Hawk - Rear Shock

[Weldangrind]

Originally Posted by jimwildman

I will likely add a second shock mount lower on the swing arm.. also closer to the fulcrum so likely to make the suspension softer by increasing the leverage on the shock. ill need an adjustable shock.

I'm looking forward to that!

[jimwildman]

I hadnt thought of how to install the bolt with the mount in the ideal position its right between the rails of the swing arm,,

using a steel plate i tested the leverage change that occurs when moving the fulcrum either forward or backward.

with the fulcrum 1 inch forward seat hieght is up about 2" the shock is way too soft, bottoms right out on a light bounce, and i only weigh 165.

with the fulcrum moved back 1 inch, shock is in the way of the tire.. so most of the chain adjustment is gone , but the shock is stiffer and about 2.5 inches lower..

if you look at pictures of a honda nxr 150 thats about the spot is sits now and i like it..


what i discovered while looking this all over is the hawk has a common issue where the chain gets tighter as the suspension compresses. so if you run your chain too tight it will likely streach.

i suspect a snaller rear sprocket will lessen. the effect. now im looking at a 45 rear, and going back to 15 fromt to see if that helps.

more later,

[pete]

Originally Posted by jimwildman

what i discovered while looking this all over is the hawk has a common issue where the chain gets tighter as the suspension compresses. so if you run your chain too tight it will likely streach.

All bikes do that... why yer have a lose chain..
as the suspension travels the chain gets tighter then
when the engine sprocket/swing arm pivot/ rear axle
come in to alinement that is the tightest point , then as it travels
passed that point the chain starts getting lose again..
there should be a rollor on the frame above the swing arm pivot
that takes up the slack chain under full suspension compression..

there are so meany shocks out there that are suitable but the
big issue for a china bike is they cost half or more than the prise of the bike..
So to make it afordable yer stuck with nasty chinese ones..

It may be best to look for a used named brand one if yer want a shock
that works....


..

[jimwildman]

not this much they dont. i have owned hundreds of bikes.

The hawk goes from sloppy to tight in 2 inches of travel.. its a geometry flaw..
fulcrUm of the swing arm is a bit to high.

I know a few things about it. i drive a classic car with a custom one off tube frame chassis designed and built by me.

I understand all concepts of suspension geometry.

so while your right the chain should be adjusted for the longest point in travel, the chain should not fall off at rest..

I Have built a chain tensioner to take up the slack at rest. but the amount of change is still too much i didnt notice it untill i had the shock off and moved the arm through its path a few times.

this is why peoples chains fall off. and why it seems to streach soo much, i really thought the 420 was too weak but in this case a 520 would do the same.

Ive had bikes with no chain stay of any kind that never tossed a chain. and the tension change hardy perceivable.

[Mudflap]

My Lifan 200 had the same problem where chain had to have about 3.5" of slack while on the stand so it wouldn't be too tight at the tightest point in suspension movement. My solution was to move the swing arm pivot bolt down about 3/4" which required some welding and grinding on the frame. Works like it should now.

[Ariel Red Hunter]

Originally Posted by jimwildman

not this much they dont. i have owned hundreds of bikes.

The hawk goes from sloppy to tight in 2 inches of travel.. its a geometry flaw..
fulcrUm of the swing arm is a bit to high.

I know a few things about it. i drive a classic car with a custom one off tube frame chassis designed and built by me.

I understand all concepts of suspension geometry.

so while your right the chain should be adjusted for the longest point in travel, the chain should not fall off at rest..

I Have built a chain tensioner to take up the slack at rest. but the amount of change is still too much i didnt notice it untill i had the shock off and moved the arm through its path a few times.

this is why peoples chains fall off. and why it seems to streach soo much, i really thought the 420 was too weak but in this case a 520 would do the same.

Ive had bikes with no chain stay of any kind that never tossed a chain. and the tension change hardy perceivable.

Odd that whoever designed the frame didn't realise that the swing arm pivot should be as close to the countershaft sprocket as possible, and in the same plane. That geometry was figured out about 75 years ago, and is in the text books of the time. And maybe even longer ago than that, come to think of it - the 1918 Indian Chief had swing arm suspension, and I've never heard of them throwing chains.

[jimwildman]

In todays mixmatch world the frame may well have been concieved with a different engine in mind. on the way to production, some substitutions can be made with cost or availability in mind.

The engineers may not have had the forsight to see the problem they introduce. this is a common problem in manufacturing.

or they just messed up. sounds like that Lifan had it even worse.

[jimwildman]

solved my problem by making a set of adapters that move the shock mountpoint 3/4" forward and 1/2 inch lower. by bolting them instead of welding, I can install the shock bolt then swimg it downward and clamp it with the bolts.

the result is the bike is about an inch lower at rest. and about 2" lower with me on it, im 5' 10" tall and can easily touch both feet standing still.

the change of the fulcrum has the suspension a bit softer and it really feels great. I cant make it bottom out with my 165 pounds of rider.

the bike feels better and the forks dont seem too short anymore, my first impression of the hawk was forks are too short, later I realized the rear is just too high..

here are some pics of the modification, i also added a grease zerk to the swing arm for the bushings and shaft.

this pic is the peices cut from the front of the existing shock mount.

[jimwildman]

this is the adapters I fabricated.

[jimwildman]

the chain tensioner I Fabricated.

[jimwildman]

another angle of the suspension work.

[jimwildman]

from underneath

[jimwildman]

I am happy with this and it cost me nothing but my time, and some electricity.

[jimwildman]

one more

[pete]

Originally Posted by jimwildman

not this much they dont. i have owned hundreds of bikes.

The hawk goes from sloppy to tight in 2 inches of travel.. its a geometry flaw..
fulcrUm of the swing arm is a bit to high.

I know a few things about it. i drive a classic car with a custom one off tube frame chassis designed and built by me.

I understand all concepts of suspension geometry.

so while your right the chain should be adjusted for the longest point in travel, the chain should not fall off at rest..

I Have built a chain tensioner to take up the slack at rest. but the amount of change is still too much i didnt notice it untill i had the shock off and moved the arm through its path a few times.

this is why peoples chains fall off. and why it seems to streach soo much, i really thought the 420 was too weak but in this case a 520 would do the same.

Ive had bikes with no chain stay of any kind that never tossed a chain. and the tension change hardy perceivable.

sounds just like a pitbike... swing arm pivot way to high
On my boys pit bike I had to put a nylon disc each side of
the rear sprocket to guide the chain on & stop it jumping the sprocket & run the chain
all but tight when the suspension was un loaded to keep the slack chain under full compression
to a minimin..

What stops the 2 plates you made from pivoting on
the old shock mounts on the swing arm...?
Is it relieing on the plates sitting against the swing arm.
it looks as if what was a compression loading on the shock
brackets is now a tentsion loading by the way of the plates acting as a lever...
Or is there something ealse that is unseen in the pictures..

Hundreds.. thats a lot of bikes...
I'm still new to bikes then in would seem..., only had 36..




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