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'76RD, that brings up an interesting point which is the new vito's crank i am installing does not have the nubs which seemed odd at first. rather it has o-rings aligned with where those nubs line up on the bearings and that's the mechanism that keeps the outer part of the bearing stationary once the cases are back together. And thanks for the note on the bearing retainer rings, yup those are all positioned correctly and ready.

thanks striker, i'm on board with all of that and excited to start putting this thing back together. it will have to just sit for a bit once together while i build up/out the chassis but i just have to enjoy looking at it on my counter until then.

ok, excellent, that lines up with generally what I was thinking desmodrew. i'm inclined to leave it in but i will give it a nudge and see if it slips out easily. I wouldn't feel very comfortable safety wiring it as i've had safety wire on my race bike break free from one too many twists or from a unseen kink or something so if i can easily push that bushing out i'll do it but if it is solidly pressed in i'm comfortable just leaving it. same with the gear m in sc was referencing, doesn't seem like there's any risk leaving it in. thanks as always for the advice, and to the admins who keep this forum alive, man, what an incredible database of historical knowledge, really great to be able to tap into this resource. 

ok, well, my 'need reading glasses' eyes explains my confusion, it's part 15, not 19 i was referencing, i should have looked more closely at the diagram, the number looked like 19 at first glance. it is the bushing on the end of the shaft where the parts go in order 7-6-7-15. so it is part 15 I am wondering if that is ok to leave or if that needs to be removed as well. sorry about the confusion m in sc.

sorry, just to clarify, it ok to leave it in place even though i've removed all the other components? maybe it will just slide out with a little push, but curious if it is tightly pressed in or if i can nudge it out. i tried giving it a little push but didn't budge, haven't really applied any force to it. if i had to guess it should just push out?

So part 19 on this blow up is (I am pretty sure) the collar/bushing pressed into the upper case next to the tach cable drive gear in the other pic. On another thread (where i grabbed this parts diagram) it said all the components can be removed if not running an analog tach but this collar is pressed in and I want to make sure it can stay before bolting these cases back up.

Before I do this for the first time, any of you oldtimers highly experienced RD enthusiasts have any essential do's and/or don'ts as I get this fully refreshed motor back together? Just looking for any "make sure you do/don't do this" kind of hacks or warnings to limit the chance I do something dumb or help make things easier. Also, 12 year old opened tube of Yamabond4 or a new unopened tube of Hondabond4? I'm inclined to go with the Hondabond semi-drying just 'cause it is new, guessing these sealants can break down over time. Motor pics before assembly and after paint, I am really digging the satin black!

SoCal that chart is great, it isn't far off from my back of napkin calcs I've used forever. As far as the flat slides vs. round, I do like the idea of better response with the flats. Here is an absolute encyclopedia of info on the VM/TM carbs that I found, maybe somebody posted this elsewhere but this is quite the dissertation on Mikuni carbs. Not a quick read but lots of great info. https://www.vintagebikebuilder.com/mikuni-tuning-and-jetting-guide.html

I did just find this thread on here https://www.2strokeworld.net/forum/index.php?topic=775.0 which directly and indirectly answers most of my questions. 28mm VM's seem like a can't go wrong option even with some performance mods and per that thread, anything bigger would require some mods to the cases, which doesn't seem like something I want to get into, got my hands full as is with this thing. But...since I do have the performance mods going on, will 28's be a power bottleneck and negatively affect the gains from the chambers, reeds, Vape etc? If that is the case (bad pun), then I'd rather do it right, even if it requires more work or expense, modifying cases, intakes etc. I'd hate to miss out on significant front wheel liftability with carbs too small for this build. I mean really, is there such a thing as an RD with too much power?   

I'd be interested in how this goes ...

I'm running a RZ350 and did make few changes but long ways to go still.

Here's, what I've been running - https://www.2strokeworld.net/forum/index.php?topic=6963.0

Goodluck!

TeeZee, looks like you are in CO? I read your thread above, all good info. I used to calculate jet sizes based on actual O2 concentration. So if O2 concentration is about 15% less at say 5200' compared to sea level I would multiply main jet size by 85% and go with the closest jet to that number. That always worked really well with a single cyl CR250 at 10k', not sure how it will apply to the RD but that is my basic calculation starting point. Here in Boulder the O2 concentration is about 83% less than sea level.

Working on my RD250 to 350 build and I need a carb recommendation for daily riding at about 5200' and sometimes up to 7500' (stock carbs are toast). I'm good working out jetting/premix as I rode a CR250 for decades at 10k' and higher. This RD will be a street performance bike with some minor porting (on ebay cyls), Vape ignition, chambers (more midrange than top end), Vito's crank, Boyesen reeds with 3/4"spacers and stock reed blocks, pod filters. I see all the different Mikuni options on HVC and Economy but am not sure what size or type is optimal (round slide, flat slide?) for this application and altitude. Looking to make this thing feel fast as hell on the street firing from light to light, but I will not be racing it so top speed is not a concern and I do want to make it feel "rideable" on the street. Thanks in advance for hopefully a lively discussion. :-)

Thank you Striker (and m), exactly what I was looking for. My manual does not seem to have that page or diagram so this is perfect.

So I'm getting ready to reassemble the engine on my first RD250 teardown and rebuild and am wondering if it is a good idea or not to use an anti-seize thread lube on any nuts or bolts either on the cases, or various shafts, countershafts etc.

The manual also vaguely implies to install the bottom case nuts before the upper half bolts and it mentions following the order of the numbers on the bottom of the lower case for installation but says nothing about the top bolts or the order to install. Is that the way people here do it, bottom nuts first then top? I would be inclined to just follow the same basic order on the top bolts if not specified.

Thanks for that info Jung, super helpful. I'm working through pros/cons of different options and think i've got a good plan moving forward. I got a set of performance 350 heads that won't require me to deck the cylinders and have squish and CC's right where they need to be for this project (mild street/midrange porting, CDI ignition, expansion chambers) according to a few tuners i've spoken with. I have a tube of YAMABOND 5, the drying liquid gasket as well as the Hondabond HT silicone liquid semi-dry gasket. I assume the semi-dry that stays more flexible is the better option for the cases? As far as the crank, the OEM one was out of tolerance on lateral play on the large bearing end so I got a Vito's to replace it.

Ok, cases successfully split...so now what? It's unexpectedly clean inside and am unsure of what to do next or how to clean everything properly. Got a Vito's crank to install, and once the case is cleaned and ready to reassemble, I'd love to hear any insider tips and tricks to avoid any pitfalls or to make the assembly go smoothly. I've read on the forum about gaskets and seals and additional sealants or waxes to prevent leaks and stuff like that but would love any tips from the experienced so I have a successful reassembly. I have a tube of gray Yamahbond liquid gasket that I plan on using on the case mating surfaces, seems like that (or something very similar) was used at the factory, pretty sure this case had never been split before.