Hawk Talk

[pete]

Originally Posted by Ariel Red Hunter

The rear is harder, probably because the hydraulics are laid out in an almost straight horizontal line. Sincerely, ARH

other way around....
front the bleed nipple is so far below the master cyclinder
air bubble rise...



....

[Ariel Red Hunter]

Originally Posted by pete

other way around....
front the bleed nipple is so far below the master cyclinder
air bubble rise...



....

That is correct, front air bubbles rise to dissapate in the "Master Cylinder". So, any air bubbles are only in the brake caliper, and easy to get rid of. Because the rear hydraulic brake system is laid out in a almost totally horizontal scheme, air bubbles tend to want to stay in the tubing. It can take several tries (and moaning, tears, and language not spoken in polite company) to get rid of this problem in the rear. ARH

[OUTERLIMITS]

Originally Posted by Kourosh

I just got my hawk, did the assembly all is going okay except the back brake pads are locked together, anyone know how to ease them? I've tried adjusting back brake lever tension via pedal, no results, If anyone knows what I have to do it would be appreciated. Thanks.

I read this to mean that the brake lever was pulled (or pushed) before the disc was between the pads and the pads closed up. Not a problem if that's the case, just gently wedge a large flat blade screwdriver between the pads and slowly lever it open. Disregard if I misunderstood your issue.

[pete]

Originally Posted by Ariel Red Hunter

That is correct, front air bubbles rise to dissapate in the "Master Cylinder". So, any air bubbles are only in the brake caliper, and easy to get rid of. Because the rear hydraulic brake system is laid out in a almost totally horizontal scheme, air bubbles tend to want to stay in the tubing. It can take several tries (and moaning, tears, and language not spoken in polite company) to get rid of this problem in the rear. ARH

theroys are wonderful things....but in the real world it can be
a bit diffrent...
6/8 pumps I can usely do a rear...
front I usely have take the master cylinder off put it on the ground below the caliper
then 6/8 pump done.....

.....

[Ariel Red Hunter]

Everybody likes front forks on a motorcycle, because without them, we'd be riding Uni-cycles. Originally, motorcycles had forks very similar to today's beach bikes. No spring except from the front tire. In this country anyway the first bike that I know of that had anything up front was the Indian. It sprung in a fore and aft direction only. But this was a revelation when it came out (1904, or so). The roads of the day had a lot of potholes, and this fork took some of the jolt outof hitting the edge of a pot hole. A lot of city streets were paved with bricks, and the ride quality over bricks and cobblestones was much more pleasant with that front fork. That fork had only about an inch and a half travel, but it sure made a difference. As speeds increased, something better was needed. So next came the H-D leading link fork (now called a springer), and almost at the same time, Indian's trailing link fork, the one with the leaf spring on top of the fender. Both of these forks were superior road holders, for the day, because the links were paired in a tuning fork arrangement that led to the spring up at the steering head. The Indian fork had the advantage of the spring leaves sliding on each other, which provided some damping. Not a lot, but some is better than none, right? All of these early forks had pretty stiff springs, and needed them because of no/very little damping. The English manufacturers developed the girder fork, which originally wasn't very good, but which was developed into a very good fork over time. It eventually had check springs, plus suspension springs plus friction shock absorbers. Then came a new design that was a sensation. The Matchless/AJS telescopic fork with hydraulic damping, just in time for the start of world war two. Teledraulic, it was called. This was a seismic shift in front springing. The difference in ride quality was like night and day. The steering was less precise, but you could go faster because the front tire spent more time actually on the road. Cornering speeds went up. Only fly in the ointment was that they were using 20 weight non-detergent motor oil in them. Worked good on the highway, but not so good off-road because the oil would thin out from heat. They would clang and bang at every rough spot on the trail. (Clang at full extension, Bang when totally compressed). In those days, Nortons were not popular off road mounts because they used very stiff front springs to make up for poor damping. Nothing wrong with "Roadholder" Norton tellies, the oil was the problem. My Red Hunter had superb front fork action as long as it was cold. After 15 or 20mminutes in a desert race they clanged and banged at the sight of a rough piece of ground. So did BSA forks. And Triumph forks. But the scientists at Castrol gradually improved the fork oil they were making until the clanging and banging stopped. And fork oil has been improving ever since. Until China started competing in the world market. The oil that comes in their forks is not very good. It is not really a fork oil at all, but an anti-rust oil to protect the forks on those long ocean voyages to get here. Put you new Hawk together, ride it around the block a few times, then drain the forks and put real fork oil back in there. Many people on this site have used Dexron in these forks with great success. You might want to try it.

