Part 3 of the engine rebuild for the red XR125L. In this update I get the piston and barrel on. I'm making a few modifications to this engine, which I will detail below.
Clutch cover, before painting. Need to give it a good clean first, and sand down any scratches.
Repainted, this is looking really nice.
Same treatment for the stator cover.
All dry and looking good.
The inspection cap for the flywheel was badly damaged, so will need to get a replacement one of those.
New kickstarter seal installed.
Need to get rid of the surface rust from the clutch arm. Evaporust is really good at this.
This made a big difference.
Reinstalled, and didn't forget to include the little plunger too.
Fully restored and reassembled. New seals for the kickstart shaft and clutch lever. Ready to fit.
Got a new cap for the stator cover. The restoration has made the plastic sprocket cover look a little tatty where the paint has rubbed through from your foot rubbing against it.
Plastic adhesion promoter and more engine paint.
Very very shiny whilst the paint is still wet.
Looking good once it's dried.
Back to the engine casing, in goes the gear shift shaft.
New woodruff key for the primary drive.
And the primary drive gear goes back on too.
Next I want to get the barrel on, but before I can do that, I need to check the ring gap.
Smack bang in the middle of the acceptable range.
Piston ring pliers for putting the rings on the piston, and piston ring compression tool (motorbike style so I can remove it from the bottom of the barrel) for getting the piston into the barrel.
So..... this may be controversial. I'm fitting a big bore kit. To a 125. I have a full 'A' license and I will inform both the DVLA and my insurer of the change in displacement. But the technicalities of fitting the kit are where it gets interesting. The kit isn't designed for the JC30E version of the CG125 engine, it's designed for all the versions before that. The difference is that the JC30E version has a small oil gallery that goes out of the casing, into the barrel, round the side of the barrel and back into the casing. It's to supply oil to the cam pivot. You can (sort of) get away without it... if you like replacing your cam and pivot (this is not OHC, the engine is OHV, but is "cam-in-block" to use a car term). I don't want to do that. In the above spreadsheet I work out the compression ratio using the stock barrel, extrapolate the new compression ratio changing the bore size. This increases the compression ratio (not necessarily a bad thing). But, if I use a custom base gasket of a material I can cut my own gallery into, I can fit the "big bore kit" and still keep the oil gallery, whist still keeping the compression ratio the same* as stock (it drops from 9.5:1 to 9.3:1). Several people have fitted a big bore kit without making the customisation and had 1,000 plus miles before they had accelerated wear related issues (anecdotally) but I don't want to risk it. YMMV, IANAL, etc.
Let's make a custom gasket! Start with a stock base gasket as a template.
Traced onto a suitably thick sheet of copper.
New metal cutting blade for the fret saw.
Cut out.
Drill some holes, and mark the bits to cut out so you don't do something stupid...
Finish with files and some sanding.
Now the fun part. According to eBay, these are "carbide" burrs... I beg to differ, but anyway...
Into the multitool thingy you go...
And let's cut an oil gallery!
It lines up with the inlet and the outlet. N.B. The outlet from the casing has a restriction because this branch is before the oil goes up to the head, so Honda wants WAY more oil going to the head than down here, so I'm happy my gallery has more than enough cross sectional area to flow the oil.
Fits the barrel (I didn't line it up very well for the photo, it lines up perfectly, honest).
And lines up on the casing.
I installed my roller cam followers too (stock are just sliders). The barrel is ready to go back on.
Barrel installed.
Temporarily install the kickstart lever to make sure the engine turns over ok. Everything's fine. Nice :)
Rebuilt oil pump (new rotors) and clutch basket (new clutch discs and plates, as well as lifter bearing) go on and are torqued down.
Cleaned centrifugal oil filter ready to install.
That's installed and torqued (gasket and cover not shown, but they were fitted after this photo). Next the cylinder head.
Again, slightly controversial, but I'm using a JC27E cylinder head from a CG125. I couldn't get a JC30E cylinder head and this engine is being made up from parts. The JC30E cylinder head used on a CG125ES doesn't have the top engine mount, where the JC30E head in an XR125L does. The compromise is to use the head from a JC27E CG125(W?) since that does have the top engine mount. The only difference is I lose the PAIR valve port and slightly larger valve stems (5.5mm instead of 5.0mm). Not an issue, I can live with these differences. First I need to clean it up and inspect it before I put it back into service. This is cleaning the carbon deposits off the valves.
Next I want to take the valves out so I can inspect the seats and guides, and replace the valve stem oil seals, so out comes the valve spring compression tool.
Squish, squishy.
Well, fsck. That's a chipped valve seat. To be continued...
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