Stock appearing kt100

T

Twinenginekart

Member
What's everyone fav way to build a stock appearing kt100

I got a custmor that wants one built all I have every built is legal ones
And yes I know there is better engines to use but it's a kt100 only class
On gas I had some links saved to old fourm but I can't get to them
And this is mild build
Thanks jerry
 
Buying a new head, one that has not been cut, is the first thing I would do. Then I would mill the barrel down to get seven cc in the combustion chamber. That's without the spark plug hole included. Then I would raise the exhaust port 5 degrees and cut eyebrows to either side.

I would then have more counterweight put in the crank. Atkins, or High Rev in California, can do that for you If you can get a good crankshaft, one that has no run out, that would be ideal. Put a colder plug in it, you may even have to go to a retracted gap plug. Cut the piston skirt just like in a stocker.

Open the carb fuel passages to feed it. Bore the carb out as much as possible.

If you can retard the timing, that would also be good. Run 110 octane fuel.
 
Someone was selling a reed cylinder and case that i had (stock appearing), id look for it, add biggest piston i could fit, leave cylinder at stock height, increase blowdown to 30-32 %, set head to around 7-8cc's..

I'd put a iame rod in it.. if on gas, i may not squeeze the head as much.. I wouldn't worry about adding weight to crank... the shape of the head is important,,, needs to be cut for power band you intend to run engine..

Bottom line, you'll have a 1500-2000.00 engine worth 500.00... been there done that...
 
Put a TT25 crank in it to stroke it. Cut piston skirt on intake side and eyebrow exhaust. Make sure all cases and crank alignment are true.
 
jack burroughs said:
It can be done using a shorter rod., and no spacer, if you can find one, haven't been made for a while.
Click to expand...
I wonder about that Jack, a longer stroke with a shorter rod, one might defeat the purpose of the other.
Seems like I've heard of people cutting too much off the barrel or cases and having to use a thicker spacer. And that's in stock class. I could be wrong. I would check with the track tech person.
And, depending on the stroke increase, if the piston doesn't go too high, it might eliminate the need to cut the top of the barrel. It would be interesting to see.
 
Cut eyebrows both sides, easier said than done, to do it right. I will share with you though , be careful you don't get too wide and break out into the area where you access the cylinder studs. The simplest way for you to boost the compression will be like Al said , get an uncut stock head, but here's where we differ. It's much easier to set the head up in a lathe and cut the .050 relief off of it rather than setting up the cylinder on a rotary table on a mill and machining the sleeve and then the alloy to retain the head gasket in place. No proven performance difference done either way. With the head at zero relief you will use the appropriate gasket thickness to get about .035 squish clearance, gasket thickness will depend on whether the piston is in the hole some or out. The small stock combustion chamber will give you about 7.5 cc's not including spark plug volume, plenty high to wake it up. You will want to back the timing up with the higher compression. Best way to know where to move it would be to put a dial indicator in the plughole, roll the piston to .136 before TDC and make a mark on the rotor right at the edge of the top coil leg, that's the fire mark. The you can take the key out of the crank, slip the rotor back on lining that fire mark back up but with the piston at about .100 BTDC, stock timing will lead to some pretty heavy detonation, If your not gonna turn it past 14,000 or so you can back it up a little more. Carb " bore it as big as you can" well the throttle bore will break out into the fuel chamber at 1.125, a shutter out of a wb20 at 1.100 works real well, then a venturi cut to around 1.025 will leave enough of a V. to T.B. ratio to create a good signal for the high side circuit. Carb alone can make a huge difference in performance and if done optimally should flow 90 CFM compared to 65 CFM out of the stock WB3A. You need to bore the alloy and phenolic as well as match the port to throttle bore size. You'll be surprised how strong it will be if your used to stockers, and before your done you'll understand why a real one cost so much. Jon
 
Carb wise don't waste your time messing with it. Just buy that really nice on that Buller sells. I have one and it is awesome. As far as timing goes I just left mine stock. I ran the dog crap out of mine with no issues.
 
