Gregory Bender

2013 February 17: Scientific Test 2 complete


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This entry is extracted from a series of email exchanges between myself, Charlie Mullendore of Antietam Classic Cycle and Gordon Kline of MG Cycle. Both Charlie and Gordon were very supportive and helpful.

Hi Gordon and Charlie,

This morning I pulled the breather off of my Ambassador and fit it to my Convert. Then, I test rode again. Similar results, though not as much as last time. I'm not worried about the volume differences, last time I had a really good stretch uphill at 80 - 85 MPH plus that pushed out the most of the oil. This time I was blocked by traffic and couldn't go as fast. All the same, there was oil in my catch can.

I suspected these results. As Gordon suggested, it was an easy test and confirms I do not need to worry about the breather itself (at least in comparison to my Ambassador's breather). Breathers are back home on their respective machines and I'm happy not to have to wrestle that breather on the Convert again for a while (the loops are soooo much easier to work on).

I think I am down to rings/pistons/cylinders. First, though, I am going to drop my sump and cut off the end of the return line pipe. I do not believe this will solve any problems, but I did have to bend it up when I fit the sump spacer/windage plate. I figured I might as well do that. I want to adjust my oil pressure relief valve a little bit, anyway, so it is not much additional effort to just cut it off. Of course, I will test again afterward.

Speaking of rings, what are your thoughts on this method of breaking in rings immediately on start up? I did not hear much in the way of any comments when this was posted on the forum, and I was honestly hoping several others would chime in with additional confirmation/refutation.

The reason I ask is because I certainly did not do this with my Convert. It has been a while, but I remember struggling to get it running because it was only running on one cylinder (til I swapped a spark plug). I may very well have left it idle too long without revving it.


Gregory Bender

Charlie's reply to Gregory:

I pretty much agree with both Steve's advice, but don't do the 2000-2500 for 7-10 minutes thing - just the way I always do whether it was a top-end rebuild or complete engine rebuild - start it up a run it for approx. 15 minutes while I check the timing with the strobe and twiddle the carbs, blipping the throttle as needed to check carb sync. Then let it return to ambient temp, retorque the heads and test ride.

I don't change the oil nearly that much either - usually at five heat/cool cycles or 150 miles and then again at 500. I can just hear a customer's complaints when I bill him for 3 gallons of Rotella...

Never had any ring sealing issues whether iron bore, replated or Gilardoni; or rings from MG Cycle or Deves.


Gregory's reply to Charlie:

Hi Charlie,

You have pretty much described what I do as well. I start it up and tune the carbs for 15 minutes or so then let it cool, retorque, etc.

As for oil changes, I do drop the oil immediately after that first 15 minutes just to get all of the assembly lube out of the system. After that, I probably change again after the first good test ride of 100 miles or more. Then I'm off to the raced with regular intervals.

I've rebuilt a number of engines for guys, but then I deliver the engine and haven't been around for the initial run-in for most of them. So, I haven't got a ton of experience with what works and what doesn't. Dave Richardson doesn't seem to think that nikisil requires any special treatment (at least in my version of Guzziology).


Gregory Bender

Gordon's reply:

Well, good you ruled out that particular breather box as being an issue, probably felt like a waste of time, but knowing is good. The oil return pipe is curious. There was a time when I thought the engines with the sump spacers had a slightly longer pipe (hollow bolt) in order to keep the outlet underneath the oil level in the sump. I thought that was a fact for a long time, and I extended a couple of them after fitting sump spacers. Now I'm wondering where that idea came from. I've looked in parts books and find no evidence of more than one part being used on any of them. Maybe I got the idea from a tips book.... In any case, it seems Guzzi made an attempt at keeping that outlet beneath the level of the oil. What do you think of that idea? Seems fairly popular.

I think the break in procedure is a little over the top. I've never concerned myself with the first minutes of operation other than to get it stabilized well enough to do a rough carb synch and find a decent idle. For me, a little extra time on the bench without a fan while you get it sorted, or get two cylinders firing, isn't doing any harm to anything. I've never heard of anybody having the kinds of problems described. Surely if they did they'd be calling to tell me that the parts were defective, and you'd have probably read all about it on the internet. No body has done that. I don't think I've ever heard of a break in related problem.


Gregory's reply to Gordon:

Hi Gordon,

I've read a lot about whether or not to keep the return oil pipe under the level of the oil or not. I know Guzzi did on all of the old machines and even returned oil to the drain plug on the older models with oil coolers (I think). I've heard this maintains a pressure differential (less pressure under the oil than on top of the oil) and thus makes it easier for the oil to return from the breather box. I believe it also serves as a one-way valve preventing dirty air from entering directly into the sump.

I do not know if that is true or not (the pressure differential argument) and I do not know anyone who has measured it (seems theoretical). I can tell you the following:

  1. My Ambassador has had that pipe cut for eons with no breather problems whatsoever.
  2. My Convert had breather problems with that pipe under the oil level.
  3. My Convert has breather problems with that pipe bent up to clear the sump spacer/windage plate.

I have heard that it is possible, given too much pressure inside the crankcase, for oil to be pushed up and out of the return line into the breather and out to atmosphere. If this were the case, you could pump your engine nearly dry in short order.

Like the pressure differential argument, I do not know if that is true or not and I do not know anyone who has measured it (again, it seems a theoretical argument). I do know that right now my Convert is pumping a lot of oil into the catch can and the return line is above the sump spacer.

Honestly, with the catch can in place and alleviating nasty clean-up routines, I didn't mind the breather box test even though I suspected the results. Not having to clean up a filthy oil mess is a huge relief.

Thanks for the input regarding break in procedures. Seems you both do things similarly to what I have done.


Gregory Bender

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