Cam Tower Crack?

[csmutty]

Really? *Waits for next obscure motard problem*



Now my question is..I had heard that the top of the head is mated to the individual cam tower. I have a spare cam tower. Could I put that on and be fine?

[Degsy]

Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_0_2 like Mac OS X; en-us) AppleWebKit/532.9 (KHTML, like Gecko) Version/4.0.5 Mobile/8A400 Safari/6531.22.7)

They are a matching pair on some bikes. Did you loosen the bolts in the right order, bit by bit.

I would give it a try with the spare you have.

[csmutty]

Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_0_2 like Mac OS X; en-us) AppleWebKit/532.9 (KHTML, like Gecko) Version/4.0.5 Mobile/8A400 Safari/6531.22.7)

They are a matching pair on some bikes. Did you loosen the bolts in the right order, bit by bit.

I would give it a try with the spare you have.

It was cracked before I loosened it. But this cam tower has been on and off a bunch of times. (Have to take it off to adjust the valves.)

And thanks. I'll try the spare tomorrow. The bike wouldn't even start at the end of the last weekend. So I am hoping this is why.

[Degsy]

Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_0_2 like Mac OS X; en-us) AppleWebKit/532.9 (KHTML, like Gecko) Version/4.0.5 Mobile/8A400 Safari/6531.22.7)

I'd give it a shot if it was my bike. Not on a customers, but my own, yes.

[Ryno]

I'd be careful. They are line bored on most bikes and the cam cap needs to stay with the head. It might work but....

[butcher bergs]

If it's machined as a matched set, no way. Not worth the risk, IMO.

[joeswamp]

Pardon my ignorance here, but I thought they were always machined together. How else would you make it?

Usually the shop manual points this out in multiple places, i.e. make sure you put the caps back on in the same places you found them

[butcher bergs]

Christian -

I know I said "no way" earlier but if you plan on using your spare parts anyway I highly suggest using Plastigauge to spec out the tolerances of the bearing surfaces before subjecting any of those parts to the stresses of racing. What you spend time-wise will potentially save you $$$ if there ends up being clearance issues.

[csmutty]

Pardon my ignorance here, but I thought they were always machined together. How else would you make it?

Usually the shop manual points this out in multiple places, i.e. make sure you put the caps back on in the same places you found them

The shop manual might not point it out in this case because it is a unicam motor so the assembly can only go on one way.

Christian -

I know I said "no way" earlier but if you plan on using your spare parts anyway I highly suggest using Plastigauge to spec out the tolerances of the bearing surfaces before subjecting any of those parts to the stresses of racing. What you spend time-wise will potentially save you $$$ if there ends up being clearance issues.

And how would I measure this? Install the new cam tower and torque it down? And then use the gauges to measure?

[Kurlon]

What is there to loose by trying? If they are matched, his head is toast anyways. If they aren't, it should work?

[Falko]

Not knowing about these smaller engines, but are oversized bearings available? If so, you can put the other cap on, have it line honed to spec of the oversized bearings and you should be good.
As to why a cam cap broke, that's poor quality. What bike is this on?

[tls25rs]

What is there to loose by trying? If they are matched, his head is toast anyways. If they aren't, it should work?

The question is more of what else could be damaged if the cam cap not being matched causes a catastrophic failure of some type that takes out the piston and cylinder etc.

Joel

[Paul_E_D]

Engine Dynamics can fix that. They weld and re-bore for like 250 or something.

[Kurlon]

Wait, it's a Honda. Shouldn't Soichiro magically appear if you rub the cam three times while peeing on an expansion chamber to fix the bike for you?

[csmutty]

Just to clarify itd not a cap, its a one piece assembly. The whole tower is one piece.

[Paul_E_D]

same same.

[Degsy]

Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_0_2 like Mac OS X; en-us) AppleWebKit/532.9 (KHTML, like Gecko) Version/4.0.5 Mobile/8A400 Safari/6531.22.7)

Guys, don't over think it. It's holding the camshafts down, it's not like it's rod journals or something. There are no bearings.

