Project xs750 lowrider

Weather was nice yesterday... so I worked outside and enjoyed the sun. Got the newly restored exhaust mounted. Still have to rebuild the right rear exhaust mount so that it aligns better.
 

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Still having trouble trying to mount the front exhaust system bolts to the engine... no matter how I configure them they still don't seem to be cinching tightly. Right now I am at my house in the city. I will return to continue the work on the motorcycle in a couple of days. Then, hopefully, I'll be able to finish the seat base, foam pad, and cover for the seat by next week. Then it will be time to dedicate myself to the building and fabrication of the fiberglass molds for the gas tank and side panels.
 
Well... after a 5 day respite, it's back into the shop. Final smoothing of the tank and pre-fiberglass epoxy. (5 coats this time... not taking any chances) Going to work on the new seat base and right rear exhaust hangar as well.The tailight arrived, as well as the blinkers, so the final mods to the Fat Bob rear fender can be done and the fender can go into paint.
 

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On the last lap... exhaust issues resolved. Tail light mounting bolts welded in the rear fender and the base coat of the front and rear fender applied. New metal seat pan made and at getting covered. Next on the agenda, fiberglass tank and side panels. Good day.
 

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THE SAGA OF THE FIBERGLASS GAS TANK...

Of everything I've built and fabricated on this low rider motorcycle project, the gas tank and the seat are turning out to be the most challenging. I don't have the proper power tools like a shaping hammer that would allow me to make a steel gas tank, which would be my preference. So I am left with only one option... a fiberglass gas tank.

That means sculpting a solid replica of a gas tank using a block of foam. After the replica is hand carved to the approximate dimensions, various fillers are used to do the final shaping. It is a process of applying filler, sanding it smooth, painting the replica with primer... and doing it again, and again, and again, AND AGAIN, AND AGAIN... AD NAUSIUM.

I am getting close to completing the replica, but it has to be perfectly smooth... and I mean "automotive paint" type smooth. If it's not glassy smooth, when the replica is used to make the "female" fiberglass molds, the molds may not easily pop off the replica. Every imperfection is a spot that the molds will want to "stick" to the replica. I've already been informed by several experts that even with a glassy smooth finish on the replica, removing the molds from the original replica will be a major wrestling match. This confirms what I was told by several great guys here, d9canada, pacomotorstuff, doc_rot, Maritime, and jpmobius who kindly and unselfishly took the time to write extensively and in great detail to help me through this process. I could not have made any progress without your advice and I am truly awed and humbled by your generosity. (not to mention the others who offered an encouraging word when I was ready to throw in the towel... I am humbled and grateful for your kind thoughts.... it motivates me to move forward.

I've already had one epic failure on my first attempt to build a fiberglass gas tank, so I am trying my best to do everything perfectly. This is my second attempt... and of the 500 hours of work on this project, roughly 1/3 has been spent on the gas tank. My eyes are starting to glaze over and my head is reeling.... but I don't have a choice. No one builds a tank in the shape I want that will fit snugly to the extreme engine hugging backbone of this frame, which is what allows this bike to have a seat height nearly 14 inches lower than a stock XS 750 se.

I guess I knew it would take time and be a learning experience, but even if I valued my time at minimum wage, the time value of building this tank would easily exceed 1100 dollars. BUT... time I can give and if everything goes well, there will be the satisfaction of knowing that this motorcycle will be unique. (Maybe awful.... but unique) That's what keeps me moving forward. I can't bear the thought of this tank suffering the same fate as the last one...stuck on the tines of a pitchfork like a flaming torch wielded by some crazed posse member looking for a wanton criminal. I mean, burning the last tank attempt was a fun way to blow off a little steam over my first epic tank building failure, but I'm hoping to never have a repeat of that first fiasco. I just want it to be done. I want to ride it. I want to cruise to Sturgis this summer to see and to be inspired by all the cool bikes from the guys that are REALLY great builders.

If, however, by chance, it turns out okay I know I'll feel a certain satisfaction for accomplishing a difficult task that I've never done before.... but I think next time, I crotchet a quilt. LOL! Here's the stages of progress so far.
 

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Looks smooth and fair enough to me - your painter can do the final massaging with filler.
Try about 8 coats of mould release wax and then PVA on the master (mentioned in a previous post).
I "think" you should be able put a parting line down the center of the top and have a 2 piece top mould, but you can check for sure by putting the master on a flat table and moving around it with vertical straight edge.
The tunnel might be able to be a one piece mould.
Parting lines are tricky - I used to build a tank where the upper was a 5 piece mould and the tunnel was a 3 piece. An undercut on the mould means it will never come off the master and a part will never come out of the mould and I was really anal about the project - and it doesn't take much of a negative draft to make your whole day bady.
Err on the side of caution here; you're getting the tank painted and the parting line flashing will disappear during paint prep.
Ya, prototyping for composites can consume a lot of manhours - always had a problem with customers on that respect.
Keep up the good work.
Pat.
 
