Author Topic: priming freshly rebuilt engine  (Read 2191 times)

Offline amamet

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priming freshly rebuilt engine
« on: April 25, 2020, 12:50:39 PM »
please excuse my lack of knowledge on this subject.  this is my first engine rebuild.  complete rebuild of the 77 lemans.  fresh oil, no plugs, cranked the starter for about 5 seconds stopped and started again.  did that 3 times and then saw oil slowly forming at the top of all four rocker spindles.  is that it?  does that mean as long as everything was torqued, sealed and bolted, the engine can be started?  im not quite ready for that yet, just need too do some small things but was just wondering if oil delivery can be "checked" off
thx
allen

Offline wirespokes

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Re: priming freshly rebuilt engine
« Reply #1 on: April 25, 2020, 01:06:57 PM »
With the plugs out, kill switch on kill, I'd crank it till the oil pressure light goes out. The plugs need to be grounded or the coils or electronics can be damaged, so it's easier just to hit the kill switch.

If it's got new rings, I've found the best way to break them in is the dry method: only a drop of oil on each side of each piston skirt. No oil on the rings or cylinders. Have the carbs set to the stock settings, timing ready to go... fire it up, and without warming up or anything, ride off for a 20 or 30 mile ride up and down steep hills and work the engine without high revs - get on the throttle and compression brake. When you get back home the rings will be all bedded in.

Offline dxhall

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Re: priming freshly rebuilt engine
« Reply #2 on: April 25, 2020, 01:22:21 PM »
I think most engine builders now days are using the “dry” break in method.  One more thing, though:  the idea of starting the newly rebuilt motor with dry rings is that the rings will quickly wear to the shape of the cylinder.  The wearing of the rings and cylinder walls produces microscopic grit.  Most builders who use this method run the motor at varying rpm for a few minutes and the immediately change the oil and filter.  You do not want to run the motor for any length of time with the break in oil in it.

Offline amamet

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Re: priming freshly rebuilt engine
« Reply #3 on: April 25, 2020, 01:31:25 PM »
Bike is still in my basement (going to be tough to get it out with social distancing). Bodywork still needs to go out to get painted, so riding it isn’t going to happen soon. I can start it with the bilco doors open, but riding it won’t happen for a little while. Just wanted to make sure my oil delivery to the heads was proper

Offline amamet

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Re: priming freshly rebuilt engine
« Reply #4 on: April 25, 2020, 01:35:45 PM »
Hey wirespokes (sorry, don’t know your proper name), you mention spark plugs out but they need to be grounded, how are you grounding them when they are out?

Offline Andy1

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Re: priming freshly rebuilt engine
« Reply #5 on: April 25, 2020, 02:29:08 PM »
Did the crank come out - there are special moly pastes that are worth using to avoid start up wear.......maybe too late now
AndyB

Offline Testarossa

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Re: priming freshly rebuilt engine
« Reply #6 on: April 25, 2020, 02:36:23 PM »
When I rebuilt the T I cranked the engine by hand, without turning on the ignition. Oil flowed in the heads after half a dozen revs and I called that good. Break-in for the rings is as described: a few cycles of full throttle at medium revs (climb a steep hill!) to make enough combustion pressure to seat the rings. Two or three full heat cycles, then change the oil/filter and retorque the heads.
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Offline moto-uno

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Re: priming freshly rebuilt engine
« Reply #7 on: April 25, 2020, 02:48:01 PM »
  FWIW , the dry fire up has typically been done when the cylinder final hones are very fine , not the usual finish at all auto machine shops . Peter

Offline amamet

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Re: priming freshly rebuilt engine
« Reply #8 on: April 25, 2020, 02:57:22 PM »
complete engine rebuild,  used redline assembly lube when put back together.  buttoned up the engine a while ago though. end of last summer I believe.  Gilardoni cylinders, mike rich did the heads and balancing.  I just basically just put it all back together,  he helped me time it with the new megacycle cam.

Offline wirespokes

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Re: priming freshly rebuilt engine
« Reply #9 on: April 25, 2020, 04:01:35 PM »
Oil drains off lubed parts after a while, so hopefully the pistons and rings are dry by this time.

If the kill switch is on the kill position, then there will be no spark - no need to ground the plugs. At least that's the way it works on my 80s geese. Otherwise, laying the plug down on the head so it can ground to the aluminum works too.

Doesn't seem logical there would be a problem with a plug not being grounded and wanting to spark, but electronics gurus say it is. Another similar thing I never would have expected is that a coil has to work harder jumping a spark in compressed air than at one atmosphere.

Offline moto-uno

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Re: priming freshly rebuilt engine
« Reply #10 on: April 25, 2020, 06:15:48 PM »
 When the coil is told to spark , it's sole desire is to create that spark ( jump the plug gap ) ,without the plug gap , the spark will
get to ground via the coil winding's , there by setting the stage for future sparks to find an easier route to ground ( the new path
created by sparking without a plug gap ) . And that's one of the main reasons to keep a plug grounded while cranking the engine.
Most stock bikes won't let the starter actuate with the kill switch on .  Peter

Offline Chuck in Indiana

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Re: priming freshly rebuilt engine
« Reply #11 on: April 25, 2020, 06:58:10 PM »
Quote
Most stock bikes won't let the starter actuate with the kill switch on . 
Most old Guzzis just kill the power to the coils with the kill switch. It'll crank until the cows come home..
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Offline moto-uno

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Re: priming freshly rebuilt engine
« Reply #12 on: April 25, 2020, 10:09:13 PM »
  By old , are you talking pre 78 ? My Le Mans 2 wouldn't let me do it , damn good thing too  :azn: , Peter

Offline Old Jock

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Re: priming freshly rebuilt engine
« Reply #13 on: April 26, 2020, 05:40:07 AM »
  By old , are you talking pre 78 ? My Le Mans 2 wouldn't let me do it , damn good thing too  :azn: , Peter

Think pretty much all of them pre ECU, probably up to mid to late 90s will crank with the kill switch "OFF" AFAIK

Offline chuck peterson

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Re: priming freshly rebuilt engine
« Reply #14 on: April 26, 2020, 08:02:28 AM »
Sooo glad you said assembly lube... :popcorn:
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Offline amamet

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Re: priming freshly rebuilt engine
« Reply #15 on: April 26, 2020, 09:00:28 AM »
thx chuck, hope that wasn't sarcasm :)  anywho, im actually not too worried.  worse case is i start over, they're just machines (with souls).  I only learn by doing and reading.  I don't have anyone to show me anything and never wrenched as a kid, its all trial and error for me

Offline sib

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Re: priming freshly rebuilt engine
« Reply #16 on: April 26, 2020, 01:14:47 PM »
...Most builders who use this method run the motor at varying rpm for a few minutes and the immediately change the oil and filter.  You do not want to run the motor for any length of time with the break in oil in it.
I thought that the oil filter was supposed to prevent recirculation of grit.
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Online John A

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Re: priming freshly rebuilt engine
« Reply #17 on: April 26, 2020, 01:39:07 PM »
I thought that the oil filter was supposed to prevent recirculation of grit.



that's true but in the case of an overhauled engine youre trying to get rid of the small wear particles that otherwise will imbed in the bearings if they get by the filter.  while probly not technically necessary, its good practice , exspecially after the time and effort spent already.
John
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