I have a 1991 MC21 SE, and recently am getting no spark to the right cylinder. A few weeks ago it ran fine on both cylinders. I got the thing started today but it only ran on the left cylinder. I swapped coils and it still only ran on the left cylinder. I stuck a nail into the right plug cap, held on to it and had a friend kick it through. I got a good shock. I swapped plugs in the right cylinder thinking the other one was fouled and still wouldn't fire on the right. I tried the 'feel' method again with the nail in the plug cap and a friend kicking it through, this time no shock.

What could be wrong? I am considering a bottom and top rebuild but before I dump a grand into it I want to sort all the little things first. Thanks for the advice.

Skunkbait

My favourite first things to check are the pick-ups down by the flywheel. The wiring to them can get chafed and wear through. Then they can short out against the crankcases. It can be an intermittent fault depending on how the vibrations affect the wiring.
You need to remove them to check their condition.

Loose plug-cap to lead?
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

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Last edited by DifferentStrokes on Mon Sep 28, 2009 6:45 pm; edited 1 time in total

DifferentStrokes wrote:
Well, to be sure; you should grip the nail with the back most mollers - preferabley the ones with some gold in them - to check...

Nice!
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Andy.
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Thanks for the advice.

I'll try the 'nail between the teeth' method next time.

Although I have no idea which connectors went to what, I disconnected and reconnected every one I could find under the tank and fairing. Must have had some moisture or corrosion in one of them because when I tried to start the bike after that it fired up on both cylinders.

The bike sat in storage for two years and I recently moved it to the North Carolina coast where it's very damp.

I also adjusted the air screws on the carbs while I was at it. They were set at about 2.5 turns out. I turned them in to 1.5 turns. It seems to be starting better, idling better, and running well.

I'm still debating on dumping the cost on a bottom and top end rebuild.

Skunkbait

Skunkbait wrote:
I'm still debating on dumping the cost on a bottom and top end rebuild.

Skunkbait

Difficult one to call, but a top-end refresh is never going to be a bad thing.

Cranks generally tend to deteriorate rather than lunch themselves, so it can be [a] difficult to tell when they are one the way out, and [b] don't usually take anything else with them when they expire, so I'd be inclined to source a new/rebuilt one for the future, as you will need one at some point if you are keeping the bike like most of us do.

I think I have three cranks in the cupboard... but four bikes, two of which have "special" cranks!
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Andy.
NSR-WORLD.COM

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Thanks, Andy.

Are you willing to part with one of your spare cranks?

Skunkbait

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Last edited by DifferentStrokes on Mon Sep 28, 2009 6:45 pm; edited 1 time in total

DifferentStrokes,

I tried viewing the spark at the plug but at the time was parked in my neighbor's driveway where it was very bright and sunny. Even with shading it the best we could, our 50-year-old eyes couldn't see the spark so we used the old-school method.

Since it was my bike I was the one that had to hold the nail. I had forgotten how pleasant an ignition shock was.

I've been in touch with Redline and have a quote for the crank. Tyga has the same thing for quite a bit less even with shipping.

Thanks for the advice though.

Skunkbait

o o


Last edited by DifferentStrokes on Mon Sep 28, 2009 6:45 pm; edited 1 time in total

Skunkbait wrote:DifferentStrokes,

I tried viewing the spark at the plug but at the time was parked in my neighbor's driveway where it was very bright and sunny. Even with shading it the best we could, our 50-year-old eyes couldn't see the spark so we used the old-school method.

Since it was my bike I was the one that had to hold the nail. I had forgotten how pleasant an ignition shock was.

===>snip

Might I suggest next time that you use an insulated pair of pliers or something like that to hold the nail. You can then hold the bits far enough to see the spark.

If the jolt travels the wrong way it can tinker with your heart's timing.

I do find it fascinating all the old school methods that were very effective and simple.

Don't see what's wrong with popping the plug back in the cap and holding the base to the engine, so you can see the colour of the spark...
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

There's a HRC crank on sale at Yahoo Japan, the bid starts at 10,000 Yen and closes on 25h April, you guys are paying way too much in UK and USA ! Ofcourse the crank's shipping costs from Japan is a factor. Check out this crank at :

http://page14.auctions.yahoo.co.jp/jp/auction/s127189459

Thats an RS250 crank and won't fit in the NSR's.

Stock cranks come up quite a bit though for sensible money.
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If I have to take the carbs off once more...