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Hi Ben.

C700 ?

You know of CMSNL.com for the exploded views...

Converted to cdi, does that system automatically advance the ignition with revs ?

You have a strobe signal check timing marks on the alternator rotor.
 

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Also, remove plugs and look at the piston crowns. They may be a bit coked by now, but can you see any bright alloy in valve pocket area and crown periphery, made by contact with valves or head ?

Have the spark plug gaps closed up at all ?

I assume engine is tight in frame and stuff like number plate is not vibrating .
 

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Could you take a vidio from a bit further away please and at revs so the nouise/vibration can be heard please with bike on centre stand. Yes it will be messy with some oil loss.

I assume you can see the timing marks clearly so no over advance.
Can't see the tdc reference mark/tab on the stator. Rotor wobbles a bit ?

Intrigued about welded on crank reference ?
 

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If you can acquire a spare alternate rotor cover, you can drill a suitable hole in it to reduce oil exiting the engine and still do the strobe timing check. You could also made a see thru window from plastic to stop all oil exiting.

Alternatively if you can get some plexiglass sheet and make a see thru cover....

As it's not often needed too check ign timing, a little oil loss and mess is tolerable.

You say no bright alloy showing on piston so no piston/valve and piston/head contact, which is good, but I wonder how the cylinder head gasket was altered due to bore size increase, perhaps a new gasket was made, from some copper sheet perhaps ???

Anyways a better vidio and sounds of engine revving to hear the noise yiu mention....

I notice a few chewed screws and nuts, hope that's not a bad sign...
 

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What rpm is the vibration occuring ?

What sort of noise is it ?

Does it vibrate in every gear or just in top gear ?

How is the rear wheel drive chain ?

I assume stuff like tank rubbers are good and the tank is not touching the frame etc..

Plug gaps look a bit wide.

Colour looks a bit on the weak side.

Left plug thread looks troublesome ?

How is that cylinders plug hole thread ?

You have a plug hole thread cleaner/chaser ?

Be extremely carefull with that plug hole...always start plugs into plug holes by hand...

Picture of engine from a little further away, to show timing pointer on stator.....

Just to clarify, cam chain is on left of engine ?

To hear the noise at the vibration revs would be good.

You sure it's not wheel vibration or exhaust system vibration ?

From memory handle bars are rubber bushed ?

Will check on CMSNL with your bike details given.....

Another busy day for me so back much later...

Over....
 

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Well well well, seems that CMSNL cb125k3 handlebar exploded view has a mistake.

View part 6 looks like rubber cones but in part numbers list part 6 us a steering head race cone....

I personally do not remember this model which may have been a bit rare in UK.

Pistons in phase, they go up and down together, so may have "bad vibes" at revs, no balance system other than crank webs etc..

Cb125s, a very popular single cylinder bike in UK was not really a "bad vibes" bike from memory. It also had cushed handlebars.
 

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Well well well, seems that CMSNL cb125k3 handlebar exploded view has a mistake.

View part 6 looks like rubber cones but in part numbers list part 6 us a steering head race cone....

I personally do not remember this model which may have been a bit rare in UK.

Pistons in phase, they go up and down together, so may have "bad vibes" at revs, no balance system other than crank webs etc..

Cb125s, a very popular single cylinder bike in UK was not really a "bad vibes" bike from memory. It also had cushed handlebars.
 

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Hi Ben,

Only one vidio showing the tdc reference wire pointer ?

Seen your picture of the cdi crank position sensor......

So there is some "wobble" of the alternate rotor, but it's within spec ?

How much of a wobble is it ?

1mm or more ?

Also some end float seen, in and out movement, how much is it please ?

The rotor timing marks are a bit difficult to see in your vidio, but you may see them very clearly. You sure they are to spec and not over advancing ?

So no frame and cycle parts vibrating badly making a buzzing noise.

The ign " bolt" welded to the crank may be an issue, adding or subtracting to imbalance, but it will have some effect.

As you know, it's mass may be small, but a 5k revs, it's "effective mass" may be considerable. What's done is done.

Do you have the old parts to convert it back to points ignition ?

Cylinder head gasket protrusion into the combustion space may be/could cause an issue but you are confident the piston crowns do not make contact.

I wonder how the head gasket sealing ring is surviving it's "torture"....

Back later after chores and a re read of your last post....
 

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Hi Ben, I will have a proper view later this evening, I must crack on with the car, due for its annual mot test very soon. An annual safety inspection.

Do you have Vernier gauge it can measure endfloat ?

