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Slash2
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I've been cruising on my 88 R100RS all summer and did a fair number of miles today with no issues as usual. The evening took me up to the highest point in my town to watch the sunset with my fiancee and a few friends. It was a rather eventful and strange sunset but that's beside the point. After everyone else had driven back to the road, we donned our helmets and gloves and were about to descend the somewhat rutted up dirt track back down to the road but the bike had other plans. It was in the mid 80's all day and as the choke was unnecessary I hit the starter and while the bike started up and began idling, it was clearly running only on the right cylinder. I did some perfunctory checking and finally pulled the left plug to find it a bit sooty. Fortunately I had a few spares under the seat, so I pulled out a fresh one and stuck it in. I also verified spark and then fired up the bike. No change at all. I should mention that I pulled both bowls to verify fuel and both were filled (to the same level). While the tank wasn't filled to the brim, it had several gallons. Being that it was now completely dark and we were several miles outside of town with 2 large hills to climb and a cell phone that was just about dead from using it as a flashlight during my futile efforts to restore the bike to her previously perfectly running state, we had no choice but to limp home.

The strange thing was how perfectly she ran all day with zero issues to speak of and then after sitting for about an hour, the left cylinder refused to fire. At this point I'm wondering if I dislodged some bit of dirt while climbing the rutted out cow path through the field and it found its way into my jets. If the carb is getting gas, and the cylinder is getting spark, yet the cylinder is not running... Any other ideas?

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64' R60/2 - 66' R27 - 51' R67 - 68' R69S
88' R100RS - 06' K12R

tonyhutchinson
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Durham England
Joined: 08/17/2015
Posts: 98
Im thinking its something

Im thinking its something pretty basic, just a matter of finding it. Before anything try swapping the plug leads over, it may sound odd but Ive had trouble with them in the past, if the problem persists then its most probably not electrics. Carbs are easy enough to remove and strip down, take the jets out and blow them clean with carb cleaner and check the rubber O rings have not deteriorated and got stuck in the jets.

You could also check the diaphragm with the carb off and make sure that the choke mechanism is working ok - you did mention that the plug was sooty. Good luck

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Tony

Slash2
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Thanks for the tips Tony. As

Thanks for the tips Tony. As soon as life affords me a few spare minutes I'll give those ideas a try. In the mean time, here's a shot of the bike from a field known locally as "the top of the world" as it provides a pretty great view of surrounding area as well as the sunset. The bike carried us up there without issue but apparently enjoyed the sunset far less than we did.

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64' R60/2 - 66' R27 - 51' R67 - 68' R69S
88' R100RS - 06' K12R

Slash2
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Joined: 10/17/2015
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Bad Lead?

Tony,

As per your recommendation, I swapped the leads and found the non-running left cylinder to begin firing while the previously running right cylinder was now quiet. Is the solution as simple as a few new leads?

Chris

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64' R60/2 - 66' R27 - 51' R67 - 68' R69S
88' R100RS - 06' K12R

strichzwei
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For those of you that did not

For those of you that did not see the bike in the photo above, it is on the left!
Wink
Scott

schrader7032
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VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
Posts: 6540
Chris - Did you just swap the

Chris -

Did you just swap the ends at the spark plug or did you swap the coil end of the high tension cable? I think you need to continue to troubleshoot to isolate if it's the wire or the coils.

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

Slash2
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Kurt, I took the entire left

Kurt,

I took the entire left cable lead and stuck it on the right cylinder and the right to the left. I think I see what you're saying about the coil. Is it possible that the coil is providing juice to the right lead but not the left? I suppose I assumed that if the coil is toast, it's complete toast.

When I started the bike the night this issue emerged, I noted that the left cylinder came in a few times as I raised the RPM's before totally ceasing the fire altogether.

Chris

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64' R60/2 - 66' R27 - 51' R67 - 68' R69S
88' R100RS - 06' K12R

schrader7032
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San Antonio, TX
Joined: 10/27/2006
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Be sure there's no corrosion

Be sure there's no corrosion in the towers of the two coils.

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

tonyhutchinson
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Durham England
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I would start with the easy

I would start with the easy and cheap option and just replace the Ht lead and plug cap. I like Scott's comment though

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Tony

Slash2
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Should have checked the lead first.

I ordered up a set of new leads from my local dealer on Thursday and had them in my hand on Saturday afternoon. Walked up to the garage and pulled the tank. This revealed the answer to the problem. The left side lead had popped out of the coil.

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64' R60/2 - 66' R27 - 51' R67 - 68' R69S
88' R100RS - 06' K12R

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