Crosshatch???

[Kara25]

zuluwiz wrist pins,circlips of course will get replaced the whole project is for a 550/673 conversion so time is not limited my 550 runs very well and i have plenty of other scoots to ride. Just got the top end of a 650g and measuring cleaning and reconticioning everything that they will be put to storage untill i start tearing down the 550. I am not in a hurry to avoid mistakes. Suzukian thanks for your positive contribution sir i really apreciate it.this forum over the years is keeping up as the most famous for vintage UJMs in my opinion thanks to people like you. Reading old posts i cant seem to wonder were are some other members with crazy skills and knowledge that were posting here regulary like Tknet,SuzukiDon,Ray. Only nessism seems to be the timeless eternal guru of this site

[Suzukian]

I left this site a very long time ago when a group of people would just savagely attack anything I posted. The Moderators and Admins would do nothing, so I left. I have a forum of 55K people, I am the Admin there. It has nothing to do with motorcycles, but I do know how to run a forum. If a member *@%^$*@%^$*@%^$*@%^$es on another member's leg in my forum, I kick the *@%^$*@%^$*@%^$*@%^$er out. If people have differences of opinions and can discuss them civilly, that's fine. This forum doesn't seem to have Moderators, so people say really snarky little remarks. There are enough decent people, so the balance scale is tipping in favor of staying.

What I mean about the piston pin holes, is to drop the cylinder with thee piston pin holes in the position they would be when the rod is inserted, so you know how the piston fits in relation to it is actually going to be used. You could actually take thin sheets of paper, and measure the gap between the piston and the wall. We have plastic shim stock for that, I don't know if you have some, or have some available. I used to re-cone high end speakers, rewinding the voice coil, and you would use the shins to center the voice coil over the magnet while the glue dried around the new rubber surround seal.Great stuff if you happen to have it.

This stuff from Amazon comes a .001" in., so you can double and triple it up to see how much clearance you have, it's PVC, so it's durable.

shim stock.jpg

[Nessism]

Okay, one more opinion...

Chances are very high that your bores and pistons are fine. What I like to do is measure out of round and taper in the cylinder, and as long as it doesn't exceed .0010", you are good. The piston to wall clearance isn't overly critical, unless there is crazy wear, which doesn't appear to be the problem.

Replacing the rings would be first choice. That said, there have been members here that have reused rings before with good results.

Either way, use a bottle brush hone, not a straight hone, to apply a fresh cross-hatch. A bottle brush hone conforms to the shape of the cylinder better than a straight hone. 280 grit is about right for GS engines.

I'd soak the pistons in carb dip, to soften the carbon. A wire brush on the crown works well to remove carbon once it's softened, but don't use anything abrasive on the side of the piston or, most importantly, in the ring grooves. There will be carbon in the ring grooves that needs to be removed, so take care of that task.

During assembly, a light coat of engine oil on the cylinder walls and rings is called for. Don't use assembly lube because it's too slippery. We want some friction between the new cross-hatch and the rings, so the rings wear and seat quickly.

Replacing the piston pins is fine, but you might want to measure first. For this, you need a micrometer that reads down to .0001". Many cheap mics won't read that low, so be warned.

For gaskets, OEM is best. In particular, the base gasket.

Of course, go through the head. I like to have the valves ground, and a few thousands removed from the stems. If the seats look clean, lap them to clean, otherwise have someone do a very light cleaning cut to the seats so you have a fresh surface. Don't use a drill motor during lapping. If the seats don't clean up with light pressure on a lapping stick, the seats need to be cut.

[Kara25]

