2002 Le Mans surging

[2002LeMans]

I bought a Le Mans not running with 3 k miles.

 

Did the obvious work with tank,fuel hoses,filter,oil ,filer change etc...

 

It started immediately but it runs a 4000 rpm .

 

I found that the crankcase breather hose was broken and replaced it thinking that was the cause of an air leak .

Same result.

 

Any body can throw something serious ?

 

Thanks.

 

JPh

 

 

[fotoguzzi]

is the throttle linkage returning all the way to stop?  high speed lever on left grip turned down? has someone messed with the stop screws on the throttle bodies?

[footgoose]

Welcome to the forum jph! Another neglected Guzzi rescued!

[JBBenson]

Make sure that the issues fotoguzzi mentioned are checked first. 

 

Read this first:

 

http://www.obairlann.net/reaper/motorcycle/guzzi/balance.html

 

Here is the quick and dirty method:

 

1.

Start by getting a good multimeter and vacuum meter, either simple manometer or a fancy electronic one. 

 

2.

Also get a breakout harness for the throttle position sensor (TPS): 

 

http://www.casperselectronics.com/store2/product_info.php?products_id=1621

 

3.

Remove the connecting rod from the RH throttle, hook up the multimeter, and rotate (gently) the TPS until you have a reading of 150Mv. This may take some time, as it is very sensitive. This step is crucial to getting it running right.

 

Once you have the 150Mv correct, hook up the connecting rod and fast idle again.

 

4.

Back off the RH throttle stop. Unless you have some super high mileage bike where everything is worn out and sloppy, using both will make you crazy.

5.

Open bleeds one turn each. 

6.

Hook up your vacuum meter and sync using white knob at idle. Blip the throttle and let settle. Keep doing this. You will never get them perfect, but you can get close.

 

Note: When the throttles are open (>3k) the white knob needs to be moved a lot to make any difference in vacuum. This is because the small adjustments the white knob makes gets lost in the large flow of air coming through, and tiny imbalances in throttle vanes will be hard to see on any kind of meter, even the expensive one I bought.

 

You can turn the white knob and the throttles will appear to be in balance at higher RPM's. But they're not, which you will see when it drops to idle. Then you can use the bleeds to try to even it out, which is what I did, and then it idles worse than ever.

 

In short, the ultra tiny differences in throttle openings will be revealed at idle but will be lost at higher RPM's. If the idle is balanced, then higher RPM's will be balanced too.

 

7.

Adjust idle screw at the LH throttle body if needed to get a smooth idle. Leave RH idle screw backed out so it doesn’t touch anything. 

 

You may need to adjust the white knob again as you do this. A good idle can be anywhere between 1000 and 1500 RPM.

 

This is a method that will get you running right, quickly. You can go back in later and fine tune if you want.

 

I am local in L.A. and can help if you get stuck.

[twhitaker]

Take a look at where the intake manifold rubbers connect to the throttle bodies. When mine backfired the force pushed the TB back and the revs went way up before I hit the kill switch.