[Ariel Red Hunter]

The real problem on a Hawk is the rear suspension. It is over sprung and under damped. Now if you weigh as much as I do (Just short of 300 pounds), the spring is ok. If you weigh 150....Well, things could be better. Now a better rear unit is going to cost more. The only way the factory will change to a better rear shock is if they can get it at the same price point. There is no way they can get a piggy back resevoir rear shock and offer a different spring for it for the same money and maintain the current price point. This is the trade off all manufacturers have to deal with. I know this because I used to be a production engineer at The Farmall Works in the quad cities. To me, the solution is to find a higher quality Chinese shock and offer it as an option, after sale. RPS and APSUSA would be the most likely places to do this. I found one on Alibaba, but I'd have to buy a container load to get them. I'm not about to do that. Oh yeah, why a piggy back shock? Because you can change the damping fluid to get the results you want, that's why.

[pete]

Reservoir "piggy back" shocks contain nitrogen gas in the reservior as well as in the
shock body for compression damping... as the shock compresses the gas pressure
increases in the body slowing down the compression stroke "damping it"
there is a very small hole between the reservior & shock body this hole lets the gas in the shock body & reservior equalise... the size of the hole determines the amount & time length of the compression damping before the reservior & body pressures equalise..
the shock with adjustable compression damping change the size of the hole with a
needle seat arrangment to change the hole size...
Big hole low compression damping..
Small hole high compression damping..

Some shocks did contain oil in the reservior but
those shocks are long gone.. prob since the late 70s...
I had a old pair of Girling shocks that worked that way
Were on the 1977 Montesa Cota 348 trials bike when
I bought it... very little damping , that was perfect for a trials bike
making possable to hop the rear wheel... but have since replaced
them only because the diddn't look right with a classic/vintage trials bike..




.

[Ariel Red Hunter]

Originally Posted by pete

Reservoir "piggy back" shocks contain nitrogen gas in the reservior as well as in the
shock body for compression damping... as the shock compresses the gas pressure
increases in the body slowing down the compression stroke "damping it"
there is a very small hole between the reservior & shock body this hole lets the gas in the shock body & reservior equalise... the size of the hole determines the amount & time length of the compression damping before the reservior & body pressures equalise..
the shock with adjustable compression damping change the size of the hole with a
needle seat arrangment to change the hole size...
Big hole low compression damping..
Small hole high compression damping..

Some shocks did contain oil in the reservior but
those shocks are long gone.. prob since the late 70s...
I had a old pair of Girling shocks that worked that way
Were on the 1977 Montesa Cota 348 trials bike when
I bought it... very little damping , that was perfect for a trials bike
making possable to hop the rear wheel... but have since replaced
them only because the diddn't look right with a classic/vintage trials bike..




.

Good to know. Thank you. I had a late seventies Yamaha IT 175, and it had those replaceable oil rear shocks, which is why I was talking about them.

[Ariel Red Hunter]

I just finished a rant on Mikuni vs Keihin carbs on another column. Something like "What's so good about a Mikuni". I don't want to write it again on here, because it is WORK. And, as my father told me several times, "Boy, you sure don't like work". But my definition of work is when you are sweating, doing something you don't want to do. Like shovelling out calf pens. Feeding cows? Fun. Milking cows? Fun. Tuning motorcycles? Big time fun!

