I say more than likely most people with a little mechanical ability can probably do just about any and /or everything that Rock Solid Motors is doing to these china engines with a good Dremel Tool and an old bike frame to mount the engine on and run it for a while at part throttle with a good fan blowing across it, just my opinion because unless they are actually installing high grade custom made parts then all they may be doing is smoothing up the transfer ports, exhaust port, intake port..ect. which is a good idea but not some great thing that makes the engines worth a lot more when most people who can put a kit on a bike could do all that also......
My suggestion to you would be to get a 66cc slant engine from who ever you chose, and then order a Sick Bike Parts Expansion Chamber Exhaust and a Manic Mechanics Ported Intake, get you some gasket material and make your own gasket that matches the intake and the intake port, get a NGK B6HS Spark Plug and a NGK Plug Boot or one of the high quality boot & wire combo that SBP or Pirate cycles sales, move the clip on the metering rod in the Carb. to the second notch from the top, put a hundred or so miles on it this way and then take the main jet out of the carb, put a very small piece of solder in the jet, heat it up with a propane torch until the solder melts and fills the hole in the jet, then redrill the hole with a #72 wire gauge drill bit for starters, put the carb back together on back on the engine, then take it for a 5-10 mile round trip, let it cool a bit and then pull the plug and see what color it is, if it is dark brown or black, pull the carb and heat the jet again and there should be enough solder left that it will close the hole again, after doing this use a #73 wire gauge bit and redrill the jet again, and then repeat the test after cleaner the spark plug back to new metal with a wire brush or on an electric wire buffing wheel, if the plug is light/medium brown after this test run and it doesn't 4 stroke all the time accept when going up a hill, you will have it tuned pretty good, if the plug looks pretty good but it does still 4 stroke to much, then just remove the carb. slide and move the clip on the metering rod to the top notch and that should fix it, I have this very setting I just described on 3 different engines and they all run very good like this on OPTI 2 2 stroke oil mixed @ 1.8 OZ per gallon of gas, by doing all this you'll have about $250 in your engine and most likely it will run very good and probably last just as long as those Rock Solid Engines that still have the very same internal components as you engine does, No ONE is making engines just for them and the very same engines they are buying are also out here available to the general public, all of my engines are just the the BGF kits accept for one that I'm not real sure about, it ould be the engiens BGF carries also, to me it doesnt really matter, all mine run well, but they all needed some minor mods to get them there, and the mods that do the most IMO are after market parts like the expansion chamber exhaust and the poted billet intake, and then tune the carb. and put a 36-40T sprocket on the bike unless your a super heavy weight and then the 44-48T might suit you better if you are riding in a very hilly area.
I dont want to stir a pot of poop with my comments about Rock Solid Motors, I have nothing against them whatsoever and I hope they are very successful with their smoothed up motors, but personally I think they are very over priced for us here in the USA, they still have the same cheap china made components, like the junk exhaust and the other fragile plastic parts, same carb. same sprocket, same chain, same cables, same idler/tensioner, same CDI, same gas tank, some of the engines will likely have the same high RPM vibration issues as some of the other " BRANDS " this is only my opinion which isn't claimed to be worth a plug nickle as we say around here.
In my opinion if a person can't proform some simple mods to these very simple engines then they are not very likely gonna be able to get them installed on a bike right either, and this is the problem with many of the negative comments on here about these little engines, it's not the engine that is the issue many times.......it's the installer who doesnt know how to set them up right and so the engine gets blamed for be junk, my most recent build was a prime example of this, someone scratched at trying to set the engine up on the bike but failed terribly, then they sold it to another fella for $200 that didn't have anymore knowledge about it then the first guy did and it sat useless in his garage for 1 1/2 years and then I came along and got the wreck of a deal for $75, I put it together right in approx. 8 hours with a few simple mods and now I have a great running and riding bike, that 2other fella's claimed was a piece of junk and would never work.
Get that $140 engine and do it right and most likely you'll be very happy and will likely have just as good of a set up as the RSE kit, I hope they do well but there is NO way I would spend that kind of money for an engine that is just a smoothed up version of what I can get for half the price and do the simple work myself.
Good Luck on what ever you do.....
Peace
That's where I'm at too. I'd come off some money for a quiet, balanced china engine, but not too much. My first build has been such a letdown, there's a frustration factor there that would make make me crack my wallet to make it go away, if there was a proven product out there, and as I look around these forums I think a lot of others feel the same. That's why I say there's a market vacuum (that rse is shrewdly trying to tap into).
So I was tempted by their engines until I found out the shipping cost, that capped it right there, and I started thinking in terms of, well, a disposable engine. I mean, I'm no machinist, just an amateur mechanic, so all I can do is buy a 140.00 stocker and hope it kind of accidentally runs in sweet, and if it doesn't and it can't be reasonably fixed, put it on the shelf and try another one.
I don't know, but I have an idea that's how it was with all engines and machinery, back in the day. And China is still back-in-the-day.
So my next build is a bike with a NuVinci hub - I found one for 230.00 - to smooth out that sluggish, moody 140.00 engine and give it some power, economy and longevity that I'm sure I don't have right now with my stock setup. That and an expansion chamber, and I'm tapped out, no more, that's top of the line for me.
