Installing a hitch on my AK 550 to tow a small cargo trailer

[rjs987]

Weather was nice in the garage today. Temps in the 50sF and the sun was shining outside. It just makes working in the garage with the overhead door open, well, better.
So I did some work on the bike and hitch frame.

First: I cut the 6 ft 1x1 stainless tube exactly in half. Well, as close as I could get it. Ended up with 2 square tubes 36 inches long (+/- 1/16 inch).

Second: I started working on cutting the hole in the tail for the left side. That side was easiest to work on since there are no electrical connections on that side in the rear. I have an aluminum angle bar that is 1 inch by 1 inch that I used to make it easier to mark the inside of the plastic panel. Easier because I can turn the angle so I can get my marking tool all the way back there. My marking tool is a very slender sharp pointed awl that I used to poke a very small hole in the first 2 corners (bottom corners) of where the square tube would pass through. Then I used a utility knife with a new blade (very sharp) to score... and re-score... and re-score... and re-score... a line between the small holes. Twenty thousand times of passing over that line later the tip of the knife went through the plastic. Then I marked a hole for part way up the sides of where the square tube would go through the plastic and repeated the scoring with the knife. Because the plastic panel is angled back there I was not able to just mark all 4 corners right away at the risk of making the hole the wrong size. I was VERY careful doing this to not damage the plastic outside where the hole would be.

Then I test fitted the square tube and made minor adjustments to the hole as needed. I tied the front end of the tube where it will eventually be clamped to get an accurate placement at the mud flap where the hitch tube would come to. It worked out just as I was expecting... though higher than I originally thought it would be. This was possible because I moved the forward mounting point for the hitch tube forward about 3 inches. This is better IMO.

Third: I had to relocate the tail light electrical cable since that was routed under the bike rear frame just where the hitch frame tube on the right side needs to be.

Here are a few pics of today's progress.

https://photos.app.goo.gl/dTY1DLYGReMDear37

That's all for today.

[rjs987]

Today I tackled cutting the hole on the right side.
I started by making a template matching the panel on the left side lining up with the panel seams and tracing the hole on card stock. Then I cut out the hole, flipped it over, and taped it to the right side. I used a scratch awl to mark the outline of the hole and then started in with the 1001+ times of scoring the line with my utility knife and I was through. I put both square tubes in place and verified that it all lines up perfectly. Same angle out the back and same level.

Then I leveled the bike. I did this with the help of the guy I bought the trailer from. I put a bag of rubber mulch on the passenger seat (to compensate for my riding gear and what I pack under the seat) and sat on the bike to load the suspension. My friend placed a small level on the luggage rack and put a block under one end until the bubble showed level. I took note of the block and level so I could repeat as needed. Turns out that putting the front wheel on a 2x4 block set flat and with the bike on the center stand then the bike is level as when the suspension is loaded for riding.

With the frame tubes in place I measured the angle the frame tubes are offset from vertical. I have the adapter my friend used when the trailer was hitched up to his bike. It is a 31/59/90 triangle. I re-measured and found it was a bit off. Even though one or two degrees is not enough to really matter I know that if I start accurately in the plan the end result will be better. The Uni-Go receiver is bolted to the long side off the 90 deg angle leaving a 31 and 59 deg angle. I plan to weld the long side between the 31 and 59 deg angles to a 1/4 inch plate that will be attached to the ends of the hitch frame tubes. I measured the frame tube angle as it comes out of the bike at 86 deg from vertical. I'll have the 31 deg angle of the adapter pointing down. Therefore I will need to put a 55 deg bend in the frame tubes to end up with the Uni-Go receiver set vertically. The receiver must be vertical for the best result and stability of the trailer. Lots of geometry that I never thought I'd use. Just to verify I drew it all out on paper with a protractor. [corrected after measuring more than once].

While the frame tubes were set in place I test fitted the storage box to see if I measured right for clearance. I didn't... exactly.
I did measure right for where I originally intended the ends of the frame tubes to attach on the bike frame but then I moved that point forward some inches. That was enough so that each of the frame tubes are about 1/2 inch too wide at the very ends.

So on to plan B. And I actually did think up a plan B several days ago just in case. I'll be welding a length of 1" x 1/4" stainless steel flat bar to the outside of each frame tube and back down the square ends about 7 inches. This is best to maintain the clearance around the mud flap for the hitch frame tubes. The bend will be right at the top of the mud flap so the tubes need to clear each side.

