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Discussion Starter · #1 ·
I'm doing my very first bike tear-down and build on a bike that a buddy of mine practically gave me. So, I decided that I want to try to do as much as I possibly can on this bike by myself over the next few years in order to teach myself and have fun.

Engines have always intimidated me, but I was thinking that I would see if I can at least do some of the less difficult items and cleanup with the manual as my guide.

Well, I dropped the engine out last weekend, and needed to take off the left-side cover to do that. What I found inside was pretty scary. The flywheel is all rusted and it has corrosion everywhere. It looks like and smells like mold/mildew in there. Water got in and sat there at some point?

Well, now, I'm about 300% more intimidated than before.
Does anyone have any tips on where to start with this for a beginner and what I can do?

FYI - the engine ran before I dropped it. There was an intermittent issue with starting, but I figured maybe a bad solenoid or now I think maybe it could be this mess (pic)?

Thanks in advance!
Leslie

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Most of the grime on these is superficial. The three things you want to check:

1) Air
2) fuel
3) spark

If you have those three things it will run. It’s common for beginners (myself included) to “fix” things that don’t need to be fixed.

If the motor ran before I would just do the maintenance outlined in the service manual. Pull the carbs and give them a once over making sure all the passages are clean and it should fire right up.

Maybe change the oil to make sure it’s what you want.


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Discussion Starter · #4 ·
Hey, J-T.

Thank you for the link here. I'll read absolutely anything that I can get my hands on.

The starting issue was this - it would turn over, but not fire up. I checked the spark it was good before disassembly.

Pics attached here.
Two before pics and one right before I took everything off the frame.

This bike was full of gunk, old wasps nests, etc. It feels good to start cleaning it up.


cm400_2.jpg
cm400_3.jpg
cm400_4.jpg
 

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Make sure you have a workshop manual and parts catalogue.
Did it smoke when it ran?
Do a compression test, normally anything over 100psi is good. Do the first test and record pressure. Then squirt some oil in the bores. If the first reading is low and the second reading high you have shot rings. If the readings low and are the same after oil in the bores you have to check the valves.
Replace the points and condenser.
Make sure you have fresh petrol in the tank.
Definitely change oil.
Take lots of photos when stripping down.
I used to be scared of stripping engines, still am really. Take your time check everything at least twice. Enjoy it or pack up.
 

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CDI ingniton system so no cb points but a condenser/capacitor although for a slightly different function. Research.

The cdi system is non battery dependent and a self contained modern "magneto" of sorts.

The flywheel externals are quite rusty/corroded, so how are the internal magnets ? These are a bit delicate as is the stator, its coils and the external alloy casting, but it did produce ht ( along with the cdi and ht coil etc..).

The engine did turn over all ok, so they should be reasonable, and no stuck valves.

You have a manual and know of cmsnl for the exploded views.

These engine have some "honda" design so familiorise your self with the unit.

For your info, the 4 centre head bolts can be problematic. They are exposed to the outside world so can collect road salt, crap and water. So be warned about them.

Any signs of the engine been taken apart before like lots of sealer in/by the cylinder central air tunnel, and, a different colour sealer between the upper and lower crank cases?

oe stuff is like a light tan brown sort of colour. Post a picture of that joint so we can see, or look thru the site for engine images and see the colour for your self.

Has the engine got reasonable compression ?

Be careful when "wet" compression testing by adding oil, not much, say 10 to 15cc of the stuff.

If it where mine, once establishing that the engine turns over ok and no valves are sticking ( bike been standing for ages, valves ( and clutches as well as brakes etc. ) can and do stick, a stuck valve and a good whizz on the starter results in turning the engine to junk, scrap !! ), and the carb float bowls are reasonably clean etc., i would start the engine being very very gentle and adding 2t to the fuel. Just idle speed with some air cooling via fans, run just enough to "free" everything off.

The clutch will no doubt be stuck. DO NOT just grap a hand full of throttle and smash it into gear, dentists are painful and a bike going thru your or your mate next doors plate glass window will be spectacular ! Engine heat will aid freeing of a clutch.

The gentlest method is to place bike on center stand so it cannot roll off. Start and warm engine. Stop engine and engaged a high gear, say 3rd or 4th. Start engine understanding that the rear wheel will now turn under power, so the chain must be able to transmit this to the rear wheel, and, if the bike rolls off the stand you will have a dangerous uncontrollable situation.

Now blip the throttle causing some transmission "snatch", which will eventually free off the clutch, but remember all clutch sticking debris will enter the engine oil. The best way is to remove the clutch cover and clutch basket, but a peg spanner is needed for the slotted clutch nut. See manual and cmsnl and study. Has the clutch nut been butchered?

Clutch cover removal gives the ideal time to flush out the crank case floor and kick start oil trough will will have "sediment".

The clutch cover oil pressure switch area tends to fill with grit etc.. If not cleaned out this grit falls all over the crank primary gear. A case of unwanted outside crap joining the engines inside crap.

There are some other checks to be made, like the balance chain system adjusting mech and its "DOT" position.

How far of a strip down are you gunna do ?

You will need a flywheel extractor to remove it.

Do your research and enjoy, take your time.

Were the airbox mice dead?
 

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If you have not done so get some quart and gallon size plastic bags and as you take the parts off bag and label every nut ,bolt and part even if they are bad. This will save you from wondering were a part got to or where it goes.

Bill
 

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Discussion Starter · #11 ·
I can come and take a look if that'll help. I do know a little bit about these models.

WHOA, are you kidding! That is amazing!

I wouldn't want to waste your time - the engine is currently not in the frame and the flywheel is rusted on without me having a puller, but I would LOVE to talk to someone who knows about these things.
 

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Definitely take Jim up on his offer. He is our go to (guru) for these bikes. (and one of the nicest guys you'll ever meet !)
 
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WHOA, are you kidding! That is amazing!

I wouldn't want to waste your time - the engine is currently not in the frame and the flywheel is rusted on without me having a puller, but I would LOVE to talk to someone who knows about these things.
You can text me, I'm still learning to hear on the phone so that's not viable yet. 408-239-9580
I have the tools needed for the rotor and stator
 

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Yeah, Take that offer! This guy was amazing with my build/problems on my CB 400T, VERY knowledgeable (he is being modest). My flywheel was worse, got water as well. Do the ignition diagnosis: https://www.hondatwins.net/forums/6...400-450-cb450sc-manual-trans-1978-1986-a.html to make sure it is good, if it is, soak the flywheel and stator in Metal Rescue and clean the case and flywheel with wire brush. My carbs were real gummed up! The LBS did not clean them at all and did them myself. Was intimidated by it, but very easy to do with the this sticky: https://www.hondatwins.net/forums/63-fuel-supply-carburation/24191-rebuilding-vbulletin-carbs.html and soaked them up in ultrasonic cleaner as well.

Sorry, it is blurry.

IMG_0269.jpg
 

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Leslie reached out yesterday and I was waiting to hear back when I found out my phone was about to flame on. It's in the backyard in a can in case it decides to fire up. So PM sent and I'll have a new phone in a couple of days.
 

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Yup, there's a distinct pattern with old Hondas that when someone fixes up the issues they had when last parked and starts ridings them again, that the bike improves with every mile as if it starts remembering who it is and why its here.
 

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Discussion Starter · #19 ·
Jim's help was so fantastic. I took notes and have about two full pages worth of action items. I finally had a break from school and was able to tackle the cleanup of the stator, with the help of some extra confidence thanks to Jim! Many more small projects to come. Frame is torn down and nearly ready to go to powder coating. Thanks again, Jim!!

Before.jpg After.jpg
 
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