Help Needed: Cracked crank-case

[rory_gibson]

Hello people of the Hubb. Really hoping you can help on this one, although not holding out much hope!

So a friend and I spent the last 5(ish) months riding x2 Honda 125s from Ghana to the UK. Great adventure, sad it’s over but now I have a bit of a problem. One of the bikes was left damaged by some dodgy Moroccan mechanic.

Basically the mechanic in question over-tightened the drain plug (where the oil drains out the engine). In doing this, he generated too much stress/tension between the drain plug and the crank-case (where the drain plug screws into). As such, when I came to change the oil – and loosened the drain plug. Part of the crank-case had been cracked, to such an extent it literally broke off when the drain plug was removed. sorry I’m not good with technical terms, I’m new to biking but I will add some photos to help clarify.

Ideally, I would buy a new crank-case. However, the bike in question (a 2015 Honda Ace CB 125) is Nigerian made and I can’t get the part in the UK and don’t get any responses from any Honda Africa contacts I message. With that in mind, I’m thinking an aluminum alloy welder might be able to help – to rebuild the outside of the crank-case and maybe re-tap the plug hole? As I say, new to bikes. So not really sure if this is the right solution.

Financially, the bikes aren’t worth anything. However, sentimentally they definitely are. The little 125 brought us through 11 African countries and I owe it to the bike to try and save it.

If anyone can offer any advice it’s gladly welcome. Or, even better, knows of a cheap aluminium alloy welder in the Bristol area who mght be able to help.

Thanks in advance.

Rory

Oh and some photos below with explanation…

So the crank-case should look like photo the first photo

It instead looks like the second

Which means it doesn't create a seal and oil leaks out, as in the last photo

THANKS

[ccaa]

Maybe welding some very short pipe and on the other end of the pipe try to install some oil drain valve? Idea is to avoid further stress during oil changes. I am not mechanic.

[Maddin]

Hi,

maybe go to a machine shop and let them manufacture an adapter/bushing (see attached gif). This you screw in the rest of the thread and glue it in (with a glue/resin for high temperature). This bushing has than a smaller thread for a new/smaller drainplug. Bushing should be made from aluminium (same heat expansion than housing).

Cheers
Martin

[Warin]

I'd use Martins idea above .. but turn it upside down (so there is no interior lip to stop all the old oil coming out) and make it bigger in diameter so you use the same drain plug.

You will need to take the bare part to a machine shop and let them work on it. Glueing it might work .. depends on being firm enough to resist the torque of the bolt being done up and undone. Or you could have it wielded in ... on the inside surface as that will be better for sealing.

Cheap? Well that depends on your definition of 'cheap'.

Alternative? If someone travelling in northern Africa could buy and ship the part for you?

[Maddin]

Originally Posted by Warin

I'd use Martins idea above .. but turn it upside down

hm, I should have turned my image... Its meant to be mounted from below, you you would not need to dissassemble the engine for that.

and if you go to a welder, you want a good one, not a "cheap" one. Welding die-cast aluminium is not an easy task.

[navalarchitect]

Assuming you want a cheap fix given the low value of the bike I would just try using two part epoxy "liquid metal" JB Weld or similar. It's amazing what you can do with it - and the repair can be much longer lasting than the purists would like.

My process would be - roughen up then degrease the area as thoroughly as possible (including a generous margin around the damage), loosely fit the sump bolt, then build up the area with the epoxy. If you lightly grease the bolt you should be able to gently remove it before the epoxy sets hard leaving crude threads in it. In future then just gently tighten the bolt and use a bit of silicon on it as a sealant. Good luck (and please report back with how you solved it - is always nice to hear an outcome and learn which fixes work and which don't)

Sent from my Lenovo TB3-850F using Tapatalk

[g6snl]

As a complete bodge just to keep it running, maybe PTFE tape on the thread will be enough to seal the oil and prevent the plug from undoing? That way the thread area of the plug seals rather than the flat head part. Cost? about 50p now that is cheap

[richy-rich]

i second Navalarchitect idea, try and glue the piece back in with liquid metal. Id also take this as an opportunity to massively pimp your favourite bike ! i strongly suspect that any honda cb125 engine would go in. Then you can get the broken one on the bench, cleaned up and welded properly. Do some research you might find you can get a bigger motor in there, im not a honda owner so i dont really know whats out there. Id say dont be put off by any doubts you may have in your mechanical skills, this is the perfect opportunity to learn on a simple machine

[baldman1]

Go to a place that sells boat parts and get a rubber expanding plug, the type that is used in boat transoms.

