crank case transfer ports

[d dream machine n jstone]

Has any one besides me opened the bottom end up on the transfer ports i found a great gain in performance. People speak on the jug often but on the bottom i noticed a wide area for the gasket and removed around half to increase the flow from the transfer ports. I completely tour it down and rebuilt it regreasing the bearings. And cleaning the excess oil and metal shavings i also tried truing the crank from the 20thousandth variations with no success but while it was
open,cleanin and opening those ports gave me high rpms. I will get a tachometer soon. Agianst a friend who builds and sells bikes, after he hit full throttle, i was gaining on him. How much gasket room is needed to create the seal for compression? I would like the area of the intake ad exhaust to stay within a ratio similair to the original but with an inch piping or bigger. Is that suitable. I bought all the performance parts imaginable and with minimal porting i kept up with this biker crew. with my mods and extencive port work i hope to win. Please id love any and all advice. Thank you

 

[d dream machine n jstone]

Is it wrong to say the area or the transfer ports should be equal to the area in the circles of the intake and exhaust for free flowing un restricted breathing? Would this increase power?

 

[Davezilla]

There is power to be made by matching the transfers at the cases because most cases don't perfectly match to the cylinder. I know there is a thread in here by maniac57 that addresses thus issue and the engine he did the transfer matching on did have a very noticeable power and torque gain.

There is also a lot to be gained by opening up the transfer tunnels in the cylinder but leaving the windows the same size and shape, you can also aim the transfer flow more toward the intake side of the cylinder to prevent short circuiting and knife edge the opening at the bottom of the cylinder and the bottom of the transfer windows, then once you got the transfer tunnels opened up you can install the cylinder on the case half to match it to the transfer openings. I usually try to keep about 1/8" of the outer wall to ensure a good gasket seal but you can take off more if using a copper gasket that can't blow out. What I do is install the gasket with the cylinder installed on each case half then trim the gasket to match the opening after I get everything matched up.

this can all be done with a dremel and a good assortment of carbide burrs, but if you have access to a die grinder it will save you a lot of time doing the initial matching then switch to the dremel for the final finishing.

my last engine was easily running up to 10,000 rpm and made the bike do 42mph with the stock 44 tooth sprocket so acceleration was really nice as well as a decent top speed.

 

[Davezilla]

Ok, now that I'm on a PC instead of the tablet, here's the link you should find useful... This guy did exactly what you're asking about... it's these little extra mods that really wake these engines up... http://motorbicycling.com/showthread.php?t=57383

 

[rogergendron1]

Every single china girl i get now i tear down and split the case and with a dremal in hand ....

I debur and polish the INSIDE of the case so its like a ported finish,
Then put the jug on one half and bolt it to that case half with 2 studs and then grind that lip right off of the transfer till the jug and the case match perfectly to each other,
Now unbolt it and do the other side,
Now stuff around the bearing bosses with JB weld stick ,
After jb weld dries place crank in and note where it hits the weld and how much clearance you need and remove it and grind it off.

Now you need to smooth out any sharp corners leading to the tdransfers inside the case

ok your ready to re assemble !

make shure you use NE. Oil impregnated bronze shims on the crank

Now you have a stuffed case with perffect transfer port flow !!!!!

I find that this mod allone allomg with a moderate port job and jug transfer port clean up will dramaticaly transform the amount of power this motor will produce and drasticaly increase the rpm range wile maintaining reliability !

 

[rogergendron1]

youare on the right path everyone talks about performance mods in the parts that will add the most power but nobody seems to understand all want to put the effort in to do the real mods you see without buying a single part you can rebuild these motors to have more power then a person who buys all the most expensive bolt on parts you just have to be willing to put the time and effort in to stripping it down to the cAse halfs and by hand re building it to your spec.