weird behaviour triple engine

Bert Reganze said:
Just back from a ride. Noticed that the sound of the engine changes from normal smooth jota sound to a more loud bumpy sound, like that when the engine is started with too much choke. Could the engine somehow get to rich mixture?

Tried the kill switch trick, seems to work for a few minutes but then back in bad mode again. What also works, for a bit longer, is to close throttle-full throttle-normal throttle.

So far the bike did not let me down, that is the good part.

saluti Bert
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Bert, your description of the changed exhaust note and the strange behaviour of your bike ounds exactly what happened with my 3c a few years ago. It took me the better part of a week to find out that the float valve on the left carb had become unseated, lowering the fuel level in that bowl. Nipping up the float valve seat was all it needed to cure it. Might be worth a look on yours.

Regards,
Stefan
 
The bike was running absolutely fine when kept around 100 to 110kph, going to 130 and further up and it started to feel breathless, opening the throttle wider to compensate for it created that somehow hollow bark from the exhaust, but no more power output. Going back to 100 kph and everything went back to normal within a minute. The following search for the cause got me close to pushing the 3C into the darkest corner of the shed and never touch it again. I went to everything as being already supposed here, and beyond, before I finally tracked it down to the loose float valve seat :-X

I found then that my 9mm ring spanner had a wide spot at the ring section, which locked up with the carb body, giving the false impression of float valve seat being already proper tightened. Needless to say that I gave that sucker a run at the grinding wheel to avoid falling for that trap a second time. :D BTW, it took more than 4000km for this mishap to evolve. It was just when  breaking in of the freshly rebuild engine had ended and I started to go higher in the revs, which seemed to bring vibrations to a level sufficient for that float valve seat coming loose.

 
Rob said:
A DMC2 may well have a problem familiar to some of us - a partly broken wire in the connector plug.  Check every wire very very carefully - they can partly break just next to the crimped connector in the plug. Sometimes the plastic insulation is intact but the wires strands broken inside. 

The other thing to check is that the neutral connection (black wire) from the DMC plug goes direct to the battery, and is clean and tight.

Finally, check that your battery is being properly charged when the engine is running by measuring its voltage
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Just removed the connector plug from the DMC unit and found a good bunch of grease in the connector? IS that OK?

The black wire does not go to the battery. What to do now?

Another question, how to check if the wire strands are broken inside?
 
Paul Marx said:
Or a 3CL dressed up as a 3C?

Paul
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could also be the case. The bike got another frame after a small crash some 15 years ago. That could also explain the position of the rear shocks. What are the specs for being a 3CE?
 
Bert Reganze said:
Just removed the connector plug from the DMC unit and found a good bunch of grease in the connector? IS that OK?

The black wire does not go to the battery. What to do now?

Another question, how to check if the wire strands are broken inside?
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Black wire is ground or battery negative.  Just make sure the connection is stable.  Grease in connector is a common water-proofing method.  Jiggle and jerk every wire while the bike is running and watch for irregularities.

piet
 
sfcpiet said:
Black wire is ground or battery negative.  Just make sure the connection is stable.  Grease in connector is a common water-proofing method.  Jiggle and jerk every wire while the bike is running and watch for irregularities.

piet
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there are 2 black wires coming from the DMC connector; assume they are connected to each other in the connector?
 
Now I disassembled the carbs. Membranes are leaky, pump jet and holder in right carb is missing ???, float needles bad condition, a lot of rubbish in the middle acceleration pump. Cleaned parts in ultrasonic bath. And waiting for new parts. May be this will solve the issue
 

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The pump jet in the side of the carb body can only go in one way. There is a flat side on the brass fitting that mates with a corresponding flat in the carb body.
I would be taking these carbs all the way down for a major overhaul.
 
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