If not even a long bolt and nut, to record difference between in and out. A know pitch and number of degrees but turns to show difference...

A bit noisey here so audio not heard, cam chain very slack...

Can you take a picture further back to show top and bottom of engine please ?

Some more chewed screws seen....back later, 3 hours of daylight left. Coffee break over, back to the grindstone...
 

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Hi Ben, yes it's always helpfull to say a few "please God's". Once all the press plates where made the bearing replacement was all good, but the gauge said 4 tons to press out. A tight fit. Refitting was drama free. Both sides underneath on the front all done. Check service back end next then it's drivers seat, a little wobbly. Then all the simple stuff and get it booked in for its test. The aim is pass with no advisories as always.

Back to your bag of sweets.

You tube vidio not showing at all.

No picture of whole engine.

Would like to see vidio and listen to text.

A "still" picture of crank cam chain SPROCKET would be nice. Straight on, not a slight side view please.

Any strange noises when in gear and "drive" condition, IE throttle open, "over run" condition, IE throttle closed, and cruise condition, IE between the two conditions mentioned. Noise on clutch side perhaps......

Did you get endfloat measurement, even using a ruler ?

Looks more than one 1mm ?

I have some info but that's for after seeing/hearing vidio, and whole engine picture.

Take a measurement, ruler method you should be able to measure at least to half a mm reasonably, maybe 1/3mm or more ( less actually )...

Even a pair of dividers perhaps...

In your timing light vidio a remember seeing end float dancing, and wobble...

By dancing I mean seeing the rotor dancing in and out a bit.

Also, any evidence of a 3 leg puller being used to remove the alternator rotor at all ?

I hope you used a "bolt" the same size and thread as a "bolt" found on your bike perhaps ?

Over......
 

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Hi Ben, seen all the vision now, loved the slow motion one, and the noise !

Very rhythmic clunk.

Mark the alternator rotor "timing mark face" with a black reference line and re take a vidio. I presume your slowed the vidio via computer ?

Really good idea and very " telling" !

Out in the sticks you have to be resourcefully, adaptive, creative, inventive and all those other words and skills of a similar nature.

Dam good idea, we can all learn from that one.

I do not have specific data/info for your cb125k3 other than what is shown on CMSNL. I have another book to hunt down just in case info is in that one.

End float, in and out movement, axial play.....

Looking on CMSNL, the two main bearing crank ( with large centre rotating mass/flywheel, similar to old triumphs etc. ) Are roller type, in fact all the bearings, main and big end are roller type.


The primary drive gear which drives the clutch basket is "helical " not a straight cut gear, so during "drive" and "over run" a "thrust" is imposed on the crankshaft.

As far as I can see this thrust is controlled by a "washer".....

Looking at a picture of that thrust control ring, "washer" , it doesn't look very thick. I wonder how worn that is, or is it missing perhaps ?

End float looks a bit excessive to me.

Up and down play, radial play, again looks excessive to me.

Definite "wobble" in alternater rotor, damaged by a 3 leg puller ?, It something bent ?

Heat distortion due to that welded on "bolt" maybe ?

The picture of the engine in frame ( loose ) probably taken during assembly. Usually when engine at tdc, the cam sprocket "O" and the crankshaft "key" line up. By that I mean a line ( or straight edge, bit of string ) can get drawn thru cam shaft centre to crankshaft centre, lining up with the cylinder centre.

That's "usually" what can be done, but not always.

One of the cam sprocket bolts looks odd and I cannot see the O mark.

One of the final drive chain sprocket bolts look odd also, which can cause a problem.

Is the cdi unit "Arduino" based ?

So quite a worn engine really hut it is years old.

Why did they go down this route when the engine had points ignition ?

Why not "transistorised" points ignition, it getter still, why not light or hall effect triggered cdi system.

There is room on the oe points base disc for either, requiring a different points cam/advancer unit, or utilising the oe "twin cammed" advancer unit.

You know of xl125r I think, that has the cdi system sensor with centrifugal advancer, cam shaft driving, which "looks" as if it may fit the camshaft sticky outy shaft ?

Where do all the dead machines go to on your small island ? I found your island in the atlas.

Perhaps if there is a breakers yard or collection point for "scrap" and dead machines on the island, you should spend some time there ?

Anyways, what's done is done.

Use the bike avoiding the bad vibration period.

Avoid using instant gasket. Banana boxes have a usefull sheet of useable relatively thick cardboard that I have used, and still do, to successfully make gaskets, that work well and contain oil.

Phone battery dying now so back tomorrow, a new day.
 