Here are some pictures in a collection from today. One pic shows the bends and angles I need to make. The thick blue line is the bent frame tube and the thin blue line is the vertical reference (but obviously this is not really to scale).

trailer hitch project 2-6-2024

[rjs987]

Yesterday before I started working on the bike I pulled the trailer next to the AK and using some jumper wire in the SAE connector for the BT, which is always on, I tested each of the lights on the trailer. Tail light, brake light, left turn and right turn lights as well as the convenience light inside the trailer. There was also a battery powered light inside stuck on with Velcro but I broke a tab off opening the back to replace the batteries. Those are cheap so I'll just replace that one. All lights worked as expected. There is even a light bar above the tail light that comes on only with the brakes. It is fairly bright so that will work. That will save me from adding one.

Also last night I dug through my collection of electrical wires and relays and connectors and found that I already have the connector I need for the trailer. There is a flat 5 pin connector on the trailer wire harness and I found the matching bike side connector in my stuff that has about 3.5 ft of cable. Plenty for this project. A really nice thing about this trailer harness that I had is that each of the wires has the function printed right on them every 6 inches or so.

Today I had a medical appointment so didn't work much on the bike. I did ride my AK to get the registration changed over and get new plates. I have to wait to get a custom personalized plate that I want. I also got a bike side plug cover for when I ride without the trailer.

[rjs987]

You all know that any project plans change more than once before completion of the project. Well, now we're on to plan C.
Met with a retired metal worker and welder tonight to discuss what I have figured out so far. He is actually the husband of one of my wife's female friends who was in that career.
He had a lot of insight that was helpful given that he was here and looking at the situation in person. I was hoping he would assist with any tube bending and/or welding. But he doesn't currently have the equipment for working with stainless steel bending or welding. He did say he really liked what I was coming up with so far but had some suggestions to consider.

He considered my plan for bending the tubes but stated that most shops would do better to put a V cut where a bend is needed, bend the tube and weld it at the resulting seam. He also said the shop would put a gusset at the bend to make it stronger. That does resolve the issue of the tube deforming at a curved bend. He told me that the old adapter I was thinking of using would add a bit of complication since it is mild steel and not stainless steel like all the new metal I am using. It can be welded but the weld is not as good and the mild steel would be subject to rust as time passes. He also had a really good idea that the hitch frame tubes can be slotted and the rear plate that the Uni-Go receiver is bolted to can be fitted into the slots and welded to make it even stronger at the end. He did encourage me to add in the hanger bar as I was considering. So based just on this much information and recommendation I came up with 2 alternate setups shown in these pics.
The first is simpler but not quite as elegant yet might be stronger with only one welded bend involved with a bigger gusset. The second is closer to the original frame shape I was thinking of but will require 2 bend/welds and gussets.

https://photos.app.goo.gl/MUwNbt2vpTvTceJd8

He thought my idea of using square U-bolts was good. I asked about the issue or possibility that putting a hole and using bolts in the OEM rear bike frame might damage the integrity of the cast aluminum. As he looked at the OEM rear bike frame he immediately assured me that the OEM frame is a bit over-built and well strengthened and that drilling a hole in the upper frame on each side and a hole on the lower frame on each side where the square tubing lays against the bike frame would be no issue at all. He said he likes to do a little overkill on his projects and would have no hesitation to use hardened (grade M8 bolts and spacers to attach the hitch frame to a cast aluminum bike frame like this one. He also said that using bolts through the frame would be better than using U-bolts. I was also thinking that as well. So I think that is the direction I will go. It would make it much more secure and easier to attach. I would only need a spacer on the forward attachment point and not at the rear attachment point right at where the hitch frame goes through the plastic. Of course drilling the holes would require that I remove the rear side panels but that's OK.

As it has been so far this is a project that will require doing a little bit, test fitting, going back and doing a little more, repeat. That includes any metal bending or welding that I have done... a little at a time when I have the time.

[rjs987]

Since I'll be bolting the hitch frame to the bike rear frame I'll be needing to remove the rear bodywork of the AK. I have to do this to be able to drill the holes in the rear frame. So I was looking in the service manual that I have on how to do that. It looks like both side panels, the wheel well panel and tail light module all come off the bike as one piece. Then the different panels and tail light can be separated. Makes sense considering I previously noted that it is almost impossible to get to the screws and plastic rivets that hold just the tail light in place. It does look straight forward and not too hard to do.

