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dmxracing

Engine Idle Adjustment

15 posts in this topic

Hello, I was wondering how you guys run your idle adjustment. When I bought the bike it was set up kind of low and it was easier to stall. I increased the idle and the bike never stalls and some of the engine braking was reduced. I read in the manual that the idle should be low enough to allow engine braking. What do you guys think?

Thanks

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Truthfully run you idle at whatever speed you need to to keep your bike running. Seriously, I know people that are and A and B offroaders and run their idle so that they are is almost no engine braking (that's really high). I've always felt like I should use my idle as a training aid. As you get better with the clutch you can turn down the idle...

Good Luck!

Mr Toyz

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I have my idle set relatively high. It helps starting and forces you to go faster in turns! Later,

Garrett

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Once I get the beast started, Its WFO

I never Idle

Seriuos I have mine bumped a bit highr, I hate to get the lug on tight corners keeps the gas spitting in the bike

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Idle speed is almost as personal as control adjustments. Some like'm high some low. Mine is a tad high, helps with stalling. Go easy with the high idle deal though, it can make the beast difficult to start if you get it too high. Make your adjustment, then kill it, and make sure it will start again.

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Yes, it IS a personal issue as to where to set the idle. Personally, I set mine to where it is almost ready to stall at any moment. Why? Because I use the engine braking as a tool. It probably wouldn't matter anyway because I'm old and slow as heck.

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I like the idle a little higher when I'm riding in the woods and a little lower when on the track.

Now I mostly wrench for my kid and HE rides his CR 125 AND my 426. He tells me, Gee Dad, you should win EVERY race on this bike! Then he asks me why I "LUG" it in the turns!

Talk about makin' a guy feel OLD! LOL!!

D

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Some thoughts:

At lower RPMs you are not making a lot of oil pressure. That ain't good.

The YZF has a huge cam, and doesn't like to idle anyway.

Isn't the idle spec around 1,000 RPM???

It ain't a two stroke where an overly high idle may affect throttle response, for two strokes I generally end up with a bike that will die if you leave the throttle unattended. On a thumper you want a healthy lope going on a warmed up motor. This makes it harder to stall and more predictable to start.

My two Rupies.

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Hick, with these large bore thumpers, low idle speed causes valve train snatch which is probably more of a negative issue than low oil pressure. But, you are correct that the engine shouldn't be allowed to idle at very slow speed for more than a few seconds at a time. I simply set my idle quite low when I'm on the starting line and the sign guy motions for us to start our engines. The engine never gets a chance to idle after that.

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I set it just high enough to make it somewhat stall resistant. This way I can tap the brake in the air (clutch pulled in) or slow down on the ground with the rear brake (clutch not pulled in) and not have to worry about stalling. This seems to also keep it running better when I fall over (which I do alot). Still plenty of engine braking for me.

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Mark. I won't comment on Ego's comment. Anyway. valve train snatch is the sudden decel and accel of the valve train components, namely the cam chain. The YZ has a fairly light flywheel weight coupled with 12.5 to 1 compression ratio. At low idle speeds, there isn't much momentum to overcome the compression resistance so the crankshaft/camshafts are subjected to sudden speed changes that don't occur at higher RPM's. This causes the cam chain to be snatched back and forth. You can't REALLY hear this happening if you intentionally stall the engine by riding along in gear and applying the brakes gradually until the engine turns so slow that it stalls. Just before it stalls, there will be some very loud mechanical noises from the engine.

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Thanks, Boit.

I take that to mean the acceleration and deceleration through the stroke (very fast near the end of the power stroke, very slow climbing up compression). Makes sense.

mwc

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I see I made a grammatical error when I said "You can't really hear....". Should have been "can", not "can't".

Yes, I think you get the picture, Mark.

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