Camshaft Lift T3

[telphoto]

I have a bog standard T3 with what I suspect is a worn camshaft, I've measured the lift at around .278 for all 4 but despite searching in both the factory and Haines manuals and online I'm unable to find the correct spec? Reason I suspect the cam is that the bike sat for a long time before I got it, so long in fact that the lifters had corroded in place and were tough to free up so I think the hardening on the camshaft may have been compromised. Have already replaced lifters and pushrods are in spec but the bike is a little sluggish after eliminating all the obvious faults such as timing, carbs, ignition etc.

I'd welcome any suggestions

[rodekyll]

My only suggestion is that having all 4 lobes uniformly trashed is not likely.  Having one different than the others is more likely.

I have a valve cover off a BB right now.  I'll try a random lift measurement for you.

[rodekyll]

Well, you've got more lift than I do and my bike runs fine.

I just checked the rt valves -- 3rd year of no adjustment needed.  It's a Convert camshaft, but I don't think there's any real difference -- it's running in a Jackal engine and spanks all the other Converts I encounter.  Measuring at the top of the adjuster screw, my lift is coming in at 0.228" for the RT exhaust, which in my experience has been the one to have a problem if any of them do.

Hope that helps.

[Howard R]

According to Mr. Richardson (camshaft spec table in Guzziology v5.4) the 1st 3 Lemans & pretty much all of the Ts and 1000s including Convert all had .259 lift.  Most things 1100 including hydro lifters were .264, with the V7 Sport at .272.  The HiPerf B10 (later standard for LM & big valve 1000s) was .283.  (All are the same for in & ex.) 

So it seems the OP might have a cam from a V7 Sport, or a B10, or an out-of-cal indicator.   (telphoto, were you maybe measuring at the valve instead of the lifter?  The lifter arm is not necessarily 1:1, I think the valve moves farther than the lifter.)  As Rodekyll said, there is absolutely zero chance that all lobes would be messed up by precisely the same amount.

Hope this helps.

Howard

[acogoff]

     I believe the rocker arm maybe has a bit of differential length adding to the actual lift of the valve, but as long as cam lobes are smooth and measure the same lift on just the cam itself within a thou or three, I would not worry about it.

[rodekyll]

I'll give 0.030 to a sloppy mic anchor/irregular valve adjust post and call mine good.   

Yes, the proper way to do it is straight up from the lobe.  The most straight you can get on a quickie is trying to center on the valve adjuster post with the dial indicator pointed straight down the pushrod.  Anywhere else will really skew the numbers.

And yes, these are definitely ratio'd rocker arms.  I'm not going to measure the offset.

[telphoto]

I measured it with the dial indicator tip in the cup of the pushrod, zero'ed it when the valve was closed then rotated the engine and noted the maximum lift so I certainly could be introducing some variables in there.

[telphoto]

Furthermore, can a cam suffer from wear on the lobes but the lift remains in spec? ie: the face or ramp of the lobe is damaged but the peak is fine so the valve ultimately opens as wide as intended. Is there another way I can check the condition short of stripping the engine down and inspecting it. Thanks for your responses.

[Triple Jim]

Furthermore, can a cam suffer from wear on the lobes but the lift remains in spec? ie: the face or ramp of the lobe is damaged but the peak is fine so the valve ultimately opens as wide as intended.

I've never heard of that or seen it happen, and it seems unlikely, and I've had cams fail. 

Is there another way I can check the condition short of stripping the engine down and inspecting it. Thanks for your responses.

You already proved that your cam is OK when you found that all four lobes are the same height.

[rodekyll]

Yes, I think you're looking for trouble where there is none.  If this thing was sitting that long I'd put my angst into an evaluation of my rubber bits and steering/swing arm/wheel bearings, drive shaft splines, etc.  Many more likely points of interest.

But I think it's good that you're asking the questions.  The answers to this one should put your mind at ease.

[Triple Jim]

Is there another way I can check the condition short of stripping the engine down and inspecting it.

To give a direct answer, you can graph the lift in increments like 5 degrees through a full cam rotation, and compare all four lobes that way.  The plot will show if there are any differences between lobes.  I've done this a couple times, once to verify that a custom cam grind was made the way I specified, and another time to compare two cams that were advertized to be the same.  I don't think there's any need for you to do it in this case.

[oldbike54]

 Is it idling alright ? Have known of a valve spring to go soft , a good idle normally rules that out .

 Dusty

[Triple Jim]

Dusty, when I've had valve spring problems, they show up at high RPM, which is as I'd expect.  Why do you suggest that weak valve springs would effect idle?

[Triple Jim]

Wait , what does a too smoker guy know about valves ?

Well, I was 17 when I got my flat bottom drag boat.  I learned some about valves with the 427 Chevy that powers it.       I didn't get the H2 for another three years.

I guess if a valve spring breaks, and it's the only one on that valve, and if the piston helps it close at higher speeds, it could show up only at idle.  And before you dismiss that as improbable, I've had that happen... for a little while.  The piston helping it close part, that is.

[telphoto]

Thanks for the advice, it all makes perfect sense. I'll leave the cam alone.