2 into 1 intake...Bike revs hard and will not come down...

[remainincognito]

It sounds like your ATU springs are too weak. This is easy to verify. When it is idling high, use the clutch to drag it back down to an idle speed (bike in gear, don't touch the throttle) then pull the clutch in again. If the idle races back up after pulling in the clutch then its probably a carb/throttle issue or air leak. If the idle stays low after pulling in the clutch then your problem is likely the ATU springs. To fix it, cut a coil from each spring.

I will try this test and see where it goes...thank you.

 

[sgallaty]

I think that's a good call - weak timing advance springs would also give you erratic timing, and if it advanced too early might even cause racing (and other issues)

 

[remainincognito]

How can you tell if they are weak? They do snap back but with what force I don't know. If I cut to make the springs tighter and they become too tight, what do I look for then?

 

[mrriggs]

There is no way to tell with the engine stopped if the springs are too weak or not. Weak springs may be able to pull the weights back when the engine is stopped, and when the engine is idling, but not when the engine is spinning 3,000 rpm.

How you tell if the springs are weak is just like I said before, drag the engine back down to idle speed. If it stays there then that means that the springs have enough tension to return the ATU at idle but not at 3000 rpm.

If the springs are "too" tight then you will reach total advance at a higher rpm which could lower your gas mileage if you really lug the motor down the highway. To check for that, simply watch the timing with a timing light while you rev the engine. Note what RPM you reach max advance. If it's above your cruise RPM then the springs are too tight.

In all likelihood you will not make them too tight by removing a single coil. If anything, you may need to remove another coil from one or both of the springs to get it where you need it.

 

[sgallaty]

I've had springs that were stretched out so bad that the advance weights flopped around and moved the starter plate several degrees. they were just stretched out. They were bad at idle, okay at midrange and good at speed.

 

[pamcopete]

How can you tell if they are weak? They do snap back but with what force I don't know. If I cut to make the springs tighter and they become too tight, what do I look for then?

Remove the springs and replace them with a wire wrapped around the posts and the holes in the weights. Start the engine. It will run like crap above about 2,000 RPM, but if your problem is still there, it's not the springs.

 

[sasse]

ever figure this out? I'm having the same problem, but i went to 15pilot and 130main, its calmed down a bit but still have erratic over-revving.