Areomyst wrote:Thank you for taking the time to reply to my questions Larry. I myself find a hard time finding the time to get on forums (even one that I own) - I really appreciate the help! Surely you can tell by my questions that I am a novice, and your attempts to better educate me mean a lot.
The engines that I want to test vary from 50cc to 250cc. Most will be 50cc though. The short list below should encompass the majority of the engines I plan to work with though:larrycavan wrote:I see. What make are the engines?
Honda NPS50S (Ruckus) is a 2-valve 50cc
Yamaha YW50F (4-stroke Zuma) 3-valve, 50cc
Chinese QMB 139, also called a GY650 sometimes (crappy, but common)
Vespa LX50 (old ones are 2-valve, new ones are 4)
Most of these engines make around 3HP at the rear wheel according to my dyno. Some of them have aftermarket cams available, but none of the manufacturers really tell you much about the cam. I hope that with the flow bench, dyno, and by plotting the cams I can get a better idea of the relationships of the porting, cams and other engine mods to the power output. I have not done much with 4-stroke porting yet. I have been waiting on getting the flow bench done before doing a lot of 4-stroke port work. I have had a lot of fun with 2-strokes over the years though!
I don't know. I figured this little bench was better than no bench, but now I tend to second guess that. I was hoping for a set of instructions from Simons but as of the mail delivery today none have arrived.How do they figure 1 inch of water column is useful?
Perhaps a more realistic inclined manometer will make this at least a little more useful? I got excited about this Simons machine because it was already assembled, and I thought I was going to be able to more or less "plug and play" with this thing after making a cylinder adapter. Indeed, as you suspect, when testing any parts that I've tinkered with so far the inclined gauge was pegged...You could test the pilot fuel circuit with perhaps 1 inch of water column but certainly not the throttle bore.
Seems to me that by the time you get the slide fully open on a CV carburetor your inclined gauge is going to be pegged....
Glad to help. I'm a bike guy too so I find this interesting. I got into modifying PW50 Yam 2 strokes about 20 years ago so I also understand the interest in small motors. They're actually a lot of fun. You can make those little things fly...
For not a lot of money you can build a perfect bench for the motors you're focused on. A sheet of MDS, a few motors a weekend in time and you could be cruising. The little valves in the motors you mentioned won't require a lot of vacuum power. What are your running for carbs on the 50cc units? You might look at the SF60 for some ideas. I had a lead on a SF110 for $1000 a while back that a guy wanted to sell. I can contact him if you're interested and see if he's still got it. If he does he might be willing to negotiate the price. He's in Rochester or Buffalo NY. If you were nearby you could use my bench pretty much anytime.
You could get by with a flow element and big shop vac but the price is stupid. Better off building a bench.
Just a thought but for cams, you might want to talk to Megacycle. They do the best hard welds you'll find.
Being a 2-stroke guy, I was never really much interested into the 4-strokes until then. 
