Yamaha KT-100 Info Please

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BRMKart27

New member
Hello all, I have been running a Yamaha for my entire karting career but would like to know more from all of you guru's! I recently ran my "new" engine from what I was told but it really feels down on power from my old Adkins engine. I am going to throw a carb kit at it and pulled the head to paint the outside rib. I did notice some black build up around the rim and leading up towards the plug... was wondering if this is normal? Or do I have an issue here? Also does this head have a front or back? It looks as if both sides have been painted with engine builders names at one point and I didn't know if it could be flipped front to back? Thanks!! Colin
 
BRMKart27 said:
Hello all, I have been running a Yamaha for my entire karting career but would like to know more from all of you guru's! I recently ran my "new" engine from what I was told but it really feels down on power from my old Adkins engine. I am going to throw a carb kit at it and pulled the head to paint the outside rib. I did notice some black build up around the rim and leading up towards the plug... was wondering if this is normal? Or do I have an issue here? Also does this head have a front or back? It looks as if both sides have been painted with engine builders names at one point and I didn't know if it could be flipped front to back? Thanks!! Colin
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Adkins does build some cheater motors. If you had one of those it would be fast.

Most important with the KT is the compression pressure. Get a good gauge, (Pep Boys does not sell one) and test it often. A good reading would be 160 psi. Check the main bearings. Use a dial indicator and a magnetic base to hold it. See if the crankshaft will go up and down. Any more than .001 is bad. When you say new, are we talking out-of-the-box new or new to you? Has the engine been blueprinted? What exhaust system are you using? What is the clutch RPM coming out of a slow corner?
Checked the run out of the crankshaft. The closer to zero the better.

What class do you run and what fuel and oil do you use?

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
Hey Al, thanks for the response. The engine appeared to be new as in rebuild by a local kart shop. I actually had to take the head off before I ran it the first time because I noticed a small metal shaving and wanted to inspect... The piston was brand new when I checked it out and it appeared to have cross hatching in the cylinder. I have checked the crank with a magnetic indicator and all was fine. It has a bit of in and out play but nothing up and down. I am using a pipe set up but I'm not sure what one it is. The clutch is a new out of the box 3 disc dry Tomar that I've had great luck with before. I need more track time to get that set properly but it seemed like a long time to get on the clutch. I was running a 105 octane with burris hi rev oil. Does the head (the very top plate) have a torque sequence? What about a torque spec?
 
Also as far as the Adkins motor... I had an old kt that I sent them years ago... I asked them to build it legally and it was a beast. You could hammer that thing and lay 10 feet of black rubber marks haha... this one just doesn't seem to have the snap that one did... could be my clutch... could be I'm older.. fatter.. and took 4 years off from karting haha
 
BRMKart,

There are many possible explanations:

- The engine may simply not be "as good" as your other one. This could be due to the engine builder, or maybe not. Your current engine may have been set up absolutely correctly, but just be slower. (all engines are not created equal).

- Maybe the carb is not as good. Try running the carb from your Adkins engine on the new engine.

- There are almost unlimited reasons why one engine could be faster than another (quite often even if built by the exact same engine builder to the same specs).

- And of course, it's possible your current engine was built by someone that doesn't have the experience or tricks that Adkins has.

PM
 
You didn't mention if you had checked the compression. Very important!!! Oh and by the way, a good gauge is going to cost about $100 or more.

At what rpm is the clutch slipping coming out of the corners? With a pipe, it needs to be at about 10,300 RPM. The brand doesn't matter, unless it's completely different from the normal KT pipe.

I'm not familiar with Burris hi rev oil. If it's a synthetic blend, I wouldn't recommend it for the KT. Burris markets a good castor oil.

You don't need that much octane in a KT.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
I have not checked the compression yet but will do once I install the head again. As I mentioned I need more track time to get these answers I have not run the kart all year and only three times last fall. Pete, is there a front to back with the head? Is it able to be rotated 180 degrees or am I missing something here?
 
I was told by Adkins years ago to mix 50% of the high rev synthetic with burris castor... it's what I've done since not sure if that will cause any issues but I won a lot of heats and races and some local track records with that engine and those oils. What do you guys suggest for octane?
 
If you get to the point where you can tune that engine right to the leanest point possible, the synthetic will cook and clog the rings up in the ring groove. At this point in your learning curve you may not have to worry about that happening. If you get an EGT, (exhaust gas temperature gauge) you will be able to tune right to the edge, but without it, you're kind of running blind. Some will say that's an exaggeration. Some will say I don't know what I'm talking about. Trust me, I do know what I'm talking about.

A guy that I trained on the EGT was offered some sponsorship from a top Southern California engine builder. One day, at an IKF race, his engine builder came over and asked to check his plug. The builder pulled the plug and when he looked at it his eyebrows went up an inch. "This is way too lean" he exclaimed. Really? Well my friend had fast time and won his class so it couldn't have been all that lean. And this race was in Southern California where the competition is really stiff. My friend won the regional championship in the KT class in his second and third year karting.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
Do not think it matters which way the head goes. I would try to keep it the same , if not possible I think I put the Yamaha logo in the front.
None of my engines currently have the head off .
 
BRMKart27 said:
Pete, is there a front to back with the head? Is it able to be rotated 180 degrees or am I missing something here?
Click to expand...

It typically should no matter.

"Usually", the back of the cylinder head may show some oil spots which come from slight leakage of the coupling of the header to the exhaust pipe, and/or possibly from chain lube. That's one way you may be able to identify which direction the head was oriented originally.

PM
 
I took a hacksaw and put a small cut (1/16") on the back of my Yammi heads before removing them from the jug. You only have one fin on the exhaust side to cut and the head. Now you can line up the head and jug everytime.
 
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