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1980 CM400T
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Discussion Starter · #1 ·
Hiya folks, I’ve dreamed of owning/fixing my own bike for a long time! I’m a tinkerer by nature, learned everything I know from my Dad (and now YouTube). Got my motorcycle license 15 years ago and just found my first project bike! 1980 CM400T. It’s been sitting in the last owner’s driveway for 6 or 7 years… riding wasn’t really his thing, he says; he bought it from a guy who rode it daily. So I’ve got tons of cleanup work to do but I’m optimistic. Pandemic lockdown had me rebuilding a friend’s 150cc scooter carb, and I got ‘er running again, so I do okay with the straight up mechanical stuff. Electrical I’m a know-nothing (or maybe I know just enough to get me in trouble, haha). So glad to be a part of the group!
 

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Hi AL, so bike been standing some time....

Adopt a very carefully approach to its resurrection as stuff can stick/seize !!!!!

A stuck valve ( open usually ) can convert a viable engine to scrap in one stroke !

You have been warned.

Clutches can and do stick and need considered thought, else a dentist needed.

Brakes can and do stick, again needing some "novel" techniques to sort out, involving hot water perhaps.

You know of CMSNL.com which you will find very informative.

Electrics at 12 volts are safe for you, however electric cars can be lethal.

About 48 volts DC across your chest can kill you !

The first Jobs for me if this bike was mine would be...

Drain engine oil and filter and examine oil dregs for glitter....

Leave drain pan under dripping engine, remove spark plugs and put some redex y petrol in the bores and leave. How long did it take for red to start dripping out ?

Remove cam cover and take a few pictures...

Remove flywheel cover and take some pictures...

The flywheel rotates anticlockwise when engine running.

BY HAND ( that's BY HAND ) turn engine over very slowly. You can see valve heads thru plug holes, and see rockers moving in)in cylinder head. If engine seems to "lock", poor hand grip on flywheel, STOP !!!!

Check rockers for large gap meaning a stuck valve.

You must establish that none of the valves are stuck, else ruin the engine !

If all appears ok, lub lub lub, and turn over by hand 100 times.

Yes I know.....

Next, new oil and filter, kill ign on handle bar, fit suitable battery and whizz engine over on starter till oil light goes out.

Use starter in 5 second bursts, allow to cool then repeat.

Oil light may take more than one burst, two bursts at most to go out. Once it's gone out, how long before it came back on ?

That's the first most important abd crucial chapter. Take your time and enjoy.

Feedback and pictures when above done.

Next chapter is to get it running.

Get a multi meter, even a cheapo one.

Don't rush, hare and tortoise and all that.

Your Gunna love this bike so don't make it a hate relationship.

Study CMSNL exploded views.....particularly the balance chain system
 

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1980 CM400T
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Discussion Starter · #5 ·
Hi AL, so bike been standing some time....

Adopt a very carefully approach to its resurrection as stuff can stick/seize !!!!!

A stuck valve ( open usually ) can convert a viable engine to scrap in one stroke !

You have been warned.

Clutches can and do stick and need considered thought, else a dentist needed.

Brakes can and do stick, again needing some "novel" techniques to sort out, involving hot water perhaps.

You know of CMSNL.com which you will find very informative.

Electrics at 12 volts are safe for you, however electric cars can be lethal.

About 48 volts DC across your chest can kill you !

The first Jobs for me if this bike was mine would be...

Drain engine oil and filter and examine oil dregs for glitter....

Leave drain pan under dripping engine, remove spark plugs and put some redex y petrol in the bores and leave. How long did it take for red to start dripping out ?

Remove cam cover and take a few pictures...

Remove flywheel cover and take some pictures...

The flywheel rotates anticlockwise when engine running.

BY HAND ( that's BY HAND ) turn engine over very slowly. You can see valve heads thru plug holes, and see rockers moving in)in cylinder head. If engine seems to "lock", poor hand grip on flywheel, STOP !!!!

Check rockers for large gap meaning a stuck valve.

You must establish that none of the valves are stuck, else ruin the engine !

If all appears ok, lub lub lub, and turn over by hand 100 times.

Yes I know.....

Next, new oil and filter, kill ign on handle bar, fit suitable battery and whizz engine over on starter till oil light goes out.

Use starter in 5 second bursts, allow to cool then repeat.

