Honda Twins banner

1 - 20 of 45 Posts

·
Registered
Joined
·
26 Posts
Discussion Starter · #1 · (Edited)
In this thread I hope to save the life of a truly dear friend.

My trusty steed... my faithful companion. "Thumper," the 1981/'84 CM400/450 hybrid that I learned to ride my first miles on. That went down with me in a tangled mess time and time again as I pushed the envelope of what we - together - were capable of (I still laugh about that time I chased a silver Mercedes up a tight uphill lefthander, sharp enough to brush the asphalt with the fingertips of my glove, forgetting that I had packed two fat saddlebags full of textbooks on the back that day... I don't know if the Mercedes driver ever realized I was in pursuit, but I will say he did not turn around when I disappeared from his rearview :rolleyes:)

This same beloved bike that, less than a year after I started to ride, carried me screaming past downhill semitrailers piled full of logs, straining at their chains and streaming woodchips through my visor as I carved round two-lane forest highways in Arkansas Route 7, four hundred and sixty miles from my home in Texas, at the age of 24. The bike that launched me in and out of the curves of the Dragon at Deals Gap; we turned round four times to cross the Tennessee-Carolina border, chasing and racing the sun as I figured out how to properly downshift and roadside photographers snapped their photos for internet cash (I am not ashamed to say I paid them, weeks later, for the mementos).

thumper-deals-gap-closeup.jpg

We made it to New York City together, mostly on 2-lane roads - my God, me a rider of 10 months and my 31-year old motorcycle from Texas. It still makes me frown with concentration as I try to believe that it actually happened. None of my friends or family rode. Nearly everyone around me feared motorcycles, so I didn't tell them about Thumper unless they figured it out on their own.

This bike was my friend. I was just getting my real life started and I didn't have much to my name, but nothing made my heart jump and leap out my chest like throwing my leg over and thumbing the starter - giving him just a little throttle at the same time, of course, to get that satisfying, vintage "thrum" that always turned a few surprised heads as I pretended to ignore them. At work I daydreamed of two-lane country roads, curves and trees so dense that there was only enough room in your mind for the next corner, and blue sky with fat, thick white Texas clouds, the hot sun pounding down on us just the way we both liked it. I myself was born into the Texas heat, and well, Thumper's tires always stuck to the asphalt extra-confidently on a sizzling day.

But now, after years of heart-and-soul adventures in which the aforementioned escapades are only the tiniest minuscule percent, Thumper was sick. I consider it a testament to his personality that his final ride was faithfully carrying me and my then-girlfriend down the violence of the interstate corridor to the big theater and back for our late-night viewing of Mad Max: Fury Road. I knew that night that something was wrong, and Rebecca worried and fretted over his poor warm machine heart, for she loved Thumper too, as did everyone in my life who knew much of anything about him. (Good little bike. Faithful bike.)

But now his motor revved frighteningly high at idle, and his oil seemed suspiciously low. There was more... though the specifics of all the little worrisome issues are now hazy with time. Back then I became afraid to take him on the roads for fear of making his problems worse. I was not nearly good enough with a wrench to rescue him, and without enough cash in my bank accounts to pay a professional, he lingered unridden... protected as best I could shelter him with a simple plastic cover that I knew was not enough.

Now, today, years have passed - nearly three years, which feel like less than two, as the months race by in a Bob-Dylan-esque carnival of life events and characters and distracting buffoonery. And I still haven't saved my old and faithful friend from the plastic-tarp hell that I sacrificed him to in order to make my own life easier. It eats at me, a daily low gnawing that reminds me I'm not properly caring for a kindly old beast that only ever trusted me and helped me to grow.

Well, events have conspired to bring me to this moment - to this beautiful day. My only working car broke down recently, and I don't feel like fixing it right now. Transmission problems. Another old classic that I probably should have sold long ago, but can't, because I just... well, I just fall in love with old vehicles once they're "mine." Then I discovered I can run on foot the 14.2 miles to my office and back as long as the weather's not too bad, so now I'm doing that. But it hit me, I have all this free time, in a way. And Thumper is just sitting there, bumped up against the curb, forlorn and lonely. And it sure would help to have a ride.

So today I decided. We've gone through so much together. This is just one more trip. I'm going to learn to fix him. What have we got to lose? If I can do it, I know he'll trust me again, even after I left him out there in the cold and the rain for so long. I miss him so much. There's nothing I'd want more today than to go out for a ride together. So I'm going to learn to fix him. I always wanted to, anyway.

And I really need your help, because when it comes to motorcycle repairs, I have absolutely no idea what I am doing.

