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Old 27 May 2009
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1984 Yamaha XT 600 high RPM sutter/cutting out!!

Hi All,

I know others have experienced the same situation and I haven't heard of a cure as of yet. I have a 1984 Yamaha XT 600 that misses at 3/4 to full throttle. Even if I pull in the clutch at full throttle, it will continue to miss as if it has a rev limiter. I have double checked all the full system and carbs to make sure all is clean. Checked the secondary carb diaphram - good. I have a Super Trapp on the bike and have increased both carbs mains 2 sizes from stock with no luck. The plug and Super Trapp have black soot showing signs of plenty of fuel.... "rich" if anything. I was having a hard time figuring if it was starving for fuel or electrical, but since I have increased the jetting with the same missing occuring, I think it must be electrical/ignition realted. The kick stand switch has been bypassed. The air box and aircleaner are free/clean... no restrictions. Any ideas/cures would be greatly appreciated!
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Old 29 May 2009
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Coil/HT lead/plug?
2006 XT660R daily ride, 1994 XT600E about to be reborn, Blog: http://goingfastgettingnowhere.blogspot.com/
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Old 29 May 2009
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My '86 does it too. The only solution that has fixed it I've seen online is removing the side stand safety switch. mine already has it removed.

I've checked the jets, checked float level, cleaned the air filter, adjusted the valves, checked electrical connections, checked the plug and plug gap, adjusted the secondary linkage with the primary slide at 5mm. My next attempt will be setting the secondary with the primary slide at 7 or 8 mm, as I've seen mentioned in some forums.
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Old 29 May 2009
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I've had this on my '84 Tenere.
I can rev through to 60mph in 4th and the bike won't go much further in 5th.

There's no side stand switch so I think we can rule that out.
I think it has something to do with the air supply or fuelling myself - I just can't put my finger on it.

David Lampeth will know what it is - he doesn't give up info like this easy though (he has to make a living).
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Old 30 May 2009
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too rich?

I had something similar with my wife's 55w. Cured by a very thorough clean of the airfilter. The intake system on the older XT's is quite restrictive, so the more air you pull through the richer the mix. I'd say try the bike with the stock jets and needle settings, and with the airfilter removed (just during test). If that solves the issue buy a new air filter, keep it clean and do not over oil it.

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Old 30 May 2009
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it does sound like an air flow problem running to rich, i over jetted mine and it did the same thing.
going up two sizes is probably too much unless you go to individual filters or open up the air box and fit it with a high flow filter.

i'm going to invest in a big box of jets and spend a couple of days setting it up but i'm running twin mikuni bcr32's and 3mm oversize high comp piston so unfortunately my jetting setup wont help your bike.


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Old 30 May 2009
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84 XT 600 high RPM sputter/cut out

My 84 XT 600 did the same thing even wih the stock jetting, that's why I jetted up. The bike still does the same thing. I also ran it with the air box cover off... before and after upping the jetting..... same sputtering/missing! Finding jets for the primary carb is no problem, but where do you get bigger jets for the secondary carb? I got myself a few small # drills and slowly drilled the secondary jet hole larger. I would like to go back down one hole size now on the secondary jet, but obviously can't. Who offers secondary jets?
Thanks for the help!
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