FJRiders.com

I posted this over on FJROwners for those all concerned about overfilling/dealer overfill. Well, underfills too.....


We've all read threads about engine oil level, in particular concerns about overfilling, and there have been some threads about oil level lights coming on. So, I have done some measurements on a set of engine cases I have here and calculations on oil volume.
My measurements are OK but volume calculations should be taken as approximate. As you read on, you'll find that less of a concern.

Sight glass checks... first of all if done by the book, "a few minutes", oil viscosity, temperature, etc. all come into play and results can be quite variable. Use a stopwatch if you want to be reasonably consistent... however, I will leave it up to you to determine where the sight glass level is if you have followed the manual, filled your oil with the 4.0 L/4.23 US Qts, and have changed the filter (with the OEM short one).

I can only offer you that I usually put in 4.2 L with a long filter change (technically an overfill by the book). I find my oil level at the top mark in the sight glass, and when cold, goes over the top of the sight glass. I would prefer all my fluids to be at their max value, just me. Observation is, when the engine is started, the oil level drops to the bottom of the sight glass, maybe below, as the engine immediately circulates the oil. YMMV, which is OK.

Others have found that when they fill with a gallon jug (3.8 L), they get an oil level light when starting/running from cold, which may go away once the oil warms up and expands... technically an underfill situation. YMMV.

The concern when there is an overfill, how much is too much and we're basically concerned about oil level so high it contacts the counterweights of the crankshaft, which can cause foaming of the oil, loss of pressure, etc. Naturally, we don't want that.

The pics I've taken are looking at the lower engine case from the sight glass/oil filter end. The first photo is with crankshaft in place, and I marked a red line where the bottom of the counterweight is. I measured this to be 36mm above the Top of the sight glass. I roughly measured the surface area of oil would be 90 square inches. Basically, 125 cu. in. of oil in that 36mm depth, 2.05 L/2.16 US qts. This would be the amount of overfill required to have any contact with the crankshaft, bike on centerstand. On the sidestand, likely half that overfill, maybe less.... but keep in mind the minute you start the engine, the oil level drops an inch.... roughly speaking. I do not know the lean angle on the centerstand, or I could estimate much closer.... the excess oil would run into the stator housing first..... so, let's not speculate too much, again, it matters little really.

A further calculation, the distance between the sight glass marks is 14mm/0.4" approx., and 90 square inches calculates out to approx. 2/3 a litre or quart, or if you like a healthy half. You can decide next time you fill with oil and see what the difference is between being at the lower mark or the top one.

So any of you concerned about overfilled by half a quart should simply relax and not get all concerned about draining out a few ounces......



Pic with crankshaft in, taken so you can see the red line I marked:




Pic taken with crankshaft removed, taken as to be in line with the sight glass as best I could. Well, you get the idea, mark is 36mm higher than top of sight glass:



This pic with engine case flipped over, in the middle is the sight glass opening, and red mark shown previously is on the outboard face of the casting, at the level of the machined boss/bored hole just south of it.

Seven ways to stop overthinking things...

14mm is a tight 9/16”, 0.551”, not 0.4”.

90 sq inches x 0.551” is 49 cubic inches, 0.215 gallons, about 7/8ths of a quart.

Without filter 4 quarts is a good fill to the top of the sight glass. With filter is right at the bottom. As stated it matters whether measured cold, hot immediate, hot plus 60 seconds, hot plus 5 minutes. It seems the sight glass level is much more sensitive than 14mm of 90 sq inches, else I am not understanding. Seems to be 6 to 8 oz of oil bottom to top. Am due for oil change, will pay more attention during the change.

I don’t find the FJR oil level to be nearly as sensitive as to when it is checked as my 2016 2.5L Subaru.

I don’t recall oil filling the FJR was questionable but the Super Tenere was a real mystery.

OK, so if I cut down the maple tree over the garage so that the garage gets hotter and change my oil from 15/40 to 10/40,,, Where should the oil level be in the sight glass after my pancakes are done? Askin for a friend?

wetwolf wrote: ↑Wed Jan 13, 2021 1:02 am OK, so if I cut down the maple tree over the garage so that the garage gets hotter and change my oil from 15/40 to 10/40,,, Where should the oil level be in the sight glass after my pancakes are done? Askin for a friend?

Depends on how much syrup you were getting from the maple tree to flavor the motor oil used on the pancakes.

4 quarts with a filter change always gets me just above halfway up the glass. Been that way on both my FJR’s. Stays at that level in the glass until the next oil change.

