Elevation

[Clyde K.]

I recently moved from 2500 ft to 4500 ft and was curious as to whether elevation is a consideration when selecting jets or needle setting?

[motoman]

I recently moved from 2500 ft to 4500 ft and was curious as to whether elevation is a consideration when selecting jets or needle setting?

Stock factory jetting works excellent Clyde. Alltitude compensation is helped out with the vacuum slide carbies. Have ridden mine everthing from coastal sea-levels up to close to 14,000ft. for decades with no issues cept for the 3% power loss every 1000ft. U go up. Those that have come herefrom Caly and Texas Alamo areas will confirm that.

[Clyde K.]

Thanks Motoman. Again, just grasping at straws. My floats are set at 23mm and all four of my plugs are still fouled. Coils ohms at 1.8 (O.L through resistor caps). Cleaned caps and clipped plug wires. Starts okay, but will put new plugs in tomorrow and update. Semper Fi. Clyde

[3Phase]

I recently moved from 2500 ft to 4500 ft and was curious as to whether elevation is a consideration when selecting jets or needle setting?

That's weird, Clyde, it shouldn't start fouling spark plugs just because of a 2,000 foot change in elevation.



In no particular order:

What fuel and air jets are in the carburetors now?

Air cleaner is clean and the air intake hasn't swallowed a shop rag, missing beloved pet hamster or something?

Jet needles (slide needles) not worn and clips set in the middle position?
Needle jets (emulsion tubes) are good and not worn out and oval?

Idle mixture screws are set, tips are good and not broken off in the carb body?

Float needle valves and seats aren't leaking?
Brass carburetor floats aren't leaking and heavy so they won't close?

Pilot jet well plugs and gaskets tight and not sitting in the bottom of the float bowls?


.

[TopCatGr58]

Thanks Motoman. Again, just grasping at straws. My floats are set at 23mm and all four of my plugs are still fouled. Coils ohms at 1.8 (O.L through resistor caps). Cleaned caps and clipped plug wires. Starts okay, but will put new plugs in tomorrow and update. Semper Fi. Clyde

Hey Scott,

Didn't the above raise a red flag for you?? First, I'm hoping/assuming that when he says they ohmed out to 1.8....he was talking about the PRIMARY wires/circuit, but then he also says that he gets O.L. ?overload or out of limits, open line....in otherwords....NO continuity when measured thru the spark plug caps....which tells me he was then measuring the SECONDARY circuit. He cleaned the caps....but didn't say if he took the caps apart OR measured the caps themselves for ohms....the internal resistor can corrode and/or go bad and get O.L. just thru the caps alone.

Clyde, you need to measure the secondary circuit WITHOUT the caps, should then be ~15K +/- 10%, caps should/could be 5K or even 8K. IF you get O.L. on the coils without the caps, the coil has fried and gotten an OPEN CIRCUIT.

T.C.

[3Phase]

Hey Scott,

Didn't the above raise a red flag for you??

Actually, T.C., nowthatyoumentionit I just noticed he says that he set the floats to 23mm on his '78E -- nice black spark plugs!

Clyde, what is O.L.? The spark plug resistor caps are supposed to be at least 5K (5,000 Ohms). Sometimes they used 5K resistors for the inner plug caps and 10K resistors for the outer plug caps.

.

[motoman]

Actually, T.C., nowthatyoumentionit I just noticed he says that he set the floats to 23mm on his '78E -- nice black spark plugs!

Clyde, what is O.L.? The spark plug resistor caps are supposed to be at least 5K (5,000 Ohms). Sometimes they used 5K resistors for the inner plug caps and 10K resistors for the outer plug caps.

.

Have seen the bike and pretty sure they're OEM early carbs.............so yup, you nailed it.............definitely choking on that diet............specially since 1mm of static float setting change is equivelant to 2+mm of actual fuel levels.

[Clyde K.]

Hey Y'all! Where do I start? The jets are all stock "E" jets according to specs in the forum. Needles are all in middle groove. Floats are all new. The only thing I haven't done during the carb cleaning process is pull the emulsion tubes (on tomorrows agenda). I ohmed the primary coil wires at 1.8 and cleaned all connections while in there. I ohmed the secondary wires at 5K without the caps on and got "O.L" (open line) with the caps on. I used a dremel w/tiny fine brass brush to clean cap connectors, cut 1/4" off end of wire and reinstalled caps. I still get "O.L" when I ohm caps. I cleaned my plugs (wire brush, carb cleaner, shop air) and installed them, installed, synched & balanced carbs. It had a pretty steady idle, and I didn't notice any hesitation when I ran her up to 7200 rpm (no load). Pulled plugs again and all were just just freshly blackened (from being used and fouled?) but no fuzzy soot. Figured I'd get new plugs tomorrow and run them for a couple of minutes to see if they solve the soot problem, them probably pull and clean the emulsion tubes. If someone would tell me how to disassemble the caps I'll try that also. I need to buy at least 2 caps anyway as the ends that snap on to the plug has been run w/o the little clips that engage the plug are missing and the fittings have been hogged out -- may as well get 4.

[Clyde K.]

Also, the air filter is new and I left it off the last time I ran it (I ate the hamster last week--or did I eat the filter and put the hamster back on the parts shelf?!?). I set the floats at 23mm, taking care to avoid the tiny hump on the housing surface using a sliding scale type micrometer. Needless to say I'll recheck everything tomorrow. Thanks for all your help. Semper Fi. Clyde

[3Phase]

Take A Breath! Inhale! Good? Alright!

