Bearing 6307

sfc vintage

sfc vintage

Hero member
A technical question:on a Laverda 1000 crank, you can use a track ball bearing, instead of a roller bearing? it's on the left side
 
sfc vintage said:
A technical question:eek:n a Laverda 1000 crank, you can use a track ball bearing, instead of a roller bearing? it's on the left side
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I really wouldn't. I'd use the specified bearing, as the engineers who designed the engine knew what they were doing. Ball bearings are typically better suited for applications requiring high-speed operation due to their lower friction coefficient. Roller bearings, with their larger contact area, are ideal for applications with heavy radial loads ( the left side takes a heavy load as it's the drive side of the crank). The only time it's better to change bearings, is when you're up-specifying, i.e from a plain bearing to a roller, or ball bearing, depending on the job the bearing is to do.
 
Use what is specified, it is well proven. Generally speaking, you need the one ball bearing on the right to locate the crank axially, the rest are parallel roller bearings which not only take larger load but also allow the rest of the crank to grow with temperature and parts of it move fractionally to the left without placing side thrust on the bearings.
If you have a ball bearing both ends (or the centre mains as Laverda disasterously found out in 1979) not only does the axial spacing have to be perfect, but when the crank gets hot they are fighting each other due to the thermal expansion.
 
breganzane said:
Use what is specified, it is well proven. Generally speaking, you need the one ball bearing on the right to locate the crank axially, the rest are parallel roller bearings which not only take larger load but also allow the rest of the crank to grow with temperature and parts of it move fractionally to the left without placing side thrust on the bearings.
If you have a ball bearing both ends (or the centre mains as Laverda disasterously found out in 1979) not only does the axial spacing have to be perfect, but when the crank gets hot they are fighting each other due to the thermal expansion.
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..if the engineers knew what they were doing , how come they screwed up the centre mains?🙄
 
I'm absolutely sure the engineers will have done their best with the data they had to hand. Bearings failed (in the hands of us riders) because of a lack of verification, and validation testing.

Classis mistake when there is a lack of time and resources.
 
Haggis said:
I'm absolutely sure the engineers will have done their best with the data they had to hand. Bearings failed (in the hands of us riders) because of a lack of verification, and validation testing.

Classis mistake when there is a lack of time and resources.
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😁😁 Far too kind...they 'ucked it up..no excuses😁 Bet the accountants were less than happy at the cost of the rebuilds? Did any other makers have this kind of engine issue..we all know about Honda cam chains, CX500 VF750 disasters...so much for their Engineers. Dont they test stuff?
 
If you changed the lh bearing (back) to a ball bearing, you would reverse the improvement
the factory made.
Early twins had ball besrings on the left and right. Because of the reasons Breganzane explained (temperature)
that setup failed occasionally.
Therefore they changed the lh bearing to a roller type. Same goes for the countershaft.
General rule for roller/ball bearing cranks for the outer bearings is one "fixed" bearing, one "lose" bearing.

Ernesto
 
Vince said:
Honda Chocolate cams on V4s
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Generally caused by mechanics setting valve clearances too tight so that the follower applied pressure to the cam right around the base circle. A friend had a customer with a new Honda who understood this and rode the bike directly to him from the dealer workshop to check after it's first service (it was inspected pre service to see and record the clearances), and by the time it got to the new workshop it had begun to damage the cams, where you could force the minimum feeler gauge into clearance, they were opened back up and the bike was fine from then on. There was quite a bit of clearance in the cam bearings of the little twins and V4s and you took it up at your peril. Almost everyone wants their valve clearances to the absolute minimum within spec, for some strange reason.
 
Tippie said:
Generally caused by mechanics setting valve clearances too tight so that the follower applied pressure to the cam right around the base circle. A friend had a customer with a new Honda who understood this and rode the bike directly to him from the dealer workshop to check after it's first service (it was inspected pre service to see and record the clearances), and by the time it got to the new workshop it had begun to damage the cams, where you could force the minimum feeler gauge into clearance, they were opened back up and the bike was fine from then on. There was quite a bit of clearance in the cam bearings of the little twins and V4s and you took it up at your peril. Almost everyone wants their valve clearances to the absolute minimum within spec, for some strange reason.
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When we sold The original VF750 s/f the problems occurred from new. Honda came up with a threaded hook tool that pulled the cam up against the cam cap to increase the measured clearance prior to adjustment. They also came out with UC oil additive that was available ( still is?) as a Honda part number that I believe contained friction reducers to save the cams. Honda UK at Chiswick carried out extensive oil pressure tests ( hot & cold at various parts of the engine ) to find the problem. My mate Ron was doing the tests and found Duckhams Q to be the best oil in tests and was told that there was no way Honda would endorse it. Lots of engine rebuilds under warranty, not a good time to sell Honda. I was eighteen and given a VF750S To ride to work on loan from the Honda rep,it was light years ahead of anything I had ridden . Two weeks later the seized rear suspension link collapsed with the guy riding it. Most of the VF500/750 and even the CBX550/ VT250 ended up rattley old things that no one wanted. Honda then built the VFR and were totally forgiven.I was asked to do a test day at Brands for Honda technicians on new VFR’s - I was given the choice of Saturday or Sunday- I chose Sunday. Ron phoned me to say the mechanics had gone mad and there had been a pile up on the first lap, broken limbs and trashed bikes everywhere so Sunday was off! I was gutted but I would have been at the bottom of the pile if I had gone that Saturday..
 
For some reason the soft cams thing wasn't as bad here in NZ. But what was bad were the run bigends on the VF's. Looking at them it was very apparent that a single linishing step across the oil holes wasn't good enough. Sharp edges left on holes in the mains and bigends stripped the oil film away when the engine was put under pressure.
Luckily when it happened the cranks didn't crack so it was finish the holes off properly with a radius, linish and set up the clearances properly
I've even had to do this on a couple of RC30's. Toolroom quality indeed.
The first two NC30's to hit Christchurch went on track of course. Both grey imports with low miles. Both did cranks nearly immediately. No info available at all but I'd had a VF400 apart and still had the shells for comparison. Identical luckily so usual deal, finish the cranks etc and reclearance,

Don't know the material or heat treatment of those cranks - but do the same bearing failure on Kawasaki or Suzuki cranks of the period and they would invariably crack.
 
GregT said:
For some reason the soft cams thing wasn't as bad here in NZ. But what was bad were the run bigends on the VF's. Looking at them it was very apparent that a single linishing step across the oil holes wasn't good enough. Sharp edges left on holes in the mains and bigends stripped the oil film away when the engine was put under pressure.
Luckily when it happened the cranks didn't crack so it was finish the holes off properly with a radius, linish and set up the clearances properly
I've even had to do this on a couple of RC30's. Toolroom quality indeed.
The first two NC30's to hit Christchurch went on track of course. Both grey imports with low miles. Both did cranks nearly immediately. No info available at all but I'd had a VF400 apart and still had the shells for comparison. Identical luckily so usual deal, finish the cranks etc and reclearance,

Don't know the material or heat treatment of those cranks - but do the same bearing failure on Kawasaki or Suzuki cranks of the period and they would invariably crack.
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Early RC30 I had to change the valves and the con rods under warranty- gas filled valves stretched and the rods had too much side clearance/ loss of oil pressure. I’ve only built two but hell of a motor.
 
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