a complete 2 stroke neophyte

fuzzybutt · Post by **fuzzybutt** » Mon Feb 16, 2009 2:13 pm

all of my experience with performance tuning and modification have been with 4 stroke motors from the 45hp briggs and stratton 5hp to the 900hp 429 ford in the mustang i used to have. i am picking up my 72 t500 this weekend and as it needs a new cylinder and head anyways, i thought i'd just tear the thing down and go through the bottom end as well as do some hopups on it. i have just ordered the dam kit for the gearbox and now i need to know how to get more power out of the thing as higher lift/longer duration cams and head porting dont apply in this case. any suggestions at all, i do have access to a full machine shop and all of it's equipment.

tz375 · Post by **tz375** » Mon Feb 16, 2009 2:38 pm

Fuzzy,

Welcome to the dark side.

Think about those 4 strokes and what made them work harder and much of the same issues arise on a 2 stroke. Ports have to flow better and sometimes bigger isn't better.

In this case changing to a cam with more lift or longer duration is just opening a port earlier or later (more time available to get the gases moving) Bigger valves are like bigger ports (more area to move the gases through).

In a 2 stroke the height of a port is like changing a cam AND opening up a port at the same time. So if we want say more lift and a small high velocity port, we have a lot more thinking to do.

2 strokes have much stronger waves in the ducts and it is that wave motion and resonances that are crucial to a strong motor. Flow patterns are quite different and even small changes in port angles up/back can make a significant difference to performance.

If you want to spend time finding out what it's all about, there are several pieces of software on the market from Tom Turner's TSR which is like Alan Lockheed's Engine expert in many ways. Or Bimotion from Sweden which is great for working through what time are the motor needs.

Probably the best simulation software is MOTA from Ian Williams in South Australia.

Best books are Jennings (old and out of print but a good start) A Graham Bell 2 stroke tuning. John Robinson's 2 stroke tuning si good reading as well.

Or send the barrels and heads to Eric K (zook-e) on this board and he can port the barrels and work the heads for you. Then you'll need a good crank, new carbs and a set of pipes.

But all of tehy above is still cheaper than modifying a modern 4 cylinder street bike where pipes are 900-1000, a A bazzaz piggyback EFI box is close to $1000 for teh top of teh line stuff.

So all things considered, 2 strokes are cheap to tune if not necessarily easy.

fuzzybutt · Post by **fuzzybutt** » Mon Feb 16, 2009 6:41 pm

i just downloaded 2 stroke performance tuning my Graham from pirate bay. good stuff

fuzzybutt · Post by **fuzzybutt** » Tue Feb 17, 2009 4:40 pm

ALOT about 2 strokers are different but i'm seeing that some stuff (blueprinting to stock specs) is really universal to all internal combustion engines. i'm getting more and more excited as i read, and as time gets closer for me to go to ohio to get my t500.

H2RICK · Post by **H2RICK** » Tue Feb 17, 2009 7:30 pm

If you're a REAL fanatic, you could make up a set of water cooled heads for the old girl....or even blow the big wad and make a set of water cooled barrels as well. The possibilities are endless and only limited by the depth of your wallet.....

PS: look at the GT1000 thread in this section to see what REAL fanaticism can come up with.....

fuzzybutt · Post by **fuzzybutt** » Tue Feb 17, 2009 10:31 pm

that gt1000 thread had me drooling all over the keyboard. i am going to hotrod the titan some but i still want to retain rideability as much as possible. at first i just want to get it together and running. i know it's going to need bearings and crank seals and i might as well do an overbore to get the cylinders back to being round. i'll be needing a head and barrel too my friend tells me. it has an h2front end on it now with a disc brake but i want to retain the original look with the front drum (i love the look if the front drum) the biek has been lightened considerable he also tells me. i cant wait to get it back here to south carolina and start putting it all back together.

fuzzybutt · Post by **fuzzybutt** » Tue Feb 17, 2009 11:01 pm

how hard is it going to be for me to get the parts to do a rebuild on this motor? seals bearings and all that. also what kind of money am i looking at to get the crank redone if it isnt something i can do myself. i learned how to do harley cranks when i was at AMI but i dont have the fixture to check for straightness.