This is the next chapter of the story of Thumper and me, and if it's caught your attention, I hope you'll join us & provide advice as I share my progress.
All are welcome.

Only one request I make of you: Please bring positivity to this thread, Thumper has always thrived on positive vibes and love :)

"Before" post (for the "before and after") and first steps taken will be coming soon... and I'll keep including photos as I work.
 

·
Premium Member
Joined
·
10,203 Posts
Welcome to the group. Your little friend should find comfort in knowing there are many peers here with whom to share his experiences.
 

·
Premium Member
Joined
·
24,208 Posts
Welcome aboard. We'll get you going again. First off you'll need the FSM, factory service manual, so look for a PM.
 

·
Registered
Joined
·
399 Posts
Welcome to the forum. Well written palimpsest. Good luck on the rebuild.
 

·
Registered
Joined
·
9,796 Posts
Welcome to the forum. Great to see another 400 series here. You have come to the right place to feed your passion. There are lots of passionate enthusiasts here , ready and willing to help you any way they can. I have learned much more than I have helped here, but offer what knowledge I can.
 

·
Registered
Joined
·
26 Posts
Discussion Starter · #6 ·
Welcome to the group. Your little friend should find comfort in knowing there are many peers here with whom to share his experiences.
Thank you for making us feel welcome! We instantly felt more encouraged when I read this :)

Welcome aboard. We'll get you going again. First off you'll need the FSM, factory service manual, so look for a PM.
Awesome. We can't wait :D Thank you so much for the PDFs in the PM! I've started reading through the Honda Service Manual 1978-81 CB-CM400 as it seemed the best place to start.

Welcome to the forum. Well written palimpsest. Good luck on the rebuild.
Thank you!! I'm glad you liked it! It was a lot of fun to write since I haven't been on a bike in over a year. Hope you can come back for more updates as we make progress :)
 

·
Registered
Joined
·
26 Posts
Discussion Starter · #7 ·
Welcome to the forum. Great to see another 400 series here. You have come to the right place to feed your passion. There are lots of passionate enthusiasts here , ready and willing to help you any way they can. I have learned much more than I have helped here, but offer what knowledge I can.
Excellent, posts like yours really make me start to believe this is possible. Thank you for the encouragement and welcome to the thread of Thumper's return to life ;)
 

·
Registered
Joined
·
26 Posts
Discussion Starter · #8 ·
Thumper's "Before" Photos From March 12th, 2018

Unfortunately I gave him a good dusting and brushed off all the leaves and spiders before I remembered to take these... but maybe it's better he retain a little of his dignity :lol:

(Click to enlarge)
Thumper Before 1 Front.jpg
Thumper Right Side Full.jpg
Thumper Before Rear.jpg
Thumper Before Cockpit Full.jpg
Thumper Before Tank Top.jpg
Thumper Before Cockpit Dials.jpg
Thumper Before Top Right.jpg
Thumper Before Left Side B&W.jpg
 

·
Registered
Joined
·
26 Posts
Discussion Starter · #10 ·
You have the 3.8 gallon tank, largest one made.
Nice, I love the gas tank! Usually I'd go about 120 miles before I started getting nervous for a gas station.
The tank's color, shape, and overall patina of age have always been a big part of the Thumper experience for me.
I'm looking forward to taking off the tank during this project (for the first time) and giving it some TLC inside and out.
There's probably a good bit of rust in there.

OK, so I'm looking for replacement batteries on Amazon.
The two main candidates for me seem like:
1) Yuasa battery (the model (link) I have in there now)
This one requires me to add the charger/fluid myself, and the total is slightly more expensive
or
2) KMG battery ((link) this one, which Amazon says will fit my CM400c, but I don't know for sure)
This one comes sealed and ready to go, slightly less expensive total.

I lean towards the KMG (cheaper and ready-to-go) except I don't for sure that it fits.
The Yuasa would be a direct replacement, known quantity - and it's what my (extremely experienced) moto mechanic always used to use.
But, a few more bucks and I've gotta do the fluid myself. Could be fun.
Any thoughts?
 

·
Registered
Joined
·
26 Posts
Discussion Starter · #11 ·
Frame Rust - A Huge Problem, or No Big Deal?

Question about Frame Rust

I'm a little concerned. Is this rust on the right side of the frame too much, or will I be able to sand and repaint it?
The following pictures show the worst of the rust on the whole bike, by far.
Left side of the bike is virtually rust-free.

