Interstate Freshening

swooshdave · Mar 10, 2013

Some of you remember the road trip my brother, dad and I made to Barber a couple years ago. My old Interstate had a hard time keep up. I was chin down trying to get up the slightest inclines. We knew the engine was tired, maybe a top end job was in line. And as they say, the rest of the story...

I started getting photos yesterday:

So far so good.

Not too bad...

Touch of blowby on the rings.

The bike is a 73. I thought the soft cams were later. It seems not. Surprised it ran at all.

So a top end job has now turned into a full rebuild. The head and barrel with be going to comnoz for his special care. Just a stock rebuild. But I bet it will run a wee better.

Any suggestions on which cam to go with? The stock cam? Something a little hotter? Don't want to get crazy.

johnm · Mar 10, 2013

Make.
sure you replace or at least reface the cam followers

comnoz · Mar 11, 2013

That's not a soft cam. Just bad lube.

Webcam 12 grind. Jim

rvich · Mar 11, 2013

comnoz said:
That's not a soft cam. Just bad lube.

Webcam 12 grind. Jim

I trust your eye, but please enlighten us as to how you can tell. If its from poor lubrication, what's up? Something plugged up, poor pressure or what?

comnoz · Mar 11, 2013

The camshaft is not the style that was normally soft.

Loss of oil film strength is what likely destroyed this cam. Multi grade oils with VI additive or single grade oils from a poor base stock were common fair in the 80s and 90s and some are still around now. They broke down quickly in an air cooled motor and then it didn't matter whether the cam was hard or "soft". Jim

swooshdave · Mar 11, 2013

comnoz said:
That's not a soft cam. Just bad lube.

Webcam 12 grind. Jim

Who carries the Webcam and what do they approx. cost?

drones76 · Mar 11, 2013

swooshdave said:
comnoz said:

That's not a soft cam. Just bad lube.

Webcam 12 grind. Jim

Click to expand...

Who carries the Webcam and what do they approx. cost?

http://www.webcamshafts.com/mobile/moto ... _twin.html

swooshdave · Mar 11, 2013

drones76 said:
swooshdave said:

comnoz said:

That's not a soft cam. Just bad lube.

Webcam 12 grind. Jim

Click to expand...

Who carries the Webcam and what do they approx. cost?

Click to expand...

http://www.webcamshafts.com/mobile/moto ... _twin.html

I just found that. I wonder if this cam would make a good core? :mrgreen:

comnoz · Mar 11, 2013

swooshdave said:
comnoz said:

That's not a soft cam. Just bad lube.

Webcam 12 grind. Jim

Click to expand...

Who carries the Webcam and what do they approx. cost?

Send your cam to Webcam. They run around $375.00 on your core. Jim [Or send it and the followers to me and I will handle it]

comnoz · Mar 11, 2013

I just found that. I wonder if this cam would make a good core? :mrgreen:[/quote]

As long as the bearing journals ,keyway or gear are not damaged they can repair it. Jim

swooshdave · Mar 11, 2013

comnoz said:
swooshdave said:

comnoz said:

That's not a soft cam. Just bad lube.

Webcam 12 grind. Jim

Click to expand...

Who carries the Webcam and what do they approx. cost?

Click to expand...

Send your cam to Webcam. They run around $375.00 on your core. Jim [Or send it and the followers to me and I will handle it]

Halfway tempted to send you the whole damn engine! :mrgreen:

rvich · Mar 11, 2013

Kinda nice to have a doctor in the house!

comnoz · Mar 11, 2013

Halfway tempted to send you the whole damn engine! :mrgreen:[/quote]

I will get it handled faster if you do the dis-assembly and re-assembly and just send me the parts. I am pretty slow when it comes to a complete build. Jim

mjfriesen · Mar 11, 2013

This engine had well over 35K miles on it, and has never been apart. Most of the years I rode the bike a lot (late 90's and early 2000's) the speedo drive was broken more than not, so the 35K is just the odometer reading.

What is the expected life of a stock cam?

I certainly didnt skimp on the oil changes (if it sat for a couple of weeks it wet sumped, so time for an oil change!), and i dont recall seeing metal in the used oil. There obviously was some, so I probably just needed reading glasses sooner than I thought.

When i first saw the cam I was both relieved and sickened; relieved that I had a good explanation for the anemic performance, and sickened wondering what I should have done differently over the years. Maybe a dozen people here will tell me :wink:

comnoz · Mar 11, 2013

I don't think there is a life expectancy for a cam. It all depends on the lube and use. Low speed and short trips is tough on a cam. Oil temp plays a big part- too hot or too cold causes cam problems.

I still think a lot of the cam problems were mainly the result of the poor oils that were common from the late 70s through the late 90s. Mono-grade oils were the only oils that were suitable for a Norton until hydrocracking and synthetics became common in the last 15 years. [except for a few specialty oils] Now multi-grades have an advantage- if they are from a good base stock and have not had the additive packages legislated out of them. IE motorcycle, or truck specific oils are best. Some racing oils are good but many have additive packages that are designed for short term use only.

I have hard cams here with 10,000 miles on them that look worse than yours.

I also have 2 cams from MK3 850s that have 70,000 miles on them and look perfect and they measure very soft.

So I guess you will have to ask someone who knows more about it than me. Jim

Bob Z. · Mar 11, 2013

I imagine that the rocker/valve clearance would be rapidly be increasing with such cam wear.

In addition to feeling the power loss I suppose observing the valve movement/arc length would show that the valve was not opening fully.
I had a Mark 3 cam that looked like yours after about 35K miles.

Rohan · Mar 11, 2013

Wow !
Did you have to adjust the valve(s) every tank of fuel...... !
Or it just rattled a bit.....

swooshdave · Mar 11, 2013

comnoz said:
So I guess you will have to ask someone who knows more about it than me. Jim

They haven't made that person yet.

http://www.oldbritts.com/11_30cam.html

Would you recommend the Web Cam over the Megacycles?

Does the Web Cam 12 need radiused or flat tappets?

I should just assume that you'll set up the head for the camshaft with the correct springs and such.

bwolfie · Mar 11, 2013

Looks like a perfect time for a full JS Motorsport treatment! Rods, pistons, cam, lifters and springs.

Snorton74 · Mar 11, 2013

Sounds like your into the full meal deal. Drilled cases and breather mod should also be on the list, then you can join the oil tight club.

Pretty cool to get this in the mail.

Interstate Freshening

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