Bike wont rev out....

Well - if the plugs are black and sooty, first thing to check is if it is oil or gas causing that. If it is gas/fuel, your carbs are either running rich or they do overflow (float valves are not closing). If it is rich, you can check by engaging the choke when reaching that point where it does not want to rev anymore. If it gets better, you are to lean. If it gets worse, you are already on the rich side.

Mains play a role but only starting beyond 1/2 open throttle (or even wider open throttle). at the revs you describe the problem accures, it is either ignition related or one of the following: Float hight, float valve not closing, Choke not closing, wrong setup (needle to high, to big needle jet or idle jet).

Just my 2 cents.
 
"Reversed pickup polarity preventing advance?"

good point Rob and an obvious one to check first as it seems the outer two plugs are rich but the inner is OK. In case this is not clear (with Bosch BTZ) the outer two cylinders on a 180 use the same ignition box and a double outlet coil, the inner uses its own ignition box and a single outlet coil, so two completely seperate "ignition systems"

at tickover the timing should be TDC at above advance point (usually 1800/2200 depending on trigger gap, it should be 32 degrees BTDC or 33.30, the later doesn't work for me with modern fuels. The thing is you must check both tickover timing and full advance timing on both systems, most engines will have a mark for full advance on the outer two, but (maybe) not for the inner one, which is diametrically oposite the the other mark, and easy to make, if its not there., but before any of this you must remove the generator ( you need an extractor for this) and inspect the wiring to the pickups, it very often deteriorates due to localized heat and can cause shorting/earthing which could even be your problem, bare wires very often visible with no insulation, like a string of beads, more RPM's giving more vibrations. You can run the engine with the generator not fitted, if you find dodgy wiring and feel like some re-insulating, best to cut the iwres and use heat shrink double layered, but the rejoin of the wiring must be soldered, its an off the engine job with the back plate.

CLEM
 
Also check for the insulation of the pickup-cables. very often, they are brokend and at certain revs, they might touch each other and cause the ignition to cut out... Typically happens already on idle, but might be it happens at a certain rev...
 
Update on the 1200 soon. Once I'm up and running again I have a dyno sorted for a baseline run ... just to see where the jets are at. It will be interesting to see what happens when sitting at about 4000rpm and then take a handful (under load). Thanks for the tips!
 
mizike77 said:
Got back to the bike today very briefly. Outer 2 plugs are dark and sooty. Didnt have time to get to the center. Looks like I have BTZ on mine. Put the timing light on real quick. Turned the idle up to 1200rpm . Had to turn the dial on my strobe to 10 to get it to line up the marks at 1200rpm. I twisted the throttle and though it was tough to look at the tach and the strobe at the same time it looks like it would advance at about 2500 rpm .
Now , I am admittedly not very good with timing. I am going by the green book and it looks like my numbers are not correct.
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Black and sooty plugs with lean jets is an interesting mix of issues. Have you had the pumpers apart? It's not drowning when you open the throttle?
 
Rev the bike out as fast and as hard as you can on the HWY for say under a minute - Shut her down as fast as you can and don't let engine idle - Check the Plugs.

They should have a mild case of sot yet visibly white. If BLACK and soty lean the main Jets - If appearing white and burnt use a richer main jet. You will also note an engine lick in this case if the main jets are not rich enough and can burn a hole in the piston top in no time. Nothing worse then loading your engine at Hi-Revs with a LEAN mix.

Pending type of Carb, Air breather Vs Stacks and Exhaust System play and important part - All related to Air Flow and for good combustion.

That's providing you have the Timing on, Carbs to Spec, No air leaks, Collapsed Intake manifold hose or Gas flow issues... etc.

Your Idle and Mid Range jets can make your plugs appear rather sotie but will cleanup when you open the throttle ;o) - Good Luck.

Paul Marx is correct - You cannot judge plug reading after shutting down at idle. Idle or mid range and is not comparable to Full Throttle.

By then you're going very fast on a Breganzie and you had better hold on.

-----------------------------------

I always wanted a GUZZI 850 LeMans - Never owned or rode one ;o(

Reason Why: Which is FASTER - A 70 Breganzie 750SF or a 79 Guzzi 850 LeMans ;o)
Gotta say the Guzzie appears to an easier ride.
 
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Took the bike for a ride today. Went from my 115 mains up to 138. Much better. My engine would finally rev out and pull up high. I had a mild flat spot. Came back and dropped in the 150 mains. Flat spot is completly gone now. Pulls hard from down low all the way up to over rev. Once I get a chance to find a stretch of straight clear road in a few weeks I will do some proper plug readings. But for now I am happy.

This is my first Laverda triple. I have around 30 bikes with 7 or so being Ducatis . People ask how the Laverda feels compared. I say it feels very raw, like a big block Chevelle. Great fun.