Oil light may take more than one burst, two bursts at most to go out. Once it's gone out, how long before it came back on ?

That's the first most important abd crucial chapter. Take your time and enjoy.

Feedback and pictures when above done.

Next chapter is to get it running.

Get a multi meter, even a cheapo one.

Don't rush, hare and tortoise and all that.

Your Gunna love this bike so don't make it a hate relationship.

Study CMSNL exploded views.....particularly the balance chain system
Wow, thank you for the recommendations and I appreciate the warnings - about electric AND about going slowly and carefully. I'm enthusiastic - but I want to be smart, too. I already drained the oil, so I'll give it a go with your next outlined step: crank by hand. Thank you. -Liz
 

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I assumed you would be female, I am not sexist, in fact lady mechanic don't do bullshit I find.


Did you look on CMSNL.com for engine internals, and now have a better idea of the bits and pieces in there ?

Print them off if you can.

Research the balance shaft weights and what's involved.

There are actual pictures of the components which can show things other than the exploded views , which show what's involved.

If your bike were mine and items on the posted "list" are ok so far in so much as drained oil examined, oil filter washer not thrown away with the old filter, cylinders lubed, cam cover removed and pictures taken, flywheel rotates by hand and valves seen to open and close without sticking, I would check the position of the balance shaft weights chain drive adjustable adjusting quadrant, and the shafts "dot" position.

I will let you suss out how to view those items, just look at the CMSNL views and pictures.

Are yours a solid wieght system or cush drive ?

When you have sussed out how, you we clearly see the quadrant and it's slot. The quadrant rotates anticlockwise via a spring loaded system but can suffer from "sticktion", needing some "excercise" to free it off. Anticlockwise rotation allows balance chain tension to be adjusted from minimum to maximum.

If you look at the quadrant, you will see the 12mm lock nut. If you look forwards and upwards you will see the 14mm shaft nut, and the "dot" on the end of the shaft. This is an important little dot giving indication as to balance chain "life".

Engine static, slacken the quadrant 12mm clamping nut, the quadrant should move automatically anticlockwise, automatically adjusting the balance chain, but as said, it may be suffering from sticktion. If it is, excercise it a bit until it auto tensions, then lock via the clamping nut.

Is there any tensioning slot left now and we're is the dot. Do not rotate the crank during this checking as it will cause a miss adjustment.

Don't drop anything in the engine goes without saying, but you may be "going in there" a bit later.

I will let you suss out how to adjust the quadrant using CMSNL views.

We're is the dot ?? Using a clock face method.

You have the flywheel cover off as well as the cam cover. It's easier to remove the cam cover by removing the HT coil and cdi unit, there is a "sweet spot" to remove the cam cover, tipping rear of cover up a bit and sliding the cover out, my preference being to the clutch side of the engine. As most things mechanical, if your fighting it, your doing it wrong. Be carefull of the rubber gasket. Take your time. I like to glue the rubber gasket to the cleaned cover, helps with refitting.

Do you think the engine is safe to run with the cam cover off ?

Some bike engines are not !

What do you see on the flywheel, "X, y,z ?

What do you see on the camshaft, arrows ?

So, pictures pictures pictures, feedback feedback feedback, you are getting closer to actually starting the engine, but not yet.

Be patient, take your time and enjoy.....

Over........

Ps Some will say I am being "over the top", I say I am being cautious as I don't want to turn this bike into scrap in seconds.....

Make your own mind up, you are on a learning curve, but for all I know you may have a master's in mechanical engineering.

Ladies make very good no nonsence engineers in my experience.
 

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Oh brilliant, lost post just posted...

Feed back with pictures, did you research CMSNL, there are actually pictures of components as well as exploded views...

Research balance system and cam chain....

If you think a big screw driver will get that out, don't, think good fit washer and a lever of some sort.

It's better to offer suggestions so you can suss things out rather than appearing to preach.

Take your time, don't be afraid to ask.

Feedback and pictures....

Dad's are great ain't they.
 