Suzukian Nessism first of all gentlemen i wish you a happy new year and to be safe and healthy. Now to the matters at hand. Mr nessism valves are lapped with paying attention and measuring with a digital caliper during the proccess the seat width in case i got too carried away and got over the limit. Seats are clean with a mat silver finish and rid of any black tiny dots that were there. The valves are rotating freely on their seats no obstructions. the head is fully cleaned and blown with compressed air + all chambers passed the leak test with gas poured in them and left upside down so i think i am good i will wait for 8 OEM valve seals to reasemble the head and be done with it. Now the barrels. I will take them to a machinist friend to double check my measurements ,hone and put new STD OEM rings. I thought about it and this bike is my baby i spent in the course of 4 years more than 7000€ in upgrades parts etc so not the time now to be stingy if i am gonna make it work as a 673. For the history. I measured ring end gaps for each cylinder and the biggest feeler i could get throught the ring gap was 0.30mm no more on a limit of 0.70mm by the manual so i assume the barrels are truly from a low mileage motor. Also i took 1 piston stripped it of rings and put it upside down on each barrel inserting feelers beetween the wrist pin hole and cylunder wall on the top position and in the middle. The biggest feeler i could slide on that test was a 0.25mm so again i think i am 100% covered with a hone + new STD rings. Now for the pistons. I soaked them in turns i kero/acetone mix and cleaned the tops with a scotchbrite pad by hand there was minimal carbon anyway. As for the ring grooves i used an old piece of piston ring while soaking to soften the gunk and it removed whatever residue was there (minimal). I am moving slow dont want to screw anything up. The biggest obstacle i believe will be the crankcase relieving i detest and i think it will be out of my league to split the cases. I am discussing ideas with my buddy how i can cover the holes and rods to catch as many fillings as possible. Maybe buy a barrel of kerosene also to flush each hole after the procedure with the oil pan removed. Wrist pins and circlips i dont trust them they will all be replaced with new they are cheap enough.12151-67001 is the code for 650 pins 4 of them and peace of mind one thing less to worry about.

[rphillips]

I've been trying to keep up, and always eager to learn. Ed just mentioned something I'd been wondering about since post Groups He said, We want some friction between the rings and new cross-hatch so the rings wear and seat quickly. That's what I'd always thought, the new cross-hatch made tiny little ridges that the new rings would kind'f rub or, hone down, to perfectly match the new rings. old cross-hatch had "already been rubbed or honed down to fit the old rings". Then post Groups said the honing was for final sizing, If the pistons and rings fit, why would you hone them any more? Why take off more stock if the pistons and rings fit right?...

[Nessism]

I've been trying to keep up, and always eager to learn. Ed just mentioned something I'd been wondering about since post Groups He said, We want some friction between the rings and new cross-hatch so the rings wear and seat quickly. That's what I'd always thought, the new cross-hatch made tiny little ridges that the new rings would kind'f rub or, hone down, to perfectly match the new rings. old cross-hatch had "already been rubbed or honed down to fit the old rings". Then post Groups said the honing was for final sizing, If the pistons and rings fit, why would you hone them any more? Why take off more stock if the pistons and rings fit right?...

If you know for a fact that the rings were sealing well before, then it's best to leave everything be. Purchasing used parts kills that train of thought, though. And when removing the rings from the pistons, they may move out of shape slightly, so that's in play too.

[Kara25]

Nessism exactly what i thought bcs i got lucky(?) 3 years ago on a top end refresh on my 550 just throwing away the old cooked gaskets that were leaking when i got the bike from the PO and reput the same rings back in on a Y shape. 3 years after and the bike doesnt burn a single drop of oil. And the bores of the 550 when i tore it down were much more glazed than those 650 ones i got. But as you said on unknown parts with no prior knowledge of how it was running why gamble even if it seens low mileage??

[Rob S.]

I'm trying to keep up, and learn new things. Bottom line, a la Nessim, reminds me of my mechanic's credo: if it ain't broke, don't fix it. Or in my case, if it ain't broke, don't break it.

[rphillips]

Sorry for not exactly understanding. Is it if you use orig. sleeves, pistons, and rings, and they fit good, don't hone. If orig. sleeve, pistons, that fit good, but with new rings, do I hone to get good wear and seal on the new rings? or not hone, so not to remove more more stock than needed? I'm kind'f reading it both, or either way.

[Nessism]

Sorry for not exactly understanding. Is it if you use orig. sleeves, pistons, and rings, and they fit good, don't hone. If orig. sleeve, pistons, that fit good, but with new rings, do I hone to get good wear and seal on the new rings? or not hone, so not to remove more more stock than needed? I'm kind'f reading it both, or either way.

New rings require a fresh hone. Old rings don't, although some people do it anyway. Tom Kent used to do a hone with the old rings, or at least I think he did. Too bad he dropped out here. He was a valuable resource.

[Suzukian]

Cross hatching of a new motor helps hold oil on the bore while the engine breaks in. The rings will scrap a smooth bore dry. Once broken in, this is no longer an issue. That may be why when people use old rings, on an old bore, they don't re-hatch the bore, it makes no sense to, they are already broken it. A Brass brush will clean off the top of those cylinders, get that carbon off, and the tops of the bores do look like they could use a little more cross hatching.

[rphillips]

Got it this time, thanks