KX125-H2.. where to (re)start?

[JamesPoulton]

Hello!

A couple years ago I was working on my dad's old KX125. I had a very long thread on here full of friendly people helping out and offering advice. With one person even coming to my house and letting me borrow tools (shoutout to 72degrees).

We got the bike running, but were slightly concerned that the crank seals were shot. I had moved on to the brakes but I then had to pack up and move house. The bike went in to storage and my new house doesn't have a garage. So it sat in storage for 2-3 years and I've now finally got it out and am able to work on it again. I was planning on finishing taking the caliper off/apart, cleaning it and rebuilding it, as that's what I was in the process of doing before packing up. However after that I'm not sure what I should do, and what I should check in terms of the bike after it sat. There's no fluids in it, so I couldn't check if it ran but I'm assuming it will at least run. Perhaps I'll have to clean the carb..

Other than that I'm open to any suggestions. There was talk in the old thread about also having to do suspension work.

So, in general I'm looking for any advice on the brakes, otherwise I'll probably just strip it down following my manual, clean it out and rebuild it. Also I'll need some suggestions on what I should do next. 

Here are some pictures, I'm just so happy to be back! 

 

[72degrees]

Looks like you have made a start on a good working environment.

The brake pads look fine. The caliper pistons may be stuck. First thing would be to see if they move at all. Remove the pads and master cylinder cap.  if the pistons will push back in to the caliper and you can then pump them out again with the brake pedal (but not too far yet)  it's worth changing the brake fluid. Otherwise at least the caliper (hoping the master cylinder is OK) will need stripping down and cleaning up, plus probably new seals and possibly pistons.

It's possible to change crank seals without splitting the cases and it's possible to split the cases using a tool other than the official one  (using a flywheel puller and suitable screws/bolts) but I've never done either. I recently did a full engine rebuild on a Morini (right down to the crank) but 70's designed four strokes are easier to part and reassemble the crankcases on.

Come on you other two stroke experts (particularly KX125) out there in Thumpertalk land, give James some encouragement. Any assistance I can give these days is limited. Currently have a broken finger and thumb from dropping my Morini 350 speed hill climb bike last weekend. Cold tarmac and a cold, confessedly old, front tyre don't do much for demon braking. Can't twiddle spanners very well for a while

 

[JamesPoulton]

1 hour ago, 72degrees said:

if the pistons will push back in to the caliper and you can then pump them out again with the brake pedal (but not too far yet)  it's worth changing the brake fluid. Otherwise at least the caliper (hoping the master cylinder is OK) will need stripping down and cleaning up, plus probably new seals and possibly pistons.

From what I could tell, there's not actually any fluid in the rear brake system. I couldn't tell 100% though. Why would the piston need to be replaced? I didn't know that they were consumable parts, I just thought the piston chooched back and forth and pushed the pad. Looking on wemoto they have rebuild kits for the cylinders, I'm not sure if I'd need that, along with piston and seals kits. Would it be worth replacing the hose too? It doesn't look like it would actually be that expensive to just rebuild the entire brake system. I'm sure sitting for a total of 8 years can't have done much good for an already 26 year old bike. But just because it's not expensive doesn't mean I want to do it unless it's a good idea to.

 

2 hours ago, 72degrees said:

It's possible to change crank seals without splitting the cases and it's possible to split the cases using a tool other than the official one

I had a little  bit of a google search after you said there was a tool for it, and it wouldn't be too horrible even if I did have to buy one. I want to get this bike in to as good of a condition as possible, if I'm going to work on it, then I don't want to do it halfheartedly. Whether I ride it or sell it, I'm going to be a lot better off if i don't cheap out on things I feel. Whether that means spending money on extra tools, replacing seals and bearings that could possibly not be replaced but it would be better off changing them (i.e. the questionable output seal). If I put pride in to my work and do it properly, I'll be left with something to be proud of at the end. If I cheap out on things then once the bike is together and "finished" it'll always be on my mind "what about that one seal" or "what about that bearing". 

A prime example being that crack in the cylinder that was probably okay to not repair, but would have been nice to. I couldn't at the time because it would have been my entire budget. But as I think about it now I wish I'd got the cylinder replated and I'm actually contemplating doing it now that I have more of an income.

 

2 hours ago, 72degrees said:

Any assistance I can give these days is limited

Can't twiddle spanners very well for a while

Sorry to hear about your fingers. Though I wouldn't have been expecting you to come over to Birmingham again like you did before anyway, just helping online is more than enough. Unless you're just missing working on thumpers ? 

