Honda Twins banner

1 - 20 of 52 Posts

·
Registered
Joined
·
27 Posts
Discussion Starter · #1 · (Edited)
Woodruf key suicide [solved]

Hi,
I have a probleme with a friend's bike.
It's a CB 400 T.

He gave me the bike with the motor already open. I had to control and clean the valves, and at this point i suggested to change the rings.

I did all that, the valves are sealing good, i changed all the admission springs, the rings clearance are in the standart values, but the bike won't start. The compression seems ok!

I mixed with some parts from my bike wich is running good : carbs, cdi unit, coils. But nothing more. Checked and re-checked the valve timing...

The timing chain is pretty used, but it adds some work. Could it be the problem ?

Those bike are easy to make run, i don't understand.. It's not my first rebuild.

This is a video, you could see the bike make some little explosion but nothing more.
https://drive.google.com/file/d/1-mL5NCPKoviTDMrxfA6KM4HHW0b7C9G4/view?usp=sharing


I hope my english is not to bad, thanks in advance!
 

·
Registered
Joined
·
4,458 Posts
There are only a few reasons why an engine (any engine in fact) won't start.

1. No fuel
2. No spark
3. Mechanical interference (engine is seized?)

From your video we can rule out 3.

Did you check to see if you are indeed getting sparks from the plugs?
If those plugs check out then try spraying a little starting fluid into the carbs' intakes and try to start it. If it starts or sounds like it's starting to catch then you have a fuel delivery issue (clean the carbs, check float height, etc...)
 

·
Registered
Joined
·
27 Posts
Discussion Starter · #3 ·
There are only a few reasons why an engine (any engine in fact) won't start.

1. No fuel
2. No spark
3. Mechanical interference (engine is seized?)

From your video we can rule out 3.

Did you check to see if you are indeed getting sparks from the plugs?
If those plugs check out then try spraying a little starting fluid into the carbs' intakes and try to start it. If it starts or sounds like it's starting to catch then you have a fuel delivery issue (clean the carbs, check float height, etc...)
Hi, thanks for your answer.
I didn't mentioned it but i alredy checked the two sets of carb for bowl height, mixture screw,etc.
I have a good spark and it happens at 'F' (checked with a timing lamp and the motor running with the electric starter ).

I don't understand what is the problem ?
 

·
Registered
Joined
·
4,458 Posts
Try spraying some starting fluid into the carbs like I suggested. Just because you checked the carbs, it doesn't mean you're getting fuel into the engine.
 

·
Registered
Joined
·
4,458 Posts
Starting fluid not brake cleaner.
 

·
Premium Member
Joined
·
24,208 Posts
Once the plugs are fuel fouled, wet, they're junk.
I would check the ignition system to insure there's enough spark, https://www.hondatwins.net/forums/6...400-450-cb450sc-manual-trans-1978-1986-a.html
Compression should be ok; fresh rings, valves sealing, cam timing checked and rechecked.
You've swapped carbs but were they from a running bike?
The above covers the basics for IC engines. How old is the fuel? If in doubt change the fuel to new fresh 86-90 octane.
 

·
Registered
Joined
·
794 Posts
ngk must love you, you have ngk goofy juice ?

Check and then rule out/in sparks, get some red neon plug caps to "see" ht, they are relatively inexpensive and a good tool.

not seen you video yet....

ok, a 400t, is that the correct flywheel ? looks a bit like a 250 unit but a better picture would help.

The engine does sound as if its trying, but can i hear a "chff" or "hiss" noise when id does try to run ??

A battery powered timing strobe can tend to "amplify" the input signal from which the "flash" is derived, the red neon plug caps on the other hand rely on ht output to flash. A weak feabble flash at cranking means a weak feabble spark etc.. As revs increase the neon flashes more strongly because the spark is stronger.

The red neon plug caps I use will show a ht flash in normal not too bright daylight, with a good system.

You say the cam chain in worn, show a picture of the cam sprocket timing marks when crank set to "T", the marks should be level and inline with the cam cover sealing face on the head, with the chain in tension. Any "lean back" and how far can the cam chain be lifted off the sprocket at the top ?

Do the ht leads where they enter the ht coil "wobble" ?
 

·
Registered
Joined
·
27 Posts
Discussion Starter · #9 · (Edited)
Hi folks ! Thanks for all your answers. I don't understand everything so i will have to use google translate and make some tests tomorrow.

Also i thinked that maybe the rings wasn't mounted correctly but the results i found on the forum show me that i'm good.
Picture:

The ring with chrome line on top, the gray second and the three-parts oil ring.

