Increasing top Governer speed to 4500 on a Briggs series 950 or 1150?

[Ruckster]

I understand with a Predator 212 you can open up the idle port and the top governed speed will be about 4500, but with no idle control. That will not do. I need a governed utility engine that still idles and am looking at the new 950 or 1150 B&S. Anyone have an ideas? One contractor stated he was using his Predator engine that way commercially but he did not let on how he obtained a proper idle.

To obtain better airflow to the engine should I be looking to upgrade to a larger carburetor with similar linkage and an adapter plate or just rejet the thing and be happy with that?

Impressed with the torque curves on these new BS 950/1150 engines and their forged cranks and light weight of course. Lacking data on their torque at 4500 unfortunately.

Thanks for any tips.

 

[Dr. Shop Teacher]

The factory carburetor should be fine at 4500. I'd suggest you invest in a mini inductive tach and make adjustments to the governor controls to increase the max revs--you might get 4000-4200 with little toying around. You'll probably need to change the return spring to get the engine back to an appropriate idle. However, if you plan on sustained 4500 with a fixed throttle control operating hours at a time, you will risk busting a rod pretty quickly. The I/C engines will run all day long at 3600 but even then you need frequent maintenance. Do you need the rpm or just the torque? The torque will tail off after 3600 with a stock cam. If it's torque, then maybe a 306 is a better bet over a 206 cc engine. A little more heft, but a rock solid performer.

 

[Ruckster]

Thanks for the rpm suggestion, was concerned about that claim of being able to over rev them. The regular brigs 1150 series (250cc) drops to only marginally better than the cheap Briggs & Stratton 950 CR Series OHV Horizontal Engine — 208CC, 3/4in. x 2 7/16in. Shaft, Model# 13R232-0001-F1 at 3600rpm or even 3300.

Trouble is this cheap brigs 208cc with the forged crank and ball bearings is limited to 3300 rpm, a 8% drop over 3600. But it still has way more torque then the 212 Predator and is 4 lbs lighter (33#). I was just looking at the mini bike guys to see what they were doing to get the most out of them. The intake filter will be replaced with a large auto filter and a straight pipe will just have to be tolerated. Thought I'd do a few things as it is going to be run in the mountains, not on the beach as the gross torque ratings are developed at. That's why I was curious about the carb size.

Thanks