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youre going to need to machine the top of the cyl to fit a 400 head gasket. once you do that you  cant go back. so... will it probably work? sure. but just guessing is risky

I think the recess for the headgasket was about .025 to .03 in, so I will take that off and re measure.
My question was more is there a benefit to getting the squish tighter without hitting that .030 that I have read people use for pump gas

Well sadly I already had the engine apart before making this post. But I am putting in new pistons/bore over, and a vito's crank, so it seems worth it to measure after all of that.
Is there harm in bringing the squish closer even if it is not perfect? Say going to the 400 head gasket and just resurfacing my head?

as long as they arent flat yup. i still add some blue loctite

Mine looked pretty good but I will be double checking.

use modelling clay and get measurements front and back and then you can have it all done at one shot

Never thought of modeling clay! But what do you mean front and back? Just of the cylinder?

all of that wont hurt. the pistons, that's minimal gain at best w the weight, and honestly not something id bother with. if you must remove material around the inside of the wristpin boss, but, these pistons now adays are produced so well they will probably be the same weight.

the oiling hole is up to you , and cleaning up the ports etc never a bad idea but if you want more power, would strongly recommend head work or replacing them w more efficient ones. but modifying stock ones to tighten the squish correctly is a good place to start and one of the best bangs for the buck.  but cutting the cyl vs cutting the head...  the head is where the work needs to happen to get the cc right. a stock rd350 head gasket is around 1mm or under which is a good place to start.  however, no -real- downside to getting the cyl cut but they will then both need to be done together obviously, and then become a matched set.  IF you are paying to have all this done, it may be worth getting a set of the billet VP heads which are just a bolt on vs modifying the stock stuff my 0.02

I am hoping to use the same shop that my engine guy likes, so hopefully they know what I am asking for. Worth going to talk to them and feel them out.
So I guess the proper procedure would be to bore and assemble, then send to be cut. But my solder wouldn't even reach.
Also it is starting to sound like a performance snowball

Thats sort of what I figured. I'm guessing you feel the same about the belleville lock washers

I put this here because I feel like its all matter of opinion.
I am working on a full rebuild of my 73 RD350 at about 22k miles
When going through the transmission, all of the bearings looked good, but I figured I would throw new ones at it. The only one I haven't checked is the shift drum bearing.

Would you guys throw all new bearings at this? And what about the shift drum, considering it seems like it wouldn't take much abuse.
And what about those little Belleville spring washer guys under the clutch hub and main gear on the crank?

I am doing a full rebuild on my 73 350, and I don't think my local two stroke guy is gonna be able to do my cylinders.
I figured I would try to come on here and gather some wisdom since I am likely going to have to do it all myself. I have no issue with doing the rebuild and getting the bires done, but had performance questions.

For the ports I figured I would just knock out the casting flash and clean it up. I would really like to have a guide to do any more than that. Does anyone have somewhere to point me?

Is it of any benefit to chamfer the oil holes above the mains?

I know balancing pistons can help the motor with balance and vibration. Where is it safe to take material from?

I have seen where for some bikes a small hole is drilled in the piston to help lubrication, but since the 350 has no exhaust bridge is this unnecessary?

On a street bike running pump gas, is the corrected squish safe? I know it takes a lot to get there, and I could cut the cyl down to use the 400 head gasket to get me closer. I tried to measure, and it didnt even touch my .066 solder 

I started looking bad at my notes and things on this bike, and I think you could tell how bad it was the moment I put the chambers on. When I would watch the exhaust and listen, you could tell that the left cylinder just didn't "pop" like the right did as the exhaust came out. Which if it was like that since I got it, that would mean I have been running it like this for over a year. It always amazes me what these old two strokes can get away with.

thats usually from late ignition timing. very retarded.  not lean or oil. man that sucks

So that sounds like either it happened before I got the bike, or I just got the timing horrifyingly off.

I am tearing down my 73 RD350 to rebuild, and pulled the heads to measure squish. Right cylinder looks pretty good, but the left... well I guess I figured out why it had such low compression.
My guess on the cause of this only happening in one cylinder is ignition timing. When I got the bike I put in new points and condenser and set timing 1.8mm btdc.
When I got the bike, one side was not firing, and I don't know what it looked like inside before I got it running.
So either it had some issue before I got it, or I messed up the timing on that cylinder somehow
Points are new old stock daichi

Right
And left

Funny to think how many people just went for it. Has some useful stuff about beveling the oil passages on the crank and other simple stuff

I didn't see these posted anywhere so I thohght I would. My old clymer manual has a bunch of info on port and piston modifying and was curious if this info is outdated or still holds up. I'll attach some pics of the port maps and piston diagrams.

https://youtube.com/shorts/tr7hSFRzvts?si=GzzMYRXzE8qEHzHs

So these show the lip on the carrier that looks like strange wear.
The vid is just to show how much play there it.
I rolled the dice on an ebay part so we'll see if it is different.

I pulled the wheel and measured everything. The hub the sprocket sits on measures from 73.05 to 73.18 depending on where you measure. The sprocket center bore measures 74.35.
I put the carrier on a truing stand and I am a bit worried the carrier is out if round. Thinking back when I first got the bike, the rear sprocket was loose one day. I will post a couple pictures but there is a lip on the carrier where the sprocket sits that makes me worried the sprocket was loose for a long time and hurt the carrier.
I talked to rebel gears again, and since they are only an hour from me, they said I could bring my sprockets and carrier and they would help me figure it out.