Timing chain break in, and...

Any progress on your I started out thinking I'd only replace the timing chain and adjuster? Did it turn into a total engine tear down just because you can?

I'll be putting one of those timing chain adjusters in my 750 engine, but I'm waiting for some warmer weather. I might also get one of the JSM offset cam keys and see if I can get a little more hooligan-oriented torque out of my JS2 cam. Big maybe on that cam key though. My brain keeps telling me it's not that simple. I'm getting to the point in life where simple is my friend.

Schwany said:

Any progress on your I started out thinking I'd only replace the timing chain and adjuster? Did it turn into a total engine tear down just because you can?

I'll be putting one of those timing chain adjusters in my 750 engine, but I'm waiting for some warmer weather. I might also get one of the JSM offset cam keys and see if I can get a little more hooligan-oriented torque out of my JS2 cam. Big maybe on that cam key though. My brain keeps telling me it's not that simple. I'm getting to the point in life where simple is my friend.

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Good timing on your question. I did have to take the head and barrels off to inspect my bottom end. I tried the endoscope method to inspect my cam and followers and it can work to see if something is a disaster, but it lacks the ability to really scrutinize real surface wear conditions. It might have some use, but in every case I used it, looking at the bore, trying to inspect the cam lobes and followers, it didn't work well enough for me to be satisfied, so I took it apart to look...

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The big pin timing chain is noticeably heavier than the stock chain I took off that had 30,000 miles on it. I did change out the original metal tensioner for the rubberized one of later models. The big pin chain with shipping came to over $100. and it took 22 days to get to me. It was one of the last things I put on the bike after breaking down most of the engine. I 'll write more about this at the end of this post.

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I have a whole saga that I wasn't going to mention here but since I'm updating this, I might as well tell the truth... Many years ago, I had a circlip pop out and got a scratch in a cylinder of a fresh rebuild. I shut the bike off as soon as I heard the circlip cut loose and the bike went POP. My mechanic friend said the scratch was so low in the barrel, he guaranteed that it wouldn't smoke and it never did. I was already +.040 on the pistons and that barrel so I was at the limit anyway for rebores, so I took a chance, reassembled it and it was fine. On this rebuild I measured my bore and I was a few thousandths under 74mm, so I decided to see if I could hone out the scratch and buy new pistons and rings from Jim Schmidt for my +.040 barrel, which measured just under 74mm

I got my pistons and rings, did a double session on the hone and I had .010" ring gap and the old scratch was much less noticeable. That .010" ring gap was the minimum size end gap, so I decided to go another double session of honing both cylinders to see if I could all but eliminate the scratch in one barrel. After the second "go round" I got to .012" end gap on the ring and the scratch was just a shadow of the old scratch. I decided to leave the barrels alone at that point because that cylinder never burned oil for 20+ years that the original scratch was there. I was sure it wouldn't burn any oil now. I fit my new pistons in the refreshed barrel hoping for a good result. That was the piston and barrels situation, and again I'll write more at the end...

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The reason I had to look inside the engine was because I could hear this very low volume sounding growl at idle. I was sure it was the cam or the followers or both. I couldn't fuckin' sleep at night for a week wondering about it. I would lay in bed exhausted thinking about that growl, and that a growling noise was just the beginning of something starting to fail... Finally, I couldn't take it any longer, so I pulled the head and barrels to look at the cam and followers and here's what I found. The cam looked "fair". I measured it and it was still within a thousandth of spec in height from one lobe to the others. The surface looked good and shiny with tiny imperfections here or there. I took a chance and left the cam alone. Three of the followers looked Ok and the fourth one had some light cratering just starting. I concluded that this "texture" was the source of my growl. It' only happened at idle so I figured that at speed the texture didn't break down the oil film which is why I only heard it at idle......

