Topic: My Frankenturd

[vbtravisd]

I have owned a few bikes over the years, from an old virago 750 to an FJR1300.  I am very big into cars especially 4wds but I honestly love anything with wheels and a motor.  I like to build/fab as a hobby... I have a CNC plasma table and a full fab shop out in the garage.  My Jeep wrangler was completely custom with dana 60's front and rear, full roll cage etc... So obviously, I like to tinker with stuff and i have to have a project to play with.  Well, about a couple months ago I found out Im having my first kid!  I decided to sell my jeep (but i managed to keep my boat!).  My wife knowing that I will drive her nuts without a project to turn a wrench on suggested I find myself a motorcycle candidate.   

It all stated with me picking up a 79 frame that had "sportbike" parts on it.  I picked it up for a good deal... then within 2 weeks I found a whole 78 cb750.  I took the forks and swingarm off the 79 and sold the 79 frame and started tearing into the 78.  Turns out the forks are off of a late 90's VFR750.  The rear swingarm is an 08 gsxr1000.  I didn't like how wide the 78K tank was so I have started narrowing it.  Trimmed some of the tabs and tubes off the frame and started mocking up the swingarm and monoshock. 

One of the big things I am torn about is how far to take the motor.  The bike had 34K on the odometer.  I have a full set of gaskets/seals and plan to lap the valves.  What about that cam chain?  Replace it, the tensioner and the guide?  I am not planning on making some speed demon, but a good running fun to ride bike.  While I have the top end off, think I can get away with a hone and new rings?     

I appreciate any advice you guys can give me along the way!  I'll post up some pictures here in a bit.

[rb550four]

Pics, pics pics pics pics pics. Pics pics," Pics pics pics pics pics pics pics pics pics". Pics pics," pics pics pics pics pics pics pics".
Or none of this ever happened.

[vbtravisd]

So a ton of stuff has gone on in the last 2 months.  I welded a new tunnel on the tank, got in a new vented gas cap and bung (pretty slick with a brass vent in the cap).  I bought an all in 1 style LED tail light and got that mounted up.  One of the big things I have been waiting on is my buddy to machine some new bushings to adapt the GSXR swingarm to the 750 frame.  I got those about a week or so ago... so now the bike is a roller!  Allballs tapered bearings are installed... still have a ton of work to do but it is starting to look the way I want it to!

[vbtravisd]

Then came the fun stuff... I measured a million times... cut the upper strut mounts on the CNC and tacked everything into place... DOM tube and 1/4" mild steel... here is the strut mounts. 

[vbtravisd]

And here is how the bike sits now... Still TONS more to do!

[70CB750]

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[vbtravisd]

Just spitballing here so guys please chime in... Things I am thinking about...

I have an AGM battery for this thing... Tough to fit that big ole battery in somewhere and it not be out of place looking.  I may fire the bike off (once I build a new harness) and see what the charging system does... then look into a lithium battery.  I have a new reg/rec combo unit coming... so that should help with overcharge.  But I dont want to fry a 200 hundred dollar battery!

One of the things I am looking into is how far to tear down the motor.  I have a gasket set, clutches and springs, valve stem seals and plan to lap the valves.  Once I get the bike back to running, I plan to do a compression test on it to determine if I will need to hone and rering.  What about the cam chain?  Thoughts? 

I have a rear hugger fender on order... I plan on running a shorty front fender... not sure if I want to go old school sheet metal style or get a plastic front fender and modify it.  I am leaning more towards metal fender right now. 

A couple of things I have learned... I got a little over anxious and sold off a ton of parts that I wish I hadnt... Gauges, seat, fender.  Ahwell... So I am going to be making my own seatpan and give a go at upholstery... I have seen where a lot of guys use carpet padding.  Im going to give that a shot... and if it turns out like crap then Im out 20 bucks or so.  Another thing I am trying to figure out is where to put my oil tank.  What is the oil capacity in these bikes?

[vbtravisd]

Welded some more on the tank last night and did some pressure testing...  Tok me a while to fix all the little pinholes... but I think I got it sealed up well.  I have some tank sealer.  The inside is pretty darn clean except for some very minor surface rust.  How much rust is acceptable to seal a tank?

[vbtravisd]

Haven't had too much of an update due to 2 weeks of snow...

Started on the seat, did the carpet padding trick.  Pretty comfy.  I wasn't happy with the handle bars so I ordered some new clip ons.  I like their position better.  New front master cylinder came in so I ordered all my brake lines.  Got the rear master mount made and tacked into place.  Rear fender came in and got that mounted up.  I also found a guy with a bunch of cb750 parts... I picked up a 4 into 2 header... one that pairs 4 & 1, and 2 & 3.  Suggestions for short mufflers?

I used the old distilled vinegar trick for the surface rust in the tank.  That worked awesome!  Used that KBS tank sealer inside.  Poured it in, rolled around the tank for about 30 mins and let it drain upside down.  In a couple of hours it was cured hard.  I then started some body work on the tank... a million hours of sanding on the tank. 

Quick question about oil tanks.  I am trying to figure out where I am going to put an oil tank...  I want to say everyone makes their oil tanks with a 3 quart capacity right? 

Also, I have come to the realization that I cant fit that AGM battery I have anywhere without it looking goofy.  So I am going to order a new combo reg/rec unit and go with a lithium battery.

[rb550four]

Someone has been busy. I like the pics, now we know what you are talking about.

