'78 CB400 "Urban Scrambler" project

[TheVinci]

Did a fair bit of wrenching on my day off. Nothing major, just working on lots of the little things here and there.

Replaced the rusty rear shocks/springs with the good set from the parts bike.

Removed the front forks and disassembled them to get ready for paint on the lowers, and swapping in the better stanchions from the parts bike.

Swapped over the good rear drum, now my rear wheel can rotate!

Stared at the rear grab bar thing while holding an angle grinder for a bit. Didn't cut anything yet, but I have an idea for shortening it so I can get closer to that scrambler look I'm after.

Since I got spark, I wanted to see if I could get anything to happen with some starter fluid. Sprayed some in the air box, but got nothing. So I took the carbs off and I'm starting the fun process of cleaning them up! Figured I'd have to anyhow. These things are looking preettttyyyyy rough. I'm going to grab an ultrasonic cleaner on my way home from work today and see what that does.

Here's how they look fresh off the bike.

 

[ancientdad]

Yeah, those are pretty rough.

 

[Boosted]

Not too bad... ..A hand-polishing of the venturi throats, slide-pistons, and inner-sides of the intake "insulators" before or after the ultrasonic broiling will work wonders. If the needles are a Beryllium color and not a polished brass color - PROCEED CAUTIOUSLY ! - I began with 70% Isopropyl Rubbing Alcohol...

 

[TheVinci]

First problem to overcome is unscrewing all of the fasteners without stripping the heads!

 

[LongDistanceRider]

First problem to overcome is unscrewing all of the fasteners without stripping the heads!

Penetrating oil and a heat lamp for a day first.

 

[TheVinci]

Penetrating oil and a heat lamp for a day first.

Oooohhhh a heat lamp, that's an idea I hadn't heard of yet. I've already soaked it in PB Blaster, but I can hit it again and leave it under heat for a bit. Thanks for the advice!

Also, I believe you are just a bit South of where I'm located, so if you have any other insights regarding bikes that have sat out in our climate specifically, I'm all ears!

 

[Boosted]

I also used a $100 HarFreight counter-top ultrasonic-cleaner, hair-dryer, Liquid Wrench, and a Snap-On impact driver to loosen any stuck Phillips screws…
..which, is “Old News” on this forum… .. “Search” feature function of this VHT Forum is HIGHLY RECOMMENDED!

 

[TheVinci]

Well, they didn't have the ultrasonic cleaner I wanted in stock, so that's gonna be a couple of days, but I did break down one side of the carbs. The insides weren't as bad as I expected, I'm a novice, but I think these are serviceable.

Boosted, the needles weren't the color of beryllium, but there was what I can only imagine is leftover ancient gasoline in one of the bowls that was emerald green

Some elbow grease and a rebuild kit, and these should be in working order. Had to stop short of breaking down the other side and fully cleaning them as I had to make dinner and get the kids to bed. I feel like we're getting there slowly but surely though! Thanks for coming along on this adventure with me, more updates as they come.

 

[Boosted]

Stared at the rear grab bar handle while holding an angle grinder for a bit. Didn't cut anything yet, but I have an idea for shortening it so I can get closer to that scrambler look I'm after.

I use the grab bar handle every time I pull my 400-pound bike back onto its center stand while holding the handlebars straight with my left hand to keep it upright. Can't imagine it being less challenging without it.

Carbs notice : you'll want to replace that "uni-hoser" drain hose connecting the 2 bowl drains with 2 seperated drain hoses long enough to carry the gas to the ground and away from exhaust

Also, the "insulators" or intake manifold ducts that install between the carbs and cylinder heads are not interchangeable between the HondaMatics and manually-shifted bikes and are Unobtainium for the HondaMatics, so treat them VERY CAREFULLY

That "emerald green" residue in the float chamber bowl looks like 2-stroke oil, which some use to coat the inside of empty gas tanks for long-term storage to keep the tank from rusting

And, that needle showing in your post #51 above does appear to me to be the color of the KeiHin beryllium needles - Any identifiers punch-stamped into the large end of those needles, such as the digits 05E ?

Finally, I see either the tiny spring or the tinier metal washer in the threaded hole of the carb body for the pilot mixture screw of that one carb body in the photo above - They're re-usable but the rubber O-ring beneath both the spring and washer is likely done, judging by the condition of the other rubber in the photos...