The weather here is breaking soon. Gotta sort my RZ next, then freshen up my H2. After that the only bikes to go on the lift all summer will hopefully be just the regular services on the dirt bikes.
 
Your Wellcome ;o)

3234547471_640f5026fc_o.jpg

True 70 Z28 mounting a 625 Hp 7200rpm MKIV 460 SR BBC/M21/12 Bolt 273 12 Bolt Posi ;o)

Auzzies just don't get the Chevy hype

Good Luck with your MKIV BBC's:
2852036410_0c85e6bfe1_z.jpg

That's all Lunati and Harold Brookshire - Been there ;o)

Thing's kinda got out of control since I did not have the original 350 LT1:
48447939517_5a3eee57cc_o.jpg

I bought that car in 76 for $1600 with a 396 (Not the original Engine) The same price I paid for my 70 Breganzie 750SF as New - ONLY in Canada!

At 71 I sold both my 70 Breganzie 750SF and my 70 Z28 Camaro.

------------------------------------------------

By the way, I got a 1968 8000rpm 425Hp Grumpy Jenkins designed 333ci (327) almost complete in my closet if your interested !
If someone don't buy it I may just end up putting it in my Jeep - If I live line enough.
 
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150 main jets??? there will be more to this story than this simple ending, but we might never know what that is, and as for plug chopping, modern fuels do not leave deposits like the stuff available in 1977 did, much reduced and very much harder to read successfully, the only way to be sure you are carburatting correctly is t0 get it on the dyno, but watch the thrust bearings (ehh what, thrust bearings, my point exactly) in the clutch. on run down, in gear lever held in, worse with hydarauilic clutch but still applies to cable types.
CLEM
 
Have float-hights been checked? are the carbs and manifolds air-tight? I doubt a 150 would be right size of jet, there must be an issue and the bigger jet is just masking it. I bet there is an air-leak around the manifolds.
 
running very large main jets does make people feel good, I mean if your motor can handle it, then it must be a goodun!!! on open, main road testing there are very few oportunities to hold wide open throttle (absolutely guitar string tight throttle wire, no backing down) fully under load, for two minutes, in third or higher gear, and then cutting the motor at speed, and (wobbling) coasting, dead engine,stopping safely, so as to read the plugs, if you do not do this, you are not checking your main jets, and is why a dyno run (or ten) is a great idea.
CLEM
 
I tried it on The Carl Expressway heading towards The Sydney Harbour Bridge once years ago, won't be doing that again anytime soon.
 
Before fitting Mikunis to my Jota. I tuned the Dellortos by doing several dyno runs. The previous owner had put 145 mains in it that were way too rich. Something like 9:1 air/fuel ratio at WOT if I recall correctly. The bike still ran cleanly (no coughing or spluttering) but there was a lot of unburnt fuel going out of the exhaust pipe. The dyno bloke said the needle jet would probably not flow enough fuel for those big mains to have any effect. To prove his point, he did a dyno run with no main jets at all. It was pretty much the same as with the 145's in there. We ended up with 120 mains, which gave a reasonable A/F ratio of between 12.5 and 13.5 at WOT (depending on revs). Still a wee bit on the rich side but close enough.

So (assuming you still have the original needle and jet) you probably won't be getting any fuel metering effect from the 150 mains. All the fuel metering will be through the needle jet from about 1/4 throttle all the way up to WOT. You may as well run the bike without any mains at all.
 
Dellortoman said:
The dyno bloke said the needle jet would probably not flow enough fuel for those big mains to have any effect. To prove his point, he did a dyno run with no main jets at all. It was pretty much the same as with the 145's in there. We ended up with 120 mains, which gave a reasonable A/F ratio of between 12.5 and 13.5 at WOT (depending on revs). Still a wee bit on the rich side but close enough.

So (assuming you still have the original needle and jet) you probably won't be getting any fuel metering effect from the 150 mains. All the fuel metering will be through the needle jet from about 1/4 throttle all the way up to WOT. You may as well run the bike without any mains at all.
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I have made this point several times but people are often stuck in their misconceptions of how carburettors meter fuel and air, it falls on deaf ears. "My bike wouldn't pick up cleanly from idle so I changed the main jets and now it is fantastic".
 
BTW Needle jets and needles are pron to wearing out, finger in the bum style. That means they don't control the mixture well after mega thousands of in and out moves. Best to replace with new if your rebuilding carbs.
 
I can't wait to get home after this month's duty, but it is now fine enough (no snow) to tackle the bike again.

Hoping that lifting the needles will give me an indication that I'm headed in the right direction (richer).
 
Your engine may have a low vaccumn issue, this can be caused by a number of issues, low compression, bad cam timing, non sealing valves, non sealing inlet manifolds.
Wouldn't hurt to dig a bit deeper here!! fitting huge main jets as our strong mechanical members have suggested is not your solution, it may just feel a bit better.
 
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