Can you answer any of these questions?



1) Check out these pics of my engine internals:

Is the black stuff on the top of the cylinder head normal? This was still when I was running <20:1, so I know the oil was building up. I am now running 40:1. Could the black stuff hurt performance? The engine seems a little less powerful than everyone here on the boards is talking, and I haven't noticed all that much of a performance improvement since I leaned out the oil.

2) I read somewhere about mixing r/c fuel (5-30% nitro in the r/c fuel) to the gas/oil fuel. Anyone tried this? Any info on that?

3) It seems that the choke can change a/f ratio a bit. if I am going up a hill at mid rpms, sometimes adding a bit of choke seems to richen up the bike and give it a little more grunt. But at wide open throttle, any choke hurts performance (i'm sure because of breathing issues). I HAVE played around with changing the a/f pin. When I set it for a good mixture at high rpm, it STILL seems like a little choke helps the engine in the midrange under heavy load. Any thoughts?

4) I read about getting a thicker ignition wire. Can I get any >7mm wire and screw it on? What about the coil pack? anything worth upgrading there? Or how about the spark plug boot? I have heard the type of spark plug doesn't really matter, so I'm not even going to open up that can of worms.

5) I have also heard there is a brand of oil that is formulated to be run at 100:1 in all engines. Does anyone know where to find this? I imagine as long as it lubricates like it should, that might help performance of the engine a bit.

My bike just seems to be a bit underpowered, so I'm trying to track down any possible source.

thanks in advance!


Active Member
Nov 4, 2006
hi mrsaxman99,
nice job on your photos. I've never opened one of my engines up, so this is cool to see. I am sure the guys here can answer your performance questions.
I use Amsoil 100:1 formula oil, but I mix it 40:1

one question.... did you replace the sparkplug when you switched fuel/oil ratios?

One fact I know! the sparkplug boot that comes with our china kits WILL fail. Change it to the automotive type before you have to pedal home. :eek:



To me looks like carbon deposits do to unburn't fuel in simple terms ur motor might be running to rich

2 things u can try which also improve

1. A Hottor plug NGK B5HS
2. Semi or full sensythic oil




Chief hit it on the head your are running to rich on the oil ....I took my motor apart a few yrs ago after a run in with a car (that motor never did run right after that SUV played with it ) but I had over 1000 miles on that engine and did not have 1/2 the slug you have the spark plug tip looked ok from what I could see but it is not normal to have the build up around the threads.When you clean the cylender make sure not to scratch the thing and use a good gasket material the ones that come on them are not worth a hoot.


Looks Really Good.

That is really really Clean. Must be low miles..Sitck to the 20:1 unless you are running synthetics.


Adding RC fuel will destroy your engine unless you know what you are doing. Since you are asking very basic questions, I will have to assume you aren't familar with the dynamics of carb tuning and mixture settings.

RC fuel which contains methanol and nitromethane requires it be run at a VERY rich setting compared to gasoline. This requires rejetting of your carb at a minimum to achieve the appropriate stochiometric ratio of fuel to air.

I blend a little nitro and methanol to my fuel only because I am at 7200 feet altitude and the relative lack of oxygen with same carb jetting causes my engine to run pig rich. Running nitro and methanol at a specified setting solves this problem for me and regains performance lost.

So, in short, don't do it.


I know a whole lot about fuel mixture, tuning, and engines in general. Just don't know much about 2 cycle and THIS engine in particular. I was just curious if mixing in RC fuel, while fattening up the mixture a good bit, would yield good results...


Oh yeah, also...those pictures are taken when I was running richer than 20:1 gas:eek:il mixture...I have since leaned out the oil a bit...will the deposits on the cylinder go away with time? I switched out the spark plug when I leaned out the oil mixture as well.


As for the carbon it's to be expected if you were running 20:1 of dino oil. The carbon on the piston won't hurt anything but every 200 miles or so you should check the plug, exhaust port and exhaust for carbon. I do notice you have a little bit of blow-by on the piston, though it doesn't look too severe. I'd replace all the gaskets with high quality gasket paper when you reassemble. Next time get a compression reading before you take it apart.

I wouldn't mess with the fuel unless you've squeezed every little horsepower you can out of the motor. A tuned 50cc engine can easily exceed the safe operating speed of a bicycle on pump gas.


yeah I agree with tuning other aspects before messing with fuel.

I'm going to swap to an NGK B%HS plug, get a new/better spark wire and boot, and I just ordered some Amsoil 100:1 fully synthetic oil. Looks like some good stuff. I might take a measure or two to improve breathing a bit. Like open up the exhaust just a tad, or get a better air filter.
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