How to improve 4 stroke engine

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universal improvements
- rear sprocket bracket adapter (esp for you since you are putting in many miles)
- replace stock chain tensioner (this will fail and can be disastrous on a lonely road)

4 stroke
- not many because it is a proven and good motor
- iridium spark plug from ngk
- high air flow intake filter
- bigger jet for intake
- performance exhaust

I would get the kit first and then get the base system running well before doing any 4-stroke upgrades. also, tackle those universal improvements.
 
Cut off your muffler can and get a length of 7/8" ID flex tube. Get a better air filter and jet up. File out any existing flash in your intake or exhaust ports. Tighten your valves to .004" intake and .006" exhaust. Anything past that will cost bucks, such as a CNC flywheel or CNC conrod. Then I would suggest getting an older engine that revs over 8k rpm and scavenge the ungoverned magneto (you need to retard your flywheel 20° to use the ungoverned magneto).
 
Cut off your muffler can and get a length of 7/8" ID flex tube. Get a better air filter and jet up. File out any existing flash in your intake or exhaust ports. Tighten your valves to .004" intake and .006" exhaust. Anything past that will cost bucks, such as a CNC flywheel or CNC conrod. Then I would suggest getting an older engine that revs over 8k rpm and scavenge the ungoverned magneto (you need to retard your flywheel 20° to use the ungoverned magneto).

Gilad is planning on riding this across half of the country, I would not be advising a lot of questionable performance mods on an otherwise reputable engine with a known service record.

Reliable yes, but not modded to squeeze more power out, not a good idea. If Gilad is starting at sea level, you recommended that he 'jet up', I assume you mean richen the fuel air mixture, he's going to be going over several big mountain ranges heading east, the last thing you want is to make your fuel mixture richer before you take a mountain pass @ 6000' ~ 9000'.
 
recommended that he 'jet up', I assume you mean richen the fuel air mixture, he's going to be going over several big mountain ranges heading east, the last thing you want is to make your fuel mixture richer before you take a mountain pass @ 6000' ~ 9000'.


1. How to I jet up my motorized bike. Bear in mind I have 49cc 4 stroke engine.
2. In the break-in period of the engine, should I go easy with the engine and only turn on the engine on flat areas?
3. "the last thing you want is to make your fuel mixture richer before you take a mountain pass @ 6000' ~ 9000"? Why is that?
4. How do I cahnge the fuel mixture? I mean, I just add gas and ride. What else I can do besides that?
 
1. How to I jet up my motorized bike. Bear in mind I have 49cc 4 stroke engine.
2. In the break-in period of the engine, should I go easy with the engine and only turn on the engine on flat areas?
3. "the last thing you want is to make your fuel mixture richer before you take a mountain pass @ 6000' ~ 9000"? Why is that?
4. How do I cahnge the fuel mixture? I mean, I just add gas and ride. What else I can do besides that?


Jet up means to increase the amount of fuel your engine uses by changing the main jet in the carburetor, to one that flows more fuel. This is not needed while breaking the engine in. You might need to buy one or two steps 'leaner' which would be 'jetting down' You can buy different carburetor main jets for your HS149.

The break-in period: You should not start a long trip on a new engine. with the HS149 case, it's sufficient enough to ride it moderately and with varying throttle settings and let it cool down between short uses, for the first 3 or so local trips. Just don't run it wide open for long periods of time for the first 400 miles,( even if you are on flat land,) and change your oil at roughly the 200~300 mile point, as it will have a lot of tiny metal bits in the oil from it bedding it's parts in.

Look up the term 'stoichiometric ratio' it's a fancy way of saying an 'optimum fuel air mixture'. Earth's atmosphere gets thinner when you climb mountains and you don't need as much fuel to run a carbed engine when you are at 5000 feet elevation. Your engine will lose some power and smoke a bit, so you can install a smaller opening main jet to compensate for the altitude increase.
 
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You might need to buy one or two steps 'leaner' which would be 'jetting down' You can buy different carburetor main jets for your HS149.

Thanks. I understand everything you said except the quote above: what do you mean "buy one or two steps 'leaner' which would be 'jetting down'"?
Why should I jet down? Can't I just leave the engine as it is but just go easy on him in and after the break-in period?
 
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