1970 750:Blu flammed pipe

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pierodn

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Hi.
New exhaust pipes but only the right become blu flammed.
The left one remIns full chromed.
Bike has a stock engine with new pistons and new guides and valves, with a Pazon IE and the stock Amal full overhaulled.
What it means?
What to check?
Thank you
Piero
 
Any black smoke from the left cylinder?
What's the compression like?
I assume you have twin carburettors?
 
Go back over everything, check valve clearance etc check for air leaks on the right hand cylinder
What's the history of the downpipes? IE are they a matched pair and the wall thickness of the left pipe isn't thicker than the right?
 
Check your exhaust header temps with an infrared heat gun FIRST before you start tearing anything apart. If the temps are pretty close, it's probably the pipes.

Although it is often an indicator of mixture issues in the cylinder, as Baz noted, it could be the pipe, not the engine. Depending on the quality/depth/consistency of chrome and tubing, there could be a substantial difference in coloring. I had exactly the same thing occur years ago on a non-Norton - went over and over the mixture/timing/leak checking, etc. Couldn't figure out why one cylinder was running much hotter than the other...turns out it wasn't. A new set of pipes cured the problem.
 
What MexicoMike said.

If you have recently had all the components mentioned updated/corrected/renewed....look at the simple reasons first rather than tearing into everything immediately.

Does the spark plug on the non blue clean chrome side show indications of firing (?).....or not(?)....is it sparking?

Are your pipes a crossover configuration or independent of each other?

If not crossover then you should be able to tell the difference in heat upon startup just by placing the back of your hand in close proximity to either cylinder exhaust pipe outlet

The infrared temperature gauge is of nominal cost, could save you lot of grief, and the most accurate tool for the information you seek.

I had the same discoloration issue Mike mentioned and it was the chrome plating that was at fault...the pipe temps at the head were only one or two degrees apart in temperature.
 
Hi.
Bike starts and runs great, doesnt smoke.
But from the left exhaust (no cross over tube) air came out less hot than from the right one.
Right spark plug fires very good, the left not very dirty but a little bit black.
Thank you.
Piero
 
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Could it be that the right cylinder runs too hot ?
Right carburator too lean due to blocked idle jet ?
 
I have that same right side bluing on my 850...but I'm running a single Amal 932 so fueling differences keft/right should not be relevant. Is there something inherent in the head or header design that accounts for the difference?
 
Tornado said:
I have that same right side bluing on my 850...but I'm running a single Amal 932 so fueling differences keft/right should not be relevant. Is there something inherent in the head or header design that accounts for the difference?
Click to expand...
Back in the day single carb bikes like a BSA A10 with a single carb fitted it was more common for one side to run hotter than the other
This was said to be because of casting irregularities inside the inlet port
The answer was a tufnol angled inlet gasket
But obviously the compression needs to be the same both sides,the timing set properly,the valve clearances,camshaft wear etc all need to be the same
 
baz said:
Back in the day single carb bikes like a BSA A10 with a single carb fitted it was more common for one side to run hotter than the other
This was said to be because of casting irregularities inside the inlet port
The answer was a tufnol angled inlet gasket
But obviously the compression needs to be the same both sides,the timing set properly,the valve clearances,camshaft wear etc all need to be the same
Click to expand...
I'm planning to try moving the needle up a notch from middle to see what effect enriching off idle has. I've picked up a Gunneson ColorTune plug for next to nothing ($13 USD) and plan to check how it reads at current settings then try the needle raise.
 
Another thing you could check by sight is how aligned to the exhaust port the header pipe is. To explain, about 3 years ago I fitted a new set of header pipes to my Fastback and the pipes were so far out of alignment my arm muscles took 4 days to recover from peening the header mouths with a ball peen hammer in order to be able to fit the mufflers. The result was the RH header was about 7 degrees out from the optimal position (facing downwards) at the rose nut. The top section of the bend was blued for about 9 inches while the under side of the pipe had no discolouring. (I think that the exhaust gases were being mainly directed against the top section of the header). Anyway, you won,t notice it as much after they start rusting.
 
I had exactly the same problem. It's a process of elimination. First do a leak down test. Then with a temp sensor (I have a multimeter with one, cheap as chips), swap the plugs, run bike. Swap the coils run the bike, see if the problem moves using heat sensor. If no joy at this point I would look at the carbs, check for air leaks, then as your Amals are overhauled, swap the jets over from one carb to the other, as they can be mis-sized apparently. My problem was a coil, not helped by worn needle jets and an oil burn issue. All now cured!
One other thing with Pazon check the coils wired correctly, can't remember if it's in series or parallel.
 
@pierodn you say you have a brand new Pazon electronic ignition - this is a wasted spark type which means that both sides are firing at the same time.

So if it is electrical, it's down to a few things which you can quickly and easily try without test kit:
1) the plugs - try swapping plugs left and right as @Lineslinger says
2) the coils - i assume you are running two separate 6 volt coils in series, so try swapping left and right coils over - this will prove that both coils are good
3) the leads - they don't last forever, and break down over time, give them a visual inspection for kinks and damage. Try swapping them from left to right.

If your issue stays on the right side in all cases then you can turn your attention to fueling.

1970 750:Blu flammed pipe
 
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