[72degrees]

Brake caliper pistons can corrode to the point that they don't work properly even with new seals. The hose could be getting a bit soggy by now. A new non OEM one is probably available, or Hel will make you one to match. I had to put new seals in the 1982 Morini I just got ready for hill climbing but the pistons were OK. On the other (1980) one I have it needed new pistons a couple of years ago. The 1982 bike had been sitting in a Spanish barn for years though which is probably warmer and drier than here. You could try just putting fluid in. A small bottle of not fancy stuff DOT4 shouldn't be expensive from a motor factor. If the system is empty though you would have to bleed it before any chance of signs of movement. The easiest way, however, to get the caliper pistons out to check them and the seals properly is by pumping them out with a filled system. Otherwise you are looking at motorcycle caliper piston pliers, or using a grease gun (messy) or compressed air (possibly scary). First perhaps see if the bleed nipple on the caliper will loosen without shearing off, seeing as it has been undisturbed for years (the Plusgas may be useful for this).

Having the cylinder re-plated is pretty expensive, but I understand what you mean. Standing so long it may be main bearings and gearbox bearings are beginning to rust. Once you start aiming for a 100% checked out engine you really need to split the crankcases. There may be gearbox bushes that are past their best. Bearings are cheap and easily obtained from bearing suppliers (no need for Kawasaki branded unless they are a very special unusual type). Bushes are trickier, as some are not just plain. I had to put some 'good used' ones in the Morini because new ones weren't available and I couldn't get any made.

Still got a couple of (small)  thumpers left and a long list of jobs that need doing on all the bikes except the ER6 once my hand heals.

 

[JamesPoulton]

6 hours ago, 72degrees said:

...

 

Given that it's only £21 to replace the rear piston and seals I might just go ahead and do that. I know that the front brake works because it's what I've used to keep the bike under a bit more control when actually moving the bike. Though I would probably want to have a look at the front too at some point and at the very least change the fluid and maybe the house (the manual says to do it every two years I think it is, or maybe it's three. A Hel hose is £29 on Wemoto, including my choice of colored hose and banjo so I can get some free style points ? I do have an old bottle of DOT4 that was just in the mix of everything, way back when I first moved everything out of my Dad's garage. However I'm not sure if using old stuff from an unsealed bottle would really be a good idea, even if it was just for testing/removing the piston. I did see in the manual about removing it using compressed air if using the brake system itself to push it out isn't an option, however I don't yet have an air compressor so that's not really an option. Unless I took it to work and did it there. What about the cylinder? Should I be looking at rebuilding that too or is it unlikely that's worn? If I'm replacing the piston and line, the back of my mind tells me I should do the cylinder too but that could just be my inner completionist talking.

 

I remember from before that getting the cylinder redone would have been around £100.. maybe £90 or maybe £110 I don't remember the specifics. I know I'd have to split the case, I actually just now got an email from Rocky Mountain ATV, because earlier today I asked them if they ship to the UK as I was interested in buying a crank puller that they sell as it seems to be better quality than anything I could find from UK stores. I feel like I should at least be looking at the crank seals and bearings. Even if I didn't replace much, after it sat for so long inspecting it can't be a bad idea right?

 

I know I was just teasing you ?  I am of course grateful for any help but I wouldn't ask you to come over again. 

[72degrees]

Old DoT4 would do to pump the pistons out, you may have a problem bleeding the system. Is the bleed nipple OK?. You would obviously use new fluid after changing any seals etc. required. The master cylinder isn't quite so exposed to muck and water so may be OK. You'll get an idea if you just try re-filling and bleeding.

A crank puller isn't something you use a lot unless you intend to rebuild a lot of engines. Some people fabricate their own. It could be a welding project. Don't always judge things by immediate appearance (RIP Robert Pirsig).

http://www.homemadetools.net/homemade-motorcycle-crankcase-splitter

Knowing the internals of an engine are 'checked out and known good' is always a worthwhile idea. The problem is you may find more horrors and the parts list bill will rocket. My Morini big ends were so bad that as well as a crank regrind it needed new connecting rods (big end eyes gone oval).

[JamesPoulton]

14 hours ago, 72degrees said:

the bleed nipple OK?

