Miss firing on right side cylinder

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Skiprat
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Miss firing on right side cylinder

Postby Skiprat » Mon May 03, 2021 8:09 pm

Hi can anyone shed some light on this problem, R100RRT 1987 mono
I have just changed both throttle cables with new ones from motorworks, used then before no problems. checked cable with old ones perfect match.
All setup bike started no problem balanced up and tick over good. Took it out and after a few minuets right cylinder started missing as if it was about to go on to reserve.
Turned on reserve on both taps still missing on right side came back cleaned float bowl , no better right cylinder mis firing
Took both carbs off one at a time and stripped and cleaned with carb cleaner, rebuilt .
starts ticks over , same problem with right as before.
Left cylinder perfect running as it should.
Engine does not rev when bars are moved so cables so seem routed ok

Cheers
Paul

Mjolinor
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Re: Miss firing on right side cylinder

Postby Mjolinor » Mon May 03, 2021 8:15 pm

Swap the plugs, see if it moves then swap the HT leads over if they are long enough. If not it's a tank off job and swap the coils.

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JaggeryJoe
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Re: Miss firing on right side cylinder

Postby JaggeryJoe » Mon May 03, 2021 11:39 pm

One thing you could check is that the HT lead is making good contact with the coil. I had a bit of a misfire once and pulling the HT lead it came away a little too easily, leaving the brass end cap in the coil. Just re-soldered the end cap to the end of the HT lead and the misfire mysteriously disappeared.
R100/7 Hazel, due to finding mice had been stashing nuts in my airbox :shock:

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SteveD
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Re: Miss firing on right side cylinder

Postby SteveD » Tue May 04, 2021 3:42 am

The question to mind is...is this secondary to your recent intervention or is it coincidental?

Do the plugs look similar? Swapping the ignition stuff is probably the easiest thing to try first. If no success...

Also easy but a bit more time consuming is the fuel system. Take the bike out again. Run it until it starts missing. As soon as it's safe, whilst it's still missing, turn the left tap off, then the right asap.
Take the bowls off and carefully compare the volume. Maybe for some reason the bowl is filling inadequately? With the crossover tube it should still work but it might be fine at low rpm operation but not when demand is higher?

If that is the case, then the question is why? Stuck float? Blockage somewhere? Filters, crud in main jet...

Is the ICU paste good?
Cheers, Steve.
1982 R100RS, 2006 K1200R.

Stay horizontal!

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Rob Frankhamr
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Re: Miss firing on right side cylinder

Postby Rob Frankhamr » Tue May 04, 2021 11:01 am

On a 1987 machine, there will be only one double ended coil.

First off, if it's the original grey coil, then it would probably be a good idea to replace it anyway, whether or not it solves this problem. The original type has a reputation for cracking with symptoms similar to yours and, if it hasn't failed already. there's a good chance it will soon.

The advice to swap ignition components from side to side is good...

Swap the HT leads in the coil first, if the fault swaps sides, it's the coil, if it doesn't...

Swap the ignition leads from plug to plug leaving the coil connections as is. If it changes sides it's the plug leads... if it doesn't...

Swap the plugs over leaving the plug leads on the same side. If the fault remains in the same side after all that, it's either the coil or it isn't ignition related at all.

Rob
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SteveD
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Re: Miss firing on right side cylinder

Postby SteveD » Tue May 04, 2021 1:46 pm

Ahh yes...good job Rob. The ol' crack-o-matic coil (might) strike again.

https://forum.boxerworks.com/viewtopic. ... 64&start=0
Cheers, Steve.
1982 R100RS, 2006 K1200R.

Stay horizontal!

https://stevedoyle.smugmug.com/organize/R100RS/R100RS
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