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Looking for a solution to another of our unique BEC issues..

I'm running a stock VFR800 engine (about 105hp/ 55ft lbs) in my tiny BEC project.. haven't weighed it yet, but likely around 1300#..

My issue is that once I'm up in 4th or 5th gear, taching around 7,000/8000rpm, if I really step on it, the clutch will briefly slip until I get out of the throttle..

Now, I know I'm asking a lot more of this clutch than it was designed for, so I'm just trying to make what I have work... I installed Barnett springs, and that seems to have 'almost' taken care of the issue (it holds better now, but still not quite there).. When I went in to swap springs, I pulled the clutch pack apart and found several steel discs were heat discolored- a few of them showed signs of some serious heat; heat that I believe I put there with my "let's find the weak link and make this thing slip" excercise .. (the friction discs all looked really good- this motor has about 17K on it)

So, with my limited knowledge of MC clutches, I think I've done a few things wrong... I put the clutch back in as I found it (shame on me, I have another engine sitting in the corner that very likely has 100% perfect steel discs in it)... ALSO, I'm running Valvoline car engine oil (10-40) in the bike motor (which worked fine when the engine was in the bike), and I'm thinking I need to run 'real' motorcycle oil in consideration of a slipping clutch..

The reason for this post is to get thoughts on the next step... once I replace the oil and put in 'good' steel discs, if is still slips, it seems the next thing is an aftermarket clutch (or friction discs at least).. I've been reading up in the MC forums, and lots of guys try the Barnett clutch, hate it, and end up pulling it out... Having said that, they're not trying to propel a 1300 lb car down the road on a tiny clutch either..

Just wanted to get your thoughts/experience on this..

thanks-

ccrunner

_________________
Dean

1972 Honda N600 Restomod "ccrunner's N600 VFR800 repower"

1963 Volvo P1800 Restomod
http://locostusa.com/forums/viewtopic.php?f=36&t=16309

1959 Berkeley SE492 Restomod...
viewtopic.php?f=36&t=19397

"ccrunner's 1960 MGA coupe Restomod" found on MGExp.com

The oil is more than likely your problem. Once you change that I would put money on it being fine.

From my limited experience, the cheaper no-name generic oils available at Sheetz and such and some racing oil (IE Royal Purple) seem to be fine with wet clutches since they lack certain friction modifiers. The "better" off the shelf oils seem to have these modifiers. Since Valvoline is at least a brand name, I'd assume it also has them.

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-Andrew
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clutch steels warping, yes too much heat, however back in the days when men were men etc. we would cut a slot in the steels with a hole at the end to stop it cracking, this would allow them to expand without warping and maintain the surface area flat (ish) so the frictions could grip it better.

sintered steel plates were the next thing.

then bronze plates, we made our own from parts of an excavator, these would slip but not to the point of warping.

at the end of the day, you will need a bigger clutch or at least more plates.

have you looked at auto trans plates.

one more thing, the speed of the clutch is relavant to the speed of the crank. if you could get the whole thing turning faster it would think its in a lower gear.

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Ditto. Oil rating is very important for a wet clutch.

Only use an oil with a JASO rating of MA or MA2.

See also:

http://www.amsoil.com/techservicesbulle ... ements.pdf

The clutch diameter is small, but it has a lot of surface area. Automatic transmission clutches are very similar.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
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360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

I don't see the car weight as an issue. You would likely burn the clutch doing standing starts, that's were the weight is getting to you. At speed the weight of the car doesn't matter, if you could put 100 HP into it on the bike, you can put 100 HP into it in the car, you just won't accelerate as fast but the forces are the same. It's the standing starts that will kill you.

On my Formula Ford I use a different clutch if I expect to do standing starts, or I try not to slip it as much.

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Motorcyle engines usually require a seperate oil from the engine to the gearbox, as engine oil has additves to reduce wear these additives will cause clutch slippage if used in the gearbox..its a simple explanation as to why it does it in a higher gear..its becoming less aerodynamic and as you arent going thru the gears and its much more noticeable.Replacement of the clutch plates is the only option if this is indeed the case.If yours only takes one type of lubricant then only use mc oil.

using a cars motor oil in a motor with a wet clutch will just not work ! every one is telling you that but there is more to it than that .
once you contaminate the fiber clutch plates with a cars motor oil you have to replace them with new fiber plates or they will keep slipping .
when you install new plates you should soak the new plates in oil for 12 to 24 hours 1st before installing them . the reason is the oil soaks into the fiber .
the metal plates as long as you have not glazed or warped them they are most likely ok . most of the time you can just buy individual OE plates so if you only need the new fibers you can just get them were CO's like barnett's will only sell complete clutch kits .
when you have your clutch apart look at the clutch basket for any wear to it . you will see wear groves in the outter fingers of the basket and the same on the inner basket . if they are not to bad you can file them out .
by doing so you will get a better fealing clutch were the plates will not hang up .