Below you can see the second from the left follower has some minor pitting starting to develop. I think that was my noise maker



Being both a cheapskate and a control freak, I decide to try to surface my followers myself since they still had good geometry, but I wanted them to have a pristine surface. I actually have 3 good pairs of followers, so I figured if it didn't work on the first one I tried to surface, then I would find someone to grind 2 pair of them. I took the follower to a diamond dust impregnated steel plate that I hone blade edges for my woodworking tools with. It's a 400 grit plate and it's dead flat. I gave the most damaged follower the first 25 strokes and it was noticeably cutting away at the damaged pad. That "most pitted" follower took probably 200 strokes to remove all the cratering. I was so happy with the result that I decided to hand surface the other three followers which took much less work to achieve a decently smooth surface. Here's the picture after I surfaced the lifters and reinstalled them below



I know that I should have spent $1000. on an all new cam and followers, but my excuse not to do that was like this unfinished half of a sentence my barely english speaking Italian grandmother used to say. "If Columbus never took a chance". It was a sentence that she never finished, but I knew what she meant... I'm taking a chance too...


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So, yesterday was finally a warm day (48 degrees) and not raining, so I filled the bike with oil and squirted some oil down the pushrod tunnels to lube the cam. I pulled off the timing mark inspection plug. I connected the timing light and pulled off the points cover. I kicked and adjusted the boyer plate until I got the bike to run. It did not smoke at all on either exhaust. I held the revs up and pointed the timing light and dialed in the timing and just sat there on the bike for 20 minutes keeping the revs between 2,000 and 4,000 just blipping the throttle a bit.

The new timing chain was doing it's job. the timing light showed no distinguishable flutter in it's spark timing location unlike the old chain that seemed to have about a 4 degree variation, so that was a good sign. The bike had zero smoke coming out of either tail pipe so that's a good sign for the new pistons. I didn't get to ride it around because it started to rain right after I readjusted the carbs which I rebuilt and completely cleaned so they needed to be set up too. I did try to set the idle and the growl which was previously there at idle was now gone. (fingers crossed) All seems at least OK for now, although I need to go for about 10 local rides before I'll be sure that I'm out of the woods with my cam and followers situation...

I also rebuilt the oil pump because I feared the cam might not be getting enough oil could have been the cause of the follower wear, and the oil pump seems pretty strong if looking in the oil tank and watching the return oil squirt out of the return line is any indication of a good oil pump...

I think one of the secrets to keeping the cams and followers in good shape is if the bike has been standing for more than a few weeks take the exhaust tappet covers off and pour an egg cup of oil down the pushrod tunnels.

Also don't start it and let it idle straight away. Keep rpm to about 1500 2000 to get the oil about and up to temp.

Good outcome.

Don't lose any sleep over the cam and your DIY surfaced followers (tappets). It'll run and be quiet enough is my prediction.

A couple of ounces of STP in the oil keeps a very slippery film on every surface inside the engine during the time the bike sits.

Might be a couple of days without rain next week. Enjoy the test ride. I don't ride until the temperature is over 65 and it has been rainless for a couple of days.

Schwany said:

Good outcome.

Don't lose any sleep over the cam and your DIY surfaced followers (tappets). It'll run and be quiet enough is my prediction.

A couple of ounces of STP in the oil keeps a very slippery film on every surface inside the engine during the time the bike sits.

Might be a couple of days without rain next week. Enjoy the test ride. I don't ride until the temperature is over 65 and it has been rainless for a couple of days.

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The weatherman is calling for a high of 57 degrees on Wednesday and only a 10% chance of rain. I'll be riding a pretty tight loop near my home and up hill as much as possible just to break the new bore in and seat the rings. I've rebuilt a few different engines in my life and the norton has had 1 full rebuild and 3 head and barrel removals, but I don't do this kind of thing for a living, so I don't have the everyday track record of successes that give me confidence in my rebuilds. Maybe I'm just insecure, but I think there's a difference between me and an actual pro doing the work. I have a 5' x 10' cargo trailer that I use for firewood and dump runs. This year I'm going to set it up with wheel chocks and hooks to transport motorcycles.... This way if I blow this engine up, I'll have a method to haul the wreckage home...

Upon following this thread, I've seen where some members responding mention using an old product, STP. It was prominently advertised, long ago, on rolling billboards in NASCAR and INDY, and I still see it on the shelves in the auto stores. Depending on who was talking about it, it was sworn by and at, and as one member said, was considered by some to be "snake oil". Bought a can of it probably 50+ years ago and after seeing how "thick" it was, I don't think I ever wound it putting it in an engine, thinking it would be about like using gear lube. Anyway, wondering how many others here use it.

