On this page I'm going to add photos of engines that I rebore, whenever I can remember to photograph them that is! Most of the time I'm too busy concentrating on the job at hand to spend time getting the camera out and take photos, but when I do I'll make sure to include them on this page. That way you can see the range of bore sizes my equipment can handle, and the different types of engine that I work on.
These are some pictures of a Honda CA50 engine that I recently rebored. The engine has a standard bore size of 40mm (1.5748"). The customer supplied the new piston that was 0.5mm (0.020") oversize, and I had to bore and hone the engine to match the skirt diameter at 90 degrees to the gudgeon pin, plus 0.034mm - 0.038mm, which equates to (0.0013" - 0.0018"). The piston skirt size plus clearance as stated in the manual actually more or less tallies with standard size + 0.020". With the cylinder bored I honed it to match the size required, and used a feeler gauge of 0.0015" as my go/no go measure.
In the last picture below you can see the 0.0015" feeler gauge inserted alongside the piston at the inlet side, as stated in the manual for the machine. As you can see, it went in, but was not loose, and the piston didn't slide down the barrel as it would have done if I'd honed it any larger.
Some stills of the Lotus Elan I rebored in the chassis a few months ago. This engine has a standard bore size of 82.5mm (3.250"). There are more pics of this engine on the 'In Situ' page. Here's a link to a short video of the engine being rebored. https://youtu.be/kzeWYh-gjSA
1. In the first pic you can see the damage to the side of the no. 3 cylinder even at 0.060" oversize.
2. In the second pic you can see what the engine looked like after I'd resleeved no. 3 cylinder, and then bored all cylinders out to a matching size of 0.020" oversize.
3. In the third pic you can see the finished block, with all cylinders honed out to the correct size and finish.
These are a few pics of a Honda CG125 engine I rebored for a customer. The standard bore size of this engine is 56.5mm (2.2244"). I've included these pics specifically because there was a problem with the cylinder. If you look closely at the pics you can see that about an inch down from the top of the steel liner there is a horizontal mark that shows as brighter, shinier, and from some angles, darker than the rest of the bore.
This marking is caused by porous imperfections in the original casting of the steel liner. Nothing can be done about them other than to try to bore them out and reach better metal beneath. I had to bore the cylinder to 1mm (0.040"oversize) in order to clear the porosity on this barrel, but I'm happy to say it did clear at that oversize.
1. In the first pic you can see what the porosity looked like at .5mm (0.020") oversize
2. In the second pic you can see what it looked like at .75mm (0.030") oversize
3. In the last pic you can see that the porosity had almost entirely gone at 0.99mm (0.0389") oversize, and by the time I'd honed the cylinder to the exact 1mm (0.0394") it was impossible to see. (Sadly I forgot to take any pics of the barrel once I'd honed it. Doh!)
These pics are of a 3 ltr straight six Toyota Supra I recently rebored in the chassis. The standard bore size of this engine is 83mm (3.2677"). In the pics you can see some of the work I had to do in order to overcome damage in no. 4 cylinder.
1. In the first pic you can see that the no. 4 cylinder is a different colour from the others, indicating there was a problem.
2. In the second pic you can see more clearly the scoring in that cylinder. (no. 4 piston had two broken rings and the land between the two rings had also broken away from the main part of the piston)
3. In the third pic you can see that the cylinder cleaned at 1mm (0.040") oversize.
4. In the fourth pic you can see what all the cylinders looked like once rebored and honed to size.
Here's a link to a short video showing the block being rebored. https://youtu.be/LBX28eOEZHE
Below are some pictures of a rebore in the chassis I did recently on a Kubota digger. It's powered by a three cylinder diesel engine, and I was able to bore it in situ due to the positioning of the engine across the back of the machine.
As you can see from the pictures, clearance was a bit tight against the back of the cab, but nothing a lump hammer to the cab rear metal sheeting couldn't cure (applied by the owner I might add). Anyway, not only was it tight against the back of the cab, but there were other things very close to the top of the engine as well which made boring it less than ideal. However, with a little help from Kevin, we managed to clear all the obstructions and I was able to successfully bore and hone the engine.
You may notice that in the first of the barrel pictures you can see an area that didn't clean up from boring on one of the end cylinders. I was able to clean most of the wear during the honing process, but I also had to use a riffler file to take out what was left of the wear ridge after boring and honing were complete, so that when the new piston and its rings are fitted, the new top ring won't get damaged by coming up against the underside of the wear ridge in the bore.
The second barrels picture shows the centre barrel after being bored, but before being honed, and this one cleaned up very well indeed.
The last barrels picture shows that I was successful in clearing the wear ridge from the top of the nearest end cylinder by the time I'd finished the job.
Today I used the old Buma boring bar to rebore a pair of MZ 250 barrels. One was standard (clean fins) and had to be bored to first oversize, and the other was already at first oversize (corroded fins) and had to be bored to second oversize.
I had to use the Buma because the finning on the barrels is so big that neither of them would fit in the Van Norman boring jig. Below are a couple of pictures of one of the barrels being fitted in the jig, and then of it being bored with the Buma. Then there's a picture of the second barrel (corroded fins) so that you can see just how big the finning on this engine is.
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