Thumper BEFORE Right Frame Rust Detail.jpg
Thumper BEFORE Right Frame Rust.jpg
Thumper BEFORE Right Frame Rust from Behind.jpg
Thumper BEFORE Right Frame Rust Back Detail.jpg
Thumper BEFORE Right Frame Rust Full Scope.jpg
 

·
Premium Member
Joined
·
24,208 Posts
I've been using the MB12U MotoBatt battery for several years and bikes. Everyone that has used them loves them.
Rust looks like mainly surface stuff so clean it off and paint. These frames are thicker tubing so there's no real rust thru issues.
 

·
Registered
Joined
·
3,249 Posts
I'm looking for replacement batteries on Amazon.[/B]
Any thoughts?
I recommend https://www.batterystuff.com/powersports-batteries/sYT12C.html

AGM type, no filling or refilling, charged ready to install right out of the box. Scorpion batteries are good quality, I've been abusing one for 3 seasons now and expect it'll serve quite a few more. They ship US Postal so you may have to go pick it up at your local P.O.

Why buy from some drop-shipper on Amazon when you can buy from a place that specializes in batteries and has their own real customer service department?
They take PayPal too. I'm not affiliated, just a satisfied customer.
 

·
Registered
Joined
·
26 Posts
Discussion Starter · #14 ·
I've been using the MB12U MotoBatt battery for several years and bikes. Everyone that has used them loves them.
Rust looks like mainly surface stuff so clean it off and paint. These frames are thicker tubing so there's no real rust thru issues.
I recommend https://www.batterystuff.com/powersports-batteries/sYT12C.html

AGM type, no filling or refilling, charged ready to install right out of the box. Scorpion batteries are good quality, I've been abusing one for 3 seasons now and expect it'll serve quite a few more. They ship US Postal so you may have to go pick it up at your local P.O.

Why buy from some drop-shipper on Amazon when you can buy from a place that specializes in batteries and has their own real customer service department?
They take PayPal too. I'm not affiliated, just a satisfied customer.
Both of those AGM batteries look like beautiful recommendations, thanks guys. Both with different pros and cons.
I don't think I've ever had an AGM in Thumper and it sounds like they're well-liked on the forum.
I'll be ordering a good battery within a week or so, then can move to the next step :D

Until I can do that, studying the Clymers and Factory Manuals in detail and learning a lot that I didn't know before
 

·
Registered
Joined
·
26 Posts
Discussion Starter · #15 · (Edited)
OK, I went ahead and ordered:
- New AGM Battery
- New NGK spark plugs (identical replacement for what my mechanic used to put in)

Here's my plan to begin with, does it make sense?
- Wait for stuff in mail
- Verify the charge of new battery & trickle-charge if low
- Drain both carbs of old gas
- Drain entire tank of old gas
- Refill tank with new gas
- Change the oil
- Remove old spark plugs
- A couple drops of fresh oil through plug holes into each cylinder
- Install new spark plugs
- Install new battery
- Try the starter in several-second bursts until starts, something unexpected happens, or 'till I give up (try not to kill new battery lol).

This is my initial plan for fixing the most obvious issues first, and seeing if he'll even start with a new battery.
He's been sitting for almost 3 years, outside (with a basic bike cover).
Am I leaving anything out?

(Remember, I really have no idea what I'm doing, so you won't sound condescending)
 

·
Registered
Joined
·
475 Posts
Good call on the battery a flooded lead acid battery is only good for ruining the chrome on your mufflers!
 
  • Like
Reactions: Alan F.

·
Registered
Joined
·
45 Posts
Welcome distance seeker. I have the same bike in blue.
When you start it, you can crank it a couple of times with the kill switch on “kill” until you see the red oil pressure light go off, then turn the kill switch to “run” and start it. This prevents it from starting before it has oil pressure.
 

·
Registered
Joined
·
1,532 Posts
Im with Benjo. On some of the bikes without oil pressure lights that have been sitting awhile I kick over about 25-30 times to get oil to the top end before starting.

Just a thought.

Bill
 

·
Registered
Joined
·
3,249 Posts
If you're waiting for parts to arrive, and feel like spending some time with your bike, I'd recommend connecting up any available 12 volt battery with jumper cables or clip leads to your battery terminals, observe correct polarity.
-Then verify all of your lights and signals work correctly. Fix anything that isn't working correctly. You may find a bad ground or a blown bulb or a switch in need of cleaning. Don't touch the start button though.

Also don't forget to correctly gap your plugs before installing them, make sure the new plugs have their crush washers in place too, and don't overtighten them, good and snug is plenty but some torque to spec.

Enjoy yourself!
 

·
Registered
Joined
·
26 Posts
Discussion Starter · #20 ·
Finally got work started today.

