running lean between 6000-9000 rpm

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Teake
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Registriert: Fr 22. Apr 2005, 01:00
Wohnort: Niederlande
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Beitrag von Teake »

Hello,
<BR>
<BR>A nice set-up case to study: We tested a mito350 on the dynostar, with a very nice running engine. Not that much power, but it runs very clean and crisp. BUT... the mixture runs very lean between 6000 and 9500 rpm. What causes this, and how can it be solved?
<BR>
<BR>Setup:
<BR>* standard 1WT (unrestricted 1UA in Germany)
<BR>* Fedor Copal exhausts
<BR>* Boyesen reeds
<BR>* K&N filters
<BR>* mainjet 320, powerjets closed.
<BR>
<BR>See this discussion (in Dutch!) for more info:
<BR>
<BR><!-- BBCode auto-link start --><a href="http://rd350.motormuizen.nl/phorum/read.php?4" target="_blank">http://rd350.motormuizen.nl/phorum/read.php?4</a><!-- BBCode auto-link end -->,70946
<BR>
<BR>Results: Click for larger picture.
<BR><!-- BBCode u2 Start --><A HREF="http://www.xs4all.nl/~rensel00/streetor ... rmogen.jpg" TARGET="_blank"><!-- BBCode Start --><IMG SRC="http://www.xs4all.nl/~rensel00/streetor ... _small.jpg" BORDER="0"><!-- BBCode End --></A><!-- BBCode u2 End -->
<BR>
<BR>Movie with computerscreen during the run:
<BR>
<BR><!-- BBCode auto-link start --><a href="http://www.xs4all.nl/~rensel00/streetor ... ndrun2.MPG" target="_blank">http://www.xs4all.nl/~rensel00/streetor ... PG</a><!-- BBCode auto-link end --> (24.6 MB )
<BR>
[addsig]
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MK
Beiträge: 5801
Registriert: Di 16. Okt 2001, 01:00
Wohnort: Wolfenbüttel

Beitrag von MK »

Nice stuff.
<BR>
<BR>50 HP @ 11.000 & 38 Nm ? You really have an unrestricted bike? That's not even close to what's stock performance! Sounds rather than it's running like a pile of crap!
<BR>
<BR>My guess: The bike is too lean in midrange due to K&N's, Boyesen and maybe the pipes. You can directly see the flapspot in the power curve.
<BR>
<BR>Did you use a filter spacer or did you mount the K&N's directly to the carbs? If yes use a fitting tube of 40 - 60 mm length to get the filters away from the carb.
<BR>
<BR>Did you fit all the fuel & vacuum lines ? Maybe there's a passage where the carbs get additional air which doesn't make much influence at higher revs.
<BR>
<BR>I'd first try to increase the idle jet size and use a higher needle position.
<BR>
<BR>Maybe someone has some 31K carbs to borrow from?
<BR>I'm asking because I recently had a 1WW to care for that had a similar performance. After checking all it turned out that obviuosly some passage inside the carbs was clogged and using 31K carbs made it running like hell again. Now the owner is a REALLY happy man <IMG SRC="/phpBB/images/smiles/icon_smile.gif">
<BR>
<BR>If that doesn't help:
<BR>Put the bike back to stock condition and start to change one by one.
<BR>
<BR>Are you coming to Pottendijk next Monday? If the weather is not too bad I maybe there with some friends and we can have a chat and/or do some testriding.
[addsig]
Ciao
Martin
---------------------------------
SSDD (Stephen King, Dreamcatcher)
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Teake
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Registriert: Fr 22. Apr 2005, 01:00
Wohnort: Niederlande
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Beitrag von Teake »

Hello Martin, Thanks for your quick respons.
<BR>
<BR>I posted the same message on the english forum and someone there responded with 50bhp is a good value for a stock F2. I thought it was quit poor, as 63bhp minus 10% transmission losses is about 56 rearwheel bhp.
<BR>
<BR>Do you know what a good F2 should give at a dynostar test?
<BR>
<BR>This is a test with a light roll, being slowed down with a magnetic field. So it is slightly different from the normal tests with a heavy roll acceleration measurement.
<BR>
<BR>The carb tips you gave might do the job, we'll pass it through to the owner of the mito350. Hope it helps
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Teake
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Registriert: Fr 22. Apr 2005, 01:00
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Beitrag von Teake »

Hello Martin and others,
<BR>
<BR>I also posted this message in the english forum, which gives some interesting opinions too..
<BR>
<BR>perhaps you could respond there too?
<BR>
<BR><!-- BBCode auto-link start --><a href="http://www.yamaha-rd.com/forum/topic-25057.html" target="_blank">http://www.yamaha-rd.com/forum/topic-25057.html</a><!-- BBCode auto-link end -->
<BR>
<BR>
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