Mounting a timing wheel on a 750SF?

2 sentences of complete tosh from me that I deleted, all I got is back to basics. Fuel spark compression. Maybe it's only firing on one at speed, dinos help but not if you cannot get past what's actually wrong. I did a session once with the operator just shaking his head with a blank look on his face after months of shit running and no answers a couple of months later the one tooth out bit finally got addressed after it melted a set of plastic carby slides. CV Keians at the time, I couldn't get the engine builder back then to see reason even after months of shit running. He did 3 Laverda builds at the same time, 2 went fantastically, and mine ran like a dog. I would hate to repeat that time again.
 
Thanks Shajota,

Good idea on checking the slides, but they are fully retracting at full throttle- the back portions of the slides are longer than the front, so they don't fully retract into the bores
 

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This shows how the retracted slides look at both sides of the carb at full throttle- the slides are fully retracted upward when viewed from the air filter mount side, but hang down a bit on the manifold mounting side, and I can press the slide upwards w a finger to full retract. So is this correct or not?
If not, it may explain the weak engine response at higher speeds I've been trying to correct for a long time-
 

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No it's not correct. The slides should completely clear the carb throats when viewed from either side when the throttle cables are pulled.
 
TeddyG said:
This shows how the retracted slides look at both sides of the carb at full throttle- the slides are fully retracted upward when viewed from the air filter mount side, but hang down a bit on the manifold mounting side, and I can press the slide upwards w a finger to full retract. So is this correct or not?
If not, it may explain the weak engine response at higher speeds I've been trying to correct for a long time-
Click to expand...
"and I can press the slide upwards w a finger to full retract"
One of the reasons I asked yesterday about cables and elbows etc. Sounds like your cables aren't retracting slides fully.
If for example you had incorrect length cables or installed elbows at the top of the carbs this would reduce pull available from standard cables so you would need longer cables. (well, that's what makes sense to me - I had thought about putting elbows at the top of my VHB's because of lack of room but didn't think they would work with standard cables)
Anyway likely it would act as a mechanical restrictor as you describe...............(no doubts others will confirm or debunk)
 
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As mentioned they should 'disappear' at full throttle. Having said that, if you're struggling to get beyond 50-60mph on your 3/4 throttle I doubt this is related to the problem. Something to rectify but doubt it will resolve the issue.

Before dismantling, have you used a strobe light to check your timing marks with the engine running? Full advance should see the A mark on the starter freewheel (40 deg BTDC) lining up. Something to check once you've cleaned up the bores.

Another thing to check while you have the thing apart is valve sealing. Pour some gas (American petrol :cool: ) down the ports with both valves closed (you can rotate the cam wheel 180 deg to get closed valves on the other cylinder. There should be no leakage into the combustion chamber side of the valve.
 
Thanks Rob and Shajota,

I installed OEM carb cables w no elbows (it has the 1 into 2 splitter I'd like to change to separate cables), and since I can only see the slides from the air filter side once mounted, I never gave thought to how the other side of the slide compared, since I assumed it would be the same. So I'll see if I can get that side retracting fully into the bore.
Pirhana, a friend strobed the timing and said it was fine, and I will test the valve seals.
My friend also tested the advance on the points cam lobe by gripping the end of it and turning it clockwise, and it "snapped " back into position. Does this test prove the advance is working properly? I'm just trying to eliminate possible causes for this higher speed problem, thank you-
 
Hi TeddyG,

which Slides are mounted, 50/3 or any other?
Which Mainjet is mounted, 145?
Which needle is mounted? K2 and Clip in the Middle?

You use a different Exhaust-System as standard.
What does the Manufactor of this Exhaust tell, which Size the Mainjet should be?
Can you share a Picture of your Airfilter please?
Can you ride the Bike at more than 3500/4000 rev.?
If yes, ride some time, leave throttle in his Position and turn Ignition of.
Do the Sparks out,
than check the Color of your sparks and share Picture of the Color please.

Regards Rainer
 
Thanks Pirahana for the advance info. Rez- I installed new 50/3 slides, tried 140 then 142 mains but 140s seem to work better. Was advised to go 2 steps higher on atomizer, K2 needle and clip in middle (tried raising clip but no improvement). It has a Malcolm Cox exhaust and was told jetting varies according to elevation, etc, so no real guidance. Last time I rode at a brisk clip, pulled the plugs that were burning clean/tannish w white porcelien showing. After all the testing and since it starts immediately, I feel the ignition is not the problem. I'm trying to find a competent machinist to evaluate the cylinders, and will then have them honed or re-bored w/ new pistons. The problem could still be carb related so I'm considering ultrasonic cleaning.
 
Thanks Tippie- along w/ replacing everything on the carbs, new AB265 needles. Rez, the float distance is 18mm- the gas pumps were also measured and adjusted. Forgot to mention that DNA pod filters are installed w/ the rubber air filter snorkels to angle them downward and clear the frame, and there's no change when taking them off. The only thing not done for the carbs is ultrasonic cleaning.
Once I find a competent machinist in Portland, I'll proceed w/ reboring and new pistons and hope that helps. I'll keep you all posted...
 
Teddy - I can't find anywhere that you have explicitly answered the question about whether your bike would rev out OK in the lower gears?
 
Rob- the motor revs freely at idle and low speeds but I have avoided redlining it - I,ve gotten it up @5k rpm at over 60 mph, but the motors lack of acceleration and vibration is telling me somethings wrong and not push it. Andy- the Malcolm Cox exhaust headers are clear and I,ve always felt pressure coming from the mufflers while bike is running but I,ll check them
 
I think Andy could be on to something, here.
Try running it on just the headers?
You won't be popular with the neighbours but, at least, that would rule the silencers out as the problem.
Maybe a DPO thought it was too loud and stuffed glass fibre into them.
 
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5,000rpm should give you 80MPH (and on a triple 90MPH)
the early PHF carb slides are different to the ones supplied today, a small amount of metal needs to be machined away from the (currently available) slides in order to work them in PHF carb bodies, If you had bought your slides from a reputable Laverda dealer, or a Dellorto expert (EG Paddy) then this would have been done for you, but as mentioned, the issue of the whole slide clearing the carb throat does need to be addressed, but I also doubt that this is affecting your current problem (of reluctance to go over 3,500/4,000RPM), the slide "hanging" in the carb throat might drop max revs 1,000 or so RPM (pure guesswork)
CLEM
 
TeddyG said:
Rob- the motor revs freely at idle and low speeds but I have avoided redlining it - I,ve gotten it up @5k rpm at over 60 mph, but the motors lack of acceleration and vibration is telling me somethings wrong and not push it. Andy- the Malcolm Cox exhaust headers are clear and I,ve always felt pressure coming from the mufflers while bike is running but I,ll check them
Click to expand...
OK - so just to be clear on this key point. What gear were you in when the engine pulled 5000 rpm?

I'm keen to understand if it would rev 'freely' - i.e. up to 7,000 rpm = in neutral and also any/all of the lower gears?
 
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