Breaking In New Motor/Camshaft, etc.

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Aug 2, 2008
Just thought I check to see what your thoughts are on breaking in a new motor. I read somewhere that I shoud use 50wt mono-grade oil and keep the motor up past 2000 rpm for the first 1/2 hour of running. This is primarily for the benifit of the camshaft/lifters to keep them well oiled during the initial break in period. True or False?

I had a soft cam(factory) and the motor was recently gone's sorted out and runs good, but I haven't taken her out and broke her in yet. Still got the original tires on her and my brake system needs to be throughly cleaned before I do...waiting for parts now.

I've owned a few new scooters and broke them in without any trouble, but thought I'd see what some of your thoughts are...

Thanks in advance for sharing your knowledge...
I was old school when it came to breaking in new engines. Babied them. Now the preferred technique seems to be ride it like you stole it. I'm going with the later on my soon to be fired up new Combat.
I think it is a controversial subject so I will just say what I'd do. Since you have a new cam, hopefully whoever put it in used a special cam lube on it. If you are not sure I would find some kind of super cam lube to dump down the pushrod holes in the cylinder to make sure the new cam gets properly lubed and work it in by turning the engine over slowly. From what I've read this cam lubing is critical.

I would use 20W-50 non-synthetic (ex-dinosaur) oil with a rating of SG or before. The newest oils (SM) can have lower levels of ZDDP (zinc additive). The ZDDP is good for our engines with flat cam followers. You can always switch to a synthetic oil after 1500 miles or so. I never used synthetic oil myself but others think it is great stuff.

Other than that I would just follow the small operators manual that came with each new bike. Take it easy for first 500 miles and vary the revs and the loads up and down. (Do not drone down the highway at a constant 65 mph in other words.)

Others may disagree with the details but I think you will be OK following this plan.

batrider sounds good to me, the droning or constant rpm will cause a premature glaze in the newly machined cylinder. that in turn will not properly seat the rings, and you'll have a brand new, oil burning engine.
The two most critical engine engine parts to consider when running-in a rebuild such as yours are piston rings and cam shaft.
The cam shaft relies on oil dribbling down the pushrod tubes, as well as general crankshaft fling and turbulance. Consequently you need to keep revs consistently well over 2000 to maintain decent oil flow.
The piston rings need to maintain firm pressure with the bores to establish a good seal before the honing marks disappear, otherwise blow-by will varnish the bores and fill in the honing marks and the engine will never achieve maximum ring sealing. Combustion pressure forces the rings against the bore walls, so the only way of doing this is to repeatedly open the throttle wide and make the engine pull hard from about 2500 to 4500rpm, then roll throttle off, slow down and repeat at least 20 times. This all has to be done during the first 20 miles or so, otherwise you will lose those honing marks etc.
As prevoiusly mentioned - ride it like to just stole it!
Im about to start my fresh 71 750 in a couple of days was wondering how long after start up should you see the oil coming back to the tank,also is the oil pump worm gear nut a normal thread?
Did some more research and found the following article from the North Texas Norton Owners which makes sense. Still not exactly ride it like you stole it but not ride it like grandma would either.

I'd re-torque the cylinder and head bolts much sooner than the article states though and not just once. Re-adjust valves after each re-torquing. The bolts do loosen up a lot as the gaskets settle.

As I mentioned, look into the cam lube. Oil is not going to cut it. See the following article: ... cedure.pdf

The engine has been run already. Did the builder use moly paste or anything special on the cam lobes when he put it together?

See the Tech. Info. page on Norvil WEB site, Les Emery has some info. regarding this subject. James.
Yes, preassemply lube was used on all internal engine parts to include the Cam and lifters by a very experienced (British Motorcycle-Vintage Racing) Mechanic. The engine was fired up very briefly to dial in the timing and to adjust the carbuartor. Runs good and Idles good at 900rpm. Like I said, I have not run her since. When I do, I'll keep her above 2500 rpm for the first 1/2 hour...and run her back and forth on a hilly back country road to vary the RPMs and loads placed on the engine. Just to be safe I may pull the rocker covers and run some cam lube down the push rods...if I can. However, he did use preassembly lube on the Cam and Lifters...

The mechanic used 20-50 Valvoline non-synthetic racing oil...for the initial fire I said, it was ran for a very brief time...very brief. Cooks Norton Service did the intial fire up and I was not there when he did so. He is probably the best Norton Mechanic in Washington State...he related that the engine sounded good...I'll call him and see what he reccommends as well...just being careful and cautious...I have not fired up the bike since...nor turned her over with the kick start, etc.

I don't think I'll ride it like I stole it, but I will, for the first half hour at least, run her between 2500 RPM and 4500 RPM...Bring her back to the barn and let her sit the head, and adjust my valves...and then do it again.
Not quite ready yet, need to clean my brake system and put on some new tires before I ride. This bike has 5,976 original miles on her and still has the original Avon Roadrunners, as well as, original paint (Mint)...The original owner never sorted out the problem and had the bike sitting in his living room for 10+ years :shock: I bought the bike 14 years ago...Finally got around to getting her squared away...she sat in my living room for awhile too :)

I ride a 2003 FXDX Superglide for my daily ride, so I'm not in a hurry.

Thanks for the feed back..
The last two motors I’ve built were broken in fast and hard. Results were good; both (750 commando and TRI unit t100) are very strong with good compression that neither leak nor use oil.

The keys are high piston ring pressure and low heat. The first is very good and the second is very bad. Many short runs at high RPM and complete cool down is the basic idea. Short heat cycles and high ring pressures yield an engine that works right. I use straight 30W, re-torque and re-set valves repeatedly, and drain the oil several times too. Run it hard, don’t let it get hot. It works.

See Les Emery's advice too.
Thanks for your feedback...... :) A very cool morning run for 10 minutes...2500-4500 rpm...up and idling...shut her down. Let her cool over night, re-torque head, adjust valves, change oil and it again. I won't baby her, but I won't abuse her either...
3-4 times to be safe...Oil is cheap!

I think I'll go with a 30wt Valvoline-mono grade non synthetic....Les' article suggested 50wt., but that seems too thick for a cool morning.

I'll keep ya posted...still got to clean my brake system and get some new tires mounted...waiting for parts.
For the start-up of my 850, I used AeroShell 100 straight 50 weight. Of course, cool mornings down here are 82F!
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