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Hi Ben, seen all the vision now, loved the slow motion one, and the noise !

Very rhythmic clunk.

Mark the alternator rotor "timing mark face" with a black reference line and re take a vidio. I presume your slowed the vidio via computer ?

Really good idea and very " telling" !

Out in the sticks you have to be resourcefully, adaptive, creative, inventive and all those other words and skills of a similar nature.

Dam good idea, we can all learn from that one.

I do not have specific data/info for your cb125k3 other than what is shown on CMSNL. I have another book to hunt down just in case info is in that one.

End float, in and out movement, axial play.....

Looking on CMSNL, the two main bearing crank ( with large centre rotating mass/flywheel, similar to old triumphs etc. ) Are roller type, in fact all the bearings, main and big end are roller type.


The primary drive gear which drives the clutch basket is "helical " not a straight cut gear, so during "drive" and "over run" a "thrust" is imposed on the crankshaft.

As far as I can see this thrust is controlled by a "washer".....

Looking at a picture of that thrust control ring, "washer" , it doesn't look very thick. I wonder how worn that is, or is it missing perhaps ?

End float looks a bit excessive to me.

Up and down play, radial play, again looks excessive to me.

Definite "wobble" in alternater rotor, damaged by a 3 leg puller ?, It something bent ?

Heat distortion due to that welded on "bolt" maybe ?

The picture of the engine in frame ( loose ) probably taken during assembly. Usually when engine at tdc, the cam sprocket "O" and the crankshaft "key" line up. By that I mean a line ( or straight edge, bit of string ) can get drawn thru cam shaft centre to crankshaft centre, lining up with the cylinder centre.

That's "usually" what can be done, but not always.

One of the cam sprocket bolts looks odd and I cannot see the O mark.

One of the final drive chain sprocket bolts look odd also, which can cause a problem.

Is the cdi unit "Arduino" based ?

So quite a worn engine really hut it is years old.

Why did they go down this route when the engine had points ignition ?

Why not "transistorised" points ignition, it getter still, why not light or hall effect triggered cdi system.

There is room on the oe points base disc for either, requiring a different points cam/advancer unit, or utilising the oe "twin cammed" advancer unit.

You know of xl125r I think, that has the cdi system sensor with centrifugal advancer, cam shaft driving, which "looks" as if it may fit the camshaft sticky outy shaft ?

Where do all the dead machines go to on your small island ? I found your island in the atlas.

Perhaps if there is a breakers yard or collection point for "scrap" and dead machines on the island, you should spend some time there ?

Anyways, what's done is done.

Use the bike avoiding the bad vibration period.

Avoid using instant gasket. Banana boxes have a usefull sheet of useable relatively thick cardboard that I have used, and still do, to successfully make gaskets, that work well and contain oil.

Phone battery dying now so back tomorrow, a new day.
 

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Hi Ben, grey skies for you, it's raining 45 degree cats and dogs here today and after 20 minutes on the car I am cold and wet !

Do the cam sprocket bolts faul the alloy cam sprocket cover ?

It's a bit risky running the engine with that cover off as it controls cam shaft end float !

Since you are going to the expense of getting a new unused crankshaft, which I hope is in a wooden box or similar, get new cam sprocket and chain and the cam sprocket bolts.

How is the cam chain centre spreader, the large rubber wheel riding on the special bolt below the spark plug on the cylinder ?

It may be an idea to replace it anyway, along with the two rubber rollers/idlers/cam chain adjusters.

How is the
 

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Internet being a real pita again...i don't get this get this problem in emails
How is the rest of the cam chain adjusting mechanism, all good ?
You getting parts to restore points ignition ?

Research CMSNL for that thrust washer and peg spanner to remove the primary drive gear...

Back to the animals for me, back later....
 

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Coffee break and warm up....

The carb slide needle, top, middle or bottom groove for the little clip ?

You do have the air box/filters connected ?

Don't forget to check on CMSNL.com, you don't have to buy from them, the views are free to view.....

Also think about making a copper head gasket from sheet copper of a suitable thickness, not paper thin.....

As you know c90's have a copper ring head gasket and rubber seals.......
 

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Coffee break and warm up....

The carb slide needle, top, middle or bottom groove for the little clip ?

You do have the air box/filters connected ?

Don't forget to check on CMSNL.com, you don't have to buy from them, the views are free to view.....

Also think about making a copper head gasket from sheet copper of a suitable thickness, not paper thin.....

As you know c90's have a copper ring head gasket and rubber seals.......
 
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