1964 G15 MK2 carburation

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Hi All.
My bike starts and runs very well.
But the right spark plug is a nice white/brown while the left is very fooly.
The good spark plug is on the chopped monoblock side while the fooly one is on the monoblock float side.
Suggests are very welcome because is my first time with monoblock.
Thank you.
Piero
 
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Hi All.
My bike starts and runs very well.
But the right spark plug is a nice white/brown while the left is very fooly.
The good spark plug is on the chopped monoblock side while the fooly one is on the monoblock float side.
Suggests are very welcome because is my first time with monoblock.
Thank you.
Piero
Sorry but fooly means soot
 

texasSlick

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Piero,

The monoblocs share a common float, and both carbs have same fuel height. Therefore, your problem is not related to float setting.

First step is to be certain both carbs have identical configuration, that is jets, needles (type and notch setting), and slide cut-away.

It is also good to check original specification for the bike you have. Go to this site and find your bike:


Slick
 
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From experience also check that you mag is firing 180 degrees apart I have had a mag that was out by 8 degrees.
 
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From experience also check that you mag is firing 180 degrees apart I have had a mag that was out by 8 degrees.
Hi and thank you.
Please could you explain better, is my girst time with mag.
Piero
 
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You need to check the timing on both cylinder separately as they were not both firing on the same mark in my case the cam ring in the mag had to be modified to get both to fire at 31 degrees.
 
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I was having the a very similar issue with my G15 monoblocs. RH plug was great but the LH was running dirty and got increasingly oily. I kept chasing the issue by adjusting carburation but that wasn't apparently the problem.

My last ride before putting the bike in storage, it stopped running on the LH cylinder due to heavy oil fouling, and I started seeing oil seepage from somewhere on the rear of the barrel or head. Once I have the bike back in a few years, I'm going to get into the top and and look for problems with a valve guide, oil ring, etc., and reconfirm the timing is 180 out on both cylinders.

Doubt your issue is the same as mine, of course. My only point, based on my small bit of experience here, is that while there's certainly going to be a small variance in the carbs...and they respond best to tuning the idle mix individually, rather than setting them 100% identitically...you've probably got a different issue, such as the timing mentioned above.

Of course, it could also be that the balance tube between the carbs is obstructed somehow, but that seems like something you would have already noticed.
 
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I was having the a very similar issue with my G15 monoblocs. RH plug was great but the LH was running dirty and got increasingly oily. I kept chasing the issue by adjusting carburation but that wasn't apparently the problem.

My last ride before putting the bike in storage, it stopped running on the LH cylinder due to heavy oil fouling, and I started seeing oil seepage from somewhere on the rear of the barrel or head. Once I have the bike back in a few years, I'm going to get into the top and and look for problems with a valve guide, oil ring, etc., and reconfirm the timing is 180 out on both cylinders.

Doubt your issue is the same as mine, of course. My only point, based on my small bit of experience here, is that while there's certainly going to be a small variance in the carbs...and they respond best to tuning the idle mix individually, rather than setting them 100% identitically...you've probably got a different issue, such as the timing mentioned above.

Of course, it could also be that the balance tube between the carbs is obstructed somehow, but that seems like something you would have already noticed.
Hi and thanks.
Valves and guides are new and the mag setting is 31 degree both sides.
For first i will unscrew half turn the air of let carb.
I will let you know.
I dont know if this is the solution.
Piero
 
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I was having the a very similar issue with my G15 monoblocs. RH plug was great but the LH was running dirty and got increasingly oily. I kept chasing the issue by adjusting carburation but that wasn't apparently the problem.

My last ride before putting the bike in storage, it stopped running on the LH cylinder due to heavy oil fouling, and I started seeing oil seepage from somewhere on the rear of the barrel or head. Once I have the bike back in a few years, I'm going to get into the top and and look for problems with a valve guide, oil ring, etc., and reconfirm the timing is 180 out on both cylinders.

Doubt your issue is the same as mine, of course. My only point, based on my small bit of experience here, is that while there's certainly going to be a small variance in the carbs...and they respond best to tuning the idle mix individually, rather than setting them 100% identitically...you've probably got a different issue, such as the timing mentioned above.

Of course, it could also be that the balance tube between the carbs is obstructed somehow, but that seems like something you would have already noticed.
Hi.
Not solved the problem, left spark plug is very soot (not oil).
Please, could you explain me the best way to check and reconfirm the timing is 180 out on both cylinders?.
Thank you
Piero
 
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Hi Piero,

If you are sure you have a carbon fouled plug in the LH cylinder, your problem is probably carburettor related, but please read this:

However, before fiddling with your carb, you NEED to make sure ignition is correct on both cylinders, so please check opening of points individually against piston position or crankshaft angle. Do make sure the chain drive is under tension when doing this. Best is to turn the crankshaft in the positive sense all the time, do not turn backwards. Has your AAU been restored?

