SF2 main jet PHF 36

weirdly, I was reading these posts and  and thinking it sounded similar to a problem I had years ago, which ended up being traced to a loose connection on the timing plate, it was really hard to pin it down buy seemed rev - related, a check check and it seemed tight enough but was not and vibration caused a misfire exactly as Paul says, Stuart
 
I agree with fellow members diagnosing misfire but don't forget that deadly Lucas Ignition Switch.

I still run points in my 71/72 SF2 with open mouth VHB30A's and after a few sessions of despair in the early years can now easily remove the cover and manually run through the distributor including timing in under 1/2 hour using a 12v bulb. You can use a timing light when it's running but it's inconclusive - Thankfully, I got rid of that Lucas Ignition SX.

One  trick that saved me a lot of ignition trouble was putting a layer of Amphoric 1101 (Whatever it's called - It's Grey and made by 3M and works GREAT) engine case sealer around the Engine Distributor Cover Boss and let it set then drill a 1/8th hole in the bottom of the cover to drain dampness - Especially when you wash the bike or ride in the rain (Keeps water outta the distributor yet lets it breath and stay dry).

That Engine Case Sealer also works great on the carb insulating plates rather then using "O" rings.

Would not mind a set of 34's or 36's over my 30's on my SF so I could run an Air Filter and still hit 7800rpm without puking or leaning out. My 30's do it BUT they tend to eat dirt, demanding oil change once or twice a year depending mileage. Open Carb fuel stand off dirties your engine - but man it sounds FANTASTIC and them Hi-Velocity 30's deliver a great throttle response.
 
Laverda SF said:
I agree with fellow members diagnosing misfire but don't forget that deadly Lucas Ignition Switch.
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I have yet to find a factory-fitted Lucas ignition switch on a Laverda motorcycle.  Either Bosch or Nippon-Denso on the big Breganze bikes, CEV or Aprillia on the tiddlers.

piet
 
I have yet to find a factory-fitted Lucas ignition switch on a Laverda motorcycle.
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May be only an import to Canada, dissembled and in Wooden Crates ;o(

I don't trust any keyed ignition SX when an 18 wheeler is hogging your ass and your ride dies.

Use Heavy Duty Toggle Ignition Switches - PERIOD - That's my experience with ALL Motorcycles.

Been there: If you Guy's and Gals get into Ignition Failure - It's Not Nice.

Thanks SFC - You have my response and my care.
 
Well there have been developments. Rebuilt carbs and rechecked float hights........Miles out! Seems the idiot who checked them TWICE befor managed to check them with the fucking carbs 180 degrees from where they should have been. I may slightly resemble the said idiot. Guess that explains the crappy mileage as the bloody thing was choking on gas..
A test run shows it pulls to the redline in 5th at about 95mph  Next disclosure , the redline shows to be 6400 RPM. Subsequent discussions with Mr Potter lead me to believe I have about another 1000 to go before I hit the real redline.
Can timing is spot on and identified the cam as a 5/1 according to green book data ad opening and closing measurements. 
I have asked Wolfgang to see if he can locate a 4S cam.
Other than that I think I will enjoy it as it is until I get a hotter cam.
Thanks to all for support. Great forum, now feel free to take the piss😁
 
zorba75482 said:
Well there have been developments. Rebuilt carbs and rechecked float hights........Miles out! Seems the idiot who checked them TWICE befor managed to check them with the fucking carbs 180 degrees from where they should have been. I may slightly resemble the said idiot. Guess that explains the crappy mileage as the bloody thing was choking on gas..
A test run shows it pulls to the redline in 5th at about 95mph  Next disclosure , the redline shows to be 6400 RPM. Subsequent discussions with Mr Potter lead me to believe I have about another 1000 to go before I hit the real redline.
Can timing is spot on and identified the cam as a 5/1 according to green book data ad opening and closing measurements. 
I have asked Wolfgang to see if he can locate a 4S cam.
Other than that I think I will enjoy it as it is until I get a hotter cam.
Thanks to all for support. Great forum, now feel free to take the piss😁
Click to expand...

Good.
Paul
 
Yes, beer o'clock - very important ;-) 

Glad you solved the riddle - ignore the redline - you should be safe to 8,000 for short bursts, 7,500 any time you want. Don't bother fitting a 'hot' cam unless you want to fit a suitable exhaust system - you'll just be destroying a very strong powerband. I raced my SF on a 5/1 cam with Ducati Contis (no junction box or crossover) and a half fairing, had loads of midrange and it pulled very strongly to 8,000 (overtook a green frame in my first race) and had a top speed over 200kph (125mph).

