Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

Borat,

   Very interesting post I read today (from 2009) was signed this way by T-Man.

P.S. I LOVE the HSK850 and TVS/TVXL840 2-cycle engine. One of the
strongest engines ever built, and very simple and powerful in its design.

   T-Man was a technical guy for Tecumseh for many years and miles above anyone on the net.  His depth of knowledge about Tecumseh engines is astonishing.

   The HSK870 seems like an interesting engine.  I've never come across one.   Have you?

It's possible that a freer breathing exhaust might contribute a power gain.  However, from my experience, to gain substantial power, an air intake and carburetor enhancement is usually required to go with the improved muffler/exhaust. 

I've worked on hot-rodding my Yamaha RDs and changing the exhaust alone had some, but by itself, little effect on power gain.  Improving the air intake system and increasing the size of the pilot and main jets along with the exhaust change made all the difference in the world.  A freer exhaust will expedite gas flow but only as much as the engine can produce exhaust gasses.  Without more fuel, the engine cannot provide the additional combustion required to capitalize on the more efficient exhaust.   Being that the 850 has no air intake restriction, there is nothing to be done there to improve power. 

I'm with T-Man on this one.   We're probably looking at decal power unless the 870 engine is being run at considerably higher rpm.