[Ariel Red Hunter]

While the engine in the Hawk may not be able to win the TT on the Isle of Man, it is more than good enough for a Hawk. A semi simple, free revving, air cooled push rod engine, built for long life. What's not to like? Easily tunable with changes to the intake and exhaust systems, and can be done on a step-by-step process to reach speeds the manufacturer never envisioned. It is not perfect. There are things that could have been done different to get more power from the crankshaft to the rear wheel. A gear drive primary soaks up more power than a chain drive primary. An all-indirect gearbox wastes more power than one with a direct drive top gear. Wet sump engines are not good if you drop the bike, and the engine keeps running. Dry sump is better here. Why? Because with a dry sump engine, oil pressure and circulation is maintained even with the engine laying on its side.

Lever action valve lifters, which the Hawk has, are lighter than tappets. Short stroke means shorter and lighter push rods. A single cam, operating both valves mean, in this design, very low scrubbing of the lifters against the cam. Low scrubbing means long life. Valve timing and overlap can be changed by changing the profile of the curved feet on the lifters. Because the lifters meet the cam on opposite sides of the cam means copious lubrication of the cam/lifter interface. Gear driven oil pump. Fat torque curve. Making maximum use of that torque curve is where you get really good acceleration. Go back on this column and re-read Joe Craigs explanation of using the torque curve to maintain high average speeds. You have to read his comments very carefully to get this, as he doesn't make a big deal about it. In fact, I think I'm going to quote an ex TT winning rider, who later worked for one of the English bike mags on this very subject. June, 1950, Motor Cycling - Graham Walker speaking; Well, the sensational increase in speed of this years Manx Nortons makes it obvious that the latest Bracebridge Street models have 'got something', and all over the world there are enthusiasts who want to know just what that 'something' is. I will do my poor best to describe it, because I was one of the lucky few given the opportunity to test the winning mounts immediately after the Races. The Norton team and 'Professor' Joe Craig have evolved a gear change-to-revolution rate technique which, in my experience, is unique. Suffice it to say I have tried out the formula and it undoubtedly had an important effect upon the lap times put up by the Norton team." Essentually, Craig re-cammed the engine in such a way as to give a long almost flat torque curve, and then developed a formula for shifting gears that made the most of the fat part of that curve. Previously, engines had been tuned for top end horsepower only. Or think of it as "Bonneville Salt Flats" valve timing. Guess what kind of torque curve the engine in the Hawk has. The Norton formula is simply to run on the torque curve until in high gear, then let it stretch out to peak revs (power peak, 7500 rpm on the Hawk). If you can exceed 7500 rpm in high gear on level ground, you are geared too slow. Above 7500, horsepower is decreasing. And decreasing rapidly. If you gear it this way, you MUST have your off idle and below 1/2 throttle carburation spot on. Good luck in getting carburation as good as it should be with the stock carb. In theory, it can be done. Reality is something else. And the $30.00 Mikuni isn't the total answer either. Look at the $89.00 Mikuni with a seperate starting circuit for a pretty good answer. Not the ultimate, but damn good.

[chuck]

Originally Posted by Ariel Red Hunter

While the engine in the Hawk may not be able to win the TT on the Isle of Man, it is more than good enough for a Hawk. A semi simple, free revving, air cooled push rod engine, built for long life. What's not to like? Easily tunable with changes to the intake and exhaust systems, and can be done on a step-by-step process to reach speeds the manufacturer never envisioned. It is not perfect. There are things that could have been done different to get more power from the crankshaft to the rear wheel. A gear drive primary soaks up more power than a chain drive primary. An all-indirect gearbox wastes more power than one with a direct drive top gear. Wet sump engines are not good if you drop the bike, and the engine keeps running. Dry sump is better here. Why? Because with a dry sump engine, oil pressure and circulation is maintained even with the engine laying on its side.