It was a beautiful day to work outside! Other than the mosquitoes..
before starting work.jpg

Had to save up some cash for all the parts, tools, and supplies over the past couple months, and waited for the right moment.
But now I've set up a temporary workstation in my house.
There's a worktable near a ventilated window, and enough cardboard laid on the floor to roll Thumper in the front door and park him in my living room at night (no joke he's in here right now).

Removed the gas tank
My first time doing so.
Thought this would be harder. It was amazingly easy.
Drained the tank as much as possible first.

Draining the gas tank
draining gas from tank.jpg

The gas in the tank was semi-clear, semi-discolored.
It smelled like a gas station, but.. less pungent.

The tank is off!
gas tank is off.jpg


Degreased / rinsed the tank thoroughly
Used non-toxic KLEEN tank degreaser.
Diluted to 1:4 with water, and shook it for almost 20 minutes (5 were recommended, but I think I diluted more than necessary).
This is to remove any remaining tank coating, prior to de-rusting, before applying the new Caswell tank sealant.

This is what the tank looks like after Kleen and rinse, but before de-rusting:
tank rust pre-treatment.jpg


Began tank rust removal treatment (EvapoRust)
Using about 1.5 gallons of EvapoRust, saving about .5 gallon for a final rinse in a day or two.
It's too expensive to fill my tank to the brim, but that's apparently OK according to the instructions.
Also - added a small handful of metal BBs.
Every hour or so I roll it all around in the tank.
Hopefully it will gently, non-toxic, low-impact remove the majority of rust.
We'll see in 24-48 hours.

Leaking Non-Toxic EvapoRust Everywhere
I'm very GLAD the EvapoRust is non-toxic, and NOT bad for paint.
When I turn the fluid through the tank, it's leaking like crazy - dribbling out the petcock, and running out the gas cap when the tank is upside-down.
Evaporust has been all over my hands and the paint, although I wipe it up as soon as I can, but it supposedly will not hurt.
There don't appear to be any other leaks or holes in the tank whatsoever.

Petcock concerns
I think the Fuel Petcock needs some special TLC, but I'm not sure what yet.
It seems to drip-leak when set to "OFF".
Not sure what this is about, or how serious it is, or how to fix it.
Honestly I think it's been doing this for years, but I don't like it.
I want to be able to set my petcock to "Off" without it leaking.
Pretty sure it does NOT leak when petcock is set to "ON" or "Reserve" - at least there's that saving grace.

Visual of the petcock in question
petcock.jpg

Pulled the carbs (!)
I had plenty of extra time in the day, ahead of schedule!
So, I went ahead and slowly, carefully removed the carbs from the bike (also a first for me).

Carbs coming out
carbs partway off.jpg

Carbs almost off
carbs almost off 2.jpg

Drained one of the carbs before removal, but I couldn't reach the other one's drain screw while it was mounted in the frame.
By the time I got to an angle where I could unscrew the 2nd carb drain, it all just kind of poured out of a different spout anyway LOL :eek:

Overall, carb removal wasn't brain-dead simple (removing the throttle/choke cables had me scratching my head for a bit)
But it wasn't THAT hard at all.

This little part took me a bit to figure out - where the throttle cables connected to carb
throttle cables to carb.jpg

I was afraid the whole time I pulled the carbs of tearing or breaking the old rubber boots, especially from the airbox.
No doubt, the boots could use a replacement, but for now I'm hoping the old rubber will continue to make do.

Victory!!!
carbs are out.jpg
carbs view 2.jpg

I took plenty, plenty of pictures to help with the reconstruction.
The carb gas smelled like FRESH-VARNISHED WOOD FURNITURE. That was some nasty old gas in there.

Here's a slightly more internal view for now:
inside carbs.jpg

Tomorrow's Plans
Tomorrow the main goal is to inspect and clean the carbs, carefully, inside and out, and re-assemble - possibly even get them back on the bike.
I haven't decided yet if I'll drain the EvapoRust from tank tomorrow or the next day.
Either way, once I start back on the tank, I'll need to act very quickly afterwards to rinse, dry, and re-seal the tank before any flash rust can set in.
So, clean the carbs first, then seal the tank after giving the EvapoRust maximum time to do its thing.
That's the plan!

Looks stylin' with no tank and no carbs
no tank no carbs.jpg

It's been great getting to know Thumper on this level.
I feel our bond coming back so quickly :)
All day long I've been excited and in a good mood.
I know I can do this now.

Ladies and gentleman, your carbs are served by a sweaty man
serving up carbs.jpg

Hope to update again tomorrow.
Advice / wisdom / concerns appreciated!!
 

Attachments

1 - 20 of 45 Posts
Top