CB750 rat bike?

Honestly, I need to stay away from this bike for a while. But, parts are supposed to be in this afternoon, so.... Good thing, too because I decided to check that J cap in an F position. They had jambed screws in the cross-drilled supply holes in the cap, and RTVed the bolt holes. And of course, broke one of the cap bolts off. I was able to remove the broken bit with little drama, then spent time picking out RTV. Bolts are supposed to be included with the caps I bought, so hopefully things will get better.
 
Swapped in new (used) F and L caps after first Plastgage testing them - both between .003 and .004 inch. Measured with both cylinders on respective side with lobes away from lifters. Final assesmbly with assembly lube on the bearing surfaces. New chain came in too, but it will wait for tomorrow or Monday for installation. Good weather forecast for next week, so hopefully there will be a chance to run it through the gears to make sure that is all fit.
 
Chain is now mounted. Rolled it out this morning, hooked up the aux fuel cell with ~ 1/2 liter real gasoline, and fired it up. Once warmed enough to take off the choke I ran it through all 5 gears (on center stand). Clutch engages/disengages well, all gears work and sound pretty good (chain is hitting the plastic chain guard some, so need to adjust that). Then shut it off and hooked up the mercury sticks (old MotionPro unit). Balanced the carbs, lowered idle, balanced again. Have not touched pilot screws - all set at 3 turns open. Aircut valves are disabled.

Guess the next thing other than fixing the seat rear cowl assembly is tires (ouch$$). Thinking maybe getting a bunch of wrecked Honda plastic from the dealer and gluing it together to patch the existing cowl assembly now that I've pried 3 pounds of Bondo off of it..
 
Ordered new Kenda 657s for the '79 CB750F rat bike. Not in a hurry for them, as it will be a couple months before decent riding weather, and I have a showw in a couple weeks to get the GL1000 ready for, plus rides scheduled for the GL1800 (weather permitting).
 
The Kendas are mounted and wheels back on. That's about as far as the weather and my health could take her this week. Came down with a cold that knocked me out until yesterday, when I went to the funeral of a high school classmate and then to see a cousin in a nursing home that is not doing well at all. I still need to drain the fuel from the tank into my waste gas jug to get rid of the fogging oil and storage spray grease that I'd put in the tank and never flushed out. I'm sure that is a major cause of the smoke that she displayed before, because she doesn't smoke on the auxiliary tank. The weather has turned its typical East Tennessee January/February crud. Maybe the middle of next week it will settle and I can at least try to ride around the neighborhood.
 
Wow, I think just about everyone, including myself, have turned into Hermits.

Hunkered down in garage, trying to tinker the foul weather away.

Good to hear you're still moving right along. I put Kendas on Rachels Hondamatic (not 657s) but I love them.
 
No riding around our 'hood in all this snow and the east coast is likely to be bad for a couple of days too. Hang in there and it will eventually improve.
 
I don't think it went THAT fast!

Made it to the 40s (F) today, so she was pulled out and given her first run. Only ~2 miles total (not tagged or insured yet) revealed that the engine is getting better and better, the trans shifts fine (I just need to get used to it) at least up through 3rd. The problems; front brake is spongy but improving rapidly, rear brake feels firm but does nothing to slow me down, and there was a bit of a problem with the speedometer. Pretty happy with it overall. Guess now work on brakes, repair the speedo (I already have it apart), and go down to buy tags and register. Feels a bit different from the GoldWings that I've been riding the past 15 years or so.

I'm kinda reminded of what Elon Musk said when his Falcon Heavy lifted off. "That f***n' thing took off!"
 

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It's cool to see you persevere. Lesser men (myself included) could have cut ties at the third/fourth/fifth road block. Hoping you're stubborn enough to keep pushing along. Excited to follow
 
This is the second bike that I've had to overcome PO abuse and neglect on. Check my Hunley thread for the first one. Anyway, fixed the speedo needle with an angle of thin clear plastic from a bubble pack. Painted with some left-over florescent orange that I had for painting tiny RC heli parts with (they tend to fly off when you attempt subterranean flight, and the florescent shows up nice at night with a UV flashlight). Ordered some LED bulbs for the dash - had to keep incandescent for the Neutral, Oil, and High Beam as they are reverse polarity. Didn't try to make it pretty, just functional which is still the theme for this build. Rear brake was just a matter of better attachment for the master cylinder (I had it on with just the top bolt and it tilted - on with both now). Did the red Loctite trick on the starter clutch bolts, but they were still tight.

MAYbe warm enough to ride for an hour or so on Monday. Will still have to keep it in the neighborhood as it still needs mirrors and a horn, license and insurance to be legal. Still, it will be a kick if I can put some more miles on it (from behind the house up our steep drive, down to the road into the subdivision, down it to the cul-de-sac and back, loop down our other steep drive and repeat.