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1980 CM400T
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Discussion Starter · #10 ·
Wow, thank you for the recommendations and I appreciate the warnings - about electric AND about going slowly and carefully. I'm enthusiastic - but I want to be smart, too. I already drained the oil, so I'll give it a go with your next outlined step: crank by hand. Thank you. -Liz
Hi al, how you progressing, any pictures ?
yes, indeed - got the crankcase and cam covers off. Here are photos. Turning the crank seems a bit stiff but the parts are moving up and down and it looks like the rocker arm stays in contact with the camshaft throughout. (Some of my vocabulary may be incorrect?) how hard should it be to turn the crank?
i have a video.
Automotive tire Vehicle brake Wheel Motor vehicle Alloy wheel

Hood Automotive fuel system Vehicle Motor vehicle Coil

Helmet Personal protective equipment Gas Auto part Glove
 

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Cool, perhaps after this reply it's time to start your bikes "resurrection" thread.

I see the cam shaft area which looks good. You noticed rocker arms following camshaft, good. Means no valves "stick" open, which would be a bit of a disaster.

What do you notice with cam sprocket and camshaft left end ?

I see a white dot ( meaning last owner has been in there ) , that squarish "cut out" and very clean oil. Was the drained oil that clean ?

You may notice some yellow paint on the valve springs ?

Have a good look at the valve springs and say what you notice.

The flywheel, the F mark meaning ???? is reversed, unless you have reversed the image.

Any other letters on the flywheel close to the F ?

Have you found the "datum" mark on the upper crankcase by the flywheel and noticed anything ?

You know the four stroke cycle ?

You have removed any other casing off the engine ?

Did you find the balance shaft "dot" which is an important indicator.

Plugs out, cylinders lubed, the flywheel should turn ( anticlockwise ) relatively easily without jamming/locking which seems ok due to rockers following the cam shaft. The gearbox is in neutral so no rear wheel movement assuming the rear wheel drive chain is still on ?

Everything so far seems to be ok, so why is the engine stiff ?

The inlet valve springs on the rear of the cylinder head are relatively light.

Look how thin they are compared with the exhaust valve springs at the front of the engine.

The inlet valves can be compressed using your strong thumb, but the exhaust springs.....good luck compressing them with your thumb.

The stiffness is due to the combined compressing of the valve springs and as far as I can tell from your pictures and text is nothing to worry about, thank god.

So, feedback in a new thread titled resurrection, or what ever you want to call it.

Your doing great sussing things out and important safe progress made.

Four stroke cycle ? Dot and any other questions askednswered.

It's better you suss out stuff yourself by answering leading questions. Questions to make you think, research, gain knowledge and boost confidence.

Remember babies learn to wiggle about, crawl, walk, run, then do a marathon.

I do not want to appear as preaching, rather point, sometimes kick you in the right direction.

Your getting closer to starting the engine, but not yet.

Over.......

Ps Xmas is coming, ask santa for a cheapo digital multi meter, and a cheapo analogue multimeter. An analogue can show stuff a digital cannot, and visa versa, but that bag of sweets is for when you actually start the engine and let it run.
 

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Slight correction, seems you have not reversed the F on the flywheel, never seen that f reversed like that before. Have a good look at the mark to the right, any letter there, even a lower case letters ?

This picture is poor, but when the time comes I can copy them in the library and email them all to you.

Always be internet/email savy, so all fake but working email address. I know you live in l.a., I don't need or want any other details, be internet safe !

I could not find a video...no matter, the valves not being stuck abd engine turning over ok by hand has been clarified and all looks good in cam area so far.

Looking forward to feedback so more progress can be made. Hare and tortoise.

Automotive design Font Art Circle Monochrome
 

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Lol ppps l

Look at the cam cover chromed bolts. Then are special and easily broken, especially by gorillas !!!!

You can either cover the cam area with clean lint free cloth to keep any debris etc. out, or, temporarily refit cam cover and start the bolts off the thier holes by hand only. You will be doing other stuff in that area really soon like cam chain stuff and valve working clearance checks. Get some "feeler gauges" to check gaps. Gaps for cm400t are 0.1mm ( 4 thou of an inch ) and 0.14mm ( 5 1/2, call it 6 thousandth of an inch ).

Get what ever prefferance suits you. The feeler gauge set have many individual blades marked with Thier thicknesses. If you can get a set with the individual blades thickness of the desired thickness, do so as that is slightly easier but they are a bit more expensive. Looked after they can last a life time. I bet your dad has a good set.

DO NOT be a Gorilla and shear those chrome cam cover bolts off !!
 
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