with me whereever I go…

New ones cost just under $100 complete with bearings and hardware. It seems to be a proprietary design, made specifically for ATK back then and American Dirt Bike now. Fortunately, I’ve bought a couple used ones – one good double bearing type and a pair of salvageable single bearing type. My plan is to install new bearings in the newer type¬†and attempt to convert the older type to use two 6002 bearings,¬†hopefully making¬†them more durable. I’ll use the new type on the top position (since it will be under the highest loads) and the¬†modified older type on the bottom.

The revised, double bearing idler sprocket is at top and the older single bearing type at the bottom. The triangular plates to the right hold the idlers in position and the round objects at their ends are to adjust the idler position up and down.

The revised, double bearing idler sprocket is at top and the older single bearing type at the bottom. The triangular plates to the right hold the idlers in position and the round objects at their ends are to adjust the idler position up and down.

Worst case scenario, I’ll remove the whole¬†A-Track system from the swingarm (mounting tabs and all) and make it like a “normal” bike with plastic chain sliders and such.

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Changes

Never noticed the¬†date was incorrect before, so I set the time zone to the correct one. I’ve always hated that weird header design, but didn’t think I could change that, but what do you know, I can. So, an ATK logo looks much better, even if it is severely cropped.

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Steering head bearings

Replaced the notchy steering head bearings next. All the aluminum parts were degreased and then acid washed to return them to their original color. The new bearings were gummed up Рstuck solid Рan overnight soak in carburetor cleaner took care of that. Packed them with new grease and installed the triple clamps with new hardware.

Triple clamps installed

Triple clamps installed

Working on the swingarm bearings next…

 

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