Facts about the dreaded sticking bucket

[timbomoose]

There's been alot of confusion about the bucket sticking problem on cannondale heads. I took some pics to better describe the problem. Bucket bores cannot be checked with an assembled head. Just because the bucket rotates at the top does not mean that it will not stick as it goes down. This is an issue with 9 out of 10 cannondale heads and should be a top priority with a rebuild. 1st is to establish the problem bucket. It is the bucket under the exhuast cam opposite the decompression lever.(right side).The problem is that there is a casting seam. When metal is cast stress areas made from the pouring and cooling process. Where the cast object has a seam or meets together creates a high stress area. The way to release this stress area is by heatreating or heating and cooling.In the pic you can the the area of concern.

[timbomoose]

When the head is new and has not been run yet.The bores are all perfect. Overtime from the heating and cooling process the stress in this area is released and this area becomes distorted. It does not distort in a perfect circle but in a small area as a lump sticking out. All head do not distort the same amount a few do not distort at all and others as high as .013 which means major problems. As you can see from the pic the shape and area that is distorted. Every head is the exact same area and same shape the closer o the bottom the more the disortion.

[timbomoose]

The sticking bucket leads to cam failure and dropped valves. Now the important thing is how to fix it. I can't stress enough not to, absolutely not to,hone the bores. All that does is distort the bucket and lead to further damage. I have run into motors that people have run hones through all the bores and pretty much ruined the head. It is crucial that the tight tolerances be heald. Using a hone, since the bore is not concentric and the bore is not equal height on each side, will greatly distort the bore and not get rid of the high area.To tell if you have a properly sized bore the bucket should fall right to the bottom when the head is perfectly clean of oil and residue. When a film of oil is on the bucket is should stay up on its own.The other way is a dial bore guage. The reason why having distorted buckets is so bad is because when the bore becomes to big, oil will pass between the bucket bore and bucket causing the oil to run out. When in spec. the bores are so close tolerance that the oil will remain on the bucket. Everytime the motor is shut off the oil will run out of the bore and cause a dry condition when starting. Bye Bye cam lobes bye bye buckets. Motor stands next to no chance for long term survival. It takes time for the oil to be pumped to the head and in the short time damage is accuring. As you can see in the one pic what the cam lobes look like from bucket bores being honed and the other how the oil is still sitting there.

[timbomoose]

There are only two ways to fix it properly. Both require a machinist. 1st way is to remove the guide and have it bored. Doing it this way will require a new guide to be replaced and seat to be machined. The other and best way is to have circular interpulated on a cnc mill. This will keep it away from the guide and get rid of the high spot. Here's a pic of the high spot as being cleaned up in the mill.

[timbomoose]

The good thing is that once this problem is fixed it will not happen again. Once the stress is relieved in the aluminum thats all she wrote. When doing a rebuild this is a must. If sending out your motor make sure this update is done and ask how they fix it. If not your buckets will look like this. A good thing to do before you ride is warm up your motor before reving the snot out of it. A minimum of 30 second warm up can let oil get to all crucial areas that might not have had lube on the start up from a prolonged sitting period. As for an oiling issue with the head or rest of the motor that is a bunch of B.S. When you start the motor oil is literally flying everywhere.

[SlOoT]

I spent a lot of time on this. All the buckets now fall right to the bottom and fall out when the head is upside down.

I also checked if the oil stayed in place, and it does.

But I always let the engine idle a few minutes and then ride it carefully and only ride it hard when I know the engine is hot.

[timbomoose]

Warming up the engine definately adds life. It gives time for the oil to get to where it needs to go and also lets the piston warm up to expand where it needs to be. With a forged piston it more important to warm up the motor than a cast piston because the forged piston will exand more. My friend animalscannibal set up his status light to flash when the motor gets operating temperature and has had great reliability with his motor. Keeping the air filter clean, changing the oil, and warming up the engine can greatly increase engine life. Glad to here you spent the time to do the buckets right the extra work will pay off in the long run.

[cannondale27]

Ask Peterock about doing it right by hand. LOL I bet it took 3 hrs with a small stone just touching that little spot. Everytime you think its gone check it again and nope it's still there. To me time is $ and Timbo and his magical mill can do it so much better. Can't trust any other shops to do it right as I found out.

[peterock]

Yeah, it does take some time to do it by hand. have to make sure you are hitting the right spot and nothing else. It works, but if you are sending your head or anything to Tim you might as well just have him do it instead of wearing your finger to the bone.

[wistech]

Have you ever had a cam failure on a head that had the bores machined?