sf750 starter spinning

Geez - Just a a light application of Molly Lube in the starter clutch and star reduction cluster on the end of the starter and be done with it.

Most important things are that the rivets are not loose on the starter clutch back plate. The back plate is not dented or warped an that the starter relay is either grounded through the Tranny Neutral Switch or you have Clutch lever depress ground to engage the starter.

To repair a bad incident is ensure the crank snout is polished, probably new dogs and springs and all of the above.

The main reason reason damaging the Breganze Starter Clutch is NOT engaging the starter when the engine is running - So do all you can to prevent it after repairing it. Other words, general maintenance on a Breganzie.
 
hi all, on my sf1 with new springs and and pins and no signs of looseness of the back plate the starter clutch still spins free (with the terrible noise associated). I noticed the chain is rather loose, can this cause the problem (i honestly don't see how but...you never know)? Any spec for the play in the chain? thanks
 
Paul,

pack a liberal dose of wheel bearing grease or lithium grease in the sprag clutch and see what happens.....
 
Paul Marx said:
Chain is not an issue.
Starter clutch is. Do not insist, take it to bits again.

Paul
Click to expand...
You know Paul, think i've dismantled it a million time now, i'm trying to do a serious troubleshooting before using the hammer again. I've tried to fit steeper springs with no effect while i noticed that the roller diameter is not exactly 10mm on each of the rollers. Because their position with respect to the wheel is set by their diameter, a smaller diameter might means they do not push hard enough against the wheel hence the wheel slips ... As they are (nearly) brand new i am wondering how come. These are regular rollers from rollers bearing that have normally high dimensional accuracy. It's also hard to believe they got worn out as the steel they've made is far harder than that used for the wheel and, btw, they don't travel that great distance anyhow...just ordered a new set (aliexpress 50 for 9 bucks...) and check dimensional accuracy before fitting...just getting mad with this...do you guys have any other suggestion? thanks a lot
 
Does it engage when you assemble it free of the crankshaft? It should lock positively in the one direction. Has the freewheel surface been ground/machined down at all, it could mean that the rollers get to the end of the ramp and are still not tight in position? Is the cast section that is the ramps and that holds the springs and pistons cracked, that may prevent the rollers from engaging properly. I have seen these in pretty terrible condition with more than one stuck piston and the freewheel surface seriously gouged up and they have still worked.
 
Tippie said:
Does it engage when you assemble it free of the crankshaft? It should lock positively in the one direction. Has the freewheel surface been ground/machined down at all, it could mean that the rollers get to the end of the ramp and are still not tight in position? Is the cast section that is the ramps and that holds the springs and pistons cracked, that may prevent the rollers from engaging properly. I have seen these in pretty terrible condition with more than one stuck piston and the freewheel surface seriously gouged up and they have still worked.
Click to expand...
Hi Tippie, yes it engages pretty nicely at rest. And no the freewheel surface has not been grounded/machined down. All of the Pins are free to move in their respective hole and i can't detect any sin of crack in the ramps. while the cast part (wheel) has a longitudinal crack and it's stuck inside the outer ring of the wheel. To be accurate, it's in this conditions since a while and i've always being able to get it to work by servicing regularly pins/rollers/spring... what i am considering too is super-gluing a small stainless steel band (say 0.1mm or so) in each of the ramp exactly to offset the rollers a bit and hoping for a firmer engament with the free wheel
 
What is the diameter of the wheel bearing surface?
Do not try to shim out the rollers, if they do not retract enough when the engine starts, you will blow up the starter motor and they are very hard to find.
If the diameter of the bearing surface itself is insufficient, you need to sleeve it.

Paul
 
you have got three tiny parts in each hole havent you?
the spring, its end covering cap and the roller?
someone, who shall not be mentioned sells a "rebuild kit", which is only two of the three tiny parts

in addition different Lav models have differentsize rollers, I cant for the life of me remeber what is what but for a 750 (I think) it should be..... no cant put my finger on it.

CLEM
 
I'd absolutely be using the correct diameter rollers. Even slightly undersize may have a bad effect. I'd suggest assembling it dry - I have never lubricated mine in three decades and several hundred thousand km. It's worth a try.
 
will have to measure the diameter on the freewheel bearing surface but as said it ahs not being fiddled with and it had worked pretty nicely for more than 15 years now. Could it be it wore out ? maybe. BTW what would be the right diameter for it? . For what concerns roller diameter the one i have fitted comes from a renown german shop so i am pretty sure the original (let's say right) diameter was 10mm. BTW never in my life i could think of Massimo Laverda or riccardo ZEN to use custom-size rollers and 10x10mm is a pretty standard size for rollers for rollers bearing (at least in Europe).
 
steppenwolf said:
will have to measure the diameter on the freewheel bearing surface but as said it ahs not being fiddled with and it had worked pretty nicely for more than 15 years now. Could it be it wore out ? maybe. BTW what would be the right diameter for it? . For what concerns roller diameter the one i have fitted comes from a renown german shop so i am pretty sure the original (let's say right) diameter was 10mm. BTW never in my life i could think of Massimo Laverda or riccardo ZEN to use custom-size rollers and 10x10mm is a pretty standard size for rollers for rollers bearing (at least in Europe).
Click to expand...
Zen or Massimo Laverda didn't live long enough for 750s to show signs of wear. A lot of them are over half a century old now.
The freewheel bearing surface does wear. I remember that oversize rollers were available at one time. The rollers from Laverda Paradies are ok.
Phil Todd, Piet?

It was Luciano Zen.

Paul
 
The surface on which the rollers engage wears. Once it gets close to the limit, the clutch can become really troublesome. The inner ramp insert also wears and can break up into several pieces if slippage/malfunction is neglected for any length of time. These are easily replaced, if you know how rivets work. 750s share rollers with the MkII and 120° triples. MkI triples and 500/600 have smaller rollers, their starter clutches seem to hold up best. Springs and plungers are the same for all. I've never come across over-size rollers, they would need around +0.2-0.3mm to be of any help. Rollers are generally available over/under-size in the 0.00Xmm range.

Remove the clutch and place 2 rollers (without spring and plunger) on diametrically opposite ramps, where they are closest to another. Measure the distance between the rollers and compare with the diametre of the driving surface. You should have at least 0.5mm difference between the two, the roller distance being the smaller. If there is less than the 0.5mm, the clutch will slip, except if you substitute grease/oil for sand... maybe ;)

There have been loads of efforts to repair these things, shrinking on a hardened ring being the most common. Unfortunately, these efforts are rarely sucessful. The best I've managed was to have the surface laser-welded to HRC65, then re-ground to size. Been holding up OK for a season in a hi-comp 120 triple.

piet
 
you bet it was Luciano...then...the diameter of each of the rollers i have on now is 9.5mm while the diameter of the clutch is 4.92, which is exactly the diameter between two opposite rollers...then slippage...clearly with true 10mm rollers there should be ok. The disturbing evidence is that rollers wear...they should be hard enough though...thanks everybody
 
Are you sure those rollers were 10mm when they were new and fitted? 9.5 indicates a huge amount of wear for a roller, and I'd expect them to look really beaten up and shabby - but I'd say you've definitely found the cause of all your grief!!
 
You must log in or register to reply here.
Back
Top