1970 S: a hole between 2700/3000 rpm

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And what will raising the needles one notch tell him if his flat spot is caused by already being to rich?
 
splatt said:
And what will raising the needles one notch tell him if his flat spot is caused by already being to rich?
Click to expand...

His issue will get even worse and that will indicate to him to lower the needles instead.

I wonder if you have the wrong needles for your carbs... You should check that piero. I know there are a few different variation on needles. Make sure you have the right ones if you recently changed them.
 
o0norton0o said:
splatt said:
And what will raising the needles one notch tell him if his flat spot is caused by already being to rich?
Click to expand...

His issue will get even worse and that will indicate to him to lower the needles instead.

I wonder if you have the wrong needles for your carbs... You should check that piero. I know there are a few different variation on needles. Make sure you have the right ones if you recently changed them.
Click to expand...

Hi.
Sorry, but i must repeat.
The bike has runned 3000 km very great without problems, from restoration.
Fast and with a perfect carburation.
Carbs overhaulled with new Amal parts from Andover.
This carbs have worked great for 3000 km and i have never changed the setting.
Note that the spark plugs are of a nice brown/cleaned colour with no oil or fouling.
Could be an electrical noise?
What? A coil? But the bike starts easily first kick and the spark plugs, new, have fire.
Thank you.
 
In case, electrical what?
Click to expand...

Well anything from a loose wire to a bad coil, not using solid copper core HT leads, not having resistor caps or plugs on a digital ignition etc etc.

Not being there we can only advise what to look at, not whats wrong.
 
Just to clarify, I'm not putting forth the proposition that a properly jetted carb is suddenly needing way different settings, but rather, AS A TEST, we alter the fuel mixture significantly, and observe the results (or lack thereof). Kinda like one of those troubleshooting flow charts.... :mrgreen:

So, as mentioned piero, THROTTLE OPENING info is needed as well. Varies widely based on engine load at the same RPM.
 
concours said:
Just to clarify, I'm not putting forth the proposition that a properly jetted carb is suddenly needing way different settings, but rather, AS A TEST, we alter the fuel mixture significantly, and observe the results (or lack thereof). Kinda like one of those troubleshooting flow charts.... :mrgreen:

So, as mentioned piero, THROTTLE OPENING info is needed as well. Varies widely based on engine load at the same RPM.
Click to expand...

+1 The reason you should move the needle clip one way or the other is you're attempting to change the mixture in the range where you are having a problem. It's a TEST... to see if making that range richer OR leaner cures your problem. If one of those changes cures the issue, then you know WHAT the issue is,... but you still don't know WHY you are having this new issue until you probe further...


IF this entire carb set up ran well for thousands of miles,(as you said previously) and it's all relatively new parts so being worn out is unlikely, the next thing I would look at is a possible air leak in your intake manifold. My favorite air leak test is the spray "carb cleaner" on the outside of the carb and manifold as the bike runs. If it stumbles when you spray a certain area, look at that area carefully for a crack in the casting OR a faulty gasket..

At one point on my commando, I overtightened one of the intake manifolds and it cracked, so I developed an air leak. The crack was like a hairline and on the inside of the manifold so I couldn't see it, but the Spraying carb cleaner test made the bike stumble. I removed the 2 allen bolts from the head and the manifold broke in 2 pieces when it was free of it's mount... Give the spray test a try...
 
Hi.
Bike has stock e gine and carbs with Pazon well setted with PVL 6 V coils.
The bike has always run great.
Now has a hole between 2700/3000 rpm over that run great again.
Click to expand...

Hi Piero!, it may be telling that your problem is close to the point of maximum vibration?

My electronic ignition had a slightly fractured wire inside the points timing cover that would cause the motor to stumble around 2700rpm and then disappear as the frame smoothed out when the ISO's kicked in at 3000rpm

at this point it may be worthwhile to rewire your Pazon all the way down the frame tubes and where the wire connect inside the points cover - this just seems very much an electrical connection issue rather than carb related
 
1up3down said:
Hi.
Bike has stock e gine and carbs with Pazon well setted with PVL 6 V coils.
The bike has always run great.
Now has a hole between 2700/3000 rpm over that run great again.
Click to expand...

Hi Piero!, it may be telling that your problem is close to the point of maximum vibration?

My electronic ignition had a slightly fractured wire inside the points timing cover that would cause the motor to stumble around 2700rpm and then disappear as the frame smoothed out when the ISO's kicked in at 3000rpm

at this point it may be worthwhile to rewire your Pazon all the way down the frame tubes and where the wire connect inside the points cover - this just seems very much an electrical connection issue rather than carb related
Click to expand...
+1

Broken (formerly contact breaker points) wire to ignition failed like this.
 
