HI Idle

[dlaing]

You're an honorable man, Dave.

albeit forgetful and error prone.

I used the right set screw many times as my previous method, and our method only once.

Our method works better. But my previous method stuck in my head better.

[docc]

ALdad,

 

I looked back at your original post. Could you clarify: you set the 150mV, turned the stop screw to show 520? But then you say it shows 360 at idle?

 

How did it get from 520 to 360? I see you used the "linkage and right screw" to get balance. That may be where it's all going south. Once the stop is set for 520 (or you could try 500 to lower the idle), only use the linkage rod for balance.

[ALdad]

ALdad,

 

I looked back at your original post. Could you clarify: you set the 150mV, turned the stop screw to show 520? But then you say it shows 360 at idle?

 

How did it get from 520 to 360? I see you used the "linkage and right screw" to get balance. That may be where it's all going south. Once the stop is set for 520 (or you could try 500 to lower the idle), only use the linkage rod for balance.

 

I backed both screws out. Set TPS at 150. turned rt screw to 520. Started bike ,idle way way high.backed screw out to reasonable idle this was around 300 or so. vacuum deviation off to rt. had to increace idle on Rt with screw to ballance, now idle is a little high but ok .This is where I ended up at 360. Still have not touched the Lf screw. Hooked up rod with no tention. Fine tune ballance with white knob. Bike pops at constant speed 4000rpm and below and sometimes starting out from stop basicly not a smooth go. I ballanced with a twimax at about 1/2 on the sensitivity dial. Could the last tuner have started below 150 before the dyno. This may not be possible for some reason so I may seem stupid but I am a newbee , sorry please educate me.

[docc]

Hmmm, I still think you need to start from square one with the pinned thread and go through the procedure from A to Z.

 

Let's see what happens.

[raz]

Could the last tuner have started below 150 before the dyno. This may not be possible for some reason so I may seem stupid but I am a newbee , sorry please educate me.

It is possible. Before any tuning one should check TPS, valves, replace/clean air filter, perhaps new plugs and so on in order to have the standard baseline one can go back to. But you are right, someone could have made a tune with a wrong TPS base setting. If this is the case (and is undocumented) you now learn the hard way why this is so bad - you won't know what to set it to

 

I agree with docc, if only to convince us, and yourself, you really didn't miss something in the process.

[dlaing]

Another possibility, leaky intake manifold???

What spec did you use for the valve adjustment? As a general rule, looser valves provide higher idle.

Do you have a PCIII? That would not explain the high idle, but try disconnecting and go for a short ride. You may need to trial and error determine what TPS it was mapped to. A good starting point would be to set the idle and then adjust the TPS sensor to 500mV. I would not recommend that for anything other than a mysteriously mapped bike.

Many bikes were set to a higher TPS voltage to enrichen the mixture.

[motoguzznix]

What spec did you use for the valve adjustment? As a general rule, looser valves provide higher idle.

Sorry Dave, I must correct this!

Tighter valves provide a higer idle, looser valves provide a more stable idle. If you lower the idle speed with the tighter valves to the same amount that occurs with the loose valves, the idle will get much more unstable.

 

AlDad

 

adjust your valves to the 20/25 spec at cold engine and retry the TPS setting. Close the bypass screw on both butterflys completely. Unhook the connecting rod and make sure you really get clearence on the right butterfly linkage to the adjusting screw. Me too got it wrong once and had to go through the whole procedure twice.

Then adjust the 150 mV again and turn the right adjustment screws in to get 500 mV.

Then reconnect the rod and synch the TBs first at idle speed, then at ~3000. If the idle is too low, you can open the bypass srews to 1/2 to 1 1/2 turns. More turns out should not be necessary.

 

I'm sure there was a fault in your procedure that makes such a big difference in the idle setting.

[mark.gilmore]

Then adjust the 150 mV again and turn the right adjustment screws in to get 500 mV.

Thats not the way anyone here does it.That I no of.

[dlaing]

Sorry Dave, I must correct this!

Tighter valves provide a higer idle, looser valves provide a more stable idle. If you lower the idle speed with the tighter valves to the same amount that occurs with the loose valves, the idle will get much more unstable.

My mistake, sorry.