-Knut
 
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Hi
Hi Piero,

If you are sure you have a carbon fouled plug in the LH cylinder, your problem is probably carburettor related, but please read this:

However, before fiddling with your carb, you NEED to make sure ignition is correct on both cylinders, so please check opening of points individually against piston position or crankshaft angle. Do make sure the chain drive is under tension when doing this. Best is to turn the crankshaft in the positive sense all the time, do not turn backwards. Has your AAU been restored?

-Knut
Hi Knut.
AAU never restored.
Magneto tuned 31 degree BTDC.
I dont understand what means “every 180 degree”.
Thank you.
Piero
 
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Hi

Hi Knut.
AAU never restored.
Magneto tuned 31 degree BTDC.
I dont understand what means “every 180 degree”.
Thank you.
Piero
I have red the link sent.
I can confirm the plug is over fouled (the left of the float bowl monoblock).
Bike starts and rins great so that i can think timing is vorrect.
My be i must tuned better the left carburetor to have less reach?.
Float to make lean?
What is the way?
Air screw?
I know very well the concentrics but is my first time with monoblock.
Thank you.
Piero
 

texasSlick

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Pierro:

Have you verified both carbs have SAME jets, slides, needles, cut-away?

Knut (post #11) wants you to check timing on EACH cylinder ...... must be the same within 2 degrees.

I once had very rich mixture on right cylinder. The problem was a leaky gasket between the jet block and main body.

Slick
 
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Pierro:

Have you verified both carbs have SAME jets, slides, needles, cut-away?

Knut (post #11) wants you to check timing on EACH cylinder ...... must be the same within 2 degrees.

I once had very rich mixture on right cylinder. The problem was a leaky gasket between the jet block and main body.

Slick
Thank you.
 
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Piero,

I am concerned a wobbling and possibly jamming AAU plus an inaccurate slip ring may disturbe your timing. Best option would be to install an EI, at least as an interim solution while you chase the combustion problem.

(I never thought I would advocate an EI, but now I do. It's the least fussy ignition system available - as new at least.)

-Knut
 
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Piero,

I am concerned a wobbling and possibly jamming AAU plus an inaccurate slip ring may disturbe your timing. Best option would be to install an EI, at least as an interim solution while you chase the combustion problem.

(I never thought I would advocate an EI, but now I do. It's the least fussy ignition system available - as new at least.)

-Knut
Hi Knut,
i inderstand but i am
Piero,

I am concerned a wobbling and possibly jamming AAU plus an inaccurate slip ring may disturbe your timing. Best option would be to install an EI, at least as an interim solution while you chase the combustion problem.

(I never thought I would advocate an EI, but now I do. It's the least fussy ignition system available - as new at least.)

-Knut
Hi Knut,
I am ultra fixated with originality and I like the challenge with the old stuff.
Magneto is well setted and works fine.
I must set better the monoblocks that are the original of 1964.
They will must work well.
To day while was riding blocked the viton
Ciao
Piero
 
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Hi Piero,
I do understand your sentiment, and we have the same attitude. However, it's necessary to eliminate one potential source of problems at a time. Right now you don't know how well your mangneto works. Producing a spark per crank revolution is not enough.
You may still revert to the magneto if and when the potential carb problem has been sorted.
Just my 0.01 cent.

- Knut
 
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I must set better the monoblocks that are the original of 1964.
They will must work well.
To day while was riding blocked the viton.
I guess you refer to the viton tipped float needle. If carb bodies are original, they will probably need to be sleeved. I have done the same with Concentric carbs. Throttle valves should be hard cromed or replaced by valves made of brass as in new Monoblocks now offered. Rattling throttle valves will affect fuel mixture and if they allow false air to pass, mixture will be too rich I think.

-Knut
 
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Hi

Hi Knut.
AAU never restored.
Magneto tuned 31 degree BTDC.
I dont understand what means “every 180 degree”.
Thank you.
Piero
Piero, the idea is to check the opening of the points on each ramp against the degree wheel. They should be 180 degrees apart.

To make the math easiest, you could set the degree wheel to 0 at the points opening on one ramp, then turn the engine forward and check opening of the other ramp...should be on/near 180 degrees.

You could also forego the setting to 0, and just use whatever number it falls on...then figure out 180 degrees away from that. So if it falls on 340 degrees, the second ramp should open at 160, etc.

If they're not, apparently you can re-shape the ramps to correct the timing, but I've never done that.
 

texasSlick

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Best to get a newly made cam ring than try to reshape ramps. Newly made ones are CNC machined and are spot on 180 degrees. All one has to do is be certain the point gap is the same on both ramps by centering the ring in the housing, and the timing will be spot on in both cylinders.

Slick
 

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