engine piston check
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@MadGyver yeah it has low compression its easy to kick and had blow by when i opened it, the bike is waiting for a rebuid i just got a top end athena gasket today i will get a piston in 2-3 weeks and i will send the barrel for a rebore to 57mm im just trying to check if the crank bearings are in good condition as my bike drank coolant before and i was thinking it could of caused corrosion in the bearings and that could sent my whole engine to the moon
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@SpookDog i will make a vid when i open it up, but all im saying is if that noise is normal i think it comes from crank rotating and the pistons it should be normal as things move there and make friction. anyways i will make a video when i open it up again and send a video and we can discuss a bit more acurately
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@erion1 After you remove the top end,only an experienced one can tell you if it's ok the bottom end at a 90%.
To be sure 100% you have to dismantle the engine.
When rebuilding,changed conrod just in case,because 0f 56k km's of the engine.bearings still had life and the con-rod was so good that a friend with a machinery shop checked for tolerances and told me to keep it for backup with a new set of bearings.
I just couldn't gamble with a top end rebuild of an unknown internals condition.Piston condition was way better than yours,still have it.
You get me what I mean. No video/sound recording can replace that. -
@MadGyver yeah i get what you mean, im not woired that much about the crank i just know that it used to loose my coolant and i know that i drove it everyday and i dont think water could of stayed in the engine to cause corrosion, based on my thinking(haha) i just imagine that the water evaporated from the crank everytime i ran the bike
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In my experience with blown head gaskets. The coolant doesn’t rust the bearings or the crank. As long as it hasn’t been too long since it ran and it’s all well lubricated with 2T in the crankcase , it should be fine.
Just keep it lubed and buttoned up till you send off the barrel for reboring.If I’d had a piston disintegrate I’d at least want to flush out the bottom end with clean fuel and oil. Turn it upside down, ect…
I get the impression that you don’t want to remove the engine from the frame tho?…
I understand that we don’t all look at a situation in the same way. Not everyone wants to remove the lump and split the casings.
As long as you clean up the gasket mating surfaces, ect, there’s a good chance that you can just put a new top end on and be fine. It’s mostly about preparation and not re-using head gaskets!
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Just a quick dumb question: when you order pistons they have a size listed such as ø56.5 mm.
Is that the diameter of the piston, or the cylinder hole it is supposed to go in?
If it is the diameter of the piston as I suspect, how much larger should the cylinder diameter be?
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@Hark_Ptooie yeah its the diameter of the piston, the standard is 56.00mm if you get a bigger one you need to rebore the cylinder so that piston can fit
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Most people recommend Yamabond. It’s a silicon RTV type sealant I believe. I have used Hermatite red without any leaks or problems. I prefer it just because it doesn’t shed ‘worms’ of sealant into the gearbox. Not so important on a 2/ but can be death to a 4/ if it clogs an oilway…
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@erion1 said in engine piston check:
@Hark_Ptooie yeah its the diameter of the piston, the standard is 56.00mm if you get a bigger one you need to rebore the cylinder so that piston can fit
OK, thanks - and what would the appropriate size of the bore be? +0.1 mm? +0.5 mm? +50 µm?
I may need to swap piston in the not too distant future, and motorcycle workshops are few and far between where I live. So it may be that I will need to turn to some car shop and tell them how it should be, because they are not used to this type of engine.
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I don’t have my Haynes manual at hand, but the max recommended clearance is in there…
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Okies, thanks!
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Found it! 45-50 µm on the diameter. Wear limit 100 µm
25 µm per side is hella tight.
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Kinda pisses you off when your recently ‘rebored’ piston used to rattle back and forwards in the barrel, doesn’t it?! I had the same experience buying a REBORED barrel & piston.
I’m very particular about who does my rebores now…