Coulpe other things you can look at, try roughing up the surface of the steel plates. preload the springs with washer(s), but check for coil clearance thru the travel, Some clutch baskets have one thicker steel plate as the end plate stack. See if you place it with a standard plate, or/then just try to stack one more friction plate in the basket. Several Yammies typically had enough room to add another steel plate and friction disc. DaveW

Everybody it correct about the oil. You will really need fresh clutch parts (plates and steels) to get rid of the friction modifier contamination. If you still have problems rather than going to huge springs and/or extra plates look into a "CENTRIFUGAL LOCK UP CLUTCH" checkout http://www.kzzone.com/clutches.html scroll down towards the bottom and you will find

This serves two purposes, first, with turbos and/or nitrous bikes, the clutch will tend to slip in high gear as it can not cope with the huge horsepowers. The lockup will overcome that slippage for increases in up to 5 mph in quarter mile speeds.
Second, the initial off the line clutch grab can be softened up with light springs to prevent wheel spin and rely on the centrifugal clutch arms to provide full lock up on down the track.

I appreciate your input guys..

I figured I was my own worst enemy with the oil I've been running .. soon I'll go back in and replace the friction discs (pre-soaked) and begin running real MC oil.. I'm hopeful that will take care of it- if not, I'll post up what I find..

thanks again-

ccrunner

_________________
Dean

1972 Honda N600 Restomod "ccrunner's N600 VFR800 repower"

1963 Volvo P1800 Restomod
http://locostusa.com/forums/viewtopic.php?f=36&t=16309

1959 Berkeley SE492 Restomod...
viewtopic.php?f=36&t=19397

"ccrunner's 1960 MGA coupe Restomod" found on MGExp.com

Most mass production clutch plates come from the factory warped, bent, dished, damaged etc - some worse than others.

For racing we had a hardened steel rotating turntable that we sat the steel plates on with plenty of a silicone cutting compound and a flat weight on top and 10 minutes later perfectly flat plates. Homebods can use a piece of glass and valve grinding paste and do it by hand to finish them after figure 8'ing them on concrete first. For the lined plates I use a flat, fine concrete area and lightly do figure '8's with my hand flat on top rotating the plates often (do not use valve grinding paste with the lined plates).

I have on a number of occasions cured slipping clutches at race meetings just by figure 8'ing the lined set on a concrete surface inbetween heats.

Try lightly figure 8'ing the whole set, look at the scratches/scuff marks and you will be surprised how bad they are. I have never seen a flat standard steel plate, 7 years on the tools and raced them for 30.

The effect can be dramatic, increased surface area and even pressure maximising CoF and making for a lighter clutch action to boot.




Not many motorcycles since 1963 seperate the engine and gearbox.

Oh and check your clutch basket, sometimes the grooves that get worn in from where the tangs are driven get so deep the plates can't freely slide laterally properly.

A flat file cures that.

I was under the impression more had seperate engine and gearbox oil

Wayne,

Every machine you've mentioned has a transmission integral to the crankcase with a common cavity.

I can post drawings of the crank case for each if you'd like.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

if it were you i would just replace the clutch plates and the oil with a MC wet clutch oil .
IMO it's the oil you used that made you clutch slip .

there are many clutch mods you can do . because i started racing motorcycles at the age of 8 i have found most do nothing or little at all .

putting a washer on the clutch springs will help some what . but it's best to just have a proper working clutch with out all the mods .

sanding the metal plates does also work but it turns your clutch into a light switch .
you lose any little slip you need for a smooth engagement . it just wants to grab !

i have never found that a OE clutch kit is really any worse than a after market one ?
the only plus to an aftermarket clutch kit is most offer a stiffer rate springs .
when i test that some springs years ago they are only about 3 to 5 LBS stiffer on average .