More finds from inside the SF1 engine

When my SFC was rebuilt, it was found that the crank and rods were magnetised by the fire, therefore taking up the role of the magnetic sump plug.
Not good in a big end.
So they were demagnetised, apparently standard practice in racing engines.

Paul
 
TomL said:
Yes well.
Seriously: just make a wild guess about the cc's of plastic that came off. Then the litres of oil in there, and that would have been changed several times.
A complete non-issue. Replace, forget, be happy.
Click to expand...
Probably 7 or 8 cc of cam chain wheel tensioner on a 750 in 100 000 km that goes through 3 chain wheels.
Add to that the primary slipper debris and you're starting to accumulate stuff in the centrifugal cleaners that are the slingers. And a lot of that muck doesn't come out when you drain the oil.

Paul
 
Thomas aus LAU said:
Avoid useing silicon! E.g. Loctite 510 is an anaerobic sealant, which cures when confined in the absence of air between close-fitting metal. So useing too much sealant is no problem at all. Beside you will get an 100% non leaking motor.
Loctite 510
For covers you will reopen from time to time, you should use a non hardening sealant like Teroson Fluid D.
Teroson Fluid D

Thomas aus LAU
Click to expand...
Nothing quite like an anaerobic cam seizure.

Paul
 
My 2-1 and 2-1-2 both sit below the sump plate. I can still ride over gutters without (grounding more than once or twice and on the move you'd have to be going over some pretty serious bumps at low speed to make contact. Most sports bikes with full fairings have a lot less clearance.
 
My big bore flat style collector scrapes when I enter my yard's gutter crossing, that mainly why I avoided those triangular stacked type collectors. That would reduce my clearance too much.
 
Remember: the price including shipping for the used frames from London where 39 EUR.

Last Saturday i got a surprising „gift“ from GLS. It was a bill over 22,03 EUR.
7,51 EUR for tax, that‘s ok and 14,52 EUR for solving the things with customs. That is not ok as CN22 was filled in absolut correctly and there was no order for GLS to do anything with customs.

But the horror went on....

GLS send on Tuesday another bill over about the same article and amount (ca. 25 EUR).
Only difference: the first bill was for „glases“, the second for „frames“.

Customs say that is not ok.

I only transfer the customs fees to GLS but no more. I will not pay GLS - we will see....
This is the advice of my lawyer.

Best Thomas aus LAU who has the better nerves than GLS. :)
 
Last edited:
Tippie said:
It also polarises the molecular structure of the oil and amplifies it's effect, in a similar way to those fuel polarisers that were so popular a few years ago, miraculous!
I talked to a guy with a BMW some years ago who had just ridden over the step of a low gutter to park it, the sump plug had punched straight up into the sump, he was pretty distraught, had just bought the bike.
Click to expand...
pulled a SF2 750 engine apart 3 days ago with a similar issue, owner rode over a gutter and punched one of the sump plate studs straight through the engine case, welding it up next week

also noticed that the crank had been stripped and rebuilt when I pulled it apart, GT 750 big web crank, was impressed that whoever rebuilt the crank used NJ207 EMC3 middle crank bearings same as we use on our race cranks
pity they did not line up the crank phase when they pressed it back together, phase is way out FFS
 
redax5 said:
pulled a SF2 750 engine apart 3 days ago with a similar issue, owner rode over a gutter and punched one of the sump plate studs straight through the engine case, welding it up next week

also noticed that the crank had been stripped and rebuilt when I pulled it apart, GT 750 big web crank, was impressed that whoever rebuilt the crank used NJ207 EMC3 middle crank bearings same as we use on our race cranks
pity they did not line up the crank phase when they pressed it back together, phase is way out FFS
Click to expand...
No splines on a GT crank, Red? Didn't know that. I knew they had a stepped crankpin is all. Pretty hard to get a std SF0-1-2-3 crank out of phase (am assuming the 0 had the splined crank).
 
