Briggs & Stratton Questions ZmOz assist ?

[Bob_VT]

ZmOz you stated in another thread "I have a B&S master service technician certification, BTW... " http://forums.iboats.com/bbBoard.cgi?a=viewthread;fid=37;gtid=1159060

I need your skills/input.....

I did my final cut for the season on my lawn and the snow will be coming Time for serious engine maintenance. This year I already rewelded my deck and changed the bearings.

My mower has a Briggs & Stratton 18.5 hp and it is doing strange things......
Idle is very unstable and it surges.... ? New fuel filter, plugs, air filter every season. On the rarest occasion I will be cutting grass and the engine will smoke for 30 seconds and run like garbage then it recovers and smoke goes away and it returns to normal.
I am not sure it is reaching optimum RPM's and have considered a tach to test it. What should the RPM's be at WOT? Should I consider changing the spring ? What color should I get? Which color allows higher RPM? The Parts List has a few and then states "consult a technicion..."
My manual states to remove combustion deposits every 100-300 hours and the manual states to use new gaskets and new shields? Why the shields?
Should I consider a valve job? What should I be looking for on the valve seat or is it replacable?
And the last question..... can I boost the charging system or service it? The mower only charges the battery every other time I use it?

 

[ZmOz]

Re: Briggs & Stratton Questions ZmOz assist ?

My mower has a Briggs & Stratton 18.5 hp and it is doing strange things......

Is that an opposed twin flathead model?

On the rarest occasion I will be cutting grass and the engine will smoke for 30 seconds and run like garbage then it recovers and smoke goes away and it returns to normal.

Black or blueish smoke? Have you rebuilt the carb lately? That's where I always start.

I am not sure it is reaching optimum RPM's and have considered a tach to test it. What should the RPM's be at WOT? Should I consider changing the spring ? What color should I get? Which color allows higher RPM?

99% of Briggs engines max out at 3600 RPMs, with about 1750 at idle. Many (I think all these days) lawnmower engines are set between 2900 and 3300 RPMs because that's where the engines reach their torque peak, and reduces engine wear considerably. (whenever I build something with a B&S I usually size the engine to run around 2000 RPMs) You might want to change the spring, but I would stay with the same color.

My manual states to remove combustion deposits every 100-300 hours and the manual states to use new gaskets and new shields? Why the shields?
Should I consider a valve job? What should I be looking for on the valve seat or is it replacable?

I don't think you'll need new shields...I don't know why the manual would say that. It might be a good idea to get the valve seats ground...any mower shop should be able to do that pretty cheap. Some are replaceable, some aren't...I can't tell without the model/type numbers. You could just lap the valves if they look like they are in good condition.

And the last question..... can I boost the charging system or service it? The mower only charges the battery every other time I use it?

Again, it's hard to tell without the model numbers, but it should be at least 5 amps. Some stators are only a half circle that bolt under the flywheel, others are a full circle. Obviously the full circle produces more power. Some have additional AC circuits for lights too, if yours does, you can convert that to DC and use it to charge the battery as well. Or you could just get a good charger like this and skip the alternator...your battery will last twice as long at least. http://www.vdcelectronics.com/batteryminder_12117.htm
(cheaper on ebay)

 

[Bob_VT]

Re: Briggs & Stratton Questions ZmOz assist ?

Model 42A707 opposed twin . I absolutely do not want to go with a maintainer/charger since there is not power in the shed. I do have an assortment of trickle chargers already.

Well at least that's a start. I am going to be tearing into it this winter along with rebuilding my inline 6

Thanks.

 

[ZmOz]

Re: Briggs & Stratton Questions ZmOz assist ?

Are you sure your battery isn't just worn out? Also check to make sure the wires are still in good condition. Even a 3 amp alternator should have no trouble keeping the battery charged if you mow for an hour or so. You might want to check the WOT voltage too.