Like reading tea leaves

[duane]

This plug is brand new and has been in a running engine for about 30 minutes.



Based on this picture,

Are the carburetors ideal or too hot (lean).


I have what seems to be a common problem, I've synced the carbs and the bike idles well.  After the bike has warmed up and I blip the throttle, the RPM's drop to zero and rise back up or else the bike dies. This is indicative of a vaccum leak?  Yes or no?  

If I spray carb cleaner where the leak might be, are the RPM's suppose to rise?  Any Ideas how to trouble shoot this?

Thanks, Duane

[Krautwagen]

Plug looks too new to me to say...


But, the general procedure for tuning with looking at the plugs:
-WARM ENGINE!
-Run bike in rev range you are trying to troubleshoot for a few minutes/as long as possible.  i.e. bottom end = slow around town cruising, low throttle openings; mid range = highway consistent low-half throttle; top end = full throttle pulls through a few gears (be careful).
-shut engine off ASAP after running though desired range.
-pull plugs and inspect.


General low end/off idle tuning:
-WARM ENGINE!
-lightly 'blip' the throttle.
-If RPM's drop or engine dies, you're too rich
-If RPM's rev up and take a long time to come back down to idle, you're too lean.
-find the happy medium.

So, it sound's like you're too rich on the pilots.

[Red01]

It looks like it has a lot of deposits on it for only having 1/2 hour of use.

[duane]

It was hot, I droped it on the garage floor.  (ya, smooth)

[Red01]

FWIW - if you ever drop an aircraft spark plug, you have to throw it away. Since these babies run $25 and up a piece, you don't want to have to throw it away, so you be VERY careful.

[interfuse]

A better question might be what did your OLD plugs look like? Post a pic. I'm curious!

[Racerruss-ducati]

The problem you are desribing is usually the result of the air screws being adjusted incorrectly.  If the screws are in too far, the idle will be high for a few seconds after revving it up.  If they are out too far, you will have the problem you are describing.  Assuming you haven't changed the stock jetting from stock or did anything to significantly alter the airflow (cut holes in the airbox, took out the air filter, etc), it should adjust out with the air screws.

You should screw all airscrews in until they seat and then back them out.  I would start at 2 turns out as a baseline and then adjust all 4 in or out (based on the symptoms above) by 1/4 turn increments and you should find the sweet spot.

Hope this helps.

Russ

[duane]

A better question might be what did your OLD plugs look like? Post a pic. I'm curious!

Here they are:


It looks like a lot of deposits on them but in real life it it doesnt seem that way. I think it may be the flash from the camera that highlights it.  
Anyway, Do you think it might have been too rich?  It had 105 main jets.
Duane

[Krautwagen]

Finding the correct main jet and trying to troubleshoot the off-idle bog are 2 totally different things.

If the bike pulls good over half throttle above about 7k, then your mains are close to correct.

Because your engine bogs or stalls when you blip the throttle in neutral off idle, your pilot mixture is too rich.


See:
http://www.factorypro.com/tech/carbtune,CV,high_rpm_engines.html
For more info.

[duane]

Finding the correct main jet and trying to troubleshoot the off-idle bog are 2 totally different things

Thanks for the reply, I am clear on that.  First, I  need to get the thing so I simply ride it on the street before I'm able to trouble shoot the main jets.  Even if it's stumbling badly, that would be better than the way it's dying right now.

Your right, main jets first, then work my way back.

[interfuse]

Here they are:
Anyway, Do you think it might have been too rich?  It had 105 main jets.
Duane

Depends on what your running (exhaust, airfilter, airbox, needles, etc) but from the factory the bike came with a 105 mj (or 102.5 somthing close 105). So it's probably close to alright. The old sparkers don't look too bad so i'd leave the mj alone for now.

It's just speculation, but from the sounds of what your describing it could be one of three things.

Either what Racerruss-ducati discribed in detial (air/fuel screw is out spec, has someone already drilled out the brass plug over the air fuel screws?)

or your float hieght (fuel level) is out of wack. What did you set your float hight at? When you had the carb apart did you check the o-rings on the floats? If gas seeps past those your fuel level in the float bowl will go up causing richness at idle.

or your needles are raised too high, are you needles adjustable? are they shimmed?

As an example, here's my setup:
Yosh exhaust, modified airbox, k&n airfilter, dynojet needles
105 mj
Center needle clip
15mm float hight
2.5 turns out.

[pmackie]

Hey Duane
Your old plugs look pretty good. I'm not sure what mileage is on them, but they do NOT look like the bike is running rich overall. Colours on my screen look whitish with slight tan, no evidence too much heat from a lean condition. Overall, you should be in the ballpark for where you ride most of the time (needles & needle jet cover approx 1/4 to 3/4 throttle openings.)
However, this doesn't necessarily mean the mains and pilot circuits are OK. Your concerns sound more like pilot circuits and air screws to me.

[gsxr400 racer]

burning oil

[gsxr400 racer]

heres the kicker is most of these bikes are 10 years old or older and have never had a top end rebuild or a valve job , just keep beatin your meat guys im sure they all need freshened up!
cheers
jsy