I read with interest the bit about oil filtration. I can add a little on the topic.
Aermacchi flat singles have a very similar setup to the Laverdas. A gauze filter in the sump surrounding the oil pump pickup. 8mm wide gear pump, roller bearing big ends and the odd plain bearing here and there.. When we started replacing OE big ends and rods we had a very hard look at the oiling system with the aim of providing at least better filtration.
What we came up with was a BMW paper filter element which we cut to fit in the OE space.around the pickup- about 90mm high by 50mm diameter. One BMW element makes two filters. The OE sheet metal cap over the filter is still used. The paper fits inside it neatly.
To check the flow ability of this setup, we motored the bike on powered rollers with the rocker feed disconnected and going to a container.
No difference in the quantity delivered with or without filter element.
From this we decided to run with the paper filters.

My Aermacchi customers have been using this setup since the 1990's. No probs and visibly cleaner oil.
 
Very similar to Guzzi Nuovo Falcone, people have fitted a paper element instead of nylon mesh tube with no ill effects..
expensive experiment if you get it wrong though. I was wondering if you could have partial filtration, Apparently partial filtration works Very well, your just filtering the oil at a slower rate, might be a bit safer. there must be a reason Laverda reverted to a courser mesh early on, saying that they also increased the pump speed as well.
 
piranha-bro2 said:
No splines on a GT crank, Red? Didn't know that. I knew they had a stepped crankpin is all. Pretty hard to get a std SF0-1-2-3 crank out of phase (am assuming the 0 had the splined crank).
Click to expand...
They're all splined, Quentin.

Not unusual to find the phasing out by a few degrees, not much you can do about it except to use it as a boat anchor... or try your luck with an assortment of splined centre journals. I've only been able to salvage one such crank, got it to +/- 0.02mm, hardly measurable in degrees, instead of the +/- 8° that I initially found. Luigi apparently had more bad days than one would like to imagine... ;)

All very time-consuming as the centre pieces and inner webs are unique and normally only fit as a set.

Only the very earliest GTs had the stepped pin, the factory quickly switched to the single-diametre pin for all models. Only the '73-onward SFC cranks had webs with integral pins and plain centres.

piet
 
Exmoor beast said:
Very similar to Guzzi Nuovo Falcone, people have fitted a paper element instead of nylon mesh tube with no ill effects..
expensive experiment if you get it wrong though. I was wondering if you could have partial filtration, Apparently partial filtration works Very well, your just filtering the oil at a slower rate, might be a bit safer. there must be a reason Laverda reverted to a courser mesh early on, saying that they also increased the pump speed as well.
Click to expand...

If you want an example of partial filtration, I'll advance the Benelli 650 twins.

In response to the US agent's demand for a "proper" oil filter, they installed a replaceable paper element - under the center of the crank.

When I came to rebuild one, I was extremely surprised to find that the oil pump output was split. One part goes to the engine bearings, The other to the filter. The outlet from the filter is directly under the flywheel in the center of the crank - straight into the crankcase volume.

In this case, the more restrictive the filter, the better the oil pressure at the bearings.

As to the reasons the works make changes. Sometimes the answers aren't obvious. An example is in the history of the BSA singles. As a result of experiments with plain big ends - which never came to production - they got a better oil feed system.
 
My understanding is that the splined centre is synced left-to-right so the only way they could get the phasing out is by getting it wrong when they swage the webs on. From memory, when I rephased an SF2 crank using the splined centre the closest I could get to 270 was 272 because the ratio of splines to degrees limited me to that figure.
Piet, does your experience mean they didn't use some sort of jig - which is what Red has made and uses - that holds the unit at 360 deg when swaging? Primitive indeed if true!
 
GregT said:
If you want an example of partial filtration, I'll advance the Benelli 650 twins.

In response to the US agent's demand for a "proper" oil filter, they installed a replaceable paper element - under the center of the crank.

When I came to rebuild one, I was extremely surprised to find that the oil pump output was split. One part goes to the engine bearings, The other to the filter. The outlet from the filter is directly under the flywheel in the center of the crank - straight into the crankcase volume.

In this case, the more restrictive the filter, the better the oil pressure at the bearings.

