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Truenotch's dirt bike powered grass kart


Truenotch

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Owning a gokart has been a bit of a life long dream for me, so when 10-5 bought his new house and suggested we build karts to skid around on the paddock I was excited.

 

After a bit of mucking around thinking about building one I ended up searching trademe and found a mad little creation. I happened to be sitting next to VG's mad 750cc kart project at the time and all the boys in Whakatane were in support of me buying the one I'd found, so I negotiated a price with the advertiser and god Lee to pick it up from Havelock North for me.
 

400286652.jpg

 

It's powered by a 185cc 2 stroke dirt bike engine and 5 speed box. It's a Suzuki and the pull start leads me to believe it's probably from an Ag bike - Probably a TS185.

 

This how it looked when I picked it up:

IMG_0429.jpg

 

There are a few things to do on it... The engine wasn't bolted in properly, it only had one bolt at the front as the rear one didn't even have a nut. The seat needs to be mounted and the shifter was mounted on a ball joint which meant the shifter flopped around in all directions instead of just forwards and backwards. I'll be changing the direction of the shifter too since it was set up for 1 back and 4 forward - not very racecar! The clutch doesn't seem to disengage either, so I'll need to do some research on these engines and boxes to figure out how to get that going.

 

It also needs some form of brake caliper to work with the rotor that's on there, a better steering wheel and some work on the steering setup at the front. So I need to do those things, mount the fuel tank, add an airbox and filter and we're away skidding.

I had a play with it today and chopped a few things off.

 

Here's where it's at:

IMG_0439.jpg

Need to have this finished in a month for Paddock Bash!

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I pulled a few bits off the engine today for a closer look. After removing the self-mix pump cover I got a surprise - turns out it's a Yamaha, not a Suzuki as advertised. I'm pretty happy about this because Yamaha's are the shit! It also means that it might end up on the little Yamaha YB50 that I have sitting at Matangi.... After a healthy dose of grass skids of course.

 

I'm pretty sure it's a DT175, which appears to be a bit more performance oriented than a TS185 Suzuki. An added bonus is that one of my customers is a Yamaha dealer, so I have a good parts source and knowledge base if needed.

 

Under the clutch cover it's all nice and clean. I gave the clutch plates a wee wiggle and they don't seem to be stuck together, so I think the clutch should work OK after it's done a bit of work.

 

I think the sticky clutch might be due to being a wet setup. I've cable tied it on which is a common trick and apparently it's also useful to run it up in 6th gear on a stand until the oil gets nice and hot, then it should free up.

 

IMG_0440.jpg

 

Looks reasonable under the pull start cover too. The CDI etc all seems to be in decent condition.

 

IMG_0441.jpg

 

Had a look through the exhaust port to get an idea of what the cylinder condition is like - there's a bit of scoring on the cylinder wall and a bit on the piston, but I've seen worse. I might pull it apart and give the cylinder and crank case a good clean out to make sure it's going to be all good.

 

Next up is giving everything a good clean and then I can work on putting it back together and sorting out the steering geometry.

Little bit of inspiration:

http://youtu.be/Cv43JfE9_eg

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Does anyone know how the fuel is pumped from the tank to the carb on most karts? I'm keen for a plastic tank between my legs, but this engine is designed for gravity feed. 

 

I think there are axle mounted pumps that you can get but I can't find much info on them. This kart already has a cam screwed onto the axle, so I can probably fit one easily. 

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They get powered by either vacuum from the inlet manifold or you can also use crank case pressure. My engine has a clear tube coming out of the crank case already that I assume will work for one of these pumps. On the 4stroke karts that run GX200's in the states they tap a fitting into the valve cover and add pressure from there. 

 

I think they'll work with either pressure or vacuum. 

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i run something like that on my shifter kart (125cc 2 stroke) runs off crank case pressure works good pumps a shit ton of fuel through, make sure you run a return line to the tank inbetween the pump and the carb or your airbox will full with  fuel. 

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Ooh, that'll be the one! I was drawing blanks on the pullstart when googling for information.That appears to be exactly what it is!

 

I've been mucking around trying to get the steering right. Got a few ideas from race kart steering arms and ended up making very long arms and welding them on. The old ones were only about 50mm long and the new ones are more like 150mm. I've made it with a lot less ackerman than the "suggested" method of pointing at the centre of the axle  - this is because most of the race karts I've looked at don't have much ackerman.
IMG_0442.jpg

 

It turns this way:
IMG_0445.jpg

 

And that way:
IMG_0444.jpg
 

Rounded the arms off and gave them a lick of paint to stop them from rusting:
IMG_0446.jpg
IMG_0447.jpg

 

Also cleaned and painted the motor mount area:
IMG_0448.jpg

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