Thanks Pat...

Unfortunately... I am my paint guy. LOL! But at this juncture, things are getting much smoother. I did not include pictures from after yesterday's work... Left the camera in the shop and I was just too tired to go back out there to get it.

I was thinking that a three piece mold will work because I shaped the tunnel so that the deepest part of the tunnel was slightly narrower than the gap across the tunnel at the bottom of the tank. I tried to shape things so that the seams of a three piece mold (two sides and the tunnel) would meet and be able to most easily slip off the plug. I'll be sure to use many coats of mold release wax and spray on the PVA as per your and everyone else's advice. I really appreciate the input. The info has been invaluable. I have been pouring over all the comments over the past three weeks. It helped a lot.

Just to be clear, you're saying that after the three molds are formed on the original plug and then removed that the top two molds will be re-bolted together as a single "top" mold, and the tunnel will be molded as a separate piece, correct? This is what I was envisioning.

After the top of the tank and the tunnel are formed on the molds, they need to be joined together. I assumed that I would be carefully trimming the two completed pieces to fit each other, and then cutting a large opening from the completed "top" of the tank to give me access to the inside of the tank so that the junction between the top and tunnel can be heavily reinforced with fiberglass from the inside of the tank. (allowing access to be able to reinforce the fuel petcocks on the inside of the body of the tank and the cafe style gas cap that be added to top of the tank piece that was cut out to gain access. Then just epoxy the access panel back into the tank, fiberglass over the seam, bondo it up and be good to go to the next steps of lining the tank.

Is that the general idea?

Just out of curiosity... What was the purpose of a five piece mold? Did you incorporate a top access port into your molds... or were your pieces just really intricate? I am hoping to get by with less mold pieces... but if I am making molds... might as well make it so that the final assembly of the tank pieces is easier.

Thanks again, Mark
 
datadavid said:
Starting to sound like the air hammer would have been cheaper and more relaxing in the end?

Yea... I think you're right on that one! Ha ha ha ha.... But then again, there will be that primal satisfaction of knowing that this whole thing was built with hand tools. (Primal grunting sounds) LOL
 
Stick with it.
I'm in the same boat. Working on a boat and I am absolutely at my wit's end with fiberglass. There's just nothing fun about it. Just tedious pain in the ass work. Never again!
 
SONIC. said:
Stick with it.

+1
Keep at it! Been following along on this thread and I appreciate your persistence. Anytime in a thread that some one shares a major frustration and gets right back at it, I remember it when I’m ready to throw in the towel myself. Can wait to see the finished tank and seat. Loving the lines on it thus far.


Sent from my iPhone using Tapatalk Pro
 
Thanks Drey...

I appreciate the kind comments. I'm still chiseling away at the tank trying to get the shape right. I found a little trick.

I was initially working with automotive body filler. But it kept working itself into rough and smooth spots. So I decided to try one of D9 Canada's suggestions and use drywall mud. At first it didn't work the way I thought it would. But then I started spraying the sanded drywall mud with a non Automotive primer. That primer seemed to fix the drywall mud so that it wasn't so easily sanded away. Because of that I was able to shape the tank without sanding through what I had done before. It seems to be going well but I'm sure that it's going to require a few more coats and a little more smoothing before it's ready for the epoxy finish.

I'm looking forward to getting this plug, this replica, done so that I can move on to the making of the fiberglass molds...but I'm still a little apprehensive about doing something I've never attempted before.

It was great having all the guys post all of those long, detailed threads sharing their experiences working with fiberglas and the shortcuts they learned through experience. It has made everything go considerably easier. I'll keep at it and post a picture of how the drywall filler is coming. Drywall filler! On a motorcycle.! LOL
 
I just want to say that I can't believe how flammable that foam was. I mean, they insulate HOMES with that CRAP. I nearly burned my hair off. Remind me never to put that garbage in my own house.
 
In your big post you mentioned being inspired by real builders at Sturgis. I’m inspired by builds like yours. Guys who just have some know-how and determination. Watching someone keep plugging along to get the bike they want is great.


Sent from my iPhone using DO THE TON
 
Wow John thanks. I don't really have any experience building bikes. I had three dirt bikes as a kid. I disassembled and reassembled them hundreds of times just to wash them because I like them to be clean. But I have never built a frame, or a gas tank, or a seat before... I've never built anything. I just know how to weld with a torch. I just have a nice DeWalt Grinder. I spent 25 years doing woodwork in new houses... so I know how to use a Binks cup gun. (Illegal now, BTW LOL) If the welds are bad I grind them down. If the tank isn't shaped right I just keep adding filler. I hope to have something that is a representative of the guys that I think are really good. I see them all the time on tv and admire the great bikes they make. So many great bikes here. Cafe racers with mono shocks. They are awesome. I just want you to know that I appreciate the kind words. I get a little tired but this far along in the game I just wanted to be done so I can ride to town and have a beer. Thank you very much for your encouragement I can't tell you how humbling it is.
 
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