Ok, so the bike seems to be running really good. Nice throttle response and great power distribution from bottom to top. Looking at the spark plug, it looks grossly lean. I check the float height as follows: put a clear hose on the carb drain. Opened it up. Set the bike up level. Fuel filled up to as far as the float bowl gasket. But then, decided to start the bike to see how bad it fluctuates. When giving the throttle a few good cracks, the level drops to almost the bottom of the bowl. i know that it's suppose to drop some because of the fuel going through the jets, but this just seems a little too much. It's weird though cause the height looks good up until I rev the bike into the high rpms. The tank's pet**** is clean and flowing good. The carb is extremely cleaned and getting fuel as it should. I'm stumped. Should I raise it?
The float high sounds too high if it comes right up to the float bowl (AKA float chamber) mating surface. It should be just under the float chamber mating surface. I other words, the fuel level should be 7.5 ~ 9.5 mm from the top of the float bowl.
Sounds like you bent the float when messing with the carb?
You are not supposed to start the engine while checking the float level so any test you have done there is irrelevant.
However, this does not explain a lean condition as if the fuel level is too high, the carburetor will flood and cause a rich condition.
If adjusting the float level does not help, maybe your problem is not the carb at all but rather the valves or rings. Worth checking if nothing else works.
Jarrah
__________________
2000 TT-R250M-
Spoiler
Ported & polished, 73mm bore, Wizeco piston, US header pipe, FMF Q4, #150 main jet, #52.5 pilot jet, throttle stop screw adjusted, larger snorkel, GYT-R air filter, NGK Iridium spark plug, 14/51 gearing, NOS +
If it is running good, why worry?
but anyway, my 2 cents worth...
the level is supposed to be about 8mm below the gasket (engine off), but it could look a little less due to the miniscus in the tube.
The clear plastic tube tube only measures levels when the air pressure is the same at both ends.
If when revved, the pressure in the float chamber drops, the indicated level will drop even if the actual fuel level does not.
The *actual* fuel level (as opposed to indicated "fuel level") should not change when revved in the garage or even when ridden flat out under load, because the capacity of the fuel delivery far exceeds the usage rate of the engine.
I would have thought that the pressure in the float chamber would not drop significantly however as it has to be at a significantly higher air pressure than the venturi area to enable fuel to flow to the jets, and is vented accordingly (but maybe slightly blocked in your case?).
Sure the fuel level is SUPPOSED to be 7.5-9.5mm but (unless someone wants to deliberately test with incorrect settings and report back to the forum), we do not know HOW critical that level is - after all, if you turn off the fuel tap while riding, the bike goes ok for quite some time, even though obviously the fuel level in the float bowl is dropping considerably.
Regarding the spark plug, some people stick with the ideas of 40 odd years ago when plugs, electrical systems, fuel, state of tune etc were quite different and spark plugs could acquire artistic patinas and organic growths that the wise could divine and interpret after a proper high speed "plug chop", but these days combustion is much cleaner and plugs tend to "look a bit lean" to the casual glance when all is actually ok (but others may disagree).
The plugs looks pretty white, not just slightly lean, but for sure lean. I'm running a 145 main jet, needle in clip 3, and a 52.5 pilot and the is from US. Still, lean. But the bike is working great ( oddly). I'm supposed to go on a big run today. I'm ganna move the needle clip one spot richer and see what happens.
brindabella, why worry if it's running good? Because if it is infact burning as lean as the plug is showing, then I don't want to have my piston rings and cylinder wear down prematurely.
and the test that I did with the bike running was to prove the fact that the motor is drinking the fuel out of the carb at too fast of a rate. I'm going to put my snorkel back in to see if it reduces the airflow which should reduce the rate that the fuel is being burned.
-- Edited by Terrence R on Sunday 8th of June 2014 04:37:03 PM
The'' plug'' you mean and if it is white, there is no doubt that it is running lean. The thing about these bikes is that they can run lean no problems (given that you are not way out of spec), but a rich condition will effect them if even slightly rich. I am not saying that it is okay for the engine to run like this, only that it will.
If the float height is too high it WILL cause a rich condition, and if it is above the float chamber mating surface it will cause problems with flooding in the carb, whether you notice it or not, especially on hills.