I've ordered some 1" steel tubing to fab into the final baffle in the pipes that a PO had removed. Just need to find something about the diameter of a Mason jar lid to attach them to and then screw onto the end plate of the muffler. I don't think my welding skills are up to that, so it will probably be some kind of pop-riveted affair.
 

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Made up final baffles for the exhaust to knock the racket down some. Hopefully they are pretty close to the original. Used 1" tubing cut ~5" long tacked to some disks that I made out of some spare 20 gauge. Really sounds a LOT better setting still. Only ~45F today, so I will wait for the forecast 60F tomorrow to try it some.
 

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Nice day today, so I took the CB750F for a loop over Norris Dam. Running great, I think. Accelerates much harder than my GoldWings but vibrates a lot more. Handles well. Everything mechanical that I could find wrong has been fixed except the speedometer error, which is ~ +10mph @ 55mph. She really smooths out at ~5000 RPM (~55 mph by GPS) all the way to ~7500 RPM - the highest speed I took her. Didn't have the GPS then, so I don't know how fast that was. I was wearing ear plugs, and above 55mph all that I could hear was the air intake and wind noise. So different than a GoldWing though! I like the ergonomics with these Euro handlebars. Only a little 40 miles but the 66 year old body felt like I had done it on the GL1800. The original bars were identical to the GL1000 stock bars, and I always got stabbing back pains in 15 miles with them.
I guess she will go on Craigslist soon. She was always meant to be a winter project that I intend to get my investment back from, so I'll let her go for $1500. Not bad with it running well and new tires and chain, GL1000 front end, all sorted. I doubt anyone on here is interested but if you know of anyone wanting to do a custom CB750 but not needing to fix mechanicals - or someone that wants a "rat bike", let them know.
 

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She is as finished as I plan to go. The seat cowl is mounted with a luggage rack that the PO threw in with it also. I like luggage racks. Took some photos for the listing on Craigslist Knoxville and did a video in case someone wants one (didn't link it on the listings, though). She is running good and the weather looks promising for this week. Tomorrow we are having six big windows that lost their seal replaced. Crap - they cost about $50 each when we built the house ('85) and it's going to cost $2400 to have them replaced.
Here is the Youtube link and Craigslist link for entertainment:
https://youtu.be/RIit7Tl6Eyc
https://knoxville.craigslist.org/mcy/d/clinton-79-honda-cb750f-rat-bike/6838380958.html
 
Window replacement not going well. Three were fine, but two have water damaged sills and framing under down to the plates. Hope to have that repaired today and get the window guys back out tomorrow, because I just have plastic tarps stapled over the openings right now.
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pidjones said:
Window replacement not going well. Three were fine, but two have water damaged sills and framing under down to the plates. Hope to have that repaired today and get the window guys back out tomorrow, because I just have plastic tarps stapled over the openings right now.
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Nothing worse than rotted window sills...I replaced a few on my buddys house a few years back, not a fun job but they haven't leaked since (or he hasn't told me LOL)

This will be a great buy for someone who wants to build a cafe. Good luck with sale
 
Rode it in to Knoxville last night for Time Warp Vintage Motorcycle Club meeting. My first time to be at their meeting (and join). Several old GoldWing friends there, and made many new friends. The CB750F ran fine! Only problem noticed was that the idle gets higher and higher as it warms up. I was barely able to get throttle increase from the choke full-out when I did the rebuild. Couldn't find a reason for it, and compared setup to photos in the SeanG document. So, I have to crank the throttle stop up a little to keep it running until really well warmed up then back it down, but seems to continue to creep up after that. I'll do another vacuum leak check soon with it both cold and again after about 20 miles of riding.

Also, mounted (just wedged in above the ignition switch) a cheap ebay digital voltmeter temporarily and connected it to the tail light fuse. Charging system seems great! Running at 14.1 volts over (I think) 3k rpm. Rode home with it turning dark, and headlight was adequate. Might need aimed just a little higher.
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Next ebay purchase may be a cheap digital tach. I'm having trouble believing the mechanical tach - seems to be reading high while the speedometer is obviously optimistic by a bunch.
 
BTW, the windows came out Ok. Had to replace the wood all the way down to the plates. Dug out soft wood on sides and spliced, used Minwax wood hardener on some - worked great, turned balsa soft into spruce density. Also used their wood filler which is a two-part Bondo-like with a lot of strength. Plus a new oak inner sill and new cedar outer sills (sloped well away this time). Calked, painted and done. I'd rather work metal.
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Well, it is idling without messing with the fast idle stop now. Took it for a ~ 40 mile ride (now have over 170 miles on it since rescue). Did a quick demo compilation to link on my Craigslist post. It's pretty quiet in it because the camera was in a water-proof housing that muffles it pretty well. Digital tach indicates that the mechanical is very close, and so is the speedometer (well, within the 80's Honda optimistic region).
https://www.youtube.com/watch?v=VqDorR_nC_c
 
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