Hot cams are NOT bolt-on power. Don't be fooled.
 
zorba75482 said:
Well there have been developments. Rebuilt carbs and rechecked float hights........Miles out! Seems the idiot who checked them TWICE befor managed to check them with the fucking carbs 180 degrees from where they should have been. I may slightly resemble the said idiot. Guess that explains the crappy mileage as the bloody thing was choking on gas..
A test run shows it pulls to the redline in 5th at about 95mph  Next disclosure , the redline shows to be 6400 RPM. Subsequent discussions with Mr Potter lead me to believe I have about another 1000 to go before I hit the real redline.
Can timing is spot on and identified the cam as a 5/1 according to green book data ad opening and closing measurements. 
I have asked Wolfgang to see if he can locate a 4S cam.
Other than that I think I will enjoy it as it is until I get a hotter cam.
Thanks to all for support. Great forum, now feel free to take the piss😁
Click to expand...

5/1 cam is actually one of the peakier road cams, 4S was designed for the small-valve engines and has a little more duration but less lift iIrc.

7/1 is a nice road cam, a bit down on max. power compared to the 5/1, but better torque across the entire rev range.

piet
 
sfcpiet said:
5/1 cam is actually one of the peakier road cams, 4S was designed for the small-valve engines and has a little more duration but less lift iIrc.

7/1 is a nice road cam, a bit down on max. power compared to the 5/1, but better torque across the entire rev range.

piet
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Thanks Piet
 
sfcpiet said:
5/1 cam is actually one of the peakier road cams, 4S was designed for the small-valve engines and has a little more duration but less lift iIrc.

piet
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Yes, too true - the profile actually looks very similar to a 5/C, but the 5/1 will run well on a std exhaust whereas the 5/C won't - they're designed to sing with the VERY loud open reverse cone mega factory 2-1. You can baffle them, but you still lose a bit of the strong top end.
Quentin
 
For information on the continuing saga, you may remember that the smaller mains jet I used the better the bike ran as all the symptoms pointed to an over rich mixture.
I was down to 130s and scaring myself and many others across the pond.

I spent a bunch of time talking to both Scott and Wolfgang and discovered a few things.

Petrol is  different to gasoline.
Rubber mounted carbs vibrate less.

Apparently larger mains are required to compensate for fuel foaming on metal mounted carbs, combined with the fact US gas is a mess so I need smaller Jets than others.

Following Clem's early advice I finally found a shop with a Dyno out here in the sticks. With 128 mains am still rich at 3/4 to full throttle. Dyno starts at 10:1 and was south of that!
So now have some 125's to try.

 
That really is bizarre. 125 mains too rich for an SF. Are you certain all your other settings are correct, cam timing etc? One tooth advanced makes for very rich running but it will run. I have never heard this compensating for foam theory. I have gone from alloy to rubber mounted and jetting was not affected. Sure is an epic saga.
 
Interesting. The RGS takes a much smaller main jet than the 180s. 108s from memory, and even the Corsa only has 118s.
 
Running the standard 140s with rubber mounted carbs on mine and all's well.
Experimented with smaller mains when I tried running without the under engine balancer, anything under 140 is too lean.

Paul
 
have to agree about the mains - recently set up an SF1, running on unleaded and 140 mains with no balancer were fine. I'm with Tippie on this, that you may have the cam timing a tooth out. Just doesn't add up - I've worked on loads of SFs and never seen ONE that ran smaller than the stock 140 mains. What type of air filter are you running?
 
And hear we go: What type of Exhaust and Air filters are you running Vs Jets with 36's - There's no way you can use an air filter on 30A's but you can change the jets ;o)

My take is you have 2 or 3 main jets of various sizes in your pocket and open the throttle wide open into 5th and when it stops licking(Pinging) run the next higher# that is the next richer main jet for every day use.
 
It has already been on a dyno, where you get a print out of AFR, more accurate than seat of the pants blasting down the road and listen for pinking.
 
Grant said:
It has already been on a dyno, where you get a print out of AFR, more accurate than seat of the pants blasting down the road and listen for pinking.
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High-speed pinking/knock is inaudible anyway! :D

You can live with low-speed pinking under acceleration and eventually dial it out (sometimes with endless numbers of road trials), but high-speed knock only has to occur once without the rider noticing...  ::)

piet
 
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