Making a AG100 go crazy fast

**WuZards-Eugene** · 22nd July 2010, 13:56

I put a 1mm oversize piston and had the barrel bored out, richened the mixture a little and it hauls pretty good for an AG. Still has all the bottom end, but when it reaches mid to top end it sort of explodes into life alot like hitting a power band. Changed the gearing a bit as well, and managed to get 130kph out of it (revving like shit). Still has all the fangles on it.

**cheese** · 22nd July 2010, 20:09

Originally Posted by Reckless

Jeepers Cheese??? You should know this??
Your own bike has them from factory??
Here 2004 Cr250 Piston

Attachment 213512

They are called boost port windows or Transfer port windows in the piston.

Attachment 213513

They let extra fuel into the crankcase as the piston passes the inlet port. So when the piston comes down it has more to push up the transfer ports?? I suppose it lightens the piston but that is not the main purpose. Its about stuffing more fuel into the chamber. We did this to our kart pistons, or made them bigger.
Early bikes or non performance bikes didn't have them so they where drilled or machined in.

My last two pistons haven't had them!

**cave weta** · 22nd July 2010, 20:26

Dont file or drill anything!! you can so easily make it worse.
The best mods are the YZ exhaust, then put two cylinder base gaskets on to it and machine the head by 80-90 thou. that raises the ports.
If you are rebuilding the bottom end then stuff the crank. Force cork or balsa plugs into the crank balancing holes to increase primary compression.
Give it a CDI unit instead of points and a 28mm mikuni carbie.

Do all this and my CT90 will still beat you! Come summertime.....

The Over The Top Adventures

World's Fastest Postie Bike
will amaze and astound you......

a stripped and streamlined postie bike with rearsets and clipons, a 149cc big bore kit, tuned exhaust and a 36mm Mikuni running methanol, 12,500 rpm and 112Db!!!

photos coming soon to a computer near you!

**carver** · 22nd July 2010, 20:36

I see a cold war developing across the K gorge cave weta....

What can build the worlds most powerful ag bike...

Danny C will see that victory is ours....!

**carver** · 22nd July 2010, 20:38

oh, the big end is pretty fucked, and who wants to balance a crank on a ag?

**Ktmboy** · 22nd July 2010, 20:50

We used to mod Ag 100 and 175cc up north and fit side cars onto them. Had a group of 20 odd units racing at the saloon car club days. Couple of ambulances to each meet so the numbers dropped of a tad over a couple of years.

But we used to do exactly what Cave weta mentioned. even down to the 28mm carb. Pommy wizard by the name of Roger Wilkins used to port them sweet.

80 mph was the top speed we got on cemetry straight Kaikohe.

We used to lengthen the swing arm so they handled a bit better on the corners. No filter box and fitted Z bars to reduce the drag.

In fact its really me on my avater. Ha ha.

**cave weta** · 22nd July 2010, 20:53

Originally Posted by Ktmboy

We used to mod Ag 100 and 175cc up north and fit side cars onto them. Had a group of 20 odd units racing at the saloon car club days. Couple of ambulances to each meet so the numbers dropped of a tad over a couple of years.

But we used to do exactly what Cave weta mentioned. even down to the 28mm carb. Pommy wizard by the name of Roger Wilkins used to port them sweet.

80 mph was the top speed we got on cemetry straight Kaikohe.

We used to lengthen the swing arm so they handled a bit better on the corners. No filter box and fitted Z bars to reduce the drag.

In fact its really me on my avater. Ha ha.

LOL @ Tony!

**tommorth** · 22nd July 2010, 20:57

did they even bother putting holes in a ag crank ?? Where will this great race be held ? I'd like to watch.
Used to have an old cz that we modifyed a bit cut all the gaurds down ,fited a trumpet to carb, enlarged the ports and filed some of the piston skirt , removed lots of extra bits longer shocks , replaced the wireing used it to race a mates kt250 round flat track we had in a paddock .We also used to put a little meths in our fuel made the bike s sound awsome plus big back fires on the over run .None of it was very technical but when your 15 and live in a small town theres not much else to do

maybe there could be a under 100cc race seperate class for 2t and 4t no bikes based on rm/cr/kx80s etc farm trail type only any mods possible ... would be a good laugh
say b loop at thunder or even just the top paddock

pick is before it got xr shocks

**honda_power** · 22nd July 2010, 21:12

Originally Posted by cheese

From memory I think that you can add a MX electrical system to make them liven up too. Open the air box and see if you could fit a YZ piston.