[Redtape]

This is a non stress area and non pressurised oil holder.

So as mentioned the two part epoxy weld, JB etc will work, obviously an aluminium weld is better but costly.

However as a cheap easy one to do yourself is a visit to your local
B&Q (where you can also pick up that nice flowering pot plant for someone special in the garden section or that extra large roll of insulation you always wanted)

Or a plumber shop and pick up a compression coupler with lock
nuts and rubber washers, use this to cover the hole and then use a blanking cap to hold the oil back.

Metal and plastic parts are available.

I had a look at Screwfix and Toolstation both have the parts also

Compression Coupler Male 15mm x 1/2" or bigger as necessary.

Bolt though with large rubber/plastic washers and use the "Stop end" to finish the job.

Take your sump pan with you and play with the parts........

Have a FUN day out.

[mollydog]

I've seen JB Weld two part Epoxy do repairs on much worse damage than your bike. Follow Naval Arc. advice ... take your time ... it will work! The stuff is simply amazing!

[Tony LEE]

As long as there are four or five turns of thread intact and there are no cracks extending up through the wall of the crankcase, thread tape should do the job. Two or three turns of tape and then screw the plug in until it is firm or until the bolt head touches the crankcase but do not reef it up tight. The tape will seal without excessive torque on the bolt.
This section is called bodger fix for a reason.

[mollydog]

From the pics and description, looks as if it may CRACK further without good reinforcement. Before using thread tape, I would seal up any cracks and glue back in missing pieces that broke off. Once all dry and solid, then the thread tape would be good as you don't have to tighten it much for it to hold firm.

Other thing about cracks or weak areas ... if not reinforced, riding, hitting bumps
or rocks could easily crack the whole crank case wide open. One good shot could do it.

But if the JB Weld Two Part is done well ... and possibly in multi stages ... it could be pretty strong ... with luck ... YES, still a bodged fix!

[backofbeyond]

I suspect a welder would just want to be given the crankcase half to work on so that would mean an engine strip. I'd be surprised if you could find anyone willing to work on an upended complete engine. Even if you did get the area built up with weld it would then need to be milled back level so the sealing surface was flat. That's not going to be cheap in the UK and may well exceed the sentimental value of the bike.

Personally I'd go down the JB Weld route. The bolt's only purpose is to allow you to drain the oil so I'd firstly drill another smaller hole right through the bolt and tap a thread into it so another smaller bolt + fibre washer could be fitted / removed for oil draining.

I'd then clean up the entire area with solvent and epoxy the original bolt in place - including the thread area. If you have the pieces that broke away I'd epoxy those back in place as "spacers". Getting the whole area clean and roughened up to give the epoxy something to "bite" into would be crucial though. I'd even consider drilling some small holes into both bolt and crankcase mating faces to give the epoxy more interaction area. If you don't get it clean the epoxy won't do much more than a superficial stick.

There are various grades of epoxy and this (IMHO) is not one for the five mins or one hour stuff. You need the "takes a day to two but sets like concrete" stuff. Just don't get any of it dripping inside the engine!

[Tomkat]

I saw this thread a while ago and funnily enough was just thinking about it yesterday. If you're back home and not out on the road needing to rely on the engine a 'bodge' fix could well be the best thing for you. Obviously the 'Rolls-Royce' solution is get the broken area filled with weld, dressed back and re-threaded, but you'd need to strip the engine and take it to a good machine shop for that.

If you've still got the broken-off piece of case you could degrease the parts thoroughly then glue it back into place with Araldite. You need to use an adhesive that sticks with a very thin film or else the threads in the broken part won't line up. Of course, this won't be as strong as the original but by assembling the sump plug with lots of RTV you should be able to achieve a seal with relatively little torque. If you're worried about it backing out, drill the plug and lockwire it against rotation.