Gas consumption is way too HIGH, Mileage too low

[RichV]

I it still rough when you stop and idle? See if #2 fires a timing light,

I would but my timing light is broken. Is there some other way?

[MPittma100]

Plug Fouling

From previous posts I've seen concerning crank seal replacement, some have had repeated leaking and had to secure the seal into the block with RTV sealer.

You say that you have "good enough compression with new rings". You should have very good compression with new rings. If you do not, we need to determine why not.

At this point you need to do a cylinder leakage test - especially on number 2 cylinder. Should not have over 15% leakage. If you do, VERIFY (don't guess) where the leak is.

The 4 possibilities are - head gasket, intake valve, exhaust valve, and rings. If the leakage is by the rings, this could contribute to the seal leak by building to much crankcase pressure. Oil pressure has nothing to do with this.

Let us know what the leakage % is and where it is going. No short cuts here. Must have accurate numbers from this test.

If you do not have a cylinder leakage tester, beg, borrow, steal, or buy one.

[RichV]

Let us know what the leakage % is and where it is going. No short cuts here. Must have accurate numbers from this test.

If you do not have a cylinder leakage tester, beg, borrow, steal, or buy one.

I will try to locate one tomorrow. I live out in the country and have to travel 20 miles to a place where they sell these type of tools. Maybe I can borrow one from one of the auto parts stores in town.

Another possibility is that the head gasket is leaking into the camchain space. This would produce the same symptom as passing the rings.

If it is passing the rings, that would indicate that I installed bad rings. I measured the ring gaps and cylinder widths and everything was within tolerance. Although a possibility, it's not the most likely.

As for the seal, I used RTV when I installed it.

The compression was reported at 120-125 for #1, 3 and 4 with #2 at 115. I would like them higher but they were mostly the same.

Many of the tweaks performed thus far have improved the performance greatly and this last problem is getting better over time.

[MPittma100]

Leak

The compression should be closer to 135 (throttle wide open when checking). Leakage test will point you to a problem if you have too much >15%. Head gaskets usually are not a problem, but you will be able to pin point any issues with this test.

You can feel the amount of blow by through the crankcase vent tube while running. Some is normal. Keep a close look at the oil making sure the level is correct and that there is no fuel contamination.

[RichV]

The compression should be closer to 135 (throttle wide open when checking). Leakage test will point you to a problem if you have too much >15%. Head gaskets usually are not a problem, but you will be able to pin point any issues with this test.

Okay, I forgot to do the throttle wide open. I reran the dry test this morning with new results.

#1 - 140
#2 - 145
#3 - 140
#4 - 140

So all four cylinders are in spec. I also ran a wet test (even though it's not required) and the compression rose on all four about 10 PSI which is not a big jump. The bike was warmed up before the dry test.

In light of this do I still need to perform a leak test or continue to ride the bike and try to "burn it out". I'm having difficulty finding a tester locally.

[skids]

Those numbers are damn good!

[TopCatGr58]

Hey again Rich,

YES...those comp levels are right at NEW SPEC!!! So the compression rings are working....but the oil rings in #2 may still not be right since you're still OIL fouling the plug. You say you have a bunch of spare plugs...but I was thinking that you might want to try a 1 step hotter plug to see if it would help you go longer before it eventually fouls? Hopefully you're keeping track of how many miles you go before it starts acting up/missing, and that the distance may be increasing??

I'm concerned about the cam chain tunnel leaking?? But I just reread it, and you were just postulating there....before you ran your WOT comp test. Not sure if you got a gasket set, you had a newer engine in an older frame IIRC, just wanted to make sure that IF you had found a rubber cam chain seal, that you didn't use it, Yamaha eliminated the rubber seal early on, the newer head gaskets are used WITHOUT the rubber cam chain seal! With those comps, I don't think you're loosing any compression much anywhere!

T.C.

[RichV]

YES...those comp levels are right at NEW SPEC!!! So the compression rings are working....but the oil rings in #2 may still not be right since you're still OIL fouling the plug. You say you have a bunch of spare plugs...but I was thinking that you might want to try a 1 step hotter plug to see if it would help you go longer before it eventually fouls? Hopefully you're keeping track of how many miles you go before it starts acting up/missing, and that the distance may be increasing??

The range has increased from about 10 miles to 20 miles. The MPG also is now at about 26 MPG up from 20 MPG the other day. I'll be going for a test ride tomorrow again. I look at the plugs after every run and only #2 is still getting the oil. Do you know the number for the hotter plug? I'll pick some up tomorrow.

I'm concerned about the cam chain tunnel leaking?? But I just reread it, and you were just postulating there....before you ran your WOT comp test. Not sure if you got a gasket set, you had a newer engine in an older frame IIRC, just wanted to make sure that IF you had found a rubber cam chain seal, that you didn't use it, Yamaha eliminated the rubber seal early on, the newer head gaskets are used WITHOUT the rubber cam chain seal! With those comps, I don't think you're loosing any compression much anywhere!

That's correct, I was just postulating. I was trying to think of ways that could cause the pressure to build up in the crankcase. I used a new head gasket that came with the gasket set. No special rubber gasket was in the set nor was there one on the engine to begin with.

