Author Topic: 550K1 - carb questions (022A)  (Read 6572 times)

Offline K2-K6

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Re: 550K1 - carb questions (022A)
« Reply #45 on: August 02, 2019, 01:30:01 PM »
Thinking about this Erny over a few days, did you see a previous thread on here with very similar problem (I forget which owner) and it was a problem none of the suggestions we made got the problem.

Finally turned out to be the original exhaust of one cylinder was partially blocked within the first section. It seems it was manufactured with the pipe's inner skin deformed about 200mm down into the pipe from front entry. 

If you removed the pipe from cylinder two and either put a camera down there or something to see if there's a restriction it would tell you.

Offline Erny

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Re: 550K1 - carb questions (022A)
« Reply #46 on: August 02, 2019, 01:45:39 PM »
hmmm, interesting idea. Will try to check that, just not sure how long cable my camera has. But in theory it could explain too.
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Offline K2-K6

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Re: 550K1 - carb questions (022A)
« Reply #47 on: August 02, 2019, 01:54:27 PM »
I've tried searching for it but so far can't find the thread,  someone else may help remembering to give us a link.

Pictures of it posted and cut open afterwards as pipe was scrapped.

Offline Erny

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Re: 550K1 - carb questions (022A)
« Reply #48 on: August 02, 2019, 01:59:59 PM »
my pipes does not look bad from outside but have tiny holes at the bottom silencer rim. So shall not be normally bad
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Offline K2-K6

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Re: 550K1 - carb questions (022A)
« Reply #49 on: August 02, 2019, 02:10:00 PM »
That problem could not be seen from the outside.

The original pipes are double skinned,  so one pipe inside the pipe you see from outside.  They did this to prevent the pipe's discolouration from heat of exhaust which is why they don't normally go blue from running.

It's just the inside pipe that was buckled from original manufacture it appears,  so was like it from being a new bike,  the problem must have been there all along.

Offline Trigger

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Re: 550K1 - carb questions (022A)
« Reply #50 on: August 03, 2019, 08:20:13 PM »
I think people read too much in to plug colour. I have had a look at the pictures of the plugs and would run with them.
To get the so called perfect plug colour you would need a new exhaust, new carbs and a fully rebuilt top end. You can get a dark plug from a valve not seating properly .

Always better to have a slightly darker plug than one that is running too lean  ;)

Offline Erny

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Re: 550K1 - carb questions (022A)
« Reply #51 on: August 05, 2019, 09:50:21 PM »
Graham, thanks for your opinion, I start to feel the same now :)

I managed to have another coil (from 550F 1976) to test - result is no change, plug 2 still darker than others.

Next:
waiting for intake manifold to replace mine w/o grooves. Carbs will go off again, so time to re-check around air screw (did not checked before).
if no improvement, I'll try to look at another carb set  :-\
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Offline deltarider

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Re: 550K1 - carb questions (022A)
« Reply #52 on: August 05, 2019, 09:55:03 PM »
Without having read all the above... have you checked the plugcaps, both connections as well as resistance?

Offline Erny

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Re: 550K1 - carb questions (022A)
« Reply #53 on: August 05, 2019, 10:19:42 PM »
yes, they are all checked, are new NGK, I even swapped cap 2 and 3, issue remains on cyl2

Moreover, ign coil I had for test had came with caps, so I tested another coil and another cups. No change
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Offline jon stead

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Re: 550K1 - carb questions (022A)
« Reply #54 on: August 09, 2019, 07:05:20 PM »
Thinking about this Erny over a few days, did you see a previous thread on here with very similar problem (I forget which owner) and it was a problem none of the suggestions we made got the problem.

Finally turned out to be the original exhaust of one cylinder was partially blocked within the first section. It seems it was manufactured with the pipe's inner skin deformed about 200mm down into the pipe from front entry. 

If you removed the pipe from cylinder two and either put a camera down there or something to see if there's a restriction it would tell you.

Hi, yes, it was me that had the collapsed inner pipe on number 3 cylinder. However, in my case, the engine ran lovely at lower revs and struggled at higher revs, which would fit with a partially blocked exhaust.
2015 Triumph Bonneville T100 Newchurch

Offline jon stead

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Re: 550K1 - carb questions (022A)
« Reply #55 on: August 09, 2019, 07:16:10 PM »
I've tried searching for it but so far can't find the thread,  someone else may help remembering to give us a link.

Pictures of it posted and cut open afterwards as pipe was scrapped.

http://www.sohc.co.uk/index.php/topic,13971.msg119059.html#msg119059
2015 Triumph Bonneville T100 Newchurch

Offline Erny

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Re: 550K1 - carb questions (022A)
« Reply #56 on: September 02, 2019, 09:15:02 AM »
Graham, thanks for your opinion, I start to feel the same now :)

I managed to have another coil (from 550F 1976) to test - result is no change, plug 2 still darker than others.

Next:
waiting for intake manifold to replace mine w/o grooves. Carbs will go off again, so time to re-check around air screw (did not checked before).
if no improvement, I'll try to look at another carb set  :-\
After some time update :
- intake manifold replaced (thanks Phil again!)
- carbs checked again, especially around air screw on carb 2

Result - no change, plug 2 still darker than others.

Next: will try to tune airscrew (now all 4 are still at standard settings 1.5turns out).

For this would be great to have good RPM meter, I have one digital from China, but not good for this application as it refreshes each 1s (I think) and rpms resolution seems to be +/- several tens..
Can someone recommend good sensitive  RPM meter for idle?
CB750K7 US model (1977)
CB550K1 US model (1975)

Offline K2-K6

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Re: 550K1 - carb questions (022A)
« Reply #57 on: September 02, 2019, 09:46:29 AM »
Some multi meters will give you a frequency readout that you can use,  just connect to one of the points trigger wires to read crankshaft rotations.

That's what electronic tachometer do when installed in vehicles (although some read frequency from alternator output).

As a cross check of rich running carburettor,  you should be able to swap that idle jet with another carb to see if the problem moves. It will give you a cross check of relative calibration of one jet to another.

Offline Erny

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Re: 550K1 - carb questions (022A)
« Reply #58 on: September 02, 2019, 10:13:51 AM »
Thanks, great idea with freq meter, I should have some.
CB750K7 US model (1977)
CB550K1 US model (1975)

 

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