I downloaded my official service manual file from the Kymco HQ web site in Austria (not Australia). I've always known it was the service manual written for the Euro 4 model and estimated that it applies to at least the 2020 model. I have not found any differences between this SM and my bike... until now. The SM does not show, nor does it make any mention of, the rear reflectors and bracket sitting just above the plate lamp on the rear fender (mud flap license plate holder). Looking at pictures of the 2020 Euro model I now notice that bracket and reflectors are not there. But they are present on all USA models. Likely due to regulation or law about having rear reflectors in addition to the front reflectors on the front forks. I also notice there is an extra brace at the front of the rear fender that is bolted to only the plastic of the wheel well panel. That is also not indicated in the SM. I really don't have a clue why that addition unless to improve stability of the rear fender but it seems minor since it is not bolted to any frame part but only to the plastic of the wheel well. The other 3 bolts for the rear fender are bolted to the frame and hold very firmly.
Here is that reflector bracket that I used to mount my LED brake light bar to in 2022.

[Ruffus]

Very interesting and dilligent project.

Q: Do you have in your state annual or biannual MOT inspections?
If NOT, great!
If YES what is the technician thinking there about the changes.
Here in Europe would this changes /modifications immedeately render this vehicle illegal for use on public roads. Licence plate and title gone, because its not this vehicle as described within title anymore.

Even I as an certified machine building and automotive engineer could not do this changes without proofed certificates of materials used, welding (x-rayed) certificates and final approval from a state authority to make it street legal.

Would be interesting to know how this is handled in your place.

[rjs987]

Very interesting and dilligent project.

Q: Do you have in your state annual or biannual MOT inspections?
If NOT, great!
If YES what is the technician thinking there about the changes.
Here in Europe would this changes /modifications immedeately render this vehicle illegal for use on public roads. Licence plate and title gone, because its not this vehicle as described within title anymore.

Even I as an certified machine building and automotive engineer could not do this changes without proofed certificates of materials used, welding (x-rayed) certificates and final approval from a state authority to make it street legal.

Would be interesting to know how this is handled in your place.

No inspections in my state but there are in other states in the USA. These changes I mentioned would not in any way render this vehicle illegal. The only real significant change is the addition of an extra set of reflectors. The license plate holder is just below the bottom of that picture (you can just barely see the top of the plate) and the vehicle is titled and plated the same as any other motorcycle/scooter. Besides, if the added reflectors are a problem with passing MOT inspections in your area that reflector bracket can easily be removed and the result is just as the 2020 Euro 4 model was. They were added for safety.

What are you referring to when stating "License [sp] and title gone" in your post?

As shown here the tail of the AK 550 USA version is exactly the same as the 2020 Euro 4 version except for the reflector bracket sitting on top the rear fender.

[Ruffus]

Txs a lot for your response!
Sorry, my excourse became bit lenghty...

Interesting that you don't have tech inspection in your state, would be wonderland for me to innovate certain projects.
I remember when we lived in Texas and California I had to show up with our cars once a year to be checked.

Ref. plate and title:
-here in Italy, Germany, Austria, Slovenija and most other european countries you have to see annualy or biannually an state authority or a workshop which is authorized to do technical checks on any vehicle.

-here is within the title a pretty accurate description or pic and description how your vehicle orginally looked like
(pls see pic as an example)

-during inspection, which consists of a list of around eighty positions, the tech hooks off each single one of them, including rolling brake test on a rolling road tester
(at scooters METIN box out to see any manipulation on carb or air intake)

-any changes the tech recognizes are reported on this checklist and put into a general  ( computerized) statewide, system
-after this check (if the vehicle failes) you get two weeks time to repair or changing back into original status (differs a litle bit from state to state)

-non compliance or NO show means report to the general vehicle registry, insurance company and you as the owner get a summon to deliver your plate and title to authorities, where you have then again time to appeal, etc.
This I meant with plate and title gone.

[rjs987]

I see no issues with the bike passing such an inspection. There is only one LED light bar that I put on for added visibility and safety in braking that can be remove for such an inspection if the technician doesn't like it installed. Easy to do without affecting anything. We do have to verify that a vehicle meets certain standards before title and plates are issued. Usually it is glossed over as the authority simply looking on the previous title if it is being transferred as in a sale. If being newly titled then they will likely take a look to ensure certain features are present and operating and then a title is issued. Then in my state there is no more worry about modifications unless it is something that the law enforcement pulls me over concerning... which is a whole other problem to resolve.

