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Oil in the carb after valve adjustment
- Thread starter misiek303
- Start date
Have you checked compression?
How's the oil level. Smell the dip stick?
How's the oil level. Smell the dip stick?
I just checked compression on a cold engine. All cylinders equally 170. Oil level between marks. I don't think I smell gas in the oil cap.
Pressure is kind of weird. My book says min 128, max 156. But on the warmed engine.
I can't start the engine yet. It runs barely on choke only.
A little bit of history.
I rebuilt the carbs without replacing the main needles with new ones. The engine was running okay, idling, and on high RPMs after carb rebuilding.
I noticed that I had a choke open the entire time in half ways. When I closed it, I could not start.
I decided to do the valve adjustment and replace the main needle that came with the kit (Y140).
Since then, the engine runs barely on choke. I opened the filters ( PODS, image attached ) and notice the OIL in the canter filter. I checked the fuel in the carb and was very dark. So center and right carb have the same issue with oil, but the center is the worse.
Pressure is kind of weird. My book says min 128, max 156. But on the warmed engine.
I can't start the engine yet. It runs barely on choke only.
A little bit of history.
I rebuilt the carbs without replacing the main needles with new ones. The engine was running okay, idling, and on high RPMs after carb rebuilding.
I noticed that I had a choke open the entire time in half ways. When I closed it, I could not start.
I decided to do the valve adjustment and replace the main needle that came with the kit (Y140).
Since then, the engine runs barely on choke. I opened the filters ( PODS, image attached ) and notice the OIL in the canter filter. I checked the fuel in the carb and was very dark. So center and right carb have the same issue with oil, but the center is the worse.
Attachments
Sorry, I can't see the crankcase breather set-up in that pic. I'm also unfamiliar with those exact filters: are they red foam or sprayed with red oil? What color is the oil in the carbs (intake bell I assume)?
Next, the symptoms you describe indicate a still plugged pilot circuit or something amiss. The Y140 needle designation is from what kit? Perhaps a Keyster brand kit?
PODS
https://www.amazon.com/dp/B01LX26YF7?psc=1&ref=ppx_yo2ov_dt_b_product_details
Carb kit
https://www.ebay.com/itm/201577427587
Crankcase breather pics attached.
Also I noticed an oil leak through the RPM Tach gear ( pic attached ). It's like the pressure builds up under the valve cover and push the oil through valves back to intake. Tach Gear is restored with new seals. All all valve seals have been replaces.
Attachments
If that's a plug in first pic, you'll need to run an open tube up to the backbone and down in front of swingarm. Can't tell what's going on in pic two. Tach drive could be the victim of too much pressure or bad seal or both.
the breather on the first image is open, I had a small filter but it was crappy and fall off. There is no tube yet but it is open. I left it that way for now because when the bike ran last time, I noticed blue smoke coming out. Someone on forum told me that it may smoke after replacing piston rings, which I did.
So that's the problem for another day, or maybe it is related.
Visually they are identical ( new one on the left ). But I will put the old ones back tonight and try it.
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The goal there is to ensure the crankcase and in turn the valve cover is properly vented with no restriction. I don't recall a separate vent on the valve cover, but maybe? You seem to have symptoms of too much pressure there.
IDK about those carb kits, heard good things about that supplier (mostly). So, how many turns out are the fuel screws and what position is the clip on the needle?
IDK about those carb kits, heard good things about that supplier (mostly). So, how many turns out are the fuel screws and what position is the clip on the needle?
I tried all clip positions, really. Also I tried adjusting fuel screws. Every time I changed the clip position I started from 2.5 turns. Then I went down each time 0.5 turn. Was getting worse, so I was turning 0.5 up. and it runs better I think 3.0 turns but still only on choke and it does not go high on rpm, barely runs actually. I did not notice any significant difference when changing the clips.
I ordered the color-tune tool, but that will help when I get to the point of the running bike.
So far I am sad.
I'd suggest going back into the carbs and verifying the pilot circuit is clear by spraying contact cleaner through all passages with fuel screws and pilot jets removed - also the choke circuit in the float bowl and body.
