Hey Guys,
Just got all the covers off to do the cam chain and valve adjust and found the #3 lobe has got a scar right on the top of the lobe. How big a deal is this and is it something that needs to be addressed now or is this something that will run for a good bit longer?

Thanks,








OG

ouch !!! ....cant say ive seen anythng quite like that before og.

looks as though the profile is still intact so i assume the hardening is still good .

maybe an idea to change the shim below it in any case .

usually the valve springs return from compression promote rotation of the lifter as the motor is running , but having a wear spot like that could mean that the lifter is in fact stuck in its bore ?
or is it a wound from an earlier mishap from a previous owner /service work ? (thinking something may have lodged in there after some work or the actual camshaft got droped etc )

things to do ....turn the camshaft about 90 degrees and see if you can measure the cam from bottom to high spot and compare it with another (outside calipers )
take out the shim and see if there is a wear mark , what you are looking for is if it is only in one spot or is it all around the shim this should confirm if the lifter is rotating (shims are usually made of tough stuff and polish up with use )

i guess without tension on the lifter (cam lobe away from it ) you should be able to work (rotate) the lifter around some in its bore , normally this is pretty easy to do as many lifters have small cutouts in their circumference at the shim junction and the lifter itself usually "floats" in oil within its bore , but these are sideways mounted motors so that may not be the case, which makes me think of this.

i guess others will have some ideas also og

It is pitting in the hard facing of the lobe. Probably caused by damage to the lobe at an early stage in its life, even a small knock like both the cams being roughly handled when they were at the factory or being dropped at some stage. It bruises the metal and shows up much later as pitting.
Solution is to replace the cam with one that has four good lobes without much wear.
It can be repaired but I really dont reckon you would want to pay the price.
The most common place I see this type of damage is to tapered rollor bearings that have been put in with a steel drift and it slips of the shoulder and contacts the hard facing when hit then bruising the metal. It often takes 20-30thousand k to show up.
Oh and make sure you dont use that shim again as it will most likely suffer the same fate.

Hi, I had a cam that did that (#4 intake) on the motor that came with the bike, I would call it galling. I also measured the cams to compare to spec. they were way under, I bought a new motor for that, and other reasons. Your motor looks very clean, how many miles? I dont know what I would do . maybe polish it out with 600 paper?

Brian

Thanks for the input guys! I'm trying to source a used cam.

OG

hey before you give up hope og !!!! did you measure the camlobe ?

you should be able to do it with outside calipers and feeler guages to see what difference to the others it is .....IF it were under a few thou difference (lets say 5) you could indeed linish the wear spot and install a new shim ...which would give it a new surface to mate too ...

did you pull the shim ? what was the wear patern like ? dont forget that the shim will be a contributing factor to the mark shown on the shaft .

if indeed this was the case (under 5 thou difference) ... i still see many years use before the absolute need for replacement ...important bit as long as you were able to reshim it to specs .

that gap is pretty critical and if left in a "loose" state all cams will eventually die

dont bother trying to measure the current clearance of this lobe cause it will be wrong (because of the high spot on the shim )

i drove a six cylinder localy manufactured car round here for ages with bearly any lift left in the lobe as i bought it i would say with the miles on it... it must have happened ages before i got it (common fault actually )......and being the inlet it really only noticeably affected the idle ....now if it were the exhaust thats a different matter .

pull the shim ...take a pic and show us mate ..

Thanks for all the great input Charlie. I really appreciate all you guys helping out on this one! I've got to get after some work responsibilities, but by the weekend after a bit of time to chill out I will pull all the bits and make a decision about the bike.
Thanks again mate!

OG