I'm not a 750 guy but, I do have questions, and I'm not making fun of your bike , and certainly not you or your vision (Some guys have soft skin and feel hurt easily)
Q 1: I really like the swing arm and I was wondering how many more inches of wheel base it gives? Will you need a chain tentioner ? How do you think it will handle on the curves ?
Q2: Is that the final choice for the headlight? Just wondering, so much work to make this all cafe and mount a chopper light on it?
Q3: the seat, why so long and flat? I was thinking , if you turned the back bar upwards, it would make the bike look shorter and could be easier to hang a tail light under it with no tire clearance issues
Q4: I haven't seen it before but perhaps the 3qt oil res. could be the tail with mounts for the lighting behind the seat instead of under it?
Q5:If all that could happen , would it be acceptable to mount the electrics in a drop down (hinged) easy to work on panel under the length of the seat? and is there enough room to mount the battery under the swingarm on the frame just behind the transmission?
  Like I said , I'm a 550kinda guy , not a 750 guy yet, but, you never know, so I have lots of silly questions that either you will find to be a PITA  or interesting, but by by no means meant to be unkind.
                                                                                       

[vbtravisd]

Someone has been busy. I like the pics, now we know what you are talking about.

I'm not a 750 guy but, I do have questions, and I'm not making fun of your bike , and certainly not you or your vision (Some guys have soft skin and feel hurt easily) No biggie man! Ask away...
Q 1: I really like the swing arm and I was wondering how many more inches of wheel base it gives? Will you need a chain tentioner ? How do you think it will handle on the curves ? I never did measure the stock wheelbase.  But Im sure it is a couple of inches longer, I did have to order a longer chain.  I haven't put much thought into the chain tensioner honestly.  I was mostly concerned about the suspension.  I liked the thought of a mono shock and the ability to tune the rear, adjust the ride height etc.  I wanted to emulate newer sport bike suspension hoping to get something closer to that kinda handling.
Q2: Is that the final choice for the headlight? Just wondering, so much work to make this all cafe and mount a chopper light on it?  Nah, that was a cheap headlight I picked up.  As soon as I looked at it from the side I knew I wanted to go with an 8 or 9" headlight
Q3: the seat, why so long and flat? I was thinking , if you turned the back bar upwards, it would make the bike look shorter and could be easier to hang a tail light under it with no tire clearance issues The seat is still going to get some shaping.  More importantly my wife has shown interest in riding around town with me.  So I wanted to make sure I could fit both of us.  I plan on making a removable cowl (like the pic below).
Q4: I haven't seen it before but perhaps the 3qt oil res. could be the tail with mounts for the lighting behind the seat instead of under it? I am thinking about a more rectangular flat style tank mounted under the seat where most guys put their electronics box.  I can hide my solenoid and fuses under the tank and they will still be relatively easy to get to.
Q5:If all that could happen , would it be acceptable to mount the electrics in a drop down (hinged) easy to work on panel under the length of the seat? and is there enough room to mount the battery under the swingarm on the frame just behind the transmission?
I might see if I can stash a battery under the swingarm.  The only issue is the monoshock knuckle and dog bones are down there... but that is an option I haven't thought of and will take a good look at!

  Like I said , I'm a 550kinda guy , not a 750 guy yet, but, you never know, so I have lots of silly questions that either you will find to be a PITA  or interesting, but by by no means meant to be unkind.

Nah man... Im happy to see that people are actually checking out my build.  Constructive feedback is always welcome.
                                                                                       

[SOHC4 Cafe Racer Fan]

I really like the removable cowl idea. 

[timbo750]

Great fabrication work and quick progress, that right you don't have kids yet. Love the cowl idea, I had a 95 VFR with the removable cowl and it great to put on when you just wanted to go for a ride by yourself.

[vbtravisd]

Thanks fellas... yeah, since I removed the factory gussets on the frame, I planned to cut new ones and sink a quarter turn fastener from the cowl to the gusset.  Be able to pop it off when someone wants to ride, and it can also double as a small storage spot. 

Yeah, I have been trying to work on this thing as much as possible because my free time is coming close to an end... we are around 6 weeks till the little one comes along.

[vbtravisd]

4 weeks from being a dad... so I have turned the heat up on this...  I also got picked up as an associate builder over on Chop Cult.  Pretty cool... Bear from Old Bike Barn cut me some great deals on the remainder of my parts.

Ordered a Chinese reg/rect combo... it got lost!?  So did what I should have done in the first place and ordered one from DCC... Also ordered a 7" headlight from them too.  That chopper light just aint looking the way I want it to.  I mounted the rear master cylinder and reservoir.  I ordered some custom made stainless brake lines.  I cut my chain to length and got it installed.  Rear fender is on and I have started on the front one.  Mufflers are in the mail along with new throttle cables.  I need a shorter clutch cable still.  DCC is sold out and Old Bike Barn didn't have any.  Also got 9/10ths of the way through my seat too.  Got some marine vinyl from the local fabric store and some outdoor UV resistant thread (14 bucks total)... and read the manual on the wife's sewing machine (when she wasn't looking!).  I don't think it turned out too bad... pretty comfy too. 

Still need to figure out an oil tank... going to start mocking up the rear cowl too.  Need to run the motor and make sure it wont overcharge... and order a Lithium Ion battery.  Then, pull the motor, finish weld the frame and tear apart the motor.