oil viscosity and Briggs vibration?

[NVA741]

Just wondering if anyone has a theory on this! I have a Briggs Intek - single cyl, 13hp, AVS, spin on oil filter. After break-in, I drained the original SAE30 oil, filled up with 10w30 Pennzoil Platinum.

The engine vibrated ALOT more! I only ran it that way for a short time. The PP was then replaced with 15w40 Rotella. Vibration was less (but still more than original). I then replaced the Rotella with Shell SAE30. Vibration was further reduced to about original.

I contacted Briggs and they stated that synthetic 10w30 was acceptable and should not have caused additional vibration. I'm stumped! I wanted to use syn 10w30 for easier starts and possibly more power.

 

[Master ACiD]

theres no way. it has to be something else.

 

[Quest]

oil viscosity shouldn't matter in this case.

I wouldn't worry about it if I were you for all single cyl small engines vibrate like a shivering dawg anyways, and personally I find it interesting that you are able to notice the differences between SAE30wt and 10w30 oil in terms of vibrations (these single-cyl engines do not come with balancer to begin with).

If you still having concerns, bring your engine back to where you purchase it from and see what they think.

Q.

 

[NVA741]

It definitely does not make sense to me, but there was a noticeable difference in vibration going from syn 10w30 to 15w40 to straight 30. The Intek does have some type of internal balancer - AVS.

I came up with a theory: The thinner oil causes less friction, resulting in slightly higher rpm. But this didn't pan out because because running full throttle (3600rpm) with SAE30 was still smoother than part throttle with the other oils.

I'm tempted to switch back to syn 10w30 to figure this out! I purchased the machine over the web so there is no local dealer :-(

 

[Bill Kapaun]

"(these single-cyl engines do not come with balancer to begin with)."
And just when did they quit using them?

 

[NVA741]

One more clue! I replaced the original Briggs "short" filter with a Wix "long" filter (51348). According to the Wix website, the longer filter has a smaller micron rating. Like the oil, I don't think this make a difference.

 

[Quest]

Bill-

I'm thinking of a separate counter-balancer shaft, separately driven by a gear or belt (Honda 2.4L), not the counter-balance weight on the crank.

Q.

 

[Camu Mahubah]

It seems to me you have discovered that this motor likes SAE30w of the Shell variety... did you sitting on it like I do when the Washing Machine spinning an unbalanced load gets out of control and tries to topple the trailer

...

 

[dwendt44]

Most all small engines have a governor of some type, so thin oil won't make/let it spin faster.
IIRC, most small engines are governed to about 3100 rpm, regardless of what the manual or company propaganda says.

 

[Master ACiD]

generators have to run at 1800 or 3600 rpm to have 60hz frequency. the frequency is directly controlled by the rpm's.

 

[NVA741]

I have a Sendec tach/hourmeter. The rpm varies some but I see 3570rpm the most often at full throttle and 1900-2100rpm at idle. These little tachs are really neat.

 

[Bill Kapaun]

Quote:

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Most all small engines have a governor of some type, so thin oil won't make/let it spin faster.
IIRC, most small engines are governed to about 3100 rpm, regardless of what the manual or company propaganda says.

---

That may be true of walk behind residential lawn mowers, but lawn tractors, zero turns etc. are a different beast. Many of them are governed near the max rating of the engine.

 

[Bill Kapaun]

Quote:

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Bill-

I'm thinking of a separate counter-balancer shaft, separately driven by a gear or belt (Honda 2.4L), not the counter-balance weight on the crank.
I'm not talking about the counter balance weight cast on the crank either!
I'm talking about the counter weight that is LINKED to the crankshaft on MANY of the larger Briggs.
Q.

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[Quest]

LOL Bill!

I missed out on that counter weight that LINKED to the crankshaft part...*DUHH?!*

I have serviced an Intek once (it's a 10hp?!) and no signs of that counterweight in it?

As a matter of fact:maybe it's my odd luck but it seems like here in Beaverland, I've encountered a lot of oddballl B&S these days, citing my 1994 newly bought Poulan with 4.5hp B&S classic comes with point+ condensor, something that not even my local B&S serviceman would have agreed upon (but then again, why would I bother to haul in my mower just to show them what I got??)..Thank goodness for Crraaapy Tires for carrying aftermarket points from Arnold Industries), and now an Intek with counterweight? (apparently, on B&S site, there is indeed AVS built in to all Inteks) and the one that I serviced recently doesn't come with one (yes, it does shake a little).


Q.

*boy, am I feeling lucky today*

 

[NVA741]

Just an update. Since it hasn't rained in weeks and there's no grass to mow... I changed my Intek's oil again from SAE30 to synthetic 10w30 (Q-Torque this time).

Results are the same! Noticeably more vibration. Could excessive bearing clearances cause this? There was a little valve clatter too. I'm gonna call the local Briggs service centers and see if anyone will let me take just the engine in (I don't have a way to transport the whole mower).