Yamaha Banshee

Creature Feature

Some blokes will do anything to get that horsepower figure where they want it and they don't care how much they spend. Jim Kokla must be one of those blokes. The Sydney electrician gained an interest in quads through his mate Toli Alevras, another man with a passion for going fast on ATVs, and from there they spent quite a lot of moola on this wild looking Banshee.

But it didn't happen overnight. First it was just a lazy bit of trail riding at Stockton dunes on a stock Yamaha Banshee that Jim had bought from Toli. Jim would be out there mucking around with his mate, doing all the crazy stuff quad riders do, but one evening he got home and it was… different. He had this odd idea. He couldn't get it out of his head, which is where the speed bug must have bitten him. What if they spent a bit of money on the Banshee to get that horsepower figure up? Like, way up!

And of course Jim had tapped into a gold mine. The Yamaha Banshee is possibly the most popular sports ATV ever built. What's more, being popular means that there's a whole warehouse, in fact dozens of warehouses full of go-fast parts for the Banshee, everything from billet stroker-cranks and clutch mods to intake manifolds, exotic porting specifications, custom built heads, and 'Cheetah' kits that can boost engine capacity from 400 to an unbelievable 650cc. You could build a Cheetah engine that runs on pump fuel or even methanol if that's what you're into.

And it doesn't take much effort to find all of this stuff. Fire up your computer, type in 'Patriot Racing' or 'Ohton' or 'Trinity Racing' for example, and it's like the doors to that warehouse suddenly swing open. You could go mad in there, stark raving mad with all that stuff - or go broke buying all the crazy gear that's available for Banshees

WHERE TO START
They didn't want to go broke but Toli and Jim did end up spending a "little more than expected". In the final wash-up the Banshee ripped about $23,000 out of the bank account.

And here's where the money went. Reflecting the widely held view that the most direct route to more horsepower is more cubic capacity, the first purchase was Trinity Racing's 421cc power-valve kit, supplied by Explosive Racing in Sydney. The kit comprised a 4mm stroker-crank, 20cc low comp 'domes' (inserts that vary compression ratio), and Wiseco pistons. Getting the engine out, rebuilt and back in the frame took abut two days and nights, and at that stage Jim had to admit that he didn't really know what was letting himself in for. But he was soon to find out.

First test for the powered-up Banshee involved a three hour drive to Stockton beach, then gentle riding while the boys worked their way through two tanks of gas for the run-in period. Then they gave it some stick. "I couldn't believe the power this engine was dishing out," said Jim. "That part of it was fantastic, but with a standard swingarm the Yamaha was uncontrollable. It was downright dangerous! It'd lift the front wheels, even in top gear at 100kph plus".

Somehow they managed to get through the test day with no dramas, or at least that's what they thought. When they got the Yamaha home and had a closer look at the engine there was a nasty surprise waiting for them. A compression test revealed that compression was way too low, so they looked even closer. With the top-end removed they discovered that the engine had practically lunched itself in what Jim later described as "tuning issues". It was close to destruction. Right then, Jim had a better idea of the tricks and traps in putting together high horsepower engines. It wasn't a good day.

But all was not lost. After two more rebuilds there was still a question mark over the reliability of the Cheetah engine so Jim and Toli decided to play it safe and tune the bugger on a dyno. Their persistence paid off. Several successful runs at Stockton allowed them to relax a little; then it was time to put a bit more effort into the running gear.

From Eyeball Engineering they purchased a plus-4" swingarm which helped tame the rampant Banshee and make it rideable. There was still plenty of power there but at least the beast wouldn't go off and do its own thing like drug-crazed water buffalo. The suspension was still stock while were writing this but the rubber had been well and truly sorted. The last time we saw this wild Banshee it had 10-inch SKAT-TRAKS up front and 22-inch SKAT-TRAK Haulers (with 11 paddles each on the rear).

How does Jim feel now about his brave experiment in mail-order speed. "I guess we bit off a bit more than we could chew at first," he said, "but we've worked out all the problems and I'm really stoked with the Yamaha's performance. Now I own a bike which can be used on the dunes for recreational riding as well as for drag racing. To this day, we're surprised on how well this bike runs and performs on these two playing fields, so yeah, it was worth every cent".