what's the best way to tune a standard d7 engine??

hi guys, I am building a racer out of a d7 and i would like to know what are the best ways to improve and tune the d7 engine and make it suitable for racing???
any help appreciated.

Harry.

Hi Harry,
Have you read the tuning articles on the website? Would you like a 125 or a 175cc engine? In my opinion the first place to start is to build a good bottom end. You will need a close ratio gearbox for racing regardless of whether you want a 125 or a 175, you will also need a strong and accurate crank.

Rob

hello mate, yes i have read most of the tuning articles but was just wandering how everyone else was doin it incase they knew a better way or better modifications that could be done.
i have got a whole d7 bike so i got engine etc, so i am goin 175 and you reckon it is best to start at the bottom end??
Harry

Here's some pictures to maybe help ,first is the crank bearings, only one per side with an oil seal

Next we can see the other side you'll notice the bearing up against the crank, it'll need a spacer behind it to keep here,
You'll also see the packing ring around the crank , here's a picture of the crank,
I made mine a left side gear change you may or may not want this , its all a personal thing
.
I've used an iron barrel, I do think now though an alli one have been easier


Also the ignition will need a mounting plate to be made to suit the type you'll be using
you'll need to build the crank with a new rod, I used a kx250 rod and wiseco 64mm piston, it make the little end bearing odd, so I used a crowded roller idea with two thin hardened washers either side of the rollers, I made mine from thrust bearing parts ground down to 0.5mm

these are a great help thanks really appricate it i will start posting a few pictures on the next couple of weeks.
any other help would be great.
Harry,

Hi HC,

How did you find out about bantam racing? Did you see Rob at the NEC?

If i was starting to build a cheap 175 to race i would source :-

Sandcase crankcases Stamped D5 orED7(FD7 & GD7 are die cast less meat on them)

D14/B175 cylinder not D5 D7 or D10. D14/B175 have no air gap between the fins under the inlet port.
To port a cast iron barrel is a lot of work/time - a better option is a BTW ally barrel ported to Snowy 175 spec
or a Rex Caunt 175 barrel - check out Rex Caunt racing on the net.

Get a pipe made - there are two on here 1- Fahron pipe 2- Snowy pipe

Crank rebuild with either Macio, Seedo(crankpin or flywheels will need maching) or T&G rod kit.
M/c crank to lose 7/8" seal shoulders- convert cases for inboard bearing like early D1.

Piston Suzuki TS185 64mm bore

Gearbox use road D7 and do a race parade with this set up .... more to follow....

Dan plus 175 runners can you advise more please..

I have owned a bantam for about 2 years now and i have had a intrest in racing it for a while now.
i did speak to somebody at the nec on the bantam stand but i cant remember his name but i do remember he had a beard and his bike was red???
but talking to him at the nec has made me really intrested and i have already started preping my bike.
at the moment i am really struggling to find a d14 barrel to use but i have found a todd head to use.
Harry.