Lost a cam??

[XS1100 Newbie]

Would it be at all unusual to lose a cam lobe at 40,000 miles. My number 4 exhaust lobe looks like someone has been hammering on it. I have to see about measuring the lobes.

[DGXSER]

Very Very unusual!! I would pull the cam and see if the bucket is stuck or if you have a bent valve or something similar. Sounds like your valve is putting up more resistance than the cam lobe can take, which should be A LOT!!

[TopCatGr58]

While you're pulling the cam, you can inspect it for signs of galling and such on the bearing surface also. It could be that you got some debris or sludge that blocked the oil supply for that lobe so that it ran dryer which would also generate a lot more friction=wear than usual. Good Luck!

T.C.

[BA80]

I have seen cam lobes, and other internal engine parts, damaged by rust because of sitting too long. Mileage is a lot less damaging than disuse.

[3Phase]

Newbie,

I think DGXSER has it and the #4 valve got bent or its bucket/pocket got dinged. Did the the engine make any unusual tapping noises after you buttoned it up or was quiet and just seemed a little down on power?

If the #4 valve got bent or the bucket jammed down and wouldn't come up all the way there'd be a larger than normal gap between the cam and the shim. The cam would beat itself to death while the bent valve or stuck bucket did the old Roto-Rooter trick to the head.

If the #4 valve/bucket got jammed up and wouldn't move down freely it would wipe out the oil film. Oiled or not oiled something would get out of the way whenever the cam lobe came around.


.

[XS1100 Newbie]

Hey Scott. Good thought on that. I wonder if that damn tool did something to the edge of the bucket, or i just screwed it up putting it on. That would explain the drastic change in clearances that i saw. If the bucket was stuck down, and/or the valve was bent, i would not be able to get the 130 lbs of compression that i have, would i? You just might have hit it on the nose. Time to see if i can screw it up some more by pulling the cam. (hope not) Rode it today for 6 hours, and it didn't do to bad. It would seem that if the valve was not working, that i would notice more loss of power than i do.

[MPittma100]

One More Thing

One other item to look at is the valve spring. A broken valve spring will allow the bucket/lifter to continually bounce off of the cam lobe and beat it up. Not a likely culprit, but has happened.

MP

[3Phase]

Bob, it was Don's idea! And MP has a good thought on one of the pair of valve springs too!

If you dinged the bucket/pocket or slightly bent the valve it might have taken its sweet time making itself all nice and comfortable in its happy home as the cam lobe got wiped out.


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[XS1100 Newbie]

UPDATE!!!

Got the valves run again, went through the carbs with new kits, cleaned the petcocks. Found a few passages plugged in the carbs. Put everything back together, and it will pull hard up to, and past the redline now. Only problem to work on today is idle and synch. For some reason i can't get any adjustment on #3, and the synch is just being a POS. Will report on what i find today.

[trbig]

You don't adjust #3, you adjust all the others to what #3 is.

[XS1100 Newbie]

Pullled the carbs again. Have new carb holders on order. could not get over 9 inches on the vac gauge on any carb. Took them apart again, but have not found anything out of place yet. The air fuel adjustment needs to be done on all four carbs.

[Rasputin]

As long as the vacuum reads the same on all cylinders just having 9 will do the trick, if everything else is right. I would re-check the valve timing dots and check for any intake leaks. Sounds like you may have bad carb boots or you would not have ordered any but unlikely that all would leak at the same time.
I chased my tail round in circles for quite a while before I realized that the timing was out by one tooth and was causing my low vacuum readings while still showing me a good compression ratio. If you had the cams out or other parts of the timing...ie acct install or something...it does not take much to double check while you are waiting on new carb boots any ways.

[motoman]

You don't adjust #3, you adjust all the others to what #3 is.

Think he's speaking of the idle mixture screws trbig.

[motoman]

If those are the later carbs with idle-mixes recessed, those tiny O-rings if not replaced WILL be like little hard washers and loose their seals. That would be first suspect if no change when adjusting out or in.......and low vacuum......DAMHIK......BTDT.

[Rasputin]

If those are the later carbs with idle-mixes recessed, those tiny O-rings if not replaced WILL be like little hard washers and loose their seals. That would be first suspect if no change when adjusting out or in.......and low vacuum......DAMHIK......BTDT.

Very good point!