Czakky’s T3

[czakky82]

@Wirespokes, I thought about that too, but since Guzzi used the same distributor (weights, etc) for high and low perf bikes (higher advance). Wouldn’t that mean that the springs would have to be the only way to stop advance?
I just can’t find anyway that the weights could’ve been in there wrong.

[Chuck in Indiana]

I can't imagine designing an advance system that doesn't have a positive stop for full advance? Shirley  the springs alone don't do that..

[czakky82]

I suppose static timing could be more advanced on the “high performance” distributor...

I’m even more confused. I guess I need to buy a MK1 Lemans for comparison research to make sense of all this...

[jwinwi]

I apologize for not reading the entire thread... How's your timing chain and tensioner? Excessive slack in the chain would certainly cause timing inaccuracy, right?

[wirespokes]

You're over-thinking this!

The weights and springs are the controlling and regulating factors for the spark advance.

That's all.

Your timing is spot-on at idle and full advance. Except...

It keeps going once it's reached max advance.

That can mean only one thing: The weights aren't stopping at the maximum advance setting.

You need to find out why that is and fix it. You'll have to dig down there and see what's up. I don't have a distributor apart at the moment so can't describe what's going on. But in a half hour you could have it apart, spot what the issue is, fix it, and have it all back together and running as it should.

It's not a big deal! Really.

[moto-uno]

Here are pictures of one of 2 distributors I have on my bench , from Le Mans 2 .

[moto-uno]

 On the last pic you see the bottom of the advance unit and it's 2 pins , the third pic simply shows how the distributor looks when the advance unit is removed .
The first pic shows the slots in the bottom plate that are responsible for hard limiting the advance . The second pic shows one of the advance springs position
which is loose on the pin , this is correct ( for the Le Mans 2 ) . So , if your ignition is still advancing up to 6000rpm then the pins and slots must be very worn or
the spring set is incorrect ( I doubt anyone would have lightened the advance weights so much that it required that kind of rpm to get to full advance ) . But if you're
not sure , then compare it to these pics . The pinging at higher rpm could definitely be the over advanced timing at the higher rpm . This statement is only valid if
you had set the timing at 4500 rpm .  Also I should mention that the advance weights must be free to move on their locating pins .  Peter

[czakky82]

Very helpful, thanks Peter. I will compare my distributor when I get home.

[czakky82]

Thanks again Peter. After looking at my weights, pins, etc. I don’t see anything different. If anything the locating pins on the underside of the advancing unit look less worn than yours.
With the advance unit on in full advance I get 29.4mm on the outside of the pins where the springs would go.

[moto-uno]

  Well if the springs are okay (correct ) , reassemble and set full advance timing for where the advance stops and try it from there . This has
my interest . Good luck , Peter

[czakky82]

No telling if something wasn’t right before I took it apart. I’ll report back when my new springs come in.

[wirespokes]

I took my spare apart and saw the same as pictured above.

Dave Richardson used a distributor tester to determine these Marelli distributors have 26 degrees of total  advance. The springs don't limit full advance, I'm pretty sure the downward facing pins hit the end of the slotted holes they ride in.

A Guzziology graph of the LM distributor curve shows it starting about 1500 RPM and maxing out around 4500  RPM at 34 degrees.

I see no logical explanation how your timing could be correct statically and at full advance, yet continue advancing beyond that. There is an untruth in that statement somewhere.

Seems like the solution is setting full advance maxing out at around 4-4500 RPM. The springs only determine how quickly or slowly max advance arrives.

[czakky82]

There was a noticeable difference in the new set of springs I got, the heavier spring is definitely shorter. Unfortunately though it did not change things. I was hoping that I somehow put things together wrong the first time and that I’d be fixing it by putting it back together.
Anyway it still does the same thing, after setting static I check at 4200 rpm and it’s right on but continues to advance not a lot mind you.... I’m going to try to retard it at bit and hope it doesn’t run like a turd. Otherwise I’m going to have to look in the timing chest.

[czakky82]

I have to update this in case 100years from now somebody is having the same problem.
Mark from MG Classics sent me a known good dizzy and I had the same issue of over advancing.
So I went back through the timing chest having replace the tensioner last year and my conscience had me thinking about how rough with the valtek style piece I was when installing. I installed a fresh one a bit more gently.... same exact thing.
 

[czakky82]

I’ve been noticing some extra metal in my trans oil lately. Shifting not great going from 2nd to first. Then my output seal was puking a bit of oil.
So I’m going through the transmission.... again.

I replaced bearings I should’ve the last time I had it apart and attempted to get that freaking selector spring to lay flat. Well I got the bearings replaced atleast... I also decided to give shimming the selector drum a shot too.
I stripped the housing except the drum and found it sloppy with the cover on so I added a shim, too much... deleted one from the cover side, a bit of slop, etc. I got it perfect likely adding only a bout .5mm or less. It looks like my shifting forks were more worn on the front (engine) side. So that was where I added the total shim, if that makes sense.

Not sure if any of this is important but after re-assembly I cannot shift into 2nd. Neutral and first are no problem.

I can turn the drum when the cover is off and the selector moves freely when the cover is off too.

Could my shimming have caused this? I’m lost...

[wirespokes]

It's been 4 1/2 years since the last post. Did the bike get sorted and trouble-free?

Was there a resolution to the advance issues?

[Tkelly]

I think so,I bought the bike and it runs great.

[wirespokes]

That's great!

It would be nice to know what solved the issues, especially the advance springs since I'm dealing with that now.

[Tkelly]

Ask Czakky.He is on WG.

[moto]

The main jets were way too big when I checked them.   Dropping them to just above stock picked up the performance nicely. I don't know if that problem was confounded with spring advance.

[Gliderjohn]

How big were the jets? I have a mildly modified T-3 with the big bore kit, early V-7 Sport cam and 36mm carbs. 130 mains seemed to run out the best.
GliderJohn

[moto]

How big were the jets? I have a mildly modified T-3 with the big bore kit, early V-7 Sport cam and 36mm carbs. 130 mains seemed to run out the best.
GliderJohn

142 I think. Tkelly might remember, or I may have a note I can check after the 15th.

[moto]

Since Dellorto jet numbers are diameters (unlike Mikuni numbers) these are the mixture flow values relative to the stock 120 jets, for several common sizes.

122 --> 3.4% more flow
125 --> 8.5%
130 --> 17%
135 --> 27%
140 --> 36%
142 --> 40%

With 142's installed Tkelly's bike smelled like a gasoline spill to riders following him, and had poor response. I put in 125's, roughly corresponding to the 10% greater flow recommended in Guzziology for lightly modified engines. I recall his bike has stock VHB 30mm carburetors, so I was thinking of installing [EDIT:] stock 120 122 jets.