[EndWrench]

I should probably preface this thread by saying, "I don't know what the hell I'm doing." The only mechanical experience I have is from small dirtbikes...

But! I am a good researcher and a fairly mechanically inclined individual, so I'm gonna give this a shot. This build is also going to come sporadically, and in waves, and I anticipate it taking a good while to complete - if these sort of things are ever "complete." I'm from Oregon but I'm going to college in Connecticut so at least for right now, I'll just be working on the bike in the summers and winter breaks. At school I have access to fully equipped machine and fabrication shops, so maybe once I get farther in I'll try to make a cross country journey to get the bike over there. For now, I'm stuck at home with mostly hand tools and no sheltered workspace. But shit, I forgot about the bike. So here it is, a purple pyle of a 1981 Honda CB750F I found on Craigslist a few weeks before coming home for the summer:

I've done some things to it since then... this is how it sits now:

Documented changes thus far:
- Removed all evidence of purple people eater attack on motorcycle
- stripped tank to bare metal + clear coat
- New grips, bar end mirrors, front blinkers
- refinished, painted, and wrapped headers
- Made new tail section sunk into seat

The tail section using the original seat is temporary, I think. I wanted to do a cafe style tailsection and relocate the electricals for that open mid section look.

- started on initial designs for side panels
- fought with PODS and jetting, lost battle

The bike would sorta start when I first got it (with much coaxing) but I figured it was a jetting issue. So I brought it home and bought a jet kit... only to find out that the intake boots were rotten and dead and sucking air around the seals like a mofo. So I replaced those, and tore into the carbs and cleaned 'em up. And it ran and idled right, but ran like shit. I looked into the jetting and it looks like the previous owner left the main jets the stock 68 but bumped the secondary mains from 102's to 130's.... facepalm. I fought with the jetting forever but no matter what I did the bike didn't like to run well past about 7k RPMs. No top end. The low and midrange was pretty good though. The jetting I have now is 75 mains 110 secondaries with the fuel screws 3/4 turns out and the pods 3/4 taped up -- which is the recommended recipe for the DOHCs with CV carbs. Apparently the CV carbs on these bikes are infamous for not working with pods, so I'm working on getting a stock airbox now. I've also read on here that someone had the no topend problem and fixed it by replacing gaskets. My head looks like the gasket might be about shot, so I ordered a gasket kit that should be here in a few days.

I've also had electrical issues. The bike wasn't charging the battery. The alternator passed all the tests, but the reg/rec didn't so I got a new one of those... I think it might be working, but I'm not sure. It didn't charge the other day I rode it. I've also heard that not revving in the higher RPMs could be an electrical issue. I think the reg/rec might be overheating? I'm not sure. It also might be plug wires, or coils, or... blah.

Future stuff/questions:
- I would like to use different carbs so I can run PODS successfully. Anyone know some good alternatives?
- I've heard that CBR coils are a a good plug and play replacement... I don't know much about electricals though. If I bought these would I be able to make them work?: http://www.ebay.com/itm/HONDA-CBR-1...ries&hash=item35bde4f883&vxp=mtr#ht_500wt_898

- I would like to eventually do a front end swap and get an F2 rear wheel. I've heard the swap isn't too painful.

Whew, I guess that's all for now. Thanks guys, this site has inspired me to do something I've wanted to do since I started riding dirtbikes.

 

[ultimate fighter]

Not too shabby.

 

[gsf1200R]

fantabulous

 

[sbasso]

not to bad, keep working on it and it will be good to go for everyone

 

[Shane Liberty]

photo of the oil looks like the seal around the cam chain tensioner..... not the head gasket. If your head gasket was going south the bike would be running very rough, have no power under acceleration and would be blowing oily smoke out of the tail pipe.

 

[EndWrench]

So does anyone know anything about using CBR coils? I think my plug wires are bad but it looks like to my uneducated self that the CBR coils just plug directly onto the spark plug, so if I bought those I wouldn't need to get new plug wires. Example coils: http://www.ebay.com/itm/HONDA-CBR60...ies&hash=item257103b2ba&vxp=mtr#ht_500wt_1129

I've decided my problem is probably electrical. I tickle charged my battery for a few hours the other day and when I rode it it would hesitantly rev all the way to 9k under load but wouldn't go past six when the battery was down. I think it might also be the spark unit.

 

[ultimate fighter]

Those probably wont so very well. If your plug wires are bad a simple continuity test will prove it. Also some "make your own wires" kits for cars can work. Just did so on my 1983 cb750

 

[EndWrench]

Did some work. I got the feeling that my high-revving engine problem wasn't an issue with fuels, but with ignition. I heard these bikes had some ignition issues... so I made some new plug wires and popped in 4 new NGK Iridium plugs. Boom! Bikes screams all the way to redline no problem now. It's not tuned really yet, though - I have the feeling there is more power to be had. I bought a stock airbox off of some dude just to try. I know people have put gixxer carbs on a cb750 before and made it work, so I might look into that so I can keep the pods. That's down the road.

