Bike runs good until it's warmed up, then terrible

The right side is appropriately dirty/dry.
The left side is wet, dome cleaned by excess fuel. Left side is your rich problem.
Move pistons down and closely examine condition of cyl walls, look for scrape lines, or worn spots, like if the hone crosshatching is missing. Fuel can wash-off the protective glazing on cylinder walls, leading to aggressive ring/piston wear.
If these wear signs aren't there, you can save this by fixing the left carb rich condition.
Else, rehone and re-ring may be needed on left cylinder.
There is a trick to get original rings to reseat, but we'll save that for later...
 
Move pistons down and closely examine condition of cyl walls, look for scrape lines, or worn spots, like if the hone crosshatching is missing. Fuel can wash-off the protective glazing on cylinder walls, leading to aggressive ring/piston wear..

I have less than 100 miles on my top. If it were just rich from fuel, then why would it blow white smoke everywhere from left cyl?? There is an oil issue as well, I am nearly certain. That's why I have the top end apart, so I can replace valve seals and check specs on guides, I doubt the oil is getting past the rings as they are nearly brand new. The valve seals were one of the few parts I didn't replace when I installed my 750 kit.

If these wear signs aren't there, you can save this by fixing the left carb rich condition.

You make it sound like I didn't need to pull my engine, that would be very frustrating if so.
 
Oh, no, you did good. Damage can be severe when raw fuel gets in there. Now we get to see if there's damage, or if there was previous damage prior to the fuel problem.
If there's no damage, and you're satisfied with guides/seals, then fixing the fuel problem will probably make the smoking go away.
Raw fuel is a solvent, it will dilute the oil, allow it to get into the combustion chamber, then produce that teltale white smoke. If you've got only 100 miles on this thing, you may be ok. I thought this was a hi-time engine, more susceptible to fuel-wash damage. Also, you have confirmed that the LEFT cylinder is rich, right side is okay.
Do the cylinder examination, later we'll concentrate on the left carb.
 
Great, now valve guides/seals, they wear very slowly over time.
If you had no smoking before this, they're probably ok.
A prudent mechanic would inspect the guides and replace the seals at a minimum, simply because of the fuel wash, and it's easier to do now.
That's up to you, I'd give a 5-10% chance that the seals are damaged, unless you've never replaced them, then 50/50.
Doin good so far...
 
Oh, one more thing...
Before you button it up, move that piston all the way down, mop-up all wetness with lint-free cloth, piston top and cyl walls.
Then apply a little fresh oil around the circumference of the piston, several drops will do.
Then rotate a few turns, so that clean oil gets on the rings and walls, wipe off excess.

In really bad cases, you'll find fuel in the crankcase oil, take a sample and smell it, or put some on a flat non-flammable thing, like a putty knife.
Put a flame on that sample (preferably near Enid) and see if it flashes-off.
If so, consider another oil change after this thing has a few miles.
 
I never ran the bike before I installed the 750 kit as one of the original cylinders seized on me so I don't know whether it smoked before or not. I never replaced valve seals so they may be the originals. I plan on using the method described on pg23 of this manualto check my guides. Does the method and the numbers presented there look correct to you? http://www.knucklebusterinc.com/tech/XS650.pdf

If they guides are out of spec and I install new ones, will I really need to re-cut my valve seats!?

Should I do something abt the deposits on the top of the piston or no?

Enid, Ok? You have some bad history there? Haha, Enid is pretty close to where I grew up, Kingfisher, Ok.
 
Okay, correct me if I'm wrong...
I understand you rebuilt and upped to 750 this engine, all as a single rebuild?
Since then, you've put on 100 miles since this rebuild?
Then the carb rich issue raised it's ugly head?
You've avoided long runs/trips in this condition?

Then, do you know the history of your head? Was it a known good head?

If yes to all, then this will be easy. You probably don't need to fool with head...

Lemme know, I'm here...
 
Okay, correct me if I'm wrong...
I understand you rebuilt and upped to 750 this engine, all as a single rebuild?

Yes, I've learned everything I know now along the way. I put maybe 20 miles on it around my neighborhood before I got my endorsement. Short runs(20 -30 min) every other day or so. No long trips.

Then the carb issue started happening, off idle stumble. That's the reason I really started looking into my carbs. This showed up during my longest ride ever on the bike, abt 15-20 miles on fresh plugs, by the time I got her home the left side was fouled so bad that I pulled into my driveway on one cylinder. Luckily it waited to stop firing on the left till I was very nearly home. It started stumbling abt 3 miles from the house. That was all on factory jetting.

Once more, I tore into my carbs to find my needle jets nearly falling out on their own so once I got the new needle jet o-rings from RetiredGentleman and installed them, I figured that'd fix it. I assumed fuel was being sucked up past the needle jet o-ring on the left side. While I was in there, I went ahead and went one up on the pilot jets and two up on the mains like everyone says to do when running open intake and exhaust. Still rich on the left and lean on the right like before, only now the stumble covers a slightly larger area of the throttle curve. So the jetting changes made the stumble worse.