Hey Y'all! Where do I start?

Start with the float height. If you've set them to 23mm they're too low and the fuel level in the float bowls will be too high == rich!

The float height for your '78E is 25.7 mm, not 23 mm, but don't go too high, either. Float height higher than 25.7 mm?

The jets are all stock "E" jets according to specs in the forum. Needles are all in middle groove. Floats are all new. The only thing I haven't done during the carb cleaning process is pull the emulsion tubes (on tomorrows agenda).

Alright, did you buy new brass or plastic floats?

I ohmed the primary coil wires at 1.8 and cleaned all connections while in there. I ohmed the secondary wires at 5K without the caps on and got "O.L" (open line) with the caps on. I used a dremel w/tiny fine brass brush to clean cap connectors, cut 1/4" off end of wire and reinstalled caps. I still get "O.L" when I ohm caps. I cleaned my plugs (wire brush, carb cleaner, shop air) and installed them,

The when why and how on replacing your coils
XS11 Ignition Coils FAQ
by Mike Saar, edited by JP Honeywell

How do I know when I need to replace my coils?

"Measure the resistance across the wires coming from the primary side of the coil. It should read 1.5 ohms ± 10%. The Yamaha manual says these measurements are made at 68 degrees Fahrenheit (20 degrees Celsius). With those connections still apart you can test the resistance of the secondary side of the coil. Measure the resistance across the two spark plug connectors. This measurement should be 15k ohms ± 10% at 68 degrees F. (20 deg. C.). If either of these readings is infinite resistance or past the ± 10% mark, you probably need to replace the coils."

installed, synched & balanced carbs. It had a pretty steady idle, and I didn't notice any hesitation when I ran her up to 7200 rpm (no load). Pulled plugs again and all were just just freshly blackened (from being used and fouled?) but no fuzzy soot. Figured I'd get new plugs tomorrow and run them for a couple of minutes to see if they solve the soot problem, them probably pull and clean the emulsion tubes.

The spark plugs might be a little black after the engine starts and before it warms up. Did you run it up to 7200 RPM on the center stand or out riding the bike?

If someone would tell me how to disassemble the caps I'll try that also. I need to buy at least 2 caps anyway as the ends that snap on to the plug has been run w/o the little clips that engage the plug are missing and the fittings have been hogged out -- may as well get 4.

The spark plug caps? They just unscrew off the end of the spark plug wires.

If you look inside the cap where the spark plug terminal fits you should see something that looks like a slotted screw. The screw holds the resistor in the plug cap so if you take out the screw the resistor for the cap should drop out into the palm of your hand!

And ... Exhale!

[mack]

plastic floats

He said his floats are new. If he has installed plastic floats then the 23mm would be acceptable even in the early carbs. How accurate the levels turn out is a crap shoot with them. (plastic floats) If he did find brass floats then the 25.7 is the height to stive for.

[3Phase]

Set float height by carburetor model/year not by float type

He said his floats are new. If he has installed plastic floats then the 23mm would be acceptable even in the early carbs. How accurate the levels turn out is a crap shoot with them. (plastic floats) If he did find brass floats then the 25.7 is the height to stive for.

That's what I thought too, Mack, but I remember a few discussion about it and the upshot was that floats were set by carburetor/year and not by float type. Ah, here's one:-

Brass floats, plastic floats, and the facts about fuel height


Now that's a horse of a different color but because I have not actually performed a carburetor float type switch myself I'll be perfectly happy to refill the old balloon, climb aboard and float back to Ohio!

.

[Clyde K.]

Gents, again I am in your debt. I swear that "If it weren't for flashbacks I'd have no memory at all". Rectal-crainal inversion prevented me from seeing 2 different problems. The almost uniform fouling of the of the plugs was a result of the wrong float settings, misdiagnosed as fuel level problems when in fact it was coils quitting. Sure, they ohmed good (1.8 @ 5K +/-) when cold, but I grew up knowing that if (in cars) the coil quit, let it sit for a few minutes - while you additionally check for vapor lock - fire it up and go to the parts store. As an aside, I never did figure out how to cool the bike coil down to precisely 68 degrees on a 80+ day though.

[3Phase]

Gentlemen, reset your float levels!

Clyde,

These things happen in threes and since you've still got one to go the thing that'll probably bite you is setting the fuel level in the carburetor float bowls.

Even if you compensate and use the proper altitude offset correction factors in Interimaginational metric Sc(2) units (Sealevel Centimeters squared ) from Mean Sea Level in Tokyo at 68F(20C), all of Yamaha's figures will be off due to the rise in Mean Seal Level since the date of original manufacture.

[Clyde K.]

It's me, again.

I have a new question. The resistor caps on my coil wires need replacing. The ends that attach to the spark plugs are missing the the wire spring clips and are hogged out from slopping around. I have ND shielded caps on 1 & 4, ohmed at 5.63 and 5.11. On caps for 2 & 3, there is one unshielded NGK, ohmed at 4.28, and one unshielded "no name", ohmed at 9.51. Only the NGK has a screw slot for removing the resistor. I'm headed to the bike parts store tomorrow for new caps and since I can't find anything definitive I am asking whether I need two 5 ohm and two 10's or all four of one or the other.