All,
Any insight would be great. Here is what I have. I have an MC21 and let me tell you, I'm in love with it. But, it has been sitting for at least 10 years from the guy I bought it from. When he bought it, it started on no more than 3 kicks. Here is what I am seeing now...

* Fuel flows to the carbs from gas tank
* With good voltage, I can kick until the cows come home... nothing
* Pour fuel into the carbs directly and a few kicks later she comes to life and sound great (I get all giddy about it)
* The top piston's exhaust leaks burnt fuel (very oily) from the inlet of the canister (no biggie I thought). Lots of smoke at start and a strong put-put-put feeling from the exhaust when I put my hand behind it
* The forward piston's exhaust does not put-put-put very hard at all, almost no smoke at start and my hand gets wet with (what I am guessing to be) partially burnt fuel. Also, front piston's exhaust is not getting hot
* Both spark plugs are new, both have strong visible spark when keeping the plug out of the jug but grounded when kicking starting.
* Will not idle
* will not start bak up without pouring fuel into the carbs.

My fears (by priority of OMG WTF)
1 - Front jug has no compression so time for rebuild
2 - Crankshaft seal replacement
3 - Carbs need to be rebuilt (maybe sitting that long aloud the gas to evaporate and leave nasty oil deposits that have gunked up the bowls)

Before I go tearing it all apart I thought I would ask the experts here for which things I should be looking at first. Even if I have low compression in the front jug, it did still start once when checking for spark and on one cylinder soooooo probably not the root cause. Thoughts and criticisms are welcome as maybe I am missing something simple. Thanks in advance.
- Eric

BTW - The bike does not have the oil reservoir and gear driven mixing mechanism. All fuel is pre-mixed 30:1 and added directly to the tank.

Fresh spark plugs helps immensely.
Centre crank seal may be gone, check that.
Fresh fuel (gas for someone of your inclination ), I have seen stale fuel foul plugs.
Have you done a compression test or it's all going by running diagnosis?

Search the forum for the topics, a bit has been said about them before.

Thanks. I should have mentioned that its fresh gas and that I replaced the spark plugs tonight before I started the latest test. As for the compression check, I am picking up a compression tester tomorrow and will do it then. I'll post the results.

The center crank seal, correct me if I am wrong but that means I have to crack open the motor, i.e open the bottom end up right? Thanks for such a quick response.

Also, I did some digging and simply scared myself to death thinking that this might mean I have an entire engine rebuild ahead of me. That being said, I would do it if I need to instead of running and causing more damage. Thanks again,

- Eric

That sounds like mine when I got it. It turned out to be lightly seized on one cylinder, and would run on one but not idle.

Unfortunately though, it also sounds like it could be a crank seal.
_________________
89 MC18 R5K
92 MC21 SE
91 RS250 NF5

That is my fear. Are the seals the same as the crank shaft bearings for the MC21? Or will I most likely be buying two outer bearings, one center bearing, and then seals also? Thanks,
- Eric

Hurdy brings up a valid point.

Take the exhausts off and have a look up the port, see if you can see any damage.

If you can't see much, whip the head off, make sure you have a spare set of gaskets.

If the centre crank has gone, then yes, you have to split the cases.

To save the expense of base gaskets and head gaskets (£14ea.), you can remove the barrel/head assembly complete.

The 1989~1997 (MC18R5/6K, MC21, and MC28) centre crank seal is integral to the crank bearing. Earlier (87 & 8 have a separate, unobtainable, centre seal.
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Andy.
NSR-WORLD.COM

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Took some pics after removing the carbs and vents. Don't know if the helps but if you see anything that looks a bit off, please feel free to let me know. I didn't do the compression check as I had hoped, too busy at work to go buy one.




Also, you can see a little bit of a roughed edge on a thin piece of metal and that thin piece of metal has a ton of play not sure if that means anything but I thought I would bring it up. I was very glad to see the amount of gas/oil on all of the parts of the crankshaft, housing, piston etc... that I could see. Makes me wonder why the spark plug for the front cylinder was so clean. I feel a rebuild coming and to be honest, I am not looking forward to it.

i would say crank seals as well
check the barrels as you take them off
if it has been stood 10 years they want doing