Lever action valve lifters, which the Hawk has, are lighter than tappets. Short stroke means shorter and lighter push rods. A single cam, operating both valves mean, in this design, very low scrubbing of the lifters against the cam. Low scrubbing means long life. Valve timing and overlap can be changed by changing the profile of the curved feet on the lifters. Because the lifters meet the cam on opposite sides of the cam means copious lubrication of the cam/lifter interface. Gear driven oil pump. Fat torque curve. Making maximum use of that torque curve is where you get really good acceleration. Go back on this column and re-read Joe Craigs explanation of using the torque curve to maintain high average speeds. You have to read his comments very carefully to get this, as he doesn't make a big deal about it. In fact, I think I'm going to quote an ex TT winning rider, who later worked for one of the English bike mags on this very subject. June, 1950, Motor Cycling - Graham Walker speaking; Well, the sensational increase in speed of this years Manx Nortons makes it obvious that the latest Bracebridge Street models have 'got something', and all over the world there are enthusiasts who want to know just what that 'something' is. I will do my poor best to describe it, because I was one of the lucky few given the opportunity to test the winning mounts immediately after the Races. The Norton team and 'Professor' Joe Craig have evolved a gear change-to-revolution rate technique which, in my experience, is unique. Suffice it to say I have tried out the formula and it undoubtedly had an important effect upon the lap times put up by the Norton team." Essentually, Craig re-cammed the engine in such a way as to give a long almost flat torque curve, and then developed a formula for shifting gears that made the most of the fat part of that curve. Previously, engines had been tuned for top end horsepower only. Or think of it as "Bonneville Salt Flats" valve timing. Guess what kind of torque curve the engine in the Hawk has. The Norton formula is simply to run on the torque curve until in high gear, then let it stretch out to peak revs (power peak, 7500 rpm on the Hawk). If you can exceed 7500 rpm in high gear on level ground, you are geared too slow. Above 7500, horsepower is decreasing. And decreasing rapidly. If you gear it this way, you MUST have your off idle and below 1/2 throttle carburation spot on. Good luck in getting carburation as good as it should be with the stock carb. In theory, it can be done. Reality is something else. And the $30.00 Mikuni isn't the total answer either. Look at the $89.00 Mikuni with a seperate starting circuit for a pretty good answer. Not the ultimate, but damn good.

Thank you, you are God Sent to Hawk riders.

[Ariel Red Hunter]

Originally Posted by chuck

Thank you, you are God Sent to Hawk riders.

Thanx! What a nice thing to say, Chuck.

[timcosby]

Originally Posted by Ariel Red Hunter

Thanx! What a nice thing to say, Chuck.

sharing your wealth of knowledge is much appreciated!

[Ariel Red Hunter]

After you have got your carburation and exhaust maximised, the next (expensive) step is head and valve work. "Ace" at Mondello's old garage will flow bench your head for you, if you have some loose bucks. I don't know if he would do it, but he is a Royal Enfield tuner of the top rank. How good? Good enough to have a Royal Enfield nipping on the heels of Norton Manxes, and Matchless G-50's. When I was racing a Goldstar at Ascot, Shell Thuett was running a Royal Enfield. It was fast, but it was fragile. Now, listen up, because I'm going to give you, at no charge, the two top secrets of racing. Secret number one - They only count winners at the finish line. Secret number two-if you don't have an engine with a totally bullet proof lower end, you will be re-building lower ends while your competitors are doing the hundred little things to their bikes that make them competitive. For example, the secret of the Offenhauser's success was that, if you rebuilt the engine in the winter, and did it right, you never touched it again all summer, and remember we raced every Friday night, and the Offy Sprint cars every Saturday night for six moths of the year. You can't fine tune a chassis if you are wondering how long until the motor goes off song.
If I recall correctly, Ace charges $75.00 to hook it up to the flow bench. You can easily breeze through $500.00 having the head maximised. You really want to spend almost half the original cost of the motor-cycle to get that extra performance out of it?

[Ariel Red Hunter]

I forgot to mention that the Hawks engine (shared with several other Chinese bike builders) has a very rigid crankcase and stiff crankshaft, which is the foundation that high performance engines are built on.