Note: the bike ran good before the "rebuild" even if the carbs were in very bad tune. The parts i tried work well on my bike (cdi, coil, carbs)
 

Attachments

·
Premium Member
Joined
·
24,208 Posts
The picture shows that the cam timing is retarded, most likely due to the cam chain stretch. You can try to reset the cam 1 tooth "forward" which may compensate or slightly advance the cam timing. Here's a picture with a new gear and chain.
201_4552.JPG 201_4555.JPG
Your rings are in the correct order, even if they weren't it wouldn't have much effect the starting at this point.
You received this bike with the engine apart. Why was it taken apart? Was it a running bike just prior to being taken apart or was it taken apart to solve a problem?
I would run the ignition/stator test I mentioned earlier. We recently had a non starting issue that was due to the ignition only firing from the advancer pulsar,

BTW Fred, I'm having no trouble understanding what you are writing.
 

·
Registered
Joined
·
794 Posts
Nice pictures ldr, you can see how clean stuff is and the valve springs, notice the close coils to the head.

Lean back is not good due to worn system.

I cannot seem to zoom into the pictures, so cannot really see the cam chain lift, anyways the rocker carriers are off so any chain lift would tend to be reduced with the engine in this state.

The pistons picture, you can see an oil hole in the rod upper at the rear , Yes ?

You know of cmsnl and have a manual.

Could you take a picture of the flywheel again please.
 

·
Registered
Joined
·
27 Posts
Discussion Starter · #13 ·
The picture shows that the cam timing is retarded, most likely due to the cam chain stretch. You can try to reset the cam 1 tooth "forward" which may compensate or slightly advance the cam timing. Here's a picture with a new gear and chain.
You received this bike with the engine apart. Why was it taken apart? Was it a running bike just prior to being taken apart or was it taken apart to solve a problem?
I would run the ignition/stator test I mentioned earlier. We recently had a non starting issue that was due to the ignition only firing from the advancer pulsar,

BTW Fred, I'm having no trouble understanding what you are writing.
Hi thanks,
Are u sure there is no risk to put the timing chain one tooth in advance ??
I'll run the ignition test asap.

This bike had backfiring problem. A mecanic said that it could be the valves and my friend begin begun to disassemble it for me (but i didn't request that, i just said that i would have a look to his backfiring problem).
When checking all the parts i foud one of the intake boot o ring bad sealed with some explosion marks. I'm pretty sure the problem was that. But anyway, it was the occasion for a rebuild.

Nice pictures ldr, you can see how clean stuff is and the valve springs, notice the close coils to the head.

Lean back is not good due to worn system.

I cannot seem to zoom into the pictures, so cannot really see the cam chain lift, anyways the rocker carriers are off so any chain lift would tend to be reduced with the engine in this state.

The pistons picture, you can see an oil hole in the rod upper at the rear , Yes ?

You know of cmsnl and have a manual.

Could you take a picture of the flywheel again please.
I'll post a picture of the flywheel.
I didn't notice the hole in the rod.
 

·
Registered
Joined
·
9,796 Posts
Change out that coil. You need to have a maximum primary resistance of 1 ohm. Higher than that does damage to the CDI. The damage may have already started.
 

·
Registered
Joined
·
27 Posts
Discussion Starter · #16 ·
Change out that coil. You need to have a maximum primary resistance of 1 ohm. Higher than that does damage to the CDI. The damage may have already started.
Outch !

I tried whith my cdi and coil (which have 1ohm résistance) but nothing better.

And it was running before (it drives me crazy)
 

·
Premium Member
Joined
·
24,208 Posts
OK, the flywheel is stock. I wasn't concerned about it.
The coil as Dan mentions is the wrong one for a CDI ignition. It's fine for a points ignition system.
I'm not positive that advancing the cam 1 tooth will be ok but judging from the amount of offset in the retarded position I'd say give it a shot. You can change the position, adjust the tensioner and see where it lines up w/o rotating the engine. If the marks are closer to normal then I'd slowly rotate the crank feeling for any resistance of the valves touching the pistons.
I think your friend got seriously mislead on the backfire cause and you're correct that the O-ring leak was the source. Intake backfires are typically a very lean(vacuum leak) condition or a timing problem.
 

·
Premium Member
Joined
·
24,208 Posts
I don't know, it's more advanced than I was hoping for. I would go ahead and finish assembly with the rockers and valves adjusted. Then slowly turn the crank feeling for any resistance indicating the valves are touching the pistons. If that's good then I'd go ahead and try starting it.
You typed as I was looking at the pictures and typing.
We're missing something here, so let's review.
What's the compression now with the new rings?
What spark plugs are being used?
You've got spark and at the right time per previous post.
You've got fresh fuel
Are you giving the carbs enough time to fill after turning the petcock on? and is there sufficient flow from the tank?
 
1 - 20 of 52 Posts
Top