Project Honda Ruckus cylinder head

Project Honda Ruckus Part 7: Building the Engine

By Jeff Naeyaert

In our efforts to build the ultimate Honda GET 50cc engine for our Honda Ruckus, we have learned a few things with our first iteration of our modded engine, lessons to make our second one better we hope.  In our quest to get even more power out of our little Honda we are going to build another engine, this one is going into another Ruckus in our stable. Our goal for engine number 2 is to surpass the 58 mph of our first engine and reach 60 mph with the Honda engine that came with the Ruckus.  For the Ruckus, many people simply swap the Honda engine for a larger GY6 4 stroke or a two stroke Yamaha Grand Axis or Zuma powerplant.  However for our current project, we want to push the limits of the GET Honda to max out our little Honda.

To read about our previous engine build Honda GET Engine and Ruckus Bottom End.

Project Honda Ruckus cylinder head combustion chamber
Looking at our stage 2 cylinder head we can see how our milling has given us a quench area without welding.  It also ups our compression ratio to 13.8:1.  You can see how our intake port is larger than before as well.  The frosted look of the combustion chamber is the surface that WPC treatment leaves behind.  The WPC will make our valve job more durable, important because our valve seating surface has been narrowed for the best flow.
Project Honda Ruckus modifed valves
Our valves are re-contoured and backcut for better flow.  The valve seating area has been moved outboard as far as possible to maximize the effective valve area.  Also note that the valve stem has been reduced in diameter by the head to further improve flow.  Finally the entire valve is WPC treated to reduce friction at the stem and to improve the life of the valve seat.

From our first engine experiment, we learned that we can go with more aggressive headwork.  In our first engine we were worried that going too big in the ports might reduce the velocity in the ports of our tiny 58cc engine causing us to lose bottom end torque.  We assume that the stock ports flow really poorly as our engine really responded to our first attempt at port work by gaining power at very low rpm.  Since the head is so tiny and it would take quite a bit of expensive fixturing to get the head on a flow bench, we don't have true flow data.  Since we were so concerned about flow velocity on our first head we concentrated on porting in the bowl area and directly under the valve seats with a lot of detail done in the valve job.  Still our headwork was the most extensive ever done to the GET engine and we feel that it was the main component in our exceptional performance.

Honda Ruckus exhaust port mods
In this picture you can see how we flush cut our valve guides for more flow.  You can also see how thick the valve guides are in relation to the port area and how much flow they block.  In this close up you can see the frosted look of WPC treatment and the smoothness of the radius valve job.  None of the other ported Ruckus heads on the market can say they are fully ported all the way through, particularly on the extremely curved intake port.  This is testament to DPR's skill.

Once again we turned to Dan Paramore Racing for our headwork. Since we learned that our headwork improved both bottom end as well as top end performance, we decided to go much bigger in the porting of our new engine.  We increased the port size 2mm over our last iteration, particularly in the area of the valve guides where we feel that the port is the most restricted.  We shaved the valve guides flush with the port walls and enlarged the port straight through this area.  Engines get most of their valve cooling through conduction of the valve guide and the valve guide is critical for proper support of the valve to get good valve seal. The GET engine has really long valve guides and the valve stems are well supported so we felt that it was not too extreme to cut them flush with the port to gain a lot more cross sectional area.

Honda ruckus ported exhaust port
Our exhaust port is much bigger than previously.
Honda ruckus intake port
Our new intake port is much larger than previously thought to be OK for good bottom end.


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Tuesday, February 23, 2010 4:40 AM
Love it can't wait till the summer I am going scooter shopping! I dont have a far to travel to get to work and this would be a much cheaper/fun way to arrive on most days!
Tuesday, February 23, 2010 9:58 AM
I have been following this series religiously! I am doing a similar project on a 1970 Honda CT90 and besides being air cooled, the engines look very similar. Keep them coming!
Wednesday, February 24, 2010 11:55 AM
Wow, after reading all of these, I kinda want a ruckus. It would be the perfect campus cruiser, and it wouldn't need a parking pass. And I could drive it home when I wanted to. Now where did I put my spare change?
Sunday, February 28, 2010 9:13 PM
I have been going over your project for days trying to decide what will cross over to my ct90 project. THe CT90 is older and has a fairly large domed piston already, but only 8.2:1 compression. If i decide to have my cylinder welded up like for first project, what will be my deciding factors for how high of a compression ratio that I can acheive? Does this engine being air cooled change that in any way? I am a big fan of ceramic coatings from my dd and my rally car, will they have as much benefit to the air-cooled engine? THanks, can't wit for the next installment.
Mike Kojima
Mike Kojimalink
Monday, March 01, 2010 6:46 PM
Being air cooled I would be really careful about the compression ratio. Having closer to a flat top piston with a compact combustion chamber with quench for turbulence is always more effective but not always easy to do without valve shrouding, messing up the cam timing or crating too much heat with an air cooled engine.

Perhaps I would monitor cylinder head temp. Stuff around 350 degrees is dangerous.

I think 10-11:1 would be conservatively ok.
Wednesday, March 03, 2010 12:31 AM
It's good to see North Americans tune scooters. All of Asia is racing scooters, so I've grown accustomed to seeing built-up engines on mei-mei motos...
Friday, September 23, 2011 10:22 PM
I have read this article front to back, awsome job. Im sorry to say we in hawaii have been building mopeds for well over 20yrs now, we have made yamaha razz do a easy 50mph all with porting alone. We have built mopeds to reach 100mph, and thats still not enough. So what is ruckus? I say its the future, i have great appreciation for these thumper peds, but nothing can compare to the smell, the instantaious torque of a well tuned two stroke af16 honda motor. Heres the deal any thing honda is kick butt tune able, and thumpers ARE the wave of the future. I cant wait to see how far this advances, im just waiting till i get wheeled off the line on a ruckus. P.S. I did build, own, and race a 117cc stroker honda SPREE. Try build that and whisky throttle.
Mike Kojima
Mike Kojimalink
Friday, September 23, 2011 11:04 PM
The mopeds in Hawaii are SICK!
Sunday, April 29, 2012 2:21 PM
I was wondering when are you going to post the final results of the reworked engine in part 7 of "Project Honda Ruckus"?
Friday, July 13, 2012 8:27 AM
Ditto! I wanna know how it went? Will you be making a kit available? Im not sure if all that treatment is available in Alaska, and I want a fun summer bike to build and ride around town!
Tuesday, October 02, 2012 10:50 AM
i was just wondering if you guys had a cost breakdown for each phase of this project and a total parts list for all us regular joes in the ruckus nation i have an 08 thats an old rental scooter in key west, fl it barely gets 30mph on a good day so im searching for a good upgrade project to get some ideas from and BAM i find this any info you have please assist
Mike Kojima
Mike Kojimalink
Tuesday, October 02, 2012 2:58 PM
you have all the info and links at your fingertips to determine that.
Wednesday, October 10, 2012 2:34 PM
Mr. Kojima,

Who actually did the valvetrain lightening process? It is just a matter of simply machining off/shaving down parts?

Mike Kojima
Mike Kojimalink
Wednesday, October 10, 2012 4:30 PM
I did it on an apex grinder then used a rubberized wheel on a bench grinder to polish it. You would even use a dremel tool to do it at home.
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