Tlted_Jelli

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I'm already committed to sending the crankshaft out. I'd like to avoid a rebore. I had done a compression test before this and got right around 150 on both cyclinders
I can see myself spending a little more on the tools to lap and hone and install new piston rings
 

5twins

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Whether or not you can just hone or need to re-bore will depend on the clearance you find between the piston and cylinder. New spec is .050-.055mm or about .002", and the wear limit is .10mm or about .004". If you can just hone, the Flex-Hone you need will run you about $25. It may be cheaper just to have a shop do it. Honing is quick and easy so it doesn't cost much. The cylinder is only honed for like 20 to 30 seconds.
 

Tlted_Jelli

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So a quick update. Everything is torn down and cleaned. Hugh has my crank and camshafts.
Re-enameled the sections while I was waiting.
Got new oil seals, front and rear cam guides, advance locating pin, head locating sleeves, starter gear kit, and piston rings.

Gave honing with the flex hone a go. Just waiting on Hugh before I order my gaskets, washers, and other misc bits. No shop around me would touch the Japanese bike. They're all diehard Harley shops. Gonna try grinding the first oversize rings tomorrow with one of them specialized bench grinder/files. Got all my sealing surfaces as clean as possible without removing the studs and resurfacing. Gonna use that aircraft sealer when the time comes.
 

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bosco659

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So a quick update. Everything is torn down and cleaned. Hugh has my crank and camshafts.
Re-enameled the sections while I was waiting.
Got new oil seals, front and rear cam guides, advance locating pin, head locating sleeves, starter gear kit, and piston rings.

Gave honing with the flex hone a go. Just waiting on Hugh before I order my gaskets, washers, and other misc bits. No shop around me would touch the Japanese bike. They're all diehard Harley shops. Gonna try grinding the first oversize rings tomorrow with one of them specialized bench grinder/files. Got all my sealing surfaces as clean as possible without removing the studs and resurfacing. Gonna use that aircraft sealer when the time comes.
In your pictures the bores look like they are scored and gave a bunch of pit marks. Is it the photo or are they damaged? Are you putting first over rings on a standard piston?
 

5twins

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Yes, that's an old hotrodder's trick. You file the end gaps down to the minimum spec (.008" on the 650).

If you pull the valves out for lapping, you can better clean the top of the exhausts. The valves are hardened steel so you can safely wire wheel that carbon build-up off them. It gets really baked on the exhaust valves. A "before" and "after" shot .....

ExValveFronts.jpg


If your cylinder pics are after honing, I think they could use a bit more. And for a final finish on the combustion chambers, use some chrome polish on them .....

Clean Head.jpg
 

Tlted_Jelli

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@5twins @bosco659 Yes im doing the hot rodder trick filing down first oversize 0.25mm to the spec.

the cylinder bore is after honing. not sure what the brown spots are (newbie) everything feels pretty smooth. not sure what i can do to fix those besides new jugs or a big bore. any suggestions?
i'll be taking the valves out today for more cleaning and lapping. i got one of those huge c-clamp compressor tools. good to know i can just get in there with a steel wire wheel to clean it out.

Would another 20 seconds hone on each cylinder do more bad than good?
 

bosco659

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@5twins @bosco659 Yes im doing the hot rodder trick filing down first oversize 0.25mm to the spec.

the cylinder bore is after honing. not sure what the brown spots are (newbie) everything feels pretty smooth. not sure what i can do to fix those besides new jugs or a big bore. any suggestions?
i'll be taking the valves out today for more cleaning and lapping. i got one of those huge c-clamp compressor tools. good to know i can just get in there with a steel wire wheel to clean it out.

Would another 20 seconds hone on each cylinder do more bad than good?
I had stains like that on the bore of a car engine I was rebuilding. In my case they were rust stains. If you can’t feels them with a fingernail, maybe it will be ok. What was the grit on the Flexhone used?
 

Jan_P

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If your compression before was good

Would another 20 seconds hone on each cylinder do more bad than good?

I would most likely leave it as it is Even if I not have seen spots like that in 3 or 4 cylinders.
 

bosco659

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If compression was OK I would not hone it anymore. Honing it like this on the bench is really to deglaze the cylinder to help break in new rings (plus clean up minor surface imperfections) vs machine honing to enlarge the bore to oversized specs.
120 grit on the hone is more aggressive than I’ve used in the past. The rings should wear in quickly. Make sure you wash the $hit out of the bores. I use dish washing detergent and water. Once you have it really clean, wash it again. When you believe it’s super clean, wipe it with a clean white rag. If there’s any black / grey residue, wash it again. Any residual grit from honing can ruin your engine in minutes. Ask me how I know ☹️. Once clean, I’d oil the bores to keep rust from forming.
 

Jan_P

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The oiling it something I do on every thing I work on Being Sewing machines or whatnot.
Rarely there can be to much oil --- and on the other hand to little oil fex on an Upstart
Can not only ruin the day it can ruin much more .. Making a new splitting of the engine necessary
So I pretty much soak it and keeps it soaked .. Works for me ...
 

Tlted_Jelli

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@5twins thank you!
Some additional pics after doing some more cleanup and another pass on the cylinders.
Ring filing next....
 

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5twins

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Now we're talkin', lol. Everything looks much better, lots cleaner. I have one of those ring grinder tools myself and have done up several sets of rings with it. It works well. It took breaking one while hand filing to get me to break down and buy the thing, lol .....

RingGrinder.jpg
 

bosco659

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Now we're talkin', lol. Everything looks much better, lots cleaner. I have one of those ring grinder tools myself and have done up several sets of rings with it. It works well. It took breaking one while hand filing to get me to break down and buy the thing, lol .....

View attachment 213232
I have one of those and never used it yet. Wonder where I put it. Lol.
 

Tlted_Jelli

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@Wano 21 I've got plenty😊


After getting my crankshaft back from Hugh's Handbuilt (freaking beautiful work btw) I managed to get everything all buttoned up again. I used @Jim 's top end build up thread step by step which made everything damn near idiot proof. Getting the engine mounted again was quite a show. Had to get on my knees and bearhug it back on the frame. Scraped a to of my fresh paint. I should be putting oil in it soon and start it up and we'll see what happens.

Replaced the starter gear, all new copper/brass crush washers, athena gasket kit, new rings, new front and rear cam chain guide and cam chain. all new oil seals. Plus all the cleanup in my previous posts. I also re-faced my jugs and head sections using some 2000 grit spray glued onto granite tile. Replace my valve seals and lapped them along with the jug honing. I also bent myself a new mount for my throttle cable on the bs38 carbs (i'll have pics of that later)

I pretty much did all that was needed for the poor/cheap man's rebuild.

As soon as i get it fired up i'll post a little video and we'll see how it sounds.
 

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