Christian, assemble the cams and cap with no camchain/gears (I'm not sure which that motor has) and spin the cams. Do they spin smoothly but with no up/down play? Then don't worry. Run it for a few minutes and check it out again. Lube the cam journals with assembly grease when you assemble.

If the cams feel slightly tight but you can turn them with a little effort, assemble the cap to the head with no cams and hone the 'holes' slightly, a little at a time, until the cams will turn smoothly in there with slight drag.

If you want peace of mind, use plastiguage to check the gap between cam and cap/head and check it against the spec. If it's within spec or close, don't sweat it. Just run the thing.

If it were rod journals I would not take any chances but the cam journals aren't taking the rapid change of direction forces that the rod journals are, not even close. The only force acting against the cam journals is the valve springs.

My $0.02.

[butcher bergs]

There are bearings, Derek. Other than the lobes, the surfaces within the retainer are the bearings.

Too much play and the cam walks, either side to side or up and down or both. Neither scenario leads to a reliable engine. Might not be an issue with such a narrow engine but I'm envisioning the camshaft oscillating if the clearances are too loose or burning up if it's too tight.

To each their own but it's not something I'd consider without spec'ing the tolerances.

[TheIglu]

If the exhaust valve closest to that bearing is getting too hot due to lack of back pressure in the exhaust, it could of been close to sticking shut and stressed the tower.

[Awesome]

Is this the one I sold you or yours?

I'd say try out the spare if everything else looks good. A honda will still win the race if you used 10w-40 kitty litter.

[Paul_E_D]

Things are getting wacky in this thread. That cam has roller bearings. The fracture is likely due to vibration transmitted to the cam from the non counterbalanced crank. These towers are likely matched sets with the head itself. If one is slightly out with the other, these things would wear out crazy fast.

[Degsy]

Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_0_2 like Mac OS X; en-us) AppleWebKit/532.9 (KHTML, like Gecko) Version/4.0.5 Mobile/8A400 Safari/6531.22.7)

There are bearings, Derek. Other than the lobes, the surfaces within the retainer are the bearings.

Too much play and the cam walks, either side to side or up and down or both. Neither scenario leads to a reliable engine. Might not be an issue with such a narrow engine but I'm envisioning the camshaft oscillating if the clearances are too loose or burning up if it's too tight.

To each their own but it's not something I'd consider without spec'ing the tolerances.

Yea. The cam cap Surfaces are bearing surfaces, agreed. I was answering the suggestion that "next size up or down" bearings could be used. There are no pressed in bearings.

There will be no side to side movement. There cannot be with the way these parts are made. Up and down, yes. That's why you assemble and feel for play and if necessary plastiguage to check.

You will find the spec for clearance there is quite large in range. Not like rod/crank specs which are down to tenths.

One other thing Christian, be careful to set valve clearances to the loose side of spec. That's best for a race motor anyway and will help to counteract any differences in the cam cap.

The factory recommendations to buy head and cap together is based on having a 10 year reliable motor. Chances of this motor not needing a head sometime over the next 3 or 4 years are slim being a race bike.

[Degsy]

Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_0_2 like Mac OS X; en-us) AppleWebKit/532.9 (KHTML, like Gecko) Version/4.0.5 Mobile/8A400 Safari/6531.22.7)

Is this the one I sold you or yours?

I'd say try out the spare if everything else looks good. A honda will still win the race if you used 10w-40 kitty litter.

I agree with this fwiw.

I'm no expert on this particular motor but when it comes to cams you can usually feel and see pretty quickly when something isn't right. Wanna build a race motor to be reliable? Worry more about balance and rod bearings than anything else.

[R7]

Just to clarify itd not a cap, its a one piece assembly. The whole tower is one piece.

So the tower assembly includes the top cap, bottom cap, both upper and lower bearings, and the cam?
If that's the case, then you are not changing the line bore and should be fine.

[Marc]

Isn't that cam tower a one piece thing that holds the cam, both sides, by sliding it in one end with no caps, just holes? Isn't that a replacable part that you can buy for like $90?