Project Vento has begun: help wanted.

[Duccout]

The standard clutch is pretty good for such an old design, but if you keep it pulled in for long periods of time it can overheat and drag, so riding in heavy traffic can be a problem, but if you are not doing that, or riding hard which can cause it to slip and overheat, then the standard plates are fine. The thicker clutch plates will increase spring pressure and make the clutch heavier, but more resistant to slipping and as Lacey states, more resistant to warping.

BTW, I've had four Ducati Singles and never experienced any clutch trouble; make sure the cable is routed without any tight bends and lubricated, and it will be fine. They are light too ( if you want a heavy clutch, try a modern Ducati!)

[Dodge]

I went through several sets of clutch plates on my 450 desmo but this was riding to college in heavy London traffic. At the time (1977) I was also using standard 20/50 multigrade in the engine. This was probably a mistake and contributed to the clutch slip. I use only straight 40 grade in my 250 Mk3 and have had no issues.

[cooperplace]

I hope everyone had a great Christmas and I wish you all the best for 2021.

I have a new question on which I'd be grateful for advice: bleeding the double front discs on the Vento. I've overhauled the calipers and m/cyl, put it all together, and bled it, and bled it, but the lever is spongy and almost goes back to the bar.

Any thoughts?

Thanks

Peter

[Duccout]

This is a common problem when bleeding brakes from empty; it sounds like a pocket of air is trapped somewhere. You can try removing the master cylinder ( with the cap screwed on) and turning it to different angles to try to dislodge the air, and the same with the calipers.

[George]

Another option is to pull brake lever back and tie to handlebar. Leave at least one day to allow air to find it's way out. Failing that you could fill from bottom using large syringe to force air to top. Keeping brake pulled back. Careful not to spill on paintwork. It has worked for me on Moto Guzzi with linked brakes.

[Ventodue]

Gotta agree with George and Colin, Peter. It's air.

When you say you've "bled it and bled it", what exactly do you mean? Just using the bleed valves on the calipers? That won't get out any air that is upstream of the calipers. Remember: Air wants to go UP. If there's any air in the line above the calipers, you won't be able to force it down to get it out at the calipers. Won't happen.

(And btw, when bleeding the calipers, once there are no more bubbles in the stream, stop. You're done. And it should only take 4-6 pulls on the lever. BUT, if there are constantly small bubbles in the fluid coming out of the caliper bleed valves, then you have another problem. Air is being sucked in around the bleed valves. A rare occurrence IME. Never happened to me, but people say it can).

But let's assume that is not the problem because, as the boys said, there is a much more common causes for an obstinately spongy lever.

You have an air bubble caught somewhere up-stream of the calipers. This will be somewhere where the brake line makes a change of direction. Most likely either at the splitter on the yoke or at the banjo joint at the master cylinder (not priming the m/c before connecting the line can result in an air bubble sticking here).

Wherever it is, the most that you are doing by working the lever is moving the bubble backwards and forwards a little. But it's trapped. It can't travel up the fluid column and escape - which is what it wants to do.

All 3 solutions proposed can work. Also try rapping lightly with the handle of a screwdriver or similar on any joint where the line changes direction - where you can imagine an air bubble getting stuck.

Just remember, work with nature, not against it. As I said previously, air wants to go up. Keep that in mind and you'll get here. For example, it can sometimes help to take the m/c off and hold it up as high and in as straight a line as possible. It's the only way I can get the rear brake on my Laverda RGS Corsa to bleed up.

[themoudie]

Aye Peter,

Back bleed the brakes using a 60ml syringe and tube (colostrum feeder) sold for feeding lambs, any good farm/country supplies store or vetinary will be able to supply, also available on-line:

Example_lamb_colostrum_feeder

You may require a different size piece of rubber tube to slip over the end of the tube to fit the brake caliper nipples and I also cut the end off the tube so that the full diameter is open rather than the two side holes. File the brake resevoir with fluid, slowly pull back the lever to the bar and then secure in place with a rubber band/bungie/or band cut from an old inner tube. Slacken the nipple on the caliper ( a wee bit at a time, don't need to open it right up) push the tube over the nipple and then pull the syringe plunger to the full extension and nip the nipple shut, before releasing the plunger. Repeat until the syringe fills, with brake fluid and there are no air bubbles when drawing the fluid into the syringe. ;D

You can of course reverse this and use a full syringe to fill the system from the bleed nipple on the calipers. But air can often be trapped around the splitter connection between the two calipers and the brake fluid resevoir. Some people fill each side separately before connecting to the splitter. The other problems with this method are that you must keep an eye on the fluid level in the resevoir so that it doesn't overflow and the pressure built up in the syringe can cause the pipe to shoot off from the spout and shoot brake fluid under pressure about the place. Not good for your eyes, or your paintwork!

N.B. You may need to wire/small petrol pipe clip the tube onto the end of the syringe, as the brake fluid can lubricate it and it will slide off!

I use the suction method on both Yamaha SRX and Honda brakes, having spent far to many hours trying to pump it through, even after renewing the master cylinder seals and only succeding in aerating the brake fluid!

George's method is also part of the process, with a few small but important details highlighted! With the lever tied to the bar and the feed hole in the master cylinder at its highest point, then the air (ever so slowly) rises out of the system ..... this does need to be done in a nice dry atmosphere, if the master cylinder is left open for any length of time the fluid will absorb moisture. The latter is not good, as the brakes will remain spongy and if you get them hot enough, then you can vapourise the water that leads to sponginess or loss of brakes!

Patience, some daft bu88er built it, so you can rebuild it and get it to run sweetly!

Good health, Bill

[Jordan]

Another option?
I once bled a Triumph rear disc brake that resisted the normal method, by removing the whole system from the bike.
That could be done without undoing any of the hydraulic connections.
Master cylinder mounted on the bench vice so it could be pumped.
Then the hose could be moved so that any trapped bubbles were uppermost, and easily removed.
When finished, the whole lot was then reinstalled to the bike.
It took much less time and brake fluid than I wasted trying the standard method.

[Ventodue]

I once bled a Triumph rear disc brake that resisted the normal method, by removing the whole system from the bike. <snip>

+1 to that. That way works ... provided you can then reinstall the assembled system back on the bike (I suspect Peter can on a Vento).

And as you say, Jordan: it can often work out quicker .

[cooperplace]

Hi everyone,
many thanks for all that great advice. I went with Jordan's remove-system-from-bike option. I clamped the lever onto a 3/4" socket drive lever which was clamped into my vice, at lower than bench level, sat the junction on the bench, and the calipers on top of an upturned bucket on the bench. Every line was either horizontal or pointing up towards the bleeders, and I bled it again. Out came a few small bubbles, but what a difference it made once the system was re-installed. It's still a little spongy, but I'll live with it until the bike is actually together, sometime in early 2021 hopefully, when I'll re-assess it. Clearly it doesn't take much air to give a lot of sponginess. And yes, removing and reinstalling the whole system is quick & easy.

Have a happy new year everyone!
Peter.