Good idea on getting the trailer setup for motorcycle use. All you need is a driver on standby to hook it up to a truck and come pick you and the bike up if it breaks. I doubt you'll need it for that though.

I am of the wild and crazy opinion that a Norton 750 engine is forgiving if assembled carefully and in a clean environment. Only way they break is if they don't get enough oil to the right places or if assembled in a very dirty environment with very little attention to detail and then trashed like an inline 4.

On STP use: a full container of STP would be the wrong ratio for a Norton engine. 1 or 2 ounces is OK in my use in an old air cooled Norton engine. I warm it up to where it will flow before putting any into the oil tank. It does blend in with conventional or synthetic oil. It is very clingy and lasts through a couple of oil changes. I don't add it every oil change.

Mr Comstock did a little test that showed STP does not work well at all if the only lubricant. I'm thinking he doesn't use it.

I have an oil squirt can with a blend of lubricants sitting on my garage wall shelf. I have squirted it into the pushrod tunnels before. I also lube my standard chain with it. The members here would roll their eyes in disgust if they knew what was in that oil squirt can.

I use STP mixed with my oil every oil change 1/2ltr a bottle (1ltr) to 2ltrs of motor oil (my round alloy oil tank is only 3ltr) and I have been using this since 1982 in my motor and last pull down to replace the crank cases, that was over 15 years ago now (hair line fracture at the main oils seal and a broken middle front stud on CC) but the bores, bearings, cam and lifters were is great shape, my Norton was an everyday rider since I did the Featherbed conversion back in 1980/82 and the motor has done a lot of hard miles and is ridden hard, snake oil, no way has proven to me it works and helps with long life of my motor, my mate also uses it in his 1965 650 Triumph (ex police motor) and he been using it just as long.
Everyone has their own opinion on using STP and I will keep using it, I think my motor will out last me before it needs rebuilding again, snake oil, no way.

Ashley

post #27 snip... "and then trashed like an inline 4".... Oops, should say "thrashed like an inline 4".

I just now remembered that sometime in the late 70's I put another type of popular snake oil in my Norton 750 oil tank called Slick 50. It was less viscous than STP I think. It didn't hurt anything in the engine.

I used Slick 50 on my Non-O ring drive chain. To me, it seemed helped it last longer than other oils I tried.

franko said:

I used Slick 50 on my Non-O ring drive chain. To me, it seemed helped it last longer than other oils I tried.

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It pays to be experimental in my experience.

I almost started talking about motorcycle oil. Good thing I caught myself typing motorcycle oil.

Slick 50...... wow, I remember when that first hit the market.... "It doesn't treat the oil, It treats the metal"

I think I was just a little kid at the time when it came out. I was still obsessed with automotive stuff but too young to really know very much. I probably still believed in Santa Claus too..

60 degrees and partly sunny out my way today. I gave my new pistons their first 1 hour ride. The bike ran great. Not a single puff of smoke came out of either tail pipe. I really don't know what to do to break in the rings so I just went on my normal ride and refrained from laying into the throttle too heavily. The last few days have been pretty windy, so there was shit all over the roads. No need to go fast or hurry up just to crash a bike with a fresh top end

I think the idle has a bit more of an even cadence than before the rebuild. I'm guessing that's the new timing chain because the timing light was rock steady when I timed the bike with the new chain where as before the timing light number always moved around a little bit. I also rebuilt the carbs, so maybe the more even idle was a function of both renewals. The growl that I heard at idle is gone. I'm certain now that it was a sound from the one follower that was starting to develop some "texture". Hopefully that won't return. I'm running 20-50 royal purple hps oil, but was running it before the rebuild, so I am just going to pray for some luck with my cam and lifters, but not expect either success or failure....

o0norton0o said:

refrained from laying into the throttle too heavily.

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You need to apply full throttle for just a few seconds every now and then, this increases the combustion pressures and this gets behind the rings and forces them out against the rough honed bore and beds them in. Babying the engine is the fastest way to glaze the bores and then the rings will not seal.