Thanks for the clarification. When I switched from .10/.15 to .15/.20mm it must have been the stabilization that gave me the higher idle. Others on the forum have also gotten higher idle after going to a more open clearance, again it must have been the stabilization. If valves are too tight I have experienced that idle is inconsistent, sometimes stalling and sometimes being too high. Once loose enough, stability is not an issue, right?

As for running at .20/.25mm I have had a few veterans warn me that it is too loose and will increase wear.

If a bike has been mapped to the factory setting of .10/.15 will using .20/.25mm mess up the mapping?

[Francis Chartier]

As for running at .20/.25mm I have had a few veterans warn me that it is too loose and will increase wear.

If a bike has been mapped to the factory setting of .10/.15 will using .20/.25mm mess up the mapping?

 

Here in France, there is a consensus among "traditionnal" guzzi mechanics at 0,15/0,20 mm to get an even idle at 1100/1150 rpm.

Factory setting of 0,10/0,15 is convenient for a quieter engine, but does not seem optimum from a mechanical point of view.

[motoguzznix]

As for running at .20/.25mm I have had a few veterans warn me that it is too loose and will increase wear.

If a bike has been mapped to the factory setting of .10/.15 will using .20/.25mm mess up the mapping?

My measurement of the V11 cam attached below shows very clear that there is no increased wear on the valve train when using 20/25 valve gap. As you can see, the flat ramp at the start and the end of the cam lobe is approx. 0,5 mm. So a valve clearence of 0,25 mm creates the same forces in the valve train than any smaller clearence. Above 0,7 mm valve clearence the ramp angle gets steeper creating higher forces in the valve train.

 

The advantages of the bigger clearence are evident: if going from ,015 to 0,25 on the intake the actual opening angle decreases from 389° to 363°, from 378 to 352 on the exhaust.

This diminishes the losses of charge and give the exhaust valve much more time to cool down on its seat. The compression ratio and the time to make use of the burn increase too. Al this contribute to a more stable idle.

[luhbo]

Thats not the way anyone here does it.That I no of.

 

Nevertheless this is the way everybody should do it! That's how it's described in the manual and that's how it makes sense. That's how I do it as well and this gives me perfect results. Doing it this way makes things easier as you've ever experienced on older carb bikes.

 

Maybe only one particular improvement: after adjusting the right flap to the given value, synchronise the left one to it without having the rod attached. And let the bypass screws closed so far. Ernst hasn't mentioned it explicitely, but he probably would have if he wasn't so familiar with the whole procedure.

 

The manual is the reference, not the internet.

 

Hubert

[raz]

(...) The advantages of the bigger clearence are evident: if going from ,015 to 0,25 on the intake the actual opening angle decreases from 389° to 363°, from 378 to 352 on the exhaust.

This diminishes the losses of charge and give the exhaust valve much more time to cool down on its seat. The compression ratio and the time to make use of the burn increase too. Al this contribute to a more stable idle.

Thanks Ernst! Great post, backed up with interesting graph.

[dlaing]

My measurement of the V11 cam attached below shows very clear that there is no increased wear on the valve train when using 20/25 valve gap. As you can see, the flat ramp at the start and the end of the cam lobe is approx. 0,5 mm. So a valve clearence of 0,25 mm creates the same forces in the valve train than any smaller clearence. Above 0,7 mm valve clearence the ramp angle gets steeper creating higher forces in the valve train.

 

The advantages of the bigger clearence are evident: if going from ,015 to 0,25 on the intake the actual opening angle decreases from 389° to 363°, from 378 to 352 on the exhaust.

This diminishes the losses of charge and give the exhaust valve much more time to cool down on its seat. The compression ratio and the time to make use of the burn increase too. Al this contribute to a more stable idle.

Congratulations, I think you convinced me to go with the RaceCo spec!

It might give me an opportunity to test the change's effect on idle speed.

So, if a bike was custom mapped at .10/15mm going to the RaceCo spec would SIGNIFICANTLY mess up the mapping????

[luhbo]

Ernst, could you compare these values to those shown in the Cam thread:

 

http://www.v11lemans.com/forums/index.php?...mp;#entry136976

 

I think those aftermarket cams are open even longer, but of course this depends on the given measurement clearance. What values show the original cams at 0.5 mm?

 

Hubert