500 timing

Paul Marx

Paul Marx

Hero member
Location
France
What are the figures for the 500 timing.
Full advance is 35° as from around 3000 revs.
What about at tickover speed, around 1500 revs?

Paul
 
mauricejota7604 said:
I have strobed mine at 3600 at 32 deg max, idle at 1000- 1100 about 10 deg
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Thanks Maurice. I'll look this afternoon. My wife's 500 is playing up after a partial rebuild. Uneven idle and occasional stalling. Carbs are ok but a quick strobe flash yesterday appeared to show that timing was way out, which is strange since I didn't touch the pick ups though I did have the primary cover off.

Paul
 
Getting there, a bit.
My quick strobe of yesterday was confirmed. Timing on the left pot way retarded.
So I checked the gap between pick up and rotor magnet. There wasn't any. So that was adjusted which involved taking the pick up out and a bit of Dremel work on the slots.
Gap set at 0.2mm and timing spot on. Around 10° advance at 1300-1500 revs, jumping to 36° at 3300.

Bike still lumpy at tickover. I checked the right pot. There appears to be a 0.15mm gap on the pick up but the strobe shows nearly full advance at tick over, advancing just a bit over 3000 revs.

What could be the cause of that?

I also need to sheathe the wiring to the pick ups, their insulation is totally breaking up.

Paul
 
There's your problem Paul insulation breakdown on the Bosch pickups, they can be repaired but it can be costly as they will have to epoxy the connection at the pickup itself, will solve your wild variables for sure, your max advance is up there what compression ratio in your engine??
 
mauricejota7604 said:
There's your problem Paul insulation breakdown on the Bosch pickups, they can be repaired but it can be costly as they will have to epoxy the connection at the pickup itself, will solve your wild variables for sure, your max advance is up there what compression ratio in your engine??
Click to expand...
Compression ration appears to be standard. Head was off for a gasket change and pistons were flat.

Paul
 
Well, no luck. I sheathed the wires to the pick up on the right hand side and I've still got 30° advance at tickover which will only advance a bit around 3500 revs.
Before suspecting the Bosch box, is there something I should look for wiring wise?

Paul
 
Have you checked the pickup resistance value? If so, what is it? But reckon you have a duff BTZ box.
Not familiar with 500 arrangement but presume you can swap the boxes over to confirm?
 
Rob said:
Have you checked the pickup resistance value? If so, what is it? But reckon you have a duff BTZ box.
Not familiar with 500 arrangement but presume you can swap the boxes over to confirm?
Click to expand...
Thanks Rob, I'll try swapping boxes. The system is the same as a 180 with 2 boxes and 2 pickups 180° apart.
Being a total numpty but having a multimeter, how would I check the pickup resistance?

Paul
 
Didnt someone say something about fitting the yellow wires the opposite way around polarity wise resulted in full advance at idle. Just repeating what I remember was written. I don't know why it would only affect one cylinder thought. If it isn't that it's the box. Is there 2 yellow wires per cylinder?
 
Two wires come out of each pickup. One white, one black and white. They go to the Bosch boxes, one pair either side.
At some time, the wires from the pickups to the loom and hence boxes, were cut, replaced by red and red and black wires from just after the pickups to near the boxes with dominos under the crank end ignition cover. The white goes to red and the black and white to red and black and vice versa near the Bosch boxes, follow?
I took that engine out and it seems that the pickups are correctly wired. I was of course careful but mistakes do happen. Is there a risk for the box if I invert the black and white and the white to see if my problem comes from there?

Paul
 
Vince said:
Didnt someone say something about fitting the yellow wires the opposite way around polarity wise resulted in full advance at idle. Just repeating what I remember was written. I don't know why it would only affect one cylinder thought. If it isn't that it's the box. Is there 2 yellow wires per cylinder?
Click to expand...
Correct Vince, if we are talking original Bosch inductive pickups ( PUP )and BTZ, as the impulse cam approaches the PUP a positive going pulse edge is produced, as the impulse cam trailing edge leaves the PUP a negative going pulse is produced. Possible to reverse these pulses if the PUP is reversed wired. The trailing negative pulse is what the BTZ uses for idle advance, nominal 5-8 dBTDC. Pole face distortion ( pulling towards the impulse cam lobe ) is chronic on Bosch PUPs.

The actual mean gap across the pup twin pole facs is a factor at what rpm the BTZ switches to full advance, no in between. Insulation failure at the entry to the Bosch pup is also chronic, careful insulation restoration of the entry point to the molding is effective. Though at days end the pole face pulling is a death sentence for the well old pups. Use jap inductive pups or replace the whole system if possible.

Bit tricked here, thought the mechanical advance was supporting points? Is this topic on a Laverda twin? If it is a duck then ok, ditto and more so the bosch pup bathed in oil pole face pulling. Fitted one of my last Ducati iis to a 600 pantah few years ago, that is one engine also crippled by the stone age BTZ. Refurbed the bosch pups, though have jap pups and adapter plate on hand, come the day. HTH J. BTW if you yank the primary cover on and off, the alternator wires insulation fails at entry point to the case, and a short on the field winding results, more followed as the carbies needed rejetting...just the topic for a Laverda site, wry smile.
 
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