Shortening head tube

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DannyBoy

Guest
Hello! This is my first post here so if I am in the wrong section or similar, let me know or take appropriate actions.

I have recently built my first motorized bicycle. It is a pretty standard build. 49cc Huasheng engine on a cruiser frame.
It runs great and looks great. (depends on your tastes)

I'm now in the process of buying a new front fork that can utilize disc brakes and has shock absorbers and looks good. I have decied to get one off aliexpress that fits all my needs and measurements except for one: Head-tube length.
Link to the fork is here.

My head-tube is 165mm long and the steerer-tube of the fork is 160mm.
I have googled for shortening head-tubes, but this seems to not be an existing problem because it seems that all forks have longer steerer-tubes and thus all places I've seen are about shortening the steerer-tube. Never the head-tube.

This brings me to my question of shortening of the head-tube.
Is it hard? Is it safe? How should I do it? Any methods or tools that are recommended?
Basically as much information as possible on the subject.

Image of the fork:


Product schematic:
 


Dannyw0ah

New Member
Joined
May 28, 2019
Messages
7
After viewing this forum pages and atmosphere, i decided to create an account. Great place!

There is quite a bit of extra tube above and below the tubes connected to the head-tube.
Here is the frame:


 

Spare_Parts

Well-Known Member
Joined
Nov 29, 2017
Messages
1,720
The hard part is getting a straight cut. I often use a hose clamp as a guide for a hacksaw. You will want to leave a little space between your cuts and the welds. About a 1/4". Just go slow. Don't think you will end up removing enough to fit that fork. Need room for the headset.
 

gary55

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Joined
Nov 27, 2012
Messages
3,461
After viewing this forum pages and atmosphere, i decided to create an account. Great place!

There is quite a bit of extra tube above and below the tubes connected to the head-tube.
Here is the frame:


Well it looks like you (may) have enough head tube, but if it has a recessed portion at top and bottom of head tube to fit the cups you will have to duplicate that as well. Do you have a pic of the bike with the engine in it. It looks like one tight fit. What make bike is that, and where did you get it if you don't mind my asking. Maybe if you haven't ordered the forks yet you could contact the supplier to see if they have the 180mm steer tube option.Sunlite Deluxe Springer Replica Fork 26 180x70x25.4x27 Disc Bk F/175mmstack Ht 72774283132 | eBay On second look I don't think the 180mm will work without cutting the head tube, and can't find a 200mm.
 
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Spare_Parts

Well-Known Member
Joined
Nov 29, 2017
Messages
1,720
Well it looks like you (may) have enough head tube, but if it has a recessed portion at top and bottom of head tube to fit the cups you will have to duplicate that as well. Do you have a pic of the bike with the engine in it. It looks like one tight fit. What make bike is that, and where did you get it if you don't mind my asking. Maybe if you haven't ordered the forks yet you could contact the supplier to see if they have the 180mm steer tube option.Sunlite Deluxe Springer Replica Fork 26 180x70x25.4x27 Disc Bk F/175mmstack Ht 72774283132 | eBay
I just went looking for that fork!

Good call on the recesses for the cups!
 

gary55

Well-Known Member
Joined
Nov 27, 2012
Messages
3,461
I just went looking for that fork!

Good call on the recesses for the cups!
Forks can be a pain. Looking at it again I don't think a Sunlite Monarch fork with180mm steer tube will work on the 165 mm head tube. You probably have 8mm for the cups, another 6 for the top bracket. That only leaves you 1mm for the washer and nut. The top bracket is what kills you.
 
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Dannyw0ah

New Member
Joined
May 28, 2019
Messages
7
Well it looks like you (may) have enough head tube, but if it has a recessed portion at top and bottom of head tube to fit the cups you will have to duplicate that as well. Do you have a pic of the bike with the engine in it. It looks like one tight fit. What make bike is that, and where did you get it if you don't mind my asking. Maybe if you haven't ordered the forks yet you could contact the supplier to see if they have the 180mm steer tube option.Sunlite Deluxe Springer Replica Fork 26 180x70x25.4x27 Disc Bk F/175mmstack Ht 72774283132 | eBay On second look I don't think the 180mm will work without cutting the head tube, and can't find a 200mm.
I will disassemble it later today and do some more investigation on how it looks. I'll check the headtube and see how the cups look and more.
The bike is a Swedish branded Yosemite bike bought from a hardware store called "Biltema" here in Sweden. The engine fit is tight. Barely fits. The choke-lever touches the top of the frame but is still operational and it runs fine.

I didn't even know that there were 180mm steerer-tube versions of this fork. Thank you! I hope 180mm will be enough. I will measure more this afternoon after work. Shame they don't make larger versions or just more steerer-tube. Although My 165mm head-tube is very long.
Is there any other similar fork you can recommend that has the excess tube i need?
Preferably the same look?
 
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