Happytime Essentials for economic improvment

[RMWdave]

hi all, some of you may have read my post regarding a new HT coming without a set of rings. (dont worry i never even tried to run it, im a self taught basic mechanic currently doing my small engine course )

i have a graham bells book for refrence as well for the reassembly. onto the good stuff.

i would like someone to post up some baseline numbers as i will be modifying the stock mailed engine with some clean up porting (and polish on the exhaust side) as well as jetting, a custom one off tuned exhaust, and milling of the head for a bit more compression. i will also have the crank balanced to the piston.

id like to ask our members to collaborate some of our best threads into this one (number one, so i can study it easier without having to think of everything myself) and number two, so others can view upgrading performance/reliability as we do in the pocketbike world! albeit, we dont have any real bolt on kits or performance parts.

anyway, ill be doing the clean up port/polish soon and adding before during and after pictures! i just need to find the right bits for my rotary. being absolutly precise is nessassary when porting and technically should be done with a pencil type die grinder, im not sure if ill need to just go and buy one.

 

[pdxrhett]

Well, first stop should be obviously breaking it in. Next would be any performance upgrades - expansion chamber, tuned pipe, upgraded diaphragm carb (or something better?), then move onto porting and polishing. After all that I would go with a shift kit/jackshaft. The shift kit will be the best economic improvement as far as mileage goes - instead of WOT at 30mph it could be half throttle at 30 because of the gears

 

[RMWdave]

i dont think im going to go much past the port/polish for this one. BUT
i am in the planning stage of a felt build that will be all out. walbro carb and all...

 

[RMWdave]

has anyone had any success in balancing a HT crankshaft?

 

[machiasmort]

RMW,

If you've got info for runnin a different carb, I'm highly interested!

 

[RMWdave]

welllllll then!
http://www.pocketbikesunlimited.com/19MM_DELORTO_CARBURETOR.html
this would be a 19mm dellorto replica pocketbike carb, i have never ran one on a mb kit yet, (but i do have one on my pocketbike, and it fits the intake manifold of a HT kit!

your other option, would be a walbro wt-603 diaphram carb which is tuned with high/low screws.
the only problem with running one of these types (diaphram) is that they dont like to be consistent at a medium cruising rpm.

the difference between the dellorto rep, and our stocker is the flatslide on the dellorto.

 

[give me vtec]

why does everybody talk about port and polishing these engines? It is just a big *** hole... there is nothing to port and polish like on an overhead valve engine. You can port match the intake and exhaust with a dremmel to make the hole bigger to match the ports, is that what everybody is talking about???

 

[RMWdave]

you have the idea, in actuality you dont want to polish the intake side (or transferrs) in a 2 stroke because it helps with atomization.
but you can probley haul a decent amount of performance out of the jug with a bit of porting. its all about helping the flow of the engine to make it breath better, in, up, and out/in/out. porting is always useless without a custom tuned expansion chamber.

alot of us have come to realize the benefits of certain parts over stock (for example, a pocketbike pipe works better because it redirects sound waves back into the combustion chamber and assists in "scavenging" (pushing unburnt gas/air vapor back into the cylinder before the transfers, intake and finally exhaust close for detonation) which in turn packs more punch into each power stroke)

when you start thinking about fine tuning the engine in such a way you also need to make sure the rest of the internals can take it! which leads me to the importance of having a balanced crank/piston. the vibration caused by the centrals is enough to simply disentegrate somewhere along the way with our added fuel mixture.

wrist pin and BE bearings also need to be checked. i dont exactly know how much they will take, but pocketbike rod bearings would probley be a better choice if they will fit.

i compare this engine to a pocketbike alot, pocketbikes are still made in china and arent great, but they are designed a little better with high RPM in mind, the kit motors we call happytimes just wont take it due to the ****ty state the crankshaft is in.... this is the first thing we need to look at when upgrading internal effieciency.
-dave

 

[RMWdave]

here is a Wiki to further explain engine balance and its importance.
http://en.wikipedia.org/wiki/Engine_balance

here is the article we need to think about and adapt to our setups.
http://www.pocket-bike-racing.com.a...-guide-internal-external-crank-balancing.html

now, we may be able to use the magneto for our external balance. i have a good feeling that this is where alot of our vibration is coming from to begin with. our engines run what is called a "full circle crank" which means we dont have any offset lobes, rather 2 complete circular weights. these are very crude looking to say the least and will most likely need a proper balance.....

http://www.pocket-bike-racing.com.a...sion/7839-balanced-full-circle-crank-pic.html
and above is how we would achieve balance in our crankshafts.


id like to point out that im no guru when it comes to engine building. in actuality i have yet to put my knowledge to trial. But..... i think im onto something as far as a good test bed goes lol

 

[give me vtec]

here is a Wiki to further explain engine balance and its importance.

id like to point out that im now guru when it comes to engine building. in actuality i have yet to put my knowledge to trial. But..... i think im onto something as far as a good test bed goes lol

I know all about balancing and blueprinting engines...

My point is that when you port and polish an engine it is usually where the intake tract splits the air going into the different valves and then smoothing the surface after you are done. There is nothing to port and polish on our little engines, it is just a hole, what would you do widen that hole?... No. You can port match the intake so that the little round opening (most likeley half choked off by the gasket) is the same width as the intake port. Is that what everybody is refering to? I did this mod... dont know if it helped because this is my first MB... but it does have plenty of top end grunt.

and just because you have read some wikipedia stuff on balancing engines does not make you a guru... it makes you sound ametuer. I wouldnt do a lot to the internals of any engine unless you know what you are doing.