Still having electrical issues. Looks like the bike is running off the battery, or at least discharging faster than it's charging -- I've been left stranded a few times after riding for about 60 or so miles. Not sure what it is yet, I've replaced the reg/rec and the battery is brand new, alternator components seem to pass all the tests in my manual... Need to look into it more.

More aesthetic stuff done, playin around with paint and the like. Pulled the ignition cover and a bunch of oil dumped out, was freakin' until I found out on another forum that it's supposed to be there.

New plug wires

Primer on rocker covers

Tossed a coat of gloss white and chopped up the stock side covers, added a sort of window

Making stencil for right side cover

finished side cover paint -- spray job was sloppy on purpose

Painted inset tailish thing -- still gonna dump this tail setup for something better in the future

part of cleaned up side covers and picture of DOHC nakedness

right side before more paint


I'll put everything back together in the morning and take more pics.

 

[n0regret5]

thats proper fucking nice, innit.

 

[Simpler=Better]

Adjust your valve clearance if you haven't yet, then get back to working on those carbs. Now that your ignition is sorted out, and assuming that your diaphragms are OK, you should be able to fiddle with the CV's. Or, just go buy a set of flat slide Mikunis-If I could do it all over again that's what I would have done from the start.

Can you brace on them there forks?

Looking good, I like the clean job on the header wrap

 

[dogbreath]

really coming together, cool build.

 

[EndWrench]

Adjust your valve clearance if you haven't yet, then get back to working on those carbs. Now that your ignition is sorted out, and assuming that your diaphragms are OK, you should be able to fiddle with the CV's. Or, just go buy a set of flat slide Mikunis-If I could do it all over again that's what I would have done from the start.

Can you brace on them there forks?

Looking good, I like the clean job on the header wrap

Thanks! Do you know where I could get the Mikuni flatsides? Do you know what years of gsxr's used them?

Pictures, as promised:




Area underneath sprocket cover was caked with a half inch of grease, I'm leaking oil somewhere's I think.


Found out that the threads were super done for on the valve cover bolts. Ordered a helicoil set from Napa, gonna do that tomorrow.

Previous owner had properly fucked a cut job on the sprocket cover:




The underside of oil pan is caked in grease and oil and crap, something is leakin. Oil hasn't been changed in god knows how long, will do that tomorrow after I get the valve cover nice and snug.

 

[EndWrench]

Bike is definitely not charging, and I think it's my rotor. I have two ammeter things -- one is a Fluke that I borrowed from my dad who is an electrician, which he says is designed for really huge electrical stuff so is probably inaccurate for small stuff -- and when I test between the rings with it, it fluctuates crazily but usually settles down to like 1 - 3 ohms of resistance between the two rings, and infinity resistance between the rings and the ground. My other meter is a super old Micronta from the 80's, and it says there is 0 resistance between the two rings and infinity between rings and ground. Hayne's manual says there should be some resistance... if there is zero on one meter and a really low number on the other does that mean that the rotor is bad? The stator has continuity between all the wires and the reg/rec is brand new and it's definitely not charging at all (unplugged alternator while engine was running and tested wires) so I concur that it must be the rotor.

Anyone know a good place to get a rotor / rotor puller? How much should a used rotor cost?

 

[Simpler=Better]

Will a pulley puller from autozone's rental program work? Don't know much about rotors.

As for the crap buildup, that's normal. Lots of people don't warsh their bikes, much less remove the sprocket cover. You probably don't have a leak-road gunk and a little residue from an oil change adds up fast.

 

[Harbourone]

Yea that's just extra chain lube and road crap. Some people don't ever scrape tha garbage outta there.

Fuck I don't even have a sprocket cover. Some ass smashed the top bolt hole off the case.

I just make sure my shoes have the laces tucked in haha.

 

[dunebuggyq]

are you sure that your r/r is good? ive heard that they are a problem child on the cb

 

[EndWrench]

I replaced the r/r a few weeks ago.

Haven't been riding it at all because it's been pouring down rain for the past week here... oregon. That, and the bike won't charge. :doh:

I finally admitted to myself that my rotor was bad, and pulled the trigger on a new one. Supposed to be better and more efficient than stock, but it still sucks to pay 130 bucks for something. I WAS going to pay 20 bones for a stupid Honda rotor puller, but then I read on a CB forum that the rear axel bolt had the same threads as the rotor...

so I pulled it out and smacked it carefully...

and pop. Rotor plopped right off. :shocker:

While I haven't been riding I decided it was time to redo the tail. I started hacking apart the stock seat earlier, here's a mockup of kinda what the tail will look like. Reusing the stock tailpiece.


Gonna chop up the aluminum buddypeg rearset things after I find a way to brace the centerstand, or remove it.

Stock airbox and rotor should be here in a few weeks... and then it's only a coupla weeks until I gotta head out east for the schoolyear and put this thing away until winter break.