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R50/2 149-150 Carbs fouling plugs, put 105's in and seems fine...but is it?

Thunderdome74
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Joined: Sun Dec 26, 2021 2:59 am

R50/2 149-150 Carbs fouling plugs, put 105's in and seems fine...but is it?

Post by Thunderdome74 »

Hi everyone, so i have my R50/2 with 149/150 bing carbs on it. Ever since the engine was together with 120 jets i have been fouling plugs, i mean really really throwaway sooted up.
Primarily the one side
Took some drill bits and remeasured these so called 120 main jets. I was getting 120 on one jet and 125 odd) off on the other (my drill bits are sized 1,2 and 1,3 mm, the 1.2 would have play and the 1.3 wouldn't fit

The other bike with exactly the same carbs had 105 main jets, which when measure with a drill bit were smaller than 1,05 mm, so i drilled them out and fitted them.

(I verniered the drill bit to make sure i wasnt drilling the wrong size)

Thing is the bike seems to be running very well now, i did a plug chopand the plug tab and electrode are a nice dark brown,
(in the photo they look grey but i went for another ride today and they are brown) the rest of the plug is sooty(the metal surround where the threads are), now this wasn't a long ride, so i thought would ask here first

What are my next steps... drill it out to 110? 115? leave as it and raise needle a notch(needle is position 3 from the top)

I will try buy some new jets...what ...size do you suggest

The needles and needle jet ...a small amount of play, should there be any?

This is what the plug looks like now, worries ima gonna burn a hole in the piston

Image

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schrader7032
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Re: R50/2 149-150 Carbs fouling plugs, put 105's in and seems fine...but is it?

Post by schrader7032 »

What plugs are you using? Also, how is the timing? Do you have differential timing? If there is a big difference in timing, one side could be firing advanced, the other could be firing retarded.

Maybe I'm missing something, but fouling plugs is usually too rich. Bigger mains and raising the needle will just make it richer. According to Bing's book, the main jet doesn't come into play until you get to and beyond 60% throttle. I would think your issue is not necessarily the main jet, but likely the jet needle and needle jet...basically the middle range of throttle usage.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

Thunderdome74
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Re: R50/2 149-150 Carbs fouling plugs, put 105's in and seems fine...but is it?

Post by Thunderdome74 »

Hi Kurt, tx for the reply

Basically i am trying to feel my way forward from here

Bike engine was put together by an expert, and when i mentioned these problems to him he stressed it will not be the timing and that i shouldn't mess with it as he sets it perfect(he is a vintage BMW motorad specialist)

Plugs are non resistor NGK D8EA

however the carbs are still unchanged, so perhaps it is the needle and seat being worn, which in turn was causing the fouling with the 120's

MMM, before i go further , perhaps i should get a new needle and seats?

Is this a common wear item? I mean is this often seen on these old girls?

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schrader7032
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Re: R50/2 149-150 Carbs fouling plugs, put 105's in and seems fine...but is it?

Post by schrader7032 »

What year is your bike? I'm not totally familiar with NGK notations, but the "E" indicates it is a long reach or 3/4"...is that correct for the bike? Early in production the reach was 1/2". I just want to be sure that your plugs are sticking into the chamber correctly. Also, does the "D" mean it is 12mm threads?

Also from poking around the forum, it seems that B8HS might be one that others have recommended. The "H" is for short reach while the "E" is for long reach. Don't know what the "A" means in your case.

I would still want to confirm the timing. Timing issues can mask other problems. Wouldn't hurt to put a timing light on the engine and see where the S-marks fall. Use a separate battery, not the bike's, and switch the inductive lead from side to side to also confirm.

I would make sure that the carb settings/jets/needles are stock and go from there. Replacing seats is not a typical thing that I'm aware of. If the float won't shut off flow of fuel, then something might be wrong with the float needle and/or seat.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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Re: R50/2 149-150 Carbs fouling plugs, put 105's in and seems fine...but is it?

Post by Seek »

First off, I don't think the Bing jets are meassured in diameter values. The value stamped on the jet is some kind of flow variable, but nobody seems to know what it actually is. Never mind, a larger number is a larger jet.

It's kind of hard to interpret the mixture from reading the plug. Just a bit of puttering along at idle before you pull the plug could allready leave enough sooth on the plug to make it look like the bike is running too rich. Better would be to go full throttle, pull the clutch, kill the engine and let it coast to a stop. Then look at the plug. But an even better way is to see how fast the bike goes with various jets. Get a selection, say from 110 to 125 and see how fast the bike can go. Max speed is ideal jet. The same could be done for the needle and needlejet, but then at half throttle. Needles and needlejets are wear items.

But indeed like Kurt says, check the ignition timing first. At S but especially at F, which is the more important one.

Thunderdome74
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Re: R50/2 149-150 Carbs fouling plugs, put 105's in and seems fine...but is it?

Post by Thunderdome74 »

Ok, will do some testing over the weekend

With new plugs (when i had the 120/125 jets in )the bike rand really well, but rich , for a bit then it fouled the plugs after about 5km.

With these 105's the bike is not fouling the plugs but is down on power

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Re: R50/2 149-150 Carbs fouling plugs, put 105's in and seems fine...but is it?

Post by Tinkertimejeff »

Coil, wires and caps. Sometimes the most tricky carb issues are electrical system problems. Make sure your electrics are good.

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Re: R50/2 149-150 Carbs fouling plugs, put 105's in and seems fine...but is it?

Post by Daves79x »

The charts show that 120 mains are correct for those carb numbers, but the earlier R50 carbs only use 105. Must be other differences.

Dave
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vechorik1373
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Re: R50/2 149-150 Carbs fouling plugs, put 105's in and seems fine...but is it?

Post by vechorik1373 »

Drilling out jets is tricky business, I suggest you buy NEW ones, they are available.
And while you are at it, a new needle jet (what the main jet screws into) might not be a bad idea, they can wear and become larger that will screw up the metering of the fuel.

And, assuming (the word made up of ass of U and me) your air filter is not plugging up, (look at it, when in doubt, put a new one in). Now, the only reliable way of checking/reading the plugs is to do it this way.

1. put two new plugs in.
2. put a plug socket in your pocket
3. ride the bike at highway speeds (50 or more) for at least 20 miles, and while you are going down the road at speed, and you see a good safe place to pull off, reach up there and pull the key up and pull the clutch in simultaneously. Roll to a stop, and then pull the plugs and look at them.
Ignore the outside of the plug, look at the center insulator only. If it is turning tan, your good. chalk white, too lean, soot black, too rich.
You must do it this way, because the engine always runs richer on the idle circuit. That is the way it is designed.
If you ride around, come back to the house, let it idle, center stand it, get your helmet off, and them pull the plugs you will get to see how they are running at idle.
Vech
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Thunderdome74
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Re: R50/2 149-150 Carbs fouling plugs, put 105's in and seems fine...but is it?

Post by Thunderdome74 »

Hi ...thanks everyone for all the information.

What I have done it drilled the jets (the 105s that I took from the other carbs ) to 1.15.

The bike or most definitely pulling stronger and sounding better.little to no backfiring.

So I will be taking vetches advice and getting some 120s and a needle jet.

The needle jets I have are not quite oval but I can see wear marks

I have not done a plug chop just yet as it's been raining like crazy

But it seems to definetly be a carb issue

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