Bike idling funny

[RoyMember]

Sorry to drag this up again but I finally got to give my bike a decent ride to check things over on the weekend.

Anyway the idle thing seems to be fixed. No surging.

Here’s my problem. During the cleaning process I checked the air screw etc. Found the air screw was 3.5 turns out (had to wind it in 3.5 turns before it hit solid). I’ve had the bike for 4000 odd km and 140 hours and never checked this before so I assume it has been like this since the dealer set it up for me.

I thought this seemed a bit odd as all I ever hear is 1-1.5 turns. So knowing that the more turns out I go the leaner it goes (2T remember) I figured richer is better than leaner and I then set it at 1.5 turns out.

All seemed fine on the weekend. The only minor hassle I had was it seemed to idle a little low and would stall occasionally (especially going down steep hills). I wound the idle screw up a bit to compensate for that and all fine.

The other thing is when I look up the manual the setting for all types of 300’s is 1-2 out but the 300 EXC AUS is 3.5 turns out. Should I go back to the 3.5 turns out I had originally.

Do 2T measure from the screw wound all the way in or all the way out because I think 3.5 turns from all the way in was around 1.5 from all the way out.

I think I might ring the dealer as well. Keen to maximise my potential but not keen to have it lock at the end of a straight one day.

[Aaron WildeMember]

One of the guys Shane J rides with had a 300 exe cold seize on the bitumen after a flat out run. Not funny. Could you do the plug out and check the color to see if it is running rich or lean. Being a 2T plug access is pretty good. If I am not mistaken, you can run the bike in different rev ranges and clutch and stop the bike so you can see how it is running when under load flat out etc. When I went to a Moto GP once the 125’s would do that after every practice. Then they would have to push them back to the pits. But that was when Valentino was on a 125 so a long time ago. You probably would not know him but you would have if you had gone on the Coffs Coast ride. :laugh: This is the Tech section so I hope there is some correct info in there. Could be the blind leading the vision impaired.

[DeanMember]

Bundy 1.5 turns is from fully wound in Ie richest setting to 1.5 turns out ie anti clockwise.

BTW generally if you are more than 2.5 turns out to get a good response (remeber 1/8 to 1/4) your pilot jet is to rich and you probably need to go down a size

Ollie

[Bruce CurtisMember]

Ollie is indeed correct all the symptoms you describe is that of a pilot jet too big, they do this ex-factory to ensure it works all over the country, from cold sea level to hot desert conditions.

Basic kiehin numbering system, have a look in the book see what size it is nd ask a few questions.

My YZ went from a #50 to a #40 to get it ultra crisp, 38 was too lean, even my old 300 (38mm carb, yours has 36mm) was jetted way too rich on both pilot and needle.

[RoyMember]

Thanks again for the help. Do the jets have there size written on them anywhere. I can’t remember seeing anything when I was cleaning it but that’s not to say there wasn’t something on there. Or can I measure something to determine the size.

Are all jets universal between carby models of do you know the jet size you want do you have to get one that suits your carby type.

I hate dirt. If it wasn’t for dirt in there in the first place I would still be blissfully ignorant about the carby world instead knowing almost enought to be a danger to myself.

One last thing (I know I’ve said that before), from what I’ve been told the air screw effects the bottom end of the throttle response (1/8 to 1/4). Does this mean that when I am on the pipe (I’m assuming that takes more than 1/4 throttle) then the air screw no longer has any bearing on performance? If this is true then I’m having trouble understanding things as from my limited foray into the insides of a carby the pilot jet doesn’t look like it can be blocked off, it is just a hole of a set size. To me this means that it is still letting in fuel at all revs.

Putting 2 + 2 together I assume that at hight throttle the pilot either gets cut off through some mechanism/process I don’t know about or the amount of fuel/air that goes through it compared to the main is so small it has no real bearing on the performance.

[Bruce CurtisMember]

OK Mr Roy, the jet size is in tiny little numbers either on the head or on the side near the head end on most jets.
Each brand and model range of carb usually has jets percular to that range.

Pilot and air screw are idle

[RoyMember]

Thanks again for all your help. Whilst I profess to not understanding how each item works, I’m getting a good understanding of what each item does.

I had been wondering why I had been getting no jetting issues after all the warnings I received about jetting problems and 2T’s before riding my bike. I regularly range between 300m and 1200m above sea level in any one ride and summer and winter no hassles. Sounds like I’m getting ease of use at the cost of response.

[GregMember]

Bundyroy wrote:

Quote:

Thanks again for all your help. Whilst I profess to not understanding how each item works, I’m getting a good understanding of what each item does.

I had been wondering why I had been getting no jetting issues after all the warnings I received about jetting problems and 2T’s before riding my bike. I regurlarly range between 300m and 1200m above sea level in any one ride and summer and winter no hassles.

Try this ol mate Link here may help you understand jetting, jets, throttle position and what does what

TB

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