I normally use yamalube conventional. Racing 4t from autozone if I don’t have yamalube. This time I went cheap and used valvoline motorcycle conventional. My shifter turned crunchy. Will be going back to what I usually use.

Ray - I've always thought that overfilling with oil creates pressure buildup, which leads to blown seals. I'm that guy that will drain a little out, if I feel I have overfilled. Maybe I shouldn't be so concerned about that. Thanks for the write-up!

Ray - thanks for your detailed explanation. This one is very interesting to me.

My bike is burning a (VERY) little oil. About 2-3 ounces in 4,000 miles. I'm not worried about the oil consumption. it is unnoticeable on the spark plugs, any rideability for the bike, etc. But the total PITA is having to carry oil on a tour. For my Nov. 2020 trip to Arkie, I bought 12 oz of oil as I didn't understand the extent of the issue. I mistakenly read the sight glass on uneven pavement, and that caused me to add 2 ounces to the crankcase unnecessarily. On level pavement, it was clearly overfilled. I left it there 3,500 miles ago with no adverse effects. Now, I'm just back to the top mark on the sight glass (again burning 2-3 ounces every 4K miles).

I know first hand that the oil light will come on if you are more than 1 oz BELOW the low level. It may not come on immediately, but will after some time, presumably because the oil pump is taking volume to distribute to the top end of the motor.

Blister_1, there is no way to increase pressure by adding oil.... the oil pump doesn't care.... remember your crankcase vent hose is piped straight into the air box to take care of any issue there.
Pants, if you have nailed down that oil usage that fine, then add the 2 ounces before you leave on your trip... you do not have to carry oil in my opinion.
If it helps, when cold, with the oil level at the top of the sight glass, when you start the bike do you notice the level drop until the sight glass is empty (36mm)... in a matter of seconds, that is roughly 2 quarts that got pumped into the engine to get to all the places it needs to go and is completely normal.
Another thing to keep in mind is that you cannot drain ALL the oil, the oil capacity when new and dry is 4.9 L/5.2 US qts.

Hppants wrote: ↑Wed Jan 13, 2021 2:10 pm ...I know first hand that the oil light will come on if you are more than 1 oz BELOW the low level. It may not come on immediately, but will after some time, presumably because the oil pump is taking volume to distribute to the top end of the motor.

There is no windage tray over the oil pan, nor a cover over the bottom of the engine so the oil is free to move around in the oil pan. In the early Gen IIs people discovered that during hard acceleration the oil would move to the rear of the pan causing the low oil level light to come on. What had you been doing just before the oil light came on, hmmm?

I think if you have a single cylinder bike or a two cylinder bike where both pistons go up and down at the same time like an old Norton, you could build up enough air pressure in the cases to blow a seal, if it was overfilled enough. It would be much less an issue on 3 and 4 cylinder engines.

John d wrote: ↑Wed Jan 13, 2021 6:25 pm I think if you have a single cylinder bike or a two cylinder bike where both pistons go up and down at the same time like an old Norton, you could build up enough air pressure in the cases to blow a seal, if it was overfilled enough. It would be much less an issue on 3 and 4 cylinder engines.

It looks like you blew a seal..

Nah, it's just ice cream.

Yeah Ray, that's kind of what i was thinking - overfill it by 2-ish ounces before the tour, and leave the oil at home.

John d wrote: ↑Wed Jan 13, 2021 6:25 pm I think if you have a single cylinder bike or a two cylinder bike where both pistons go up and down at the same time like an old Norton, you could build up enough air pressure in the cases to blow a seal, if it was overfilled enough. It would be much less an issue on 3 and 4 cylinder engines.

That is a big problem with Harley-Davidsons. Both conrods are on the same crank pin. Huge volume being pumped in a small crankcase. Is something H-D proudly proclaimed they had mastered several engine generations ago, but didn't admit to be a problem prior.

The crankcase can breath all right, the problem is lubrication with that much wind.

John d wrote: ↑Wed Jan 13, 2021 6:25 pm I think if you have a single cylinder bike or a two cylinder bike where both pistons go up and down at the same time like an old Norton, you could build up enough air pressure in the cases to blow a seal, if it was overfilled enough. It would be much less an issue on 3 and 4 cylinder engines.

I should correct my post here. The one and two cylinder engines I was referring to were mostly dry sump engines, so overfilling with oil was not a problem to the seals. However, if those engines sat long enough unused, wet sumping became a problem. Wet sumping meaning that oil drained down from an external tank down into the crankcase. Wet sumping made starting very difficult and then could blow oil seals, but rarely. I don't know if any single cylinder engines were designed as wet sump engines (no separate oil tank).