[rjs987]

Pulled the storage box out again to take and mark measurements on the square tubes for where welds and bends should be.
In these pics I show the 1/4" x 1" x 10" bars that I intend to weld onto the ends of the square tubes.

One picture shows them in place where they will be on the bike. Since I moved the forward mounting point about 4 inches toward the front that caused the square tubes to interfere with the storage box fitting in place. They ended up intruding about 1/2" on each side too far. Adding the flat bar as brackets on the ends straight inline with the square tubes provides plenty of space for the brackets and bolts on each side. There is no issue where the square tubes are against the lower bike frame. I also found, as I suspected would happen, that adding the flat bar brackets as shown causes the square tube to lay flush against the lower frame so no spacer or shim will be needed there. The flat bar brackets can be very slightly bent or twisted to create a flush fit at the upper frame as well.

While I had the hitch frames in place on the bike I measured and marked where the bends are needed and where the end of the hitch frame will be. Since I am now looking into the V-cut then bend and weld type of bends I can nail down how long each section is between each bend. In the other picture it can be seen that both sides will be the same. It also shows that since adding the flat brackets on the front ends there is a lot of excess square tube left over when I cut it off. Also, while I had the square tubes on the bike I measured how wide I will need for the mounting plate that will be welded between the two hitch frame tubes. This is the plate that the Uni-Go receiver will mount directly to. This plate will be 1/4" x 4" x 12 inches wide. The Uni-Go receiver is just under 4" tall (maybe 3-7/8").
https://photos.app.goo.gl/v9BkWjsFi2peWwtR9

[rjs987]

Just sitting at my kitchen counter today and decided to do a little work on the trailer harness cable. Added the coil cover over most of it, especially the part that will be exposed to whatever is kicked up from the road. I just happened to have that coil cable cover that fits this sized cable. I also added large heat shrink tubing to both ends of the coil cover to tie those ends off.

While I was at it I added the spade connectors to the 2 wires that will need them. The right turn wire (green) and the left turn wire (yellow) will need those to plug into the relays that I am waiting to arrive later this week... hopefully. The wires for ground (white) and tail (brown) and brake (blue) will simply need to have the insulation stripped and the bare wire ends will fit into Posi-Tap connectors on existing wires on the bike.  BTW- existing wires means the relay wires I already installed for the LED light bar I installed and NOT the factory wires. I never take power for any farkles from any factory wire unless it is designed specifically for something.

Many years ago I used to solder all my connections but then was reminded why automotive wires connections, as well as many aircraft wire connections, are crimped instead of soldered. Crimp connections are more reliable in environments where there is a lot of vibration. Soldered connections have a tendency to crack and fail due to the vibration.

And for those who are bitten by the image issues still happening here is the link to the photo that will show in a separate window.
https://photos.app.goo.gl/PZKokV5rnnBHG6XH9

[rjs987]

Friday the metal shop finally received their order of the proper gas needed to weld stainless steel (supply chain issues) so I went today to get the flat bar bracket extensions welded on. Now I'm waiting on some of the electrical bits (relays) that I need to install the trailer harness. Those are expected at the end of next week. After that I'll remove the rear body of the AK and line up the hitch frame as it now is onto the bike frame and drill the holes in both for mounting. I have the bolts and nuts and washers (nylon and metal) already. Once the holes are drilled and electrical done I'll reinstall the body onto the AK and test fit the hitch frame again bolting it on this time. This is so I can get a correct measurement of where and how much angle to make the bends in the square tubing.

https://photos.app.goo.gl/oBRmGVjFUvUVsgL37

I'll install the electrical parts to connect the trailer electrical harness while the body is removed since it will be easy to access everything. I'll have all the electrical connections ready to be plugged into but will wait until the hitch frame is done to actually connect it.

[Stig / Major Tom]

Getting a 404 error.
Guess I'm using a rotary phone!
Stig

[rjs987]

Getting a 404 error.
Guess I'm using a rotary phone!
Stig

On all photo links or just the last one?

Some of the forums I am on have been having display issues with all photos posted. Maybe something similar here?
My links are to my Google Photos storage.

[Neil955i]

Getting a 404 error.
Guess I'm using a rotary phone!
Stig

Working fine for me on my tablet?