BS34s and white plugs

[tommytwohands]

Hi,
I have BS34s on a Canadian 83’ XS650.
The carbs are stock jetted 132.5/42.5, float height set to 22mm, 5HX12 fixed clip needle, with mix screws turned out 3 1/2 turns.
Stock ignition.

The problem is,
Before I let the bike sit for 6 months, it ran with nicely tanned spark plugs at 2 3/4 turns out on the mix screws.
Now, after cleaning the carbs, tuning, and putting in new BPR7ES plugs, riding this weekend with the exact settings as 6 months ago yields white spark plugs indicative of a lean condition even at 3 1/2 turns out.

I’m curious where I could be leaking air or what part of the carburetor could be failing to lean both sides out?
Should I attempt to shim and raise the needle with a washer as I’ve seen talked about here?

The bike idles and pulls through all the gears nicely and doesn’t show signs of riding lean while in the saddle. But the plugs show these brand new looking white tips
Could both diaphragms be failing?

Thanks for guidance! I realize carbs are frequently brought up here, so thank you for your patience
Tommy

 

[bosco659]

How many miles are on the plugs? Was your plug check conducted with mostly low speed running or after a good highway run? Fresh fuel or 6 months old? Ethanol free fuel?

 

[jetmechmarty]

Could it be the gasoline? I understand sources may have changed recently.

My plugs above. That’s with the pilot air jet #130 and #137.5 main jet. Pilot at 42.5 like yours.
Do your plugs match? If so, I doubt it’s leaking, but I expect you know how to test with aerosol WD40 or similar.

 

[tommytwohands]

Jetmech and bosco,
This was after riding a good highway run with fresh ethanol free gas and less than 100 miles on the plugs

I spray WD40 on the intake boots and exhaust but I haven’t on the carbs themselves

 

[tommytwohands]

Could it be the gasoline? I understand sources may have changed recently.
View attachment 241263
My plugs above. That’s with the pilot air jet #130 and #137.5 main jet. Pilot at 42.5 like yours.
Do your plugs match? If so, I doubt it’s leaking, but I expect you know how to test with aerosol WD40 or similar.

I attached a photo of one plug that represents then both. Mostly plain white, whiter than yours. Perhaps float level is still off & I’ll check for leaks again

 

[jetmechmarty]

Jetmech and bosco,
This was after riding a good highway run with fresh ethanol free gas and less than 100 miles on the plugs

I spray WD40 on the intake boots and exhaust but I haven’t on the carbs themselves

Spray where the butterflies pivot. I doubt it’s leaking. My photo is also ethanol free gas. It’s running great. Starts instantly. Not much color.

You could probably stand to richen your main jet to 135. It won’t hurt.

 

[bosco659]

Can you add a photo looking down into the plug end?

 

[tommytwohands]

Can you add a photo looking down into the plug end?

Like this? I don’t have the best camera either

 

[tommytwohands]

Spray where the butterflies pivot. I doubt it’s leaking. My photo is also ethanol free gas. It’s running great. Starts instantly. Not much color.

You could probably stand to richen your main jet to 135. It won’t hurt.

I guess I’m surprised at the difference in plug color with no modification between now and 6 months ago.
Would going from BP7ES to BPR7ES change things?

 

[jetmechmarty]

We’re looking for a ring on the porcelain way down low. Look for it with sunlight or a flashlight. You might be running perfectly. No molten blobs of aluminum is a good sign.

 

[jetmechmarty]

Would going from BP7ES to BPR7ES change things?

All other things being equal? You got rid of the resistor caps? It must be the plugs.

 

[bosco659]

I guess I’m surprised at the difference in plug color with no modification between now and 6 months ago.
Would going from BP7ES to BPR7ES change things?

Plug change from non resistor to resistor should be executed along with a plug cap change to a non resistor cap. If you are running resistor caps and plugs I’m not sure it would give you this plug colouring. Something to look at for the future.

As @jetmechmarty suggests we are looking for a carbon ring further down the porcelain insulator.

 

[bosco659]

 

[tommytwohands]

Plug change from non resistor to resistor should be executed along with a plug cap change to a non resistor cap. If you are running resistor caps and plugs I’m not sure it would give you this plug colouring. Something to look at for the future.

As @jetmechmarty suggests we are looking for a carbon ring further down the porcelain insulator.

How’s this? That’s probably the best picture I can take right now

 

[tommytwohands]

Okay that video was clarifying. And certainly comforting.
Strange that seemingly only a change of spark plug type yielded this result

 

[5twins]

Yes, very good video. You might be a touch lean but not overly so. What air jet are you running? If you have a 135, reducing it to a 130 will richen the idle circuit a little and should add some color to your plugs. Also, as mentioned, the 135 main is a good mod for the factory lean BS34's, even on a totally stock bike. And if you do still have the original resistor spark plug caps, I would change them to non-resistor caps. This is best if you're going to use resistor plugs. You only want one example of resistance in each spark plug line. That can be plug, cap, or wire, but not a combination of more than one of those.

 

[gggGary]

Adding the washer is cheap, easy and has worked for me on (cough) several BS34 bikes.
I also use 50MPG, I'll let you canadianize that, as a metric. A healthy XS on the road 60MPH or so should be getting right around 50MPG, much higher or lower and something's not right. Performance mods, gearing don't seem to matter much, 50MPG.

 

[5twins]

And how do you know you have a Canadian bike? I ask because the carb jetting specs and the fixed 5HX12 needle are U.S. carb specs. A Canadian bike should have the adjustable 5IX11 needle and possibly slightly smaller mains and air jets. The needle jet is also slightly different.

 

[bosco659]

Adding the washer is cheap, easy and has worked for me on (cough) several BS34 bikes.
I also use 50MPG, I'll let you canadianize that, as a metric. A healthy XS on the road 60MPH or so should be getting right around 50MPG, much higher or lower and something's not right. Performance mods, gearing don't seem to matter much, 50MPG.

Wow that’s pretty good fuel economy and I trust you’ve stated consumption in US gallons? Our fatter gallon should yield 20% more? Unfortunately my bike had never used so little fuel. Iirc last time I checked it was high 40’s. Nice to have a target value.

 

[5twins]

I've always gotten mid 40's. That's for general use, mostly around town. I might see a few more MPG's on a tank that was run mostly on the highway, but that doesn't happen much, lol. I was surprised that a '76-'77 carb set netted a few more MPG's. I thought with the big Z-8 needle jets, it wouldn't be better. Must be the smaller mains.