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Old 06-12-2012, 11:19 PM
mkmk4 mkmk4 is offline
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Default How do you start a Yamaha kt100

I just got a go kart with a Yamaha kt100 engine. There is a 1/4 Allen key bit that connects to the crank that turns it over but nothing can turn it fast enought. (tried an electric torque gun)
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Old 06-12-2012, 11:22 PM
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Electric toque guns are far too slow

A drill maybe

Or push start it
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Old 06-12-2012, 11:38 PM
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cant push start because of the clutch
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Old 06-12-2012, 11:39 PM
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put it in nuetral, push it as fast as you can, jump in and throw it in 1st. or get a friend to push you.
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Old 06-13-2012, 12:01 AM
mkmk4 mkmk4 is offline
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Not a shifter cart. Has a 1/2 inch alen key port comming off the the crank to turn over the engine.
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Old 06-13-2012, 04:47 AM
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At a guess its meant to be started with one of these

http://www.cometkartsales.com/store/...manstarter.jpg

As far as I know they are quite expensive though so you might want to try a more powerful drill or something with a half inch allen key bit.
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Old 06-13-2012, 09:18 AM
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jman231994 is right, most guys use kart starters like this video:



You can sometimes find used kart starters selling in the $100 range like this one on ebay: http://www.ebay.com/itm/KT-100-start...7870b1&vxp=mtr

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Or you could build a DIY kart starter (using a car starter motor) like this one I used on my kart:
(It just had an old pair of jumper cables hooked up to my trucks battery, but you could instal a small motorcycle or riding mower battery on the kartstarter)



Or could even use an electric drill with an Allen bit, but dont use an impact gun, you could end up breaking the end of your crankshaft.
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Old 06-13-2012, 02:04 PM
mkmk4 mkmk4 is offline
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How did you connect an alen key bit to the starter :s can you post more pictures of it so I can build one. (I have a ford starter in my garage)
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Old 06-13-2012, 04:15 PM
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It's only a 100cc

Just cut the end of the right angle off the Allen key and screw it into the chuck of your drill
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Old 06-13-2012, 04:45 PM
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I didnt build that DIY kart starter in my pic, I just borrowed it from a buddy until I found a used Burris kart starter I bought for $100. The DIY kart starter in my pic above was made from one of the 12-volt ford starters the 272/292/312cid engines used in the mid to late 1950's. Those starter motors work best as DIY kart starters because they have a long output shaft.
They look like the pic at this link:http://www.griggslawnandtractor.com/...1a3aae5f_m.JPG


The tricky part to building your own kart starter is they really need some type of one-way bearing/clutch or ratcheting device installed in the shaft for safety reasons. Otherwise if you rev the engine (before pulling the starter out) you'll end up spinning the starters Armature too fast where it could explode/seize up. All factory made kart starters come with this one-way bearing or ratchet feature.

Comet sells a part called:
"Starter Ratchet Driver - 11" Long, Specify .500 or .510 starter shaft size and Right Hand or Left Hand rotation starter"
about halfway down the page at this link: http://www.cometkartsales.com/store/start/start.htm
It has a ratcheting feature built in. You'd want a Right-hand model for a KT100 kart. (the left hand model would just be needed for the left engine of a dual engine kart) You'd need to measure the shaft diamiter of your starter to make sure that part would fit...

Edit:
Another issue with using many automotive starters is they spin the wrong direction for a Right-hand type kart starter, but you can usually make them spin the other direction by simply reversing the brushes. This usually requires extending the brushes wire leads so they'll be long enough to reach over to the opposite sides.
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Old 06-14-2012, 12:18 PM
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Hey I was thinking a you could probably save some money on your DIY kart starter by using a 3/8" drive ratcheting adaptor as your one-way clutch. All you'd have to do is grind the end of the starters output shaft to a 3/8" square, and then tack weld the adaptor so it wouldnt fall off.



Then you could just buy whatever size 3/8" drive Allen head socket that fit your crank bolt.



Plus use any length 3/8" drive extension you might need:

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Old 06-14-2012, 12:48 PM
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Hey if your in the Seattle area, heres a kart starter for $50: http://seattle.craigslist.org/see/for/3025826671.html
That's a left hand model but you could reverse the brushes to make it spin the other way...

