Top Tier gas stations are gas stations which sell gas with the fuel detergent additive polyetheramine (PEA). I discuss what the fuel detergent additive polyetheramine (PEA) is in the article, and why it is good for keeping your motorcycle engine clean. (or any other engine for that matter…) Licensed TOP TIER™ Gasoline Retailers must adhere to the rigorous fuel detergency performance requirements. Be assured, the performance standard applies to all octane grades sold in each of the retail outlets, even if a TOP TIER™ Approved Gasoline sticker is not found on the pump.
Wiring diagram of basic scooter ignition system wiring.
Below is a basic, but accurate wiring diagram showing the connections of the stator, CDI box, coil and ignition timing pick-up. This will cover most modern chinese scooters, plus others. The CDI box (CAPACITIVE DISCHARGE IGNITION ), in the diagram, is an AC (alternating current) type, which is identified by the fact that it is powered directly by the stator. DC (direct current) CDI boxes will be powered by the battery.
This is a overview of cleaning and rebuilding this 1975 Harley-Davidson SX250 dirt bike engine, originally manufactured by Aermacchi company in Italy. My friend asked me to sell it for him and I looked at it and did some research on whats out there to get some kind of price and what not. I saw that most people just took these engines and put them up for sale however they found them. I decided that is bullshit and made the decision to take this one apart and put new crank seals etc…
To be on the up and up, I have called this a rebuild, it was more like a take it apart and clean it and replace seals and stuff. The engine was in really good shape and needed some basics. I did this so that someone who might want to buy it, isn’t buying something that’s in unknown condition and quickly becomes a money pit. It’s quite a few hours of work and since I’ve been building engines for almost 40 years, I’d figured I’d do it. It is for sale and can be found here at CosmicMoto.net
The engine was dirty, but had been stored inside for at least 20 years and had more than likely been sitting around before that. While nothing was really bad, with exception of the clutch and sprocket, it was very dirty inside and those crank seals were old and hard as I expected, and that is not good for a 2 stroke.
You can see all the dirt laying on the bottom of engine cases of the sx250You can see the dirt is all through out the engine. Nothing terrible, but you want that cleaned up so it doesn’t do any damage.cases all cleaned up
Everything got cleaned up and all the bearings checked and they were all in very good shape. The original clutch was toast, and I couldn’t find Harley SX250 plates. So I had a new Suzuki clutch from EBC and it was almost a perfect match. I had to trim the drive tabs down carefully and I also had to add another steel and friction plate to make the stack height of the clutch match the stock stack height. It worked out perfect and this way I didn’t have to put 40+ year old “new” clutch plates in. I also took the transmission completely apart and inspected everything… all of it was in good shape.
new clutch pack with extra plate conversiontransmission was taken all apart, cleaned and reassembled. Everything looks good.another view of assembled gear box. new clutch test fitted ready for final assemblycrank installed getting ready to put cases back together.
I checked out the crankshaft and it was all good, wristpin and big-end bearings are good, and i assembled everything into the right hand side case. I sourced some new SKF seals for the crank, transmission and shifter and also bought a gasket set.
new crankshaft seals installed. SKF seals were used.new SKF seals for sx250 enginepiston and rings cleaned up.view of cylinder, by exhaust portview of cylinder intake port sidegeneral view of cylinder showing it is in good shape.
Next was the top end. The piston, rings and cylinder are in very good shape and seem to be standard, stock size. Very little scuffing. It all went together as expected and there is a very good seal in the lower end, as can be observed by a piston port 2 stroke. As far as the carburetor goes, I cleaned it out pretty well, once again so the buyer can see what is really there without wasting time. I had no intentions of actually rebuilding it. What is there is in good shape.
lower end has been put together and top end is next.top end installedDelorto carburetor before cleaning. Delorto carb after cleaningcarburetor mounted on engine
Last was to check was of the electrical system. I had to repair a wire that runs between coils, but the coils look perfect. I checked the coils with a meter and also put the coils in and assembled the rotor and spun the engine with an oscilloscope attached. From looking at the scope I would expect the electrics to be working as intended. That includes both coils for charging and ignition and the small pick up that triggers the CDI box. To be clear, I do not have a CDI box.
charge and ignition coils SX250charging coil wave form SX250 HarleySX250 ignition coil wavecharging coil wave form SX250 Harley
Finished Engine
SX250 Harley-Davidson Engine – left sideSX250 Harley-Davidson Engine-frontnew drive sprocket
The following chart tells you how many ounces of oil to add to a gallon of gasoline to properly mix fuel for your 2 stroke engines. Older engines typically use 30 to 1 mixture ratio’s and new engines tend to use 50 to 1 mixture ratio’s. Always check your engine’s documentation for the proper mixture ratio. Buying a quart of 2 stroke oil and something to measure the oil in, is a lot cheaper than the little bottles of oil they sell and much cheaper than the pre-mixed gas they sell.
Because I currently use 2 stroke mix for just my weed wacker, I took an old quart gear lube bottle and used it to mix the gas in. The gear lube bottle has a nice spout on it with a cap and since I don’t use much 2 stroke mix a quart works out great. You don’t want to leave 2 stroke mix laying around and end up putting old 2 stroke mix in you engine, it can damage it. Another tip is that it is always better to have a little too much oil, than not enough. Not enough oil in 2 stroke mix will also damage your engine.
Ounces of Oil to 1 Gallon Gasoline
16 to 1 8 oz
20 to 1 6.4oz
30 to 1 4.3oz
32 to 1 4 oz
40 to 1 3.2oz
45 to 1 2.8oz
50 to 1 2.6oz
60 to 1 2.1oz
80 to 1 1.6oz
100 to 1 1.3oz
What type of 2 stroke oil should I use?
It’s not always the case, but most of the time almost any 2 stroke oil will work. Exceptions to this would be race engines and perhaps some of the newer fuel injected 2 stroke engines found on dirt bikes, boat engines and other modern vehicles. Specialized 2stroke oil didn’t really come around until the late 1970’s. “Back in the day” you would use regular motor oil, or possibly castor oil. Those oils require much more engine maintenance and spark plug changes. Modern 2 stroke oils have additives in it to lubricate better, foul plugs less, not be as smokey, and also special oil for fuel injected systems.
2 stroke oil terms
2 stroke oil is the same thing as 2 cycle oil. The mixed gas can be called 2 stroke mix, 2 cycle mix, and premix. This all means that you have mixed the gas and oil together in a jug or container. There is also the term Auto-Lube. Auto-Lube means that there is a separate oil tank that you put the 2 stroke oil in, straight, not mixed, and a special pump on the engine mixes the gas and oil together for you. Auto-Lube system makes filling the gas tank easier because you can just put gas in the tank and not have to fuss with mixing the oil in.
2 Stroke Porting vs RPM
General port timing to peak rpm
Generally speaking this is the amount of degrees the intake ports are open and the Revolutions Per Minuet that the engine should be able to spin. Obviously there are other factors involved, that is why this is just a estimate of what to expect.