All above are good things to do. Bottom line is don't over do it. The KT100 doesn't need a big whole bunch of changes to make her scream. All of my S/A's are on Alky but, my twin is currently 2 stock Yammi's on gas (What a ride!). EC was wanting me to try his version of the WB3A on gas but never got to due to his passing (RIP bud). Stroking is possible but you will have to watch your port timing. Ignition timing, never had to mess with mine. Internal reeds???? IDK. Haven't come across one of those yet but, still looking............

I've run and had,
Russell S/A
Appco S/A
Buller S/A
Turner S/A
My own S/A

Brian #89
 
Oh, and another thing. Leave the stock expansion chambers to the stock engines. They are designed for the stock port timing and fuel consumption. When you start opening up the KT, you will need to move to another pipe.

More fuel in = more exhaust out.

Brian #89
 
It might be easier to cut the head, but you gain performance benefits by cutting the barrel. The barrel has a steel liner which does not transfer heat as efficiently as the aluminum in the head. Leave the aluminum in the head to get rid of heat. It's how all the European engines do it. Every European engine that I have ever seen, the piston comes to the top of the barrel, not so with the KT. With a 7 cc combustion chamber, there's going to be extra heat, the aluminum head is much more efficient at getting rid of heat than the steel barrel. I have been telling people this since the 90s and still there is opposition. Go to a little extra trouble, do it right, there are significant benefits in doing it this way.

Almost everybody that blueprints the KT has an expanding mandrel to hold the barrel while they trim the bottom and top to make them parallel, you use the same expanding mandrel to trim the barrel as I've indicated. There are shops that advertise blueprinting but they don't do the machine work themselves. They send it to people like Pete Muller, who is very good at it, and then they just assemble the machined engine. Those shops may not have an expanding mandrel.

Good luck on your S/a KT.
 
When you cut the barrel you lose compressible volume.. I don't build a engine this way.. your most gains will come from a big bore, porting, head volume., I do have a few short iame rods around if needed.. hidden reeds will also wake it up.... someone was selling cylinder and case's i owned, check the archives problem with using short rod, with a stroker, (no spacer, stock appearing ), the skirts will shank out on the crank, unless they are trimmed, which then free ports, I guess someone needs to build one, to figure this stuff out.... just sayin...

Just keep in mind you'll have a engine that costs 4-5x's what you could ever hope to get for it... it might be better to look for a different class to run... even if you can do all the work yourself...
 
Al, do you have any data to support your assumption that cutting the cylinder instead of the head leads to " significant performance benefits"? Or is your assumption just based on observation of Italian motors? Your all about the data , have you done the testing? If so, How much better does it run ? Mike he's already got the motor sold so he's just got to figure out how much to ask for it. lol Jon
 
Jon, any motor is a crap shoot, but with a kt, its a deal of diminishing returns... its only worth what you can get for it.. at the perfect place at the perfect time.. LOL.....

Some assumptions are built on experience or lack of.... I got to ask myself, if that much alum removed affects heat dissipation..??? if it does, I wonder how much compressible volume loss effect performance?? when cutting barrel? Ill cut head,,, different builders, different ideas.... take you pick??

Jon, did you get that case and cylinder?? its pretty cool....
 
alvin l nunley said:
Every European engine that I have ever seen, the piston comes to the top of the barrel, not so with the KT.
Click to expand...

Don't know when the last time you looked at a KT was but, all the pistons on my stockers come right to the top of the cylinder. My S/A's do as well and I might have one that the piston is above the cylinder just a little bit. That one has a special head.

Brian #89
 
Pete Passalaqua tried to talk me into letting him put a Leopard liner in a KT cylinder...would make for an interesting stock appearing. :)
 
You must log in or register to reply here.
Back
Top