Power loss

Laverda1000.de

Laverda1000.de

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Location
Haßberge, Germany
Hi,
during a ride on the drummer I suddenly lost power above 2800 rpm, bike started sputtering. 73 drummer, Witt ignition, A11 cams, factory exhaust & airbox. When I trundle along at low revs just above idle for a short period (maybe a minute) it will pull cleanly above 2800 rpm for a short time and then go back into sputter-mode. The longer I trundle the longer it will take for the sputter to reappear. Ignition should't be reproducably on and off like that, so I guess it's fuel starvation, but why? Opening the tank cover made no difference and if a needle valve was stuck it shouldn't start and run fine depending at the revs. Maybe one fuel tap is blocked? I'd be grateful for ideas.

On a different not the bike was stuck in first, so I reshimmed the neutral switch. It is fine between 2nd and 5th but still very hard to shift between 1st and 2nd. So I guess it has to come out further. How much do you go up for the next step - 0,25 mm?

Thank

Chris
 
Simple things first. Try a new set of spark plugs. When my bike used to do that (with Witt ignition) new plugs would fix it. Since converting to Ignitech, it's not happened again. It seems that the Ignitech is not as fussy about spark plug condition as the old Witt unit was.

Although to be fair, in my case, the Witt unit was very old (a first edition) and was getting dementia. It became very sensitive to system voltage and would occasionally go haywire. A voltage limiter (10V) in the power supply wire kept it going for another year or so, but it eventually gave up the struggle.

Dunno about the neutral switch. I've never had to fiddle with one.
 
Check battery voltage at idle and as revs rise. Spark plugs maybe a possible culprit, my DMC 1 never eats plugs. Battery voltage seems to be a problem with the Witt ignition.
 
-change spark plugs
-check cables around the coils and to the spark plugs
-check the floats are freely moving and closing completely and that the amount of fuel is equal on all 3 cylinders
-check for water in the float bowls (sometimes builds up on the ground of the tank and when you turn, all of a sudden water get's sucked into the carbs)
-check insulation of the pickup-cables!
-check compression
-check for airleaks around the inlets

If everything is OK, new ignition coils might be on the shopping list...
 
Mkae sure the tank breather in the filler cap is clear, if OK, thentake the tank off and stand it on its rear end, hopefully you dont have too much fuel in it, remove the petrol taps and see if ethanol has melted the nylon filters. It does seem to me like partial fuel starvation, ie it is getting through, hence the happy trundle but not fast enough when you open the throttle a bit, if this proves to be OK, then remove the banjo's on the carbs fuel inlets, and check the round (again) nylon mesh filters, melted ? if they are good, then the carbs come off and you check the float needle tips first, (black tip = no good red tip =brill) then if still haveing difficulty locating the faults, a through clean and check/reset of the carbs
 
Thanks guys, I am mostly with Clem as to possible culprits. The carbs have linkages, everything has been rewired, new intakes and gaskets, carbs rebuilt, anything inside the engine should give other more constant symptoms I suppose. I'll have to get a large canister to empty the tank (it's full). I have a new pair of square fuel taps, right now there are non original new ones fitted, so I will take those off.
 
CLEMTOG said:
check the float needle tips first, (black tip = no good red tip =brill)
Click to expand...
What does this mean, brill?
CLEMTOG said:
Mkae sure the tank breather in the filler cap is clear, if OK, thentake the tank off and stand it on its rear end, hopefully you dont have too much fuel in it, remove the petrol taps and see if ethanol has melted the nylon filters. It does seem to me like partial fuel starvation, ie it is getting through, hence the happy trundle but not fast enough when you open the throttle a bit, if this proves to be OK, then remove the banjo's on the carbs fuel inlets, and check the round (again) nylon mesh filters, melted ? if they are good, then the carbs come off and you check the float needle tips first, (black tip = no good red tip =brill) then if still haveing difficulty locating the faults, a through clean and check/reset of the carbs
Click to expand...
Does ethanol melt nylon?
 
My first guess is the fuel tank vent. As you say that is Ok my next guess as you have a witt ignition is to check the charging voltage. The witt ignitions don't like voltages over about 14.5 volts. I had a regulator going bad on a RGS that was making 15.2 volts and the witt ignition did all kinds of bad things. Once the regulator was replaced it has run perfect since.
 
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