Dave, the motor works great, and I love the bike. However, I am experiencing frustrating and weird starting problems. The bike idles nicely, pulls strongly, starts easily when warm, but it refuses to start if left a couple of hours or more. With a little Aerostart sprayed into the airbox, it fires instantly. The carbs have been cleaned and set-up by a mechanic. I left it with a mechanic friend who left it overnight and it fired first kick for him with no throttle and no choke (it is summer here, 30 degrees C). Could this be my technique? I have tried all manner of kicking - even tore the sole off my Alpinestar boots... and with/without throttle/choke... it just sounds dead, like the kill switch is off (yes, I've made sure it is switched on...). The bike is stock except for the usual wire splices and a few extra holes in the airbox. Has anyone experienced this or have some advice for me?
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MC21 rider from Brisbane Australia.

Sounds exactly like mine did for years!

I finally hit the sweet spot with the jetting in the spring, and it would start first kick every time (unless there was a crowd!!), but in tweaking the jetting to try and iron out the bottom-end I went back to the awkward starter!

My problem appears to be a dodgy crank seal now, as I've eliminated everything else!

Has your bike stood for any extended period? I.e. several months? Mine stood for over 18 months whilst I was in Asia and the States, and I think the lack of use didn't do the crank seals much good! Like I say, I was able to get some semblance of starting reliability back, but I think the seals were already past their best!
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Andy.
NSR-WORLD.COM

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and also sounds very much like my R, eh Andy that also turned out to be the crank.
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MC21SP - Roth-tax
CBR400 - track
MC21R - sold
MC21SP - sold

Your crank was shagged though!

There was about 0.5mm movement in the near-side main bearing, but there is no movement in mine, so I'm expecting the centre seal to be a failing.
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Andy.
NSR-WORLD.COM

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Have you tried a compression check? You should aim to have about 120psi, and both cylinders should be within 10 psi (closer is better).

Low compression can be a factor in poor starting, and can be caused by leaking seals, or by worn rings. One is easier to fix than the other!

Do a check and let us know what you find.
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

I'd be very interested to hear what the problem is. Mine is starting to experience the same hard starting problems. Runs fine after starting but has to be kicked 20-25 times to get it going. I did a compression check this last spring and got around 120psi on both cylinders. It started fine then. Guess I'll start by checking my compression too.

It's come to light recently, that there is a lot mentioned about the centre crank seal in Japanese circles.

I'm going to do nothing else to mine (unless the bearings are shagged) than replace the seal. If it works, then I will let you all know.

I'm not saying it will be the definitive answer to all problems, but it may be an answer to the poor starting ones!
_________________
Andy.
NSR-WORLD.COM

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