If the fuel level is too low is will cause it to run lean (whether you notice it or not, especially on hills). Turning your fuel on slightly and running the engine would result in a white plug.
The fuel level is not crucial for the engine to run well, it is however pretty important if you want your engine to last. However, As long as you are within the spec or close enough, it's good enough basically (a fuel level over the float chamber is way out!).
As Brindabella seems to suggest, when the engine is running, the fuel would be sucked towards the jets and it would cause the fuel level to drop in the test tube. This does not mean that it is too low, only that you are testing it wrong.
Putting the snorkel on may work, but not in the way that you think (if you are suggesting that it will change the float height). It will make the carb run richer from the reduced air-flow and may help to cure your lean symptom.
Jarrah
__________________
2000 TT-R250M-
Spoiler
Ported & polished, 73mm bore, Wizeco piston, US header pipe, FMF Q4, #150 main jet, #52.5 pilot jet, throttle stop screw adjusted, larger snorkel, GYT-R air filter, NGK Iridium spark plug, 14/51 gearing, NOS +
Oh, you may want to check that you put the float back in the right way. If you did put it back in wrong it would make the fuel level too high. The TK should be facing down-
Ironically, I put the float in the wrong way around in my CT200 and it had the same symptoms as you describes in earlier posts.
BTW- Let me get this straight. First you posted this-
Terrence R wrote:
This thread I started is a few weeks old now. Jarrah and Brian's input has helped me significantly. Thanx guys.
I put a few Kms on the ttr today. Seems to have a very minor slight popping on deacceleration. No big backfires or real noticeable pops, but enough for me to want address it. As I now have the 140 main jet and needle in the 4th position, I'm wondering if I should try the 145 main and the clip in maybe position #2. I'm just not too sure though because it was a bit spuddery on WOT with the 145 main, but the needle was also in the 4th position. What do u guys think? Would the 145 main jet still be too rich on WOT regardless of adjusting the needle? Or could the WOT circuit be mildly adjust by moving the needle clip?
Then this-
Terrence R wrote:
Just as an update, I just got done riding the bike around after solving the problem. As I assumed, it was slightly lean on top. I raised the needle to its richest position and it now works better and has no popping on deceleration ( i'ld hate to spell that incorrectly). So it looks like the google twits were also right in this situation. Maybe it was the way I was explaining it that caused your confusion jarrah, but I don't think that there was any other way to explain it. Either way, it was lean, it's now solved, and I hope that's there's no hard feelings.
Then this (just to confirm it as correct)-
Terrence R wrote:
I raised the needle by putting the clip in position #5, which is closest to the sharp end. Which richens it if was too lean. The blue line on your needle adjustment diagram can be used as a reference.
Then you wrote this-
Terrence R wrote:
The plugs looks pretty white, not just slightly lean, but for sure lean. I'm running a 145 main jet, needle in clip 3, and a 52.5 pilot and the is from US. Still, lean. But the bike is working great ( oddly). I'm supposed to go on a big run today. I'm ganna move the needle clip one spot richer and see what happens.
If you know it is running lean why did you ''apparently'' move it to the leaner setting? Also, do you really think that one clip position is going to make all that difference if you have already tried the richest setting and it was too lean (according to you?).
You don't make any sense whatsoever and I have a feeling you have been telling porkies.
Jarrah
p.s. you might want to get that air-box fixed as it will make it run lean also, not to mention let dirt in the engine.
__________________
2000 TT-R250M-
Spoiler
Ported & polished, 73mm bore, Wizeco piston, US header pipe, FMF Q4, #150 main jet, #52.5 pilot jet, throttle stop screw adjusted, larger snorkel, GYT-R air filter, NGK Iridium spark plug, 14/51 gearing, NOS +
I try and keep out of these carby sagas in the end the ttr motor is pretty forgiving .the undrying thing is the basic one size up on standard open up the airbox .keep feeding it clean fuel and the best thing dont let it sit ride it .so there isnt any chance of fuel drying up .
as for the plug colour not only the amount of fuel determines the colour its affected by the type of fuel .the way its riden before the plug comes out basicly it can be used as a bit of extra info .
always check for airleaks around the inlet rubber .the best cause of the weird symtoms
summing up the ttr carby is an easy low maintance beast to deal with i love em.
Sent on my phone so a bit dodgey on the typing . I'm off riding now