Before looking for a break in the electrical wiring, raise the needles one notch, so you know the hesitation is not due to lean-ness. If the mixture becomes richer, it won't cause hesitation - only sluggishness. An electrical fault is likely to be intermittent and harder to find, so eliminate the obvious before searching for a break. If the hesitation is due to lean-ness, you might end up pulling your hair out looking for a break in the wiring for no gain.
One thing I'm not clear on - did this hesitation appear after you made changes to the carbs, or has it simply started during normal use of the bike ?
 
acotrel said:
Before looking for a break in the electrical wiring, raise the needles one notch, so you know the hesitation is not due to lean-ness. If the mixture becomes richer, it won't cause hesitation - only sluggishness. An electrical fault is likely to be intermittent and harder to find, so eliminate the obvious before searching for a break. If the hesitation is due to lean-ness, you might end up pulling your hair out looking for a break in the wiring for no gain.
One thing I'm not clear on - did this hesitation appear after you made changes to the carbs, or has it simply started during normal use of the bike ?
Click to expand...
Hi.
I have never changed nothing.
Piero
 
Hi.
After have well cleaned the pilot air, setted the fuel level as Amal says, checked and toghten each wire, to day i have runed with the bike.
It runned great, good carburation, no holes, 1000 rpm idle.
But, after 15 km., the bike have lost the shift gear, the lever (well tighten into the shaft, went up and down but with no changement of gears.
The bike was in second gear and was imposible to shift for other gears.
I have returned at home and desmounted the gearbox outer cover.
First, i have shift the grar with an hammer from the window of the inner cover.
The gears worked well.
The pawl, rachet plate and spring wre well in place.
I have remounted all with a new gasket and oil.
The gear shift well now.
I dont understand was hppened.
Thank you.
Piero
 
I had the gears lock up in 3rd gear once and the shift lever did nothing. It was the 'shift quadrant return spring' fell off along with the 'gearshift stop plate' from loose screws. Items 7 and 10 here http://www.oldbritts.com/1971_g7.html You might want to check proper operation and orientation of the spring.
 
pierodn said:
Hi.
After have well cleaned the pilot air, setted the fuel level as Amal says, checked and toghten each wire, to day i have runed with the bike.
It runned great, good carburation, no holes, 1000 rpm idle.
But, after 15 km., the bike have lost the shift gear, the lever (well tighten into the shaft, went up and down but with no changement of gears.
The bike was in second gear and was imposible to shift for other gears.
I have returned at home and desmounted the gearbox outer cover.
First, i have shift the grar with an hammer from the window of the inner cover.
The gears worked well.
The pawl, rachet plate and spring wre well in place.
I have remounted all with a new gasket and oil.
The gear shift well now.
I dont understand was hppened.
Thank you. its usually the hairpin spring in he outer cover try a new one in there,if you get stuck in gear you can use a spanner on the bolts on the front of the gear box to rock yourself out of gear
Piero
Click to expand...
 
baz said:
pierodn said:
Hi.
After have well cleaned the pilot air, setted the fuel level as Amal says, checked and toghten each wire, to day i have runed with the bike.
It runned great, good carburation, no holes, 1000 rpm idle.
But, after 15 km., the bike have lost the shift gear, the lever (well tighten into the shaft, went up and down but with no changement of gears.
The bike was in second gear and was imposible to shift for other gears.
I have returned at home and desmounted the gearbox outer cover.
First, i have shift the grar with an hammer from the window of the inner cover.
The gears worked well.
The pawl, rachet plate and spring wre well in place.
I have remounted all with a new gasket and oil.
The gear shift well now.
I dont understand was hppened.
Thank you. its usually the hairpin spring in he outer cover try a new one in there,if you get stuck in gear you can use a spanner on the bolts on the front of the gear box to rock yourself out of gear
Piero
Click to expand...
Click to expand...
Hi.
You say "its usually the hairpin spring in he outer cover try a new one in there,if you get stuck in gear you can use a spanner on the bolts on the front of the gear box to rock yourself out of gear".
Sorry, but i dont understand what is "hairpin".
Do you think it can happen again?
Thank you.
Piero
 
Hi Les,
thank you.
But the hairpin seemed good and was fitted new with restoration.
Piero
 
pierodn said:
But the hairpin seemed good and was fitted new with restoration.
Click to expand...

Well, some part of the ratchet mechanism must have got stuck or jammed temporarily.

As it's all working normally again, there's not much more you can do.
 
L.A.B. said:
Well, some part of the ratchet mechanism must have got stuck or jammed temporarily.

As it's all working normally again, there's not much more you can do.
Click to expand...

Here's a tip:
If you need to remove the outer cover again (for instance if the gearchange problem arises again), try moving the gearlever up and down while holding the outer cover in your hand.
That way you can watch the pawl engage with the ratchet plate and then return to its centre position.
Does the pawl begin to tilt as soon as the lever moves? Your parts are new so there should be no roughness or pitting on them. At rest, there should be a tiny clearance between the spring and the pawl on both sides.
Does it move the ratchet plate cleanly in both directions, without any drag between pawl and ratchet plate as the pawl moves back to centre?

With mine, I found that the pawl was dragging the ratchet plate back as it returned to centre, which pulled the plate back so that pawl did not engage with the next tooth on the plate. It simply engaged with the same tooth as before, so the gear did not change. The pawl was new, but I had not replaced the gearlever shaft bush so there may have been some wear there.
I resolved the problem by grinding a bit off the concave face of the pawl.
 
Hi.
Here i am again with my 1970 S that had run 3.000 km. great before.
Same problem to the gear box lever that dont shift.
The lever, in first gear, does not go to neutral and second etc.; it goes down but without engage the neutral/second gear.
But, from the first gear engaged, If you push up the lever more time, then the engage works and you will shift well all the gear.
This happen only from first gear, never from second on and back.
I have already desmount the gearbox before without see any damage.
I dont know what happen but i think should be better to change the pawl, the ratchet plate and the Hairpin spring.
What do you think about?.
Thank you.
Piero
 
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