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The mixture is fine and that's going by the plugs. The bike had the stock stuff on it when I bought it and it had the problem so what I have done to it didn't cause it.
78 XS750 with excessive oil burning and lower compression in center cyl.
- Thread starter jefferson997
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Just did a 200 mile ride and checked the oil when I got back. The ride was 95% highway and I put in around 4 oz. to bring it back up to full. Quite a bit less than the 100 mile mostly city streets mileage. Oil temp never got over 94c until I flogged it for a bit and hit 98c. Oil temps are much better with the oil cooler. Plan on making something to block air to the cooler so I can see just how much difference it makes on the same day and temps.
Incorrect. Installing pods makes the mixture drastically lean. You can't judge mixture by just pulling a plug after a some miles.
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I know how to do a plug chop. Quit acting like you know everything. It's been on a dyno too. The mixture is fine and it didn't go drastically lean.
Either you have some incredibly restrictive chinesium pods, or your data is faulty. Common high quality pods like K&N, Uni, APE, and the like, allow significantly more air into the carbs, which will drastically lean the mixture. Most bikes won't accept throttle under load until the carbs are comprehensively rejetted. And if the bike does run, it will run HOT. Realize also, that cheap china pods are NOT to be oiled. They are just paper filters. So if you oiled some, that may explain part of this conundrum.
And I'm not just talking out my backside about this subject. I have a hobby business rebuilding and restoring carbs from the '70's and '80's, and I sell O-ring kits for them. I also wrote this rebuild tutorial that's widely distributed by vintage motorcycle forums...
And I'm not just talking out my backside about this subject. I have a hobby business rebuilding and restoring carbs from the '70's and '80's, and I sell O-ring kits for them. I also wrote this rebuild tutorial that's widely distributed by vintage motorcycle forums...
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My issue is the oil burning due to stuck rings which has been the case since I bought the bike and it was dead stock at the time. The mods I have done have not caused the issue. The XS is known for center cyl. issues with many reports of people reringing them due to stuck rings. The stuck rings are due to high oil temp in the that area of the motor. The 750 should have had an oil cooler from the get go, but Yamaha didn't do it until the 850.
The pods I have on the bike are from Mikes XS and I have no idea where they are made. If I remember right the spacing or something wasn't right for the K@Ns to work.The instructions say they can be ran dry or oiled and I have done both with no change in the way the bike performed, but I'm sure you're going to rag all over them so have at it.
The pods I have on the bike are from Mikes XS and I have no idea where they are made. If I remember right the spacing or something wasn't right for the K@Ns to work.The instructions say they can be ran dry or oiled and I have done both with no change in the way the bike performed, but I'm sure you're going to rag all over them so have at it.
I like the ideas for getting the bike more level. With that, B-12 is thin (runs down the cylinder walls ) and what's left could/will be evaporating to some extent even in the upper cylinder with plugs back in. Try the soak with Marvel Mastery oil or ATF. Both have detergent qualities. It'll let out a smoke cloud for a bit after start up, but it worked very well lowering oil consumption on a 1980 XS1100 G that had sat for a long time with the previous owner before I bought it. Did it a couple times over the course of a few weeks, soaking for a couple days at a time and refilling during the soak. In my case I used MMO, but ATF is known to work as well.
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I'm going to give the B-12 a second try with the cylinders level. On the second application after rotating the motor I did notice it kind of went straight through the engine as I had the drain plug out. ATF would stay put and might be able to do it's work better.
I'm glad those guys mentioned taking the rear wheel off, although I probably would have come to that conclusion eventually as I had to take the rear wheel off my VFR in order to utilize a front wheel stand.
I'm glad those guys mentioned taking the rear wheel off, although I probably would have come to that conclusion eventually as I had to take the rear wheel off my VFR in order to utilize a front wheel stand.
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I run 2oz of MMO in every tank of gas in my 92 750 Nighthawk. Helps in the tank, petcock, carbs, compression, and exhaust.
Tested compression before 140 135 145 140
Now 150 150 155 155 That's power you can feel.
Got the bike at 20k miles, so sat a lot. Suspect stuck rings. Bottle only $8 at Wally World.
Tested compression before 140 135 145 140
Now 150 150 155 155 That's power you can feel.
Got the bike at 20k miles, so sat a lot. Suspect stuck rings. Bottle only $8 at Wally World.
Nice increase in compression. Was the Nighthawk using excessive oil (along with lower compression)? You didn't mention it, but I gather it was since you suspected stuck rings.
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No excessive oil use that I noticed. Hard to know what compression test should be, but I thought it was low so tried the MMO.
Spec. is 142-199 psi in the book. Crazy range to me. Maybe 199 is with carbon build up. I wish I had it that high. Various Nighthawks on Youtube have tested lower than me.
Years ago I got a 6 cyl mercury outboard motor unstuck, using liquid wrench. I bought a 1/2 gallon of it , poured in in the plug holes and let it sit. Once a day for a week, I would tap the flywheel a few times in each direction. Then One day it turned .I got it to run,I was happy until I saw it had a cracked block. I think your problem may just be carbon buildup on the center cyl due to heat, like you mentioned. So I did a search online for carbon remover. All the results came back saying to use Sea Foam. Either spray it in the cylinders and let it sit for a couple of days, or pour it in. If you can't find it in the auto parts store, try a marine store. Good luck.,,
My experience is if there is not an oil use issue, the rings are sealing. At that point, when there's a compression increase like you've experienced, it can be from simply running the bike because it sat for a long time. Especially if you checked comp right when you got it and then a few miles down the road after you began riding it. Like you said, the MMO is good for more than just the top end so no downside there.
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Nope, bought it, tested compression, rode it 4k miles that first season tested again, those are my first #'s.
Started adding MMO this spring, some 3k miles, then my last set of #'s.
Gotcha, wanted to verify. Definitely was a good call on that.
That engine is pretty straight already, just fill the cylinder all the way to the plug hole and that should cover the entire piston area.
If your rings get stuck in the piston groove then you would hear a knocking sound from piston slapping the cylinder wall during start up...
If the piston is silent then it's possible the cylinder wall and piston ring were never broken in properly to begin with...
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So I've now stumbled onto various posts about running TC-W3 2 stroke oil in your gas at 1 ounce for 5 gallons. This is in Corvette, Camaro, etc. forums so
you know they baby their rides.
They never mention increasing compression.
I think that is the major thing that is happening.
2 stroke oil is WAY cheaper than MMO.
IDK
you know they baby their rides.
They never mention increasing compression.
I think that is the major thing that is happening.
2 stroke oil is WAY cheaper than MMO.
IDK
I use TCw-3 and Stabil Marine in gas for my mower and generators year-round. I also winterize my motorcycles with it.So I've now stumbled onto various posts about running TC-W3 2 stroke oil in your gas at 1 ounce for 5 gallons. This is in Corvette, Camaro, etc. forums so
you know they baby their rides.
They never mention increasing compression.
I think that is the major thing that is happening.
2 stroke oil is WAY cheaper than MMO.
IDK
1oz TCw-3 per 5 gallons of gas. Stabil per the dosage on the bottle. I start using it in the bikes in October so it gets run through the system.
If I read that right, you're at 4oz per 200 miles, which is 20oz in a 1000, or 1,600mi / qt. This is rate of consumption rarely, if ever, gets resolved by piston soaks or sump additives. I think this bike needs to have the engine opened to service the piston and liners. Typically, if you are at or over ~150hr/qt, methods and products like this have their best chance.