I've not been able to check anything yet, the bike is in my grandparents garage as I don't have one at my house. I don't get chance to go there as often as I'd like. I'm thinking of getting a compressor soon anyway so I wouldn't need to put fluid in and bleed it, just to then empty it again. Would just be able to push the piston out with air once I got it on the bench. My first purchase is probably going to be a piston and seals, so I could get the caliper cleaned up and rebuild. Then a new hose in a couple weeks time so I could get the caliper put back on, then that's one thing ticked off that I know it's done fully. The problem I have is that I don't live close to them like I said. So it's not really an option to just go out and look at the bike to see what I need. I want to go there and have something to actually do for progress. So I'd like to order parts, then go out there when I have those parts and fit them, and see what I need for next time. Then go home, order the next parts during that week, go out next weekend and repeat. However what I can do is ask my granddad to go out and look at the bike and send pictures for me, or to do small things. 

14 hours ago, 72degrees said:

A crank puller isn't something you use a lot unless you intend to rebuild a lot of engines. Some people fabricate their own. It could be a welding project. Don't always judge things by immediate appearance

Would I not need a puller to pull the crank back in to the case? Is there other ways of doing it? 

I know not to judge things on their appearance but a case spliter seems like the kind of thing you'd want to have minimal flex otherwise it might bend unequally and mess something up. From what I could read in articles and such it's very important that the force be applied straight on to the crank, and square to the case. Not at an angle. And when I'm looking at the tool and can see that the welds are much smaller on one version of it compared to the other, it doesn't fill me with confidence. However I've found this one https://www.machinemart.co.uk/p/laser-4882-motorcycle-crank-case-separator/ and it looks like it might suffice. 

 

14 hours ago, 72degrees said:

The problem is you may find more horrors and the parts list bill will rocket

But surely it would be cheaper in the long run to find the problems now and replace the individual broken parts, as opposed to not actually look, not know things need replacing. Then wait until it becomes a noticeable problem and have to replace them anyway, along with having to fix any other damage that was caused? For example slop in a bearing may cause a shaft to wobble and damage gears? 

[72degrees]

Looks like a decent tool.

You are supposed to press the crank back in, but I expect a piece of suitable thick walled tube and a large vice, or a carefully wielded soft faced hammer might do. Things can often be done without special tools by getting inventive, but that may indeed carry risks. Probably best you have a good look in the workshop manual you have before delving in to the bottom end. For example, If the main bearings come out with the crank you may need a bearing puller. I've never done a 2T bottom end, only four stroke singles or twins. I managed to do the 4T Morini without having to buy many special tools. That's a 70's pushrod engine though so pretty simple. It still needs special tools for things -  like the ignition rotor  puller and the oil pump gear drive nut wrench.

Naturally, you would want to replace anything that need replacing. The problem is that on a machine that old, new parts, other than bearings, may no longer even be available.  If the big end is suspect there is no way you are going to be able to fix that at home. I know a place not too far from you that could fit a new rod, or an exchange crank may be available. You could, however, easily end up spending way more on parts, just on the engine,  than the bike is ultimately worth. Morinis are getting very sought after, so I reckoned it was worth doing on a 1977 350 engine.  I know that particular KX125 is worth more to you than just its monetary value though.

 

[JamesPoulton]

50 minutes ago, 72degrees said:

You are supposed to press the crank back in

I am actually already looking at buying a press, just a small bench mounted one. There's one with 335mm between the press and the bed, which would probably be enough. Or even making my own, with a bottle jack and some steel. There are guides for doing so on YouTube and various other sites. A press seems like a useful thing to have both for mechanic work and general workshop use. 

I wouldn't want to go straight in to the bottom end, but I was saying if the seals do need to be replaced (which they likely do but I'd like to make sure) then I'd want to do it properly, and then while having it apart I'd want to do it properly and replace things. As far as parts go, I have near enough a whole bike in parts, including an engine with seals and bearings. There's also Kawasakiparts4u.com which have everything listed, every single part. But there's no indication of whether things are in stock or not. That's where I got the power valve part from last time though, it wasn't for the correct model but they found me one  that worked. I'm imagining they would be able to do the same for other parts if necessary.

I remember we checked the bottom end for play when we had the top end off, and there wasn't any up and down so it was acceptable. I'm sure there'd be other tests that would be possible once I had the crank actually out though. 

As you said, I'm not only focused on the monetary value for the bike either. I don't mind spending money on it. I'd even be able to make parts to a certain extent. I have access to milling machines and lathes.