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Discussion Starter #1 (Edited)
Hey everybody,I’m from South Africa, just got my dream bike, a cx500t, but bought it with the motor stripped and in boxes, have no clue where to begin, all the parts are very intimidating, one thing I need is a set of pistons, anybody here from SA that can help?
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Looking at the piston, it seized inside the bore, so I think you need more then new pistons, you also need a new engine block.
Or you need oversize pistons.
I have not seen seized pistons in a Turbo, probably because the get a lot of extra oil from the cooling oil injectors. So if there was no oil how much more damage is inside the engine?
 

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Yeah, those pistons... Wow! I'm with you Pim, a thorough inspection of the rest of the engine is definitely in order.
 

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Discussion Starter #4
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The sleeves feel fine by touch, no grooves, is it possible that pre-ignition couldve caused the gland to break? Maybe a stuck waste gate causing overboost?
 

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Hmmm, hard to tell exactly what I'm seeing, but I see no up and down marks or any signs of cross hatching. Almost looks like I see circular marks with small metal fragments when I zoom in.

Did someone attempt a bore and did not finish with a hone? Also looks like a Ridge in a portion of the bottom of the cylinder, was bore not complete or crooked?.

Did u measure cylinder bore to see if is oversized? Perhaps this is why you see no damage in cylinder.

Also not sure what I am seeing with the black stains
 
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I am with Johnste, it looks like somebody already rebored the cilinders
 

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Discussion Starter #7
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ok so looks like they did a very poor hone job on the sleeves at closer inspection, the black marks seems to be corrosion marks, unfortunately I don’t have the right measuring equipment to measure the sleeves, I can get a set of standard second hand pistons which is still in spec but dont want to put them in this block if they are too worn out
 

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The 2nd set of pictures are much better. Keep in mind that I am by no means an expert. I have not rebuilt an engine yet from the ground up, but I am currently in the process of building 3. so I have done lots of research and asked lots of questions. I have a set of cylinders from a kawasaki h2c that have been professionally rebored and honed one size over std bore. I also have a 650 turbo engine with 4000 miles that a breaker got a hold of. I was able to buy the complete engine, (in parts). It is in real good shape. So take what I say with a grain of salt as I am still learning
 

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Here is a picture of the kawasaki h2c that has been professionally bored and honed. You will see metal fragments and grit, as it has not been cleaned yet. The dark spots on this one is where oil from honing process dissolved some carbon in the ports and ran down the cylinder. It wiped right off. Things to note a) you can see the process went complete length of cylinder wall from top to bottom. B) the honed marks leave a cross hatch from the honed going both up and down in the cylinder while rotating. C) the bore and honed were done taking into account the clearances specified in the manual. Piston to cylinder wall and other specified clearances.
 

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Next is a picture of one cylinder of the cx650 turbo with 4000 miles on the engine. I have done nothing yet to this cylinder. Note a) you can still see evidence of the factory hone, b) you can see a glossy or glaze in the cylinder especially in the center portion of cylinder, c) at the top of the cylinder you can see a small ring of carbon, I also see this in a cx500t block I have.

My plans for this is to do measurements to make sure all tolerances are in spec, do a light hone to break up the cylinder glazing, and re-ring the pistons.
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If the bore size checks out OK, maybe a hone will be what the Dr. ordered. I'm no expert though... Good luck on the build my friend!
 

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So after looking at my cylinders I now conclude that I do not think yours have been re-bored.

If they were, that process would’ve went the length of the cylinder and I can see marks down at the bottom that were not taken out.

So this leads me to believe that your cylinders have been honed. One seems to have been honed more aggressively than the other. The fact that the horn does not seem to go all the way to the bottom of the cylinder I do not have the experience to say if that has any effect maybe somebody else can chime in. Another reason I think both sides were honed is your cylinders do not show the carbon deposits which is typical at the top of the cylinder.

I do think you should get some measurements on the cylinders and compare them to the spec before you purchase your pistons. If the honing has been significant and the cylinder is out of tolerance you may end up needing to bore one over. in that case you would have to find oversize pistons which could be difficult to do. I have seen some on CMSL but sometimes they are two over or three over. If your tolerance is out of spec you could end up with piston slap and other potential issues. If you don’t have a bore gauge and don’t want to buy one you may want to consider taking it in to a shop that does boring as they may take the measurements for free or for a very small fee, then you’ll know for sure what you have. I bought a bore gauge on eBay for a reasonable price as I plan to do several engines.

as far as the piston that you show, I almost wonder if somebody broke that trying to get the rings out with a screwdriver or something and snap the casting in that area. As Pim said, these typically do not fail this way. I would think that if that had cracked while in the cylinder extensive damage would’ve been done. You only show the one piston how does the other one look?
 

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As far as being intimidating, I always find it easier if I do the disassembly, allows me to take notes and pictures,
. That being said,

1) get a manual if u do not have one, they r quite good. Downloadable from this site or wiki
2) the book:
How to restore Honda CX500 & CX650 –YOUR step-by-step colour illustrated guide to complete restoration
By Ricky Burns

is good. While not specific to the turbo, there r similarities. The book is detailed and shows colored photos.

3). Check out youtube. Search for cx500 engine rebuild
 

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Discussion Starter #15 (Edited)
Thanx for all the advice, I am also not an expert but with all you clever people here I don’t have to be😅 i’ve taken a measurement on the piston that has no damage on it, it measures 77.94(10mm from the bottom of the skirt) which I believe to be in specs, the set I can get measures at 77.94 and 77.95, so their still good. I have a new set of rings that came with the project so I put them in the sleeves(about 10mm from the top and 60mm) and took a ring gap measurement which was 0.4 at both points.. that is 0.05 over spec, I still have to take the block for measurement and hopefully it’s not out of spec and save me the trouble of ordering oversize pistons and sending the block for a rebore, i’ve also measured the piston to sleeve clearance which is 0.10(*after posting this I realized that its not just as easy as sticking a fueler gauge between the piston and sleeve, I need the exact bore id to work out the piston to sleeve clearance, thanx to watching some videos posted by ‘the odontologist’) . The odo is at 64k km.
 

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If your going to continue to add qu questions and information to this thread you might want to ask an administrator to move it to the turbo section that way you’ll be sure to get the attention of others that have more experience sometimes because it’s an introduction thread people don’t always get in and read these as religiously as typically they are just introduction type of post. You can always add or start a new project threadIn the Turbo section of the Forum
 

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Discussion Starter #18
If your going to continue to add qu questions and information to this thread you might want to ask an administrator to move it to the turbo section that way you’ll be sure to get the attention of others that have more experience sometimes because it’s an introduction thread people don’t always get in and read these as religiously as typically they are just introduction type of post. You can always add or start a new project threadIn the Turbo section of the Forum
Thanx Johnste I will do that thanx👍
 

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Done.

... at the top of the cylinder you can see a small ring of carbon, I also see this in a cx500t block I have.
That is normal for any engine that has been run. The width of the carbon ring corresponds to the distance between the upper ring and the top of the piston; Everything below the highest point the ring reaches will be scraped clean but the part that the ring doesn't reach isn't.
 

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Discussion Starter #20 (Edited)
Ok so i’m waiting on my set of pistons to arrive. Another thing I saw after going through the parts yesterday, is my speed sensor looks in a rough condition besides from being very dirty, the small plastic housings is cracked and over it doesn’t look good, is there a way to test the speed sensor before trying to source a new one?
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