I think I have a problem with one of the conrods - HELP

[McCabe-Thiele (Ted)]

Hi Ted,

I found that using a small paint brush dipped into a shallow cup of cellulose thinners, then gently brushed over the Hondabond joint face and left for 5 minutes, will soften it dramatically, sufficient to wipe off with a cloth.

Do you know what big end shell colour was installed previously ?

Dennis

Thanks Dennis I did that this morning its coming off quite easily especially as it isn't baked on hard. Ted

[McCabe-Thiele (Ted)]

At least you caught it early Ted. If the engine had been fully built up and in the frame that would have been soul destroying.
As you say it has only cost a bit of Hondabond (and it goes off in the tube anyway so at least you are getting VFM!) and time. The bright side is you will know your way around the engine and it's all part of the learning process.
Good luck finding the problem and I'm enjoying the posts.

I was really nervous when I assembled the crankcase halves for the first time - adrenaline rush _ I was elated when it went smoothly until I found the conrod issue. Now tbh I feel more confident for next time! Ted

[400 Cafe Racer]

Hi Ted,

Glad that the Hondabond tip helped you. Thinking about the Conrod bearing issue. Keep a note of what is being changed, but if I had the problem I would swap the shells from one of the unaffected rods and see if this resolves the problem. If so, it could be the problem shells are in some way defective. This is all assuming that there is no contamination behind the shells when you dismantle.

To measure your crankshaft journals  for ovality or taper, you need an external mic for the crankshaft. Ovality - measure at several places around the centre of the circumference of the journal. Usually most wear will occur at the “top” of the journal due to thrust on the power stroke of the engine, measuring at 90 degrees to this gives the ovality.

Taper is measured side to side.

Conrod ovality and taper are measured in a similar way but with an internal mic or dial test mic.

Hope this helps.

Regards

Dennis

[McCabe-Thiele (Ted)]

Hi Ted,

Glad that the Hondabond tip helped you. Thinking about the Conrod bearing issue. Keep a note of what is being changed, but if I had the problem I would swap the shells from one of the unaffected rods and see if this resolves the problem. If so, it could be the problem shells are in some way defective. This is all assuming that there is no contamination behind the shells when you dismantle.

To measure your crankshaft journals  for ovality or taper, you need an external mic for the crankshaft. Ovality - measure at several places around the centre of the circumference of the journal. Usually most wear will occur at the “top” of the journal due to thrust on the power stroke of the engine, measuring at 90 degrees to this gives the ovality.

Taper is measured side to side.

Conrod ovality and taper are measured in a similar way but with an internal mic or dial test mic.

Hope this helps.

Regards

Dennis

I have removed the shells from No2 Conrod - the two green shells were batch coded differently as DOE A & D10A both have the green edge markings in place. They do not have any drastic looking binding marks to me ?
Not sure what more experienced folk here have to see when looking at the pics.

Other thing I have found is the bare conrods have what looks like burnt circular bands of burn oil on them on the surface where the shells mate.

I have cleaned this off completely with some fresh Brasso Wadding - re-fitted the cleaned shells with some light oil.
Haven't time now to Torque them up as I have to see the Nurse to have some sutures removed shortly.

Will update my progress later today or tomorrow.


.Number 2 conrod shells by Macabe Thiele, on Flickr

[McCabe-Thiele (Ted)]

This is the staining on the conrod journals I have mentioned there are no grooves its just burnt oil I guess.

I have cleaned it off with some Brasso Wadding re-fitted the existing shells to No2 - re-plastgauged - reading 25 microns as before.

Removed all traces of Plastugauge from the shells - re-fitted with Red Lube - torqued up the bolts...... no high spot at all it rotates freely like the other three big end bearings.
For peace of mind I have cleaned all four conrods whilst the casing is split.

On Sunday by BiL is visiting in the morning to have a look before I close up the crankcase again.

staining on conrod by Macabe Thiele, on Flickr

[Bryanj]

If it now spins free and the clearance is OK I would say you have sorted it, doesn't take much to loose the clearance, had somebody oil the back of the shells once and that caused problems

[McCabe-Thiele (Ted)]

If it now spins free and the clearance is OK I would say you have sorted it, doesn't take much to loose the clearance, had somebody oil the back of the shells once and that caused problems
[/quote
Looking back I just don't know why I didn't clean the bearing faces - I did Evaporust the outside light surface rust from the conrods ages ago - just missed cleaning this bearing surfaces. I also double checked the mains for any high spitting as I had rotated the crank quite a lot.

Had I Torqued the crank on the bench I might have found the problem before fastening up.