If you dont live near Seattle, post your closest large town and maybe we could locate a good deal on a used kart starter in your area.
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Old 06-14-2012, 10:35 PM
mkmk4 mkmk4 is offline
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I started it with a drill seemed to work fine for now might want to build my own using anders idea. And I live in Toronto.
Problem now is once you give it gas the 1/2 bit that goes to the crank unscrews itself and falls off (the back tires never move unless the kart is on stands) no clue how to fix.


Engine runs great tho does anyone know what gasil mix I should use I started with 25:1 but it's giving blue smoke so I guess it needs more gas

Btw what I did to start it was use a hammer drill with the hammer setting off turned over easily

Btw thanks everyone for the tremendous help
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Old 06-15-2012, 12:04 AM
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How long did it run for? It would be smokey while its still cold, however 25:1 is probably a bit rich for a racing engine. For reliability I would stick with 25:1 or 30:1. But thats just me.
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Old 06-15-2012, 08:05 AM
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Using your drill (with the hammer feature turned off) Is fine. If you left the hammer feature switched on, or tried to use an Impact gun, you could end up breaking the crank snout off.

That bolt in your crank is unscrewing because you need some type of one-way clutch like I sugested before.
If that bolt hadn't unscrewed when you reved the engine, your drill would have started spinning at very high speeds and probably broke your wrist and/or fingers. Lots of guys (including me) have have had wrist injuries trying to use drills or kart starters that dont have some type of one-way clutch device installed.

You could cut the drive end of a 3/8" extension off, and then grind the extensions end to a triangle shape so it would fit/lock into the chuck of any 3/8 drill. Then simply plug in a 3/8" drive ratcheting adaptor and Allen head socket like my pics above. The ratcheting adaptor would work fine as your one-way clutch, If you shop around you could probably find one for under $20.

Here's a link to a used Snap-on brand adaptor selling on ebayca: http://www.ebay.ca/itm/Vintage-Snap-...item564ac2c1b1

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Most guys use a 20:1 premix ratio with KT100 engines. Quite a few report this engine makes even more power using a 16:1 premix ratio because it increases ring-seal. If you use less oil than a 20:1 ratio, there's a very good chance you'll seize your engine. Make sure you use 2-cycle premix oil, not just regular motor oil.
Its completely normal for KT100 engines to smoke a lot, so get used to it.
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Old 06-15-2012, 02:02 PM
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Alright I get what you're saying, but now I don't know how to stop the crank from moving so I can screw that bit back in tightly. And I made sure to pull the drill out fast once it started to turn over so it didn't jerk my arm much. Also Right now I'm using normal 2 stroke oil, could that damage the engine? Should I drain the gas tank until I get premium oil?
And the drill turns at 4000rpm so I think I'm safe as long as I don't rev it before pullin it out.
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Old 06-15-2012, 08:59 PM
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What brand of 2-stroke oil did you use?

If you feed a few inches of clean rope down through the spark plug hole, It'll stop the piston from moving up so you can tighten that bolt.
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Old 06-16-2012, 02:07 PM
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Actually I am using premium 2 stroke oil just checked :p. and nomater how hard I tighten that bit (vice grip on the crank) still unscrews itself :s I have to make it able to spin freely once the engine turns over
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Old 06-27-2012, 03:29 AM
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One way to start it is to get rid of the clutch (you'll need a sprocket) and connect it as direct drive. Then you can either push start it or put it on a stand and use a strap to pull the rear wheels around.

That's how we did it before clutches.

To push start:
Stand on the engine side, right hand on the stearing wheel, Pickup the kart by the read crash bar, run a couple of steps then drop it and keep pushing by moving your left hand on the seat back. When the engine pops step into the seat with you left foot and get your right foot to the throttle. If it goes, sit down and drive. Or just get someone else to push.

A car starter motor, usually from a Toyota Camrey is what is used mostly these days. Starter motors have an overrun mechanism so that when the engine starts the bolt won't get unscrewed and your arm doesn't get ripped off.

If you tighten the bolt up too tight all you will do is break your drill or your arm when the engine fires, and you'll never get the bolt off again because you tightened it too much.
Svend.
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Old 07-01-2012, 02:57 AM
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Quote:
Originally Posted by anderkart View Post
What brand of 2-stroke oil did you use?

If you feed a few inches of clean rope down through the spark plug hole, It'll stop the piston from moving up so you can tighten that bolt.
I have seen quite alot of pinched rings using that method, well two actually. The rope can push the piston ring groove closed. Best to get a proper piston stop which screws in the plug hole and dont over do it on the torque, as you can get a lot of leverage doing damage there..

I hope that saves a few KT's..and some cash and grief...
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