Yerf Dog Howhit 150cc GY6 GoKart Engine

When I first saw one of the Yerf Dog 3206 gokarts at my local Sam's club, one of the things that really intrigued me about this new gokart was the mysterious Howhit 150cc ATV type engine.  What was a "Howhit"?  Who made it?  Was it any good?  Questions filled my mind.  From what I could see on the surface, it definitely was not the typical cheap, "throw away" design Tecumseh gokart engine.  Sure, Tecumseh makes some nice engines too, but the ones I saw on gokarts were cheap aluminum cylinder bore engines that were designed to last around 150 hours run time.  Anyone who knows anything about engines understands that steel piston rings running in an aluminum cylinder bore is not going to last a long time.  Might be fine for some kids who drive their kart a few times a year, but I wanted something better that would last longer.  In addition, I have owned a Yerf Dog 3203 gokart that came with a cheap Tecumseh 6.5HP engine and it was very weak.  

Well, I finally decided to take the leap and purchase a 3206, and overall I have been impressed with the performance of this small Howhit 150cc engine based on a Honda GY6 engine.  It does a good job moving such a big kart around.  Sure, more power would always be nice (when is it every enough!), but considering the cost of the gokart and the small displacement of this GY6 based 150cc engine, it really is impressive how it can move the gokart around and climb hills like it does.   When I first saw the Howhit engine, I was very curious about it's design and how it was made.  Since I was a kid, I enjoyed taking apart and working on engines.  I decided that I wanted to take a peek inside the Yerf Dog 3206 & 3209 gokarts engine to see what it looked like.  Here are a few pictures and some comments about what I found inside....

Howhit GY6 Engine with Head & Cylinder Exposed

One of the first things that I noticed underneath the valve cover was that the rocker arms appeared to be high strength forged pieces.  This was apparent because of the surface finish on the rocker arms which looked to be from the forging process.  The die cast aluminum cylinder looked very nice, and it has a cast iron cylinder sleeve which should give the Howhit GY6 engine long life potential as far as cylinder bore wear is concerned (definitely longer than a junk aluminum cylinder bore).  The surface finish of the die cast cylinder head was not as pretty in some areas but outside of some minor cosmetics it looked good.

Howhit GoKart Engine with Cylinder Head Removed

When I removed the cylinder head, I noticed that the valves were about as large as could be used for the size of the combustion chamber.  The ports of the cylinder head were not ideal and could use some porting (like most production engines), so I decided to clean them up to try and improve the flow.  I also found that the camshaft rides on double ball bearings which is a very nice design feature!  In fact, the ball bearings on the cam had "Japan" printed on them, and they appear to be high quality Japanese bearings. 

Piston and Rod of Howhit GY6 Engine

I removed the cylinder to have a closer look at the piston and rod.  The piston and rings look like decent pieces.  I suspect that the connecting rod is another high strength forged part.  The Howhit GY6 crankshaft is supported by big ball bearings (very nice).  I have a tach on my kart and I have seen the Howhit rev past 9000RPM on long downhill straights before the electronic rev limit begins to cut the ignition around 9200RPM or so.  This is a very high RPM.  Cheap engine parts would not survive at those sort of engine speeds!  Keep in mind that most Tecumseh or Briggs type kart engines are governed to around 3600RPM!  Even when a Tecumseh or Briggs is set up for full kart racing, it would only be a dream to spin it up to 9000+RPM!  Even if someone spends $1000's to build a full out racing engine from a Tecumseh or Briggs, it would probably only survive around 7000RPM for short periods of time.  Even then, something would probably grenade.  There is only so much that you can do with an engine design that only uses splash lubrication like the horizontal shaft Tecumseh or Briggs engines using in karting (recreation or racing).

So, all that to say, the fact that the Howhit GY6 gokart engine can spin up to 9000+RPM safely is a testimony in itself to the good design of this engine.  The Howhit GY6 engine has an oil pump and the pressure lube system supplies the lubrication needed to help the engine survive at such high RPM's.  In the picture below with the flywheel side engine case removed, you can see a small sprocket at the bottom right that is chain driven off the crankshaft and it appears to spin the oil pump.  In the upper left side, is the gear set up for the electric starter. 

Side Case of Howhit GY6 Removed

The more I looked into the Howhit engine, the more I was impressed.  It looks to be a very good design.  The Howhit GY6 based 150cc engine is manufactured in China at the Linhai factory.  I also discovered that this engine design is a copy of a Honda scooter engine.  It looks like Linhai took the Honda GY6 design and basically copied it.  This Honda copied GY6 design probably accounts for the good design features that this engine appears to have. 

There are areas such as in the die castings where they could be finished a little more carefully.  I found some burrs and small chips in the crankcase from the die cast engine cases.  These small burrs or chips could find their way somewhere and might cause some problems.  Thankfully, the Howhit GY6 engine has a filter screen on the oil pickup so any chips that make their way back to the main oil sump should be trapped in the filter screen.  There are some other areas where perhaps material selection of plastics or rubber parts could be better.  This is all typical of Chinese manufacturing where sometimes raw materials are not the highest quality and the detailed finish work will often not be as good as found on something like a Japanese made engine.  No doubt, the Chinese factory is producing these for a very low cost, so some of these things are to be expected.  Even so, I am NOT complaining.  I'd much rather have this Howhit GY6 engine than some junk, throw away aluminum bore (made in the USA) Tecumseh engine!!  The fact is that if this same engine with all it's features were manufactured in the US or Japan, then the cost for a consumer to buy just an engine like this would probably be approaching close to what I paid for the ENTIRE GOKART!  The Howhit is an impressive little engine especially when you consider the overall cost of these gokarts.    

Overall, I am very impressed with the Howhit GY6 engine in the Yerf Dog 3206 and 3209 gokarts.  It is a powerful little engine for it's size.  The overall Howhit engine design appears to be good, and with proper maintenance it should last a long time.  It may require some more maintenance than a Made in Japan engine found on a $5000 ATV, but that's OK with me.  I don't mind having to replace some things here and there if needed.  Yerf Dog Customer Service has been very good about having parts in stock for this engine.  I picked up some maintenance items and some extra gaskets and small parts, and they were all priced very reasonably.  I paid less than what I'd expect to pay for Tecumseh type parts.  Overall, I am VERY IMPRESSED with all the features (including the Howhit GY6 engine) that Yerf Dog can offer for such a great price! 

In my personal experience with my 3206 gokart, the 3206 & 3209 are a good bang for the buck and the Howhit engine is one of the things that helps make these gokarts such a good value.  And now that I've seen more of the inside of this GY6 based engine, I am even more impressed with it.

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