Not camshaft. Can't tell from pic's orientation. IIRC it may be a vent for the driveshaft output housing. I don't have a manual for that bike
Memory is coming back a bit; the "middle gear case" bolts on to the crankcase adjacent to that breather - so that's still my guess. lol
The gear oil in that case is separate from crankcase oil.
https://www.cmsnl.com/yamaha-xs750s-1979-usa_model8713/breather-comp_2h71759000/
The gear oil in that case is separate from crankcase oil.
https://www.cmsnl.com/yamaha-xs750s-1979-usa_model8713/breather-comp_2h71759000/
I removed the carbs. There was no sign of more oil. But I found the broken tip of the fuel mixture screw. The tip sits in the hole, I tried to push it, but I think I made a larger hole instead. The tip is clogged. No way out.
It is the right carb. I have another one, but to prepare it for swap it is a few steps back. And still, no idea if that cleaning will help with anything.
Such a bummer.
It is the right carb. I have another one, but to prepare it for swap it is a few steps back. And still, no idea if that cleaning will help with anything.
Such a bummer.
Attachments
Wonder if compressed air will blow out the remainder? The outlet hole will be in the venturi right under the fuel screw location. Might even get a small piece of safety wire to poke it back up out if it's a single outlet hole (some are multi-hole)
So I fixed the carb and rechecked the valve clearance. It is a little different, 2 right exhaust valves are a little too large, should have 285 but I have 280. One intake first valve is too small, I have 265, it should be 260 now. Not a big deal. I will correct it.
But that should not be a cause of the oil in all 3 carbs. They all have an equal amount of oil. See the screenshot of the manifold.
I checked the valve head oil drains and crankcase breather. From what I understand how air circulates inside the engine it is impossible that I have an air pressure problem there.
After fixing and cleaning the carbs again, the engine starts and runs without the choke now. I kind of balanced the carbs to the point that the balance tool shows all 3 equal scales. I don't think I solved the mixture yet, probably due to the air pods.
The oil can get only from the head down or from the bottom of the cylinders. I checked the cylinders through the sparks holes, they are all wet.
So the question is:
1. do I have a problem with piston rings? - even though I installed new ones ( standard ) - need to mention one more time, that the pressure is 170 psi on all 3 cylinders on a cold engine. So it is good I think.
2. Do I have a valve issue somehow? - seals have been replaced as well and valves refurbished using the valve cleaning paste.
3. Valve guides?
I don't understand why all 3 have the same issue. If only one would be bad, I could imagine some failure somewhere, but all 3 are identical.
I scratch my head here. I could remove the valve and cylinder head to see how it all looks like there, but before I do that I need somebody to help me out and confirm that, yes that makes sense to do it next.
Thanks, guys, stay with me, please.
---
XS750F 1979
But that should not be a cause of the oil in all 3 carbs. They all have an equal amount of oil. See the screenshot of the manifold.
I checked the valve head oil drains and crankcase breather. From what I understand how air circulates inside the engine it is impossible that I have an air pressure problem there.
After fixing and cleaning the carbs again, the engine starts and runs without the choke now. I kind of balanced the carbs to the point that the balance tool shows all 3 equal scales. I don't think I solved the mixture yet, probably due to the air pods.
The oil can get only from the head down or from the bottom of the cylinders. I checked the cylinders through the sparks holes, they are all wet.
So the question is:
1. do I have a problem with piston rings? - even though I installed new ones ( standard ) - need to mention one more time, that the pressure is 170 psi on all 3 cylinders on a cold engine. So it is good I think.
2. Do I have a valve issue somehow? - seals have been replaced as well and valves refurbished using the valve cleaning paste.
3. Valve guides?
I don't understand why all 3 have the same issue. If only one would be bad, I could imagine some failure somewhere, but all 3 are identical.
I scratch my head here. I could remove the valve and cylinder head to see how it all looks like there, but before I do that I need somebody to help me out and confirm that, yes that makes sense to do it next.
Thanks, guys, stay with me, please.
---
XS750F 1979
