RPMs dropping when I push down on the accelerator????

[djd]

Baseline: I have an 03 Yamaha 200 Ox66 w/some Hydro Tec parts on it. Still don't have the prop figured out but it generally runs my 25T1 to a 6000RPM redline fast.

This weekend after a nice warmup idle my partner and I took off to our first spot. The motor ran to about 5700 RPMs then actually dropped back to about 5400 - 5500 RPMs. When I let off the gas it actually starting gaining RPMs up to about 5800. I stepped on the accelerator and it lost RPMs again. This scenario repeated all day Saturday and Sunday. Ideas???

[wildkat7]

Sounds like your o2 sensor....

[Mat_HT]

+1
I agree, it sounds like an O2 sensor issue.....when they get get dirty they start acting up at WOT. And its usually just like you described.
Just needs a good cleaning usually. I think there are several threads on this board explaining how to do this.

[headhigh]

I've heard that Seafoam works good for cleaning your O2 sensor and keeping it clean.

[wildkat7]

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by headhigh &raquo;</TD></TR><TR><TD CLASS="quote">I've heard that Seafoam works good for cleaning your O2 sensor and keeping it clean.

</TD></TR></TABLE>

either that or ringfree....a lot of discussion has been made on what oil to run as well....personal experience, I had o2 sensor issues when running yamalube (go figure) but none since switching to penzoil...whatever oil you use, make sure you use Ringfree or Seafoam to break down carbon.

[djd]

Cleaned O2 sensor this week. Ran stronger and allowed me to give it more throttle, but not all of it. Ran to almost 6000 RPMs, when I tried to push the throttle all the way down, it would drop back to 5600 RPMs. Should I try cleaning the O2 sensor again. FYI ... I found out last week my oil linkage gap was HUGE!!! Was probably running 15:1 and the O2 sensor and housing were filthy! Thoughts???

[wildkat7]

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by djd &raquo;</TD></TR><TR><TD CLASS="quote">Cleaned O2 sensor this week. Ran stronger and allowed me to give it more throttle, but not all of it. Ran to almost 6000 RPMs, when I tried to push the throttle all the way down, it would drop back to 5600 RPMs. Should I try cleaning the O2 sensor again. FYI ... I found out last week my oil linkage gap was HUGE!!! Was probably running 15:1 and the O2 sensor and housing were filthy! Thoughts???</TD></TR></TABLE>

Might be beyond cleaning...dunno...

[djd]

Replaced Yamaha O2 sensor with an aftermarket sensor being utilized by several folks here on the board. Same results. This is getting awfully frustrating. Ideas???

djd

[BlazinNow]

Hey djd,

mine did the same thing on saturday.. http://www.bbcboards.net...17716 ....

When you cleaned the 02 sensor did you have to replace any gaskets? Thanks