There was a crazy mod people were doing a few years back where you drilled two holes in the back of teh piston. No idea what that was about...

i always thought that just improved the lubrication, im pretty sure the instructions that came with a wiseco piston said you can drill holes

Originally Posted by Reckless

OH shit sorry to hijack your thread mate I must drink less and go to bed LOL!!!

no worries at all mate, a good read

Originally Posted by WuZards-Eugene

I put a 1mm oversize piston and had the barrel bored out, richened the mixture a little and it hauls pretty good for an AG. Still has all the bottom end, but when it reaches mid to top end it sort of explodes into life alot like hitting a power band. Changed the gearing a bit as well, and managed to get 130kph out of it (revving like shit). Still has all the fangles on it.

stock ones still have a 'powerband though. good to see someone using a ag as something other than a farm bike, looks like you've had some good times on yours, thanks for posting

Originally Posted by cave weta

Dont file or drill anything!! you can so easily make it worse.
The best mods are the YZ exhaust, then put two cylinder base gaskets on to it and machine the head by 80-90 thou. that raises the ports.
If you are rebuilding the bottom end then stuff the crank. Force cork or balsa plugs into the crank balancing holes to increase primary compression.
Give it a CDI unit instead of points and a 28mm mikuni carbie.

Do all this and my CT90 will still beat you! Come summertime.....

The Over The Top Adventures

World's Fastest Postie Bike
will amaze and astound you......

a stripped and streamlined postie bike with rearsets and clipons, a 149cc big bore kit, tuned exhaust and a 36mm Mikuni running methanol, 12,500 rpm and 112Db!!!

photos coming soon to a computer near you!

never heard of stuffing cork into a crank?! thats the kind of mods we're after though... free ones

. Some good advice there, thanks, have to keep an eye out for a wrecked 80's yz125.

For a cdi would any mx bike do? an old yz80 or something?

I want to see these pics, even better a vid of it running. Race is on, fuck a drag, slater mx park

Originally Posted by carver

oh, the big end is pretty fucked, and who wants to balance a crank on a ag?

pretty fucked is an understatement. who the fuck is that in your pic?

Originally Posted by tommorth

did they even bother putting holes in a ag crank ?? Where will this great race be held ? I'd like to watch.
Used to have an old cz that we modifyed a bit cut all the gaurds down ,fited a trumpet to carb, enlarged the ports and filed some of the piston skirt , removed lots of extra bits longer shocks , replaced the wireing used it to race a mates kt250 round flat track we had in a paddock .We also used to put a little meths in our fuel made the bike s sound awsome plus big back fires on the over run .None of it was very technical but when your 15 and live in a small town theres not much else to do

maybe there could be a under 100cc race seperate class for 2t and 4t no bikes based on rm/cr/kx80s etc farm trail type only any mods possible ... would be a good laugh
say b loop at thunder or even just the top paddock

pick is before it got xr shocks

its on!

**cave weta** · 22nd July 2010, 21:40

[QUOTE=
I want to see these pics, even better a vid of it running. Race is on, fuck a drag, slater mx park

[/QUOTE]

with clip ons and rear sets!!!!????
Im thinking Canal East Road- Ngatea, Hauraki Plains

**NordieBoy** · 22nd July 2010, 21:57

I've posted this before but it's a good one...

**CRF119** · 22nd July 2010, 22:32

They take alot of abuse i lernt on a CT125 that we got for free and i was jumping 20ft to flat before dad thought it was a good idea to buy me a mx bike and save his farm bike lol.

you need a reed block from a 125 with some carbon pettles and then also mod that so it flows even more.

Run Nitro methane in the fuel mix at 5% should give it a good kick

**Expert** · 23rd July 2010, 10:45

[QUOTE=cave weta;1129817447]Dont file or drill anything!! you can so easily make it worse.
The best mods are the YZ exhaust, then put two cylinder base gaskets on to it and machine the head by 80-90 thou. that raises the ports.
If you are rebuilding the bottom end then stuff the crank. Force cork or balsa plugs into the crank balancing holes to increase primary compression.
Give it a CDI unit instead of points and a 28mm mikuni carbie.

Do all this and my CT90 will still beat you! Come summertime.....

The Over The Top Adventures

World's Fastest Postie Bike
will amaze and astound you......

a stripped and streamlined postie bike with rearsets and clipons, a 149cc big bore kit, tuned

exhaust and a 36mm Mikuni running methanol, 12,500 rpm and 112Db!!!

Very slow port timing on those ag barrels, i'd go for a 2mm alumininium spacer under the barrel and a corresponding amount off the top of the barrel and raise the exhaust port 1-2mm. and all the other mods mentioned. find a expansion chamber off a kx80 or similar and bodge that on too.
This is backyard buchery at its worst but you can't fail to make those ags rev harder.

**F5 Dave** · 23rd July 2010, 12:29

Originally Posted by cheese

I think that there is heaps of mods for AG100s as they are used as bucket racers.

Wash yer mouth out with soap - I've raced buckets for well over 20 years & I can't ever remember seeing an AG engined bike. Too crap.

PS: KT100 is the std fare kart engine, not AG100 & they are a totally different beast.

Just ride the silly thing, any more power will make the gearbox ratios too far apart & handling rubbish.