I really like the compression levels. Any more suggestions on what is making the pressure go up in the crankcase? Something is pushing the oil past the oil ring and seal. Could the crankcase vent be causing the problem? Could one of the other cylinders have blow-by causing the pressure increase?

[TopCatGr58]

Hey Rich,

Okay, good MPG's, and again with those COMP levels, I can't see that there's much of any blowby of any of the cylinders to cause any increased crankcase pressure. I'm still thinking that it's just that the oil rings aren't sealing as well/properly on the #2 cylinder....if it was excessive crankcase pressure alone, then I would expect you to be fouling more than just 1 cylinder's plug! I know it's a PITA to take the carbs off, but just wondering about whether the valve seal may have gotten damaged on that cylinder vs. the piston oil rings!?

The NGK numbering system is backwards, so 5 is hotter than 6, 7 is colder.

http://www.ngksparkplugs.com/pdf/DYK...t%20Ranges.pdf

[RichV]

I'm currently running BP6ES so you are suggesting BP5ES? The local Advance Auto has them so I'll get a couple tomorrow. Should I put them on both #2 and #3 for balance?

If I don't see improvement over the next few days, I'll drop the carbs and inspect the valves. I'll also look at the exhaust side of #2. If they are okay, should I pull the head and check the valve seals directly? I hate pulling the head but I'll do it to fix the problem. It's probably the ONLY thing I haven't checked.

[MPittma100]

Results

Compression is plenty good. No leak test is necessary. Are you sure that the #2 plug is oil fouling? Could it be fuel instead? If it is oil, it can come also from valve guide/seal. And it can come from oil getting into the carb air box from having too much oil or oil/gas mix over-filling the crankcase. Look in the top of the air box with filter off and see if anything is wet.

[RichV]

Compression is plenty good. No leak test is necessary. Are you sure that the #2 plug is oil fouling? Could it be fuel instead? If it is oil, it can come also from valve guide/seal. And it can come from oil getting into the carb air box from having too much oil or oil/gas mix over-filling the crankcase. Look in the top of the air box with filter off and see if anything is wet.

The plug was covered with a wet, black liquid and the insulator is now black. If I clean and move the plug to a different cylinder, it cleans up some. Let me summarize what I've done thus far (carbs were balanced at each point and I clean and gap plugs).

1. Tore engine completely down replacing components and bearings as necessary.
2. Replaced all gaskets and seals.
3. Checked all components and clearances to make sure it was in spec.
4. Lapped all valves and replaced all valve seals adjusted cam clearance.
5. Cleaned and rebuilt carbs.
6. New cam chain and self-adjusting tensioner.
7. Installed HD mufflers on stock pipes.

At this point the engine started okay but black oil leaked out of 1-2 side muffler and gas flooding when turned off. There would be blue smoke for a while after the engine warms up. So I did the following.

1. Rebuilt the carbs with a kit.
2. Changed oil (not filter). Oil smelled like gas.

The flooding stopped but the leak was still there. So I did this...

1. Changed rings and honed cylinder walls.
2. Changed oil and filter (gas smell still there).
3. Replaced head gasket

Compression improved a lot and the problem seemed to get a little better but the engine would not hold idle. Gas mileage was 10MPG.

1. Rejetted the carbs to #115 Main Jets and replaced both with genuine parts.
2. Added Pringle vac cutoff to fuel line (octy was removed).
3. New clear fuel lines and filters.
4. Adjusted and static tested float levels on bench, on bike and while running. Replaced "sticky" #1 float. Seat and needles are all new from rebuild.

Engine now starts and runs great but the left seal leaks and the engine runs rough after about 10 miles of riding. #2 and #3 plugs were fouled. Gas mileage is "better", about 20MPG.

1. Replaced plugs.
2. Replaced plug caps.
3. Swapped out both coils (twice). All coils bench tested fine.
4. Replaced left CS seal (double).

#3 started to work okay but #2 was still fouled about the same and was "wet" (may have always been wet). New seal still leaked about the same. Mileage is now up to 25MPG.

1. Replaced seal again (double and different source).
2. Changed oil and filter (gas smell not as bad as before). Oil level is always half way between two marks while on center stand.
3. Cleaned plugs.

No change.

So I have been riding the bike to see if I can "blow out" the problem or further "set" the rings. I now have almost 500 miles on the rebuilt bike and it is improving.

At TC's suggestion, I am swapping out the #2 plug each ride tp see that helps.

Performance is really great before the plug fouls. It rocks on the interstate. My previous bikes never had this kind of torque at high speed. The HD pipes make it sound great as well.

[RichV]

Removed this comment
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[RichV]

Okay I noticed something odd today and it looks like a little oil (drops) is leaking out of the head gasket right above the CCT. I tightened the nut slightly and it did not change the leak. This is the cam chain space so oil is present behind the gasket.

Since it looks like I'm removing the head anyway, what sealant should I use on the head gasket when I put it back together? Copper coat comes to mind. Which brand should I use?

[Rasputin]

Just want to say that...Excessive crank pressure would have to be a lot as stock bikes have it sucked back in by the carb intake as well as the 1/2 inch breather hose that it has. If a crank seal was being blown out by excessive crank pressure the vent would literally have to be blocked off solidly.