As to the reasons the works make changes. Sometimes the answers aren't obvious. An example is in the history of the BSA singles. As a result of experiments with plain big ends - which never came to production - they got a better oil feed system.w
Click to expand...
The Benelli system seems fail safe and would be good on a Laverda perhaps with a 10mm gear pump.
I was racking my brains thinking of a half mesh/ half paper filter that would allow good free flow of oil but filter the other half without risking starvation. - with regards to the finer mesh , the more I think about it the oils should go through easily as it’s such a big strainer.
I had a BSA B25 scrambler with the plain big end , which was so unreliable the hot trick was to fit a Roller bearing crank from a C15.
Like your Aermachi , I‘d need to See the oil flowing to convince myself, if I get a motor in bits might be good to mock up the crank cases and run the pump to see if it copes with different filters. Piet posted flow rates for various pump/ gear sizes - I suppose if the filter could gravity Flow the same/ more it should be ok.
 
Last edited:
piranha-bro2 said:
My understanding is that the splined centre is synced left-to-right so the only way they could get the phasing out is by getting it wrong when they swage the webs on. From memory, when I rephased an SF2 crank using the splined centre the closest I could get to 270 was 272 because the ratio of splines to degrees limited me to that figure.
Piet, does your experience mean they didn't use some sort of jig - which is what Red has made and uses - that holds the unit at 360 deg when swaging? Primitive indeed if true!
Click to expand...
Quentin,

The splines were machined randomly, no 2 centre pieces are truely identical (well, there may be some, but chances are extremely slim). As these splines were used to produce the inner splines of the webs, the entire centre web assembly is unique and no individual component can be easily replaced. The centre pair of webs was supplied assembled as a spare part by the factory, as per parts manuals. The factory probably used a jig of some sort to align the webs on intial assembly, but apparently it wasn't foolproof enough for Luigi.

You would need quite a few centre pieces to find one that would result in a true 90/270° re-phase with a pair of given crank webs. Only "easy" way around that would be to use new, never-before assembled webs... ;)

piet
 
Cranks came unphased ex factory for some of them and from what I understood from Phil Todd, the splines on re-assembly do give you a certain leeway allowing you to correct it. I of course have no practical experience of crank building.
My S crank was 257° ex factory when he did it. I can feel the difference on the rebuilt bike.

Yes, only the early GT used stepped crankpins as did the S, or at least some of them.

Paul
 
Paul,

The splines of the centre journal allow absolutely no leeway for any adjustment, unless you re-assemble the crank incorrectly on purpose. If the splines are damaged upon re-assembly, chances are that the webs will work loose in a very short time, resulting in a horrible mess. The bolt that holds it all together is dependant on the splines to keep the plot in line.

You'd be surprised at how bent and wobbly most cranks are. Wear at the mains allow the cranks to throw their weight around, resulting in "they're all like that, Sir" vibes. ;) A sure tell-tale is pitting on the outrigger bearing race or even a loose race, I find up to 0.5mm (instead of `+/-0.05mm max) run-out here. The difference you felt results solely from new bearings and reducing run-out to a minimum. Even the factory balancing was well inside the ball park.

piet
 
Very informative, Piet. I had no idea they were that rando, and always assumed (stupid thing to do!) that the splined centres were all identical, as if made to a pattern. I've actually fitted webs from a different SF to my old motor (haven't I Rob 🙀) - luckily they turned out OK. But another motor I rebuilt after it had suffered a massive seizure and created a U-shaped rod had the splines round out in the right web after a few hundred km - seems the seizure had loosened the fit! Motor became a one-cylinder (points on the right, cam chain still synced to the left cyl. No other damage, thankfully - 'new' web from Red fixed it - never bothered to check the phasing as the whole bike had given me grief from go to whoa.

Converting the crank to a stepped non-splined centre and boring the webs to achieve a tighter press fit must make a big diff to crank concentricity and robusticity (:)). Steve B designed and made a few that are in some of Red's 270 motors. Would work nicely in a 360 as well.
 
You must log in or register to reply here.
Back
Top