Amckay guide says a just off idle stumble is usually indicative of pilot jets that are too large. My carbs have been identified as a 78-79 set(by 5Twins) so I know I've got the right starting point to reference from when it comes to jet sizes.

The bike was not running when I bought it. The seller bought it in a group of 10 or more other 650's with the intention of selling the good ones and parting out the lost causes. So, no, no previous knowledge as to whether the head was good or not.
 
Well, the fact that it was running fine before all this points directly to that left carb, and after your teardown/inspect confirmed left side flooding and no permanent damage means that you'll probably be fine, engine/head wise. That left cyl was pretty wet, so you've got a severe fuel issue with that left carb. The fact that the left cyl wasn't damaged means that the valves/guides/seals are probably ok. The cyl will go before the guides/seals, so if it's ok, guides/seals ok.
I'd say do the cleanup/oil mentioned earlier, button it all up, but:

Dont turn on the petcocks!
Don't start the engine!

Leave the left carb off, there's a few things to check first.

You're doin fine, hang in there...
 
The fuel issue may have been present from the beginning and I just hadn't ridden it enough for it to show up. I never pulled the plugs to see what was going on in the early stages. It wasn't until the stumbling issue reared its head that I first pulled the plugs and discovered the rich left cyl.

So you think the right carb is running correctly and the left one is the prob? What can cause a carb to run too rich? I've got a new o-ring on the jet and float level set dead on spec. Most other problems would cause it to be lean I would think. IDK.

Anyway, on to the next step. I hope to have the motor buttoned back up and back in the bike by end of the day Saturday, maybe sooner.

Until then, many, many thanks.
 
I would definitely put new valve guide seals in. It's just something you do when in there because the originals are 30+ years old. On my buddy's, they looked fine but fell apart when we went to remove them. The washing clean of that left piston could be fuel but it could be oil too. It could be those guide seals. On that rich running left carb, I would carefully check the float level, check the float needle and seat to make sure they're sealing, and pull the choke plunger and inspect it's rubber tip. If the choke plunger is bad and not sealing in the "off" position, that would be like running with the choke on or partially on all the time.
 
5twins, he put in new Mikes choke plungers, and used gasket sealer on the choke plates.
Has there been an issue with the choke plungers, like the float valve seal tips?
 
No, but they can just plain wear out. I'm assuming he had originals. Sometimes a carb is just plain screwed up, internally damaged or something. It's hard to diagnose stuff like that over the internet. Got any pics of the carbs? Are the float bowls correct for the year? Pilot jets the proper type (VM22/210)? It could be so many things and, like I said, over the internet, it's tough.

Let me relate a little local carb story. My buddy's "barn find" 650 ran terribly rich ever since he got it running. He had loud shorty mufflers and pods, and stock jetting in BS34 carbs. There was no way that bike should have been running rich. It should have been so lean that it would hardly run. He swore up and down that everything in the carbs had been replaced and things were set up correctly. When I finally did get a look in them, I could see problems right off. These were 1980 carbs with brass floats. they were shot so he put the plastic ones in. However - he set them to the brass float spec. The tang on the floats was bent down to like a 45° angle, lol. Then I pulled the needle jets. They were totally black and all gummed up. So ..... I take what people tell me they've done to their carbs with a grain of salt. Most don't have a clue what they're doing and might as well be working on the space shuttle or something, lol.
 
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On that rich running left carb, I would carefully check the float level, check the float needle and seat to make sure they're sealing, and pull the choke plunger and inspect it's rubber tip. If the choke plunger is bad and not sealing in the "off" position, that would be like running with the choke on or partially on all the time.

I just checked float level before I put the carbs back on a couple days ago, they are set dead on at 24mm.

How do I check the needle and seat to make sure they are sealing?

Float bowls, I will take a pic tomorrow and post it up. Any certain part of the bowls I need to get a shot of so you are able to identify them? They have an O stamped in the bottom of them.

Even though the plungers are new, you think I still need to pull them and inspect? The only reason I ask is bc I will have to order new gaskets and wait for them to arrive and I only have one week from tomorrow until I'm sposed to go on that 60 mile run down to Davis, Ok. I'm gonna order them right now with 2 day shipping so either way I will have them on Monday.


Yes, I'm using the 22/210 style pilots.

I plan on going through the carbs one more time cleaning them as per Amckay Guide.
 
When you get it back together, and you think the carb is ok, then we're going to do a rather unorthodox test to help isolate the problem. The test involves starting with completely dry carbs, so leave pet cock off.

Is your hearing sensitive enough to tell when that left cylinder is running, while riding?
 
While that left carb is off, check if the bowl base is perfectly flat. Some carbs that have been ham-handed in the past have the screw hole/mounting corners bent up, by tightening screws before full seating, preventing a good flat fit in the critical center area.
 
When you replaced the plungers and used gasket cement, do you think any of that stuff oozed into the enrichner area. Most gasket cement dissolves in fuel, like silicone sealer, and balls-up into real troublesome globs.
 
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