90's/vintage restoration project in Phoenix

… moving my restoration project to this thread…

I am trying to restore a few engines and karts from 90s and early 2000s.

Yamaha kt100
Rotax DSC Formula A
Parilla Leopard TAG

Roller frames:
Top Kart (small tubing)
Top Kart (larger tubing)

I raced for several years but never got to fully learn how to work on the engines and carburetors. My engine builder passed away and I want to honor him by restoring these karts (maybe even race in a vintage class if they do it here in Phoenix)

I’m a noob in terms of working on the engines so thank you in advance for your patience and help!

Question about the KT100 disassembly:

I have a long crank (for a wet clutch previously). I run direct drive so I think they put some spacer on the shaft. I have a gear puller but it isn’t long enough to reach the gear. Any suggestions on how to remove it?

I already removed the starter nut but can’t remove the spacer or the gear.

Try using a torch to heat the ring and gear to expand the metal enough to break free of the shaft and slide off. Don’t over do it or you may scorch the seals.

It’s going to take a puller of some sort. Drops mic

Thanks everyone, I picked up a gear puller set and got it off. It was just stuck on there well. Interestingly, the gear is friction fit only with no key.

Not sure what the gear was from originally.

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Please bear with me as I’m just a bit paranoid of breaking something along the way…

On the Rotax, do I just need to use a piston stopper and wrench off the rotor?

I am going to go out on a limb here and so, NO! Rotors are usually keyed to keep the timing correct with the shaft. Try using the puller tool again.

Thanks Greg. I did try again tonight with the gear puller but it wouldn’t budge and the puller kept slipping off.

I started removing the rest of the crankcase bolts so maybe I can at least take a look at the rod and crank after splitting it open.

Here is the rod and crank for the Yamaha. I think it looks ok but let me know if anyone thinks otherwise.

I’d avoid using a stopper and try an impact with the puller. Sometimes the rotor is keyed, sometimes they are just run on the taper.

The latter if done right (lapping compound) can be more reliable in a direct drive than relying on the woodruff key to hold the rotor.

Well I couldn’t remove the rotor off the Rotax. With the puller, it even cracked some chunks of the rotor off while trying. It wouldn’t budge.

I think I am just going to try it as is. It should only have an hour of use.

Since I have forgotten all the finer details over the last 25+ years, what fuel/oil ratio should I use? Also, what is the max rpm of the DSC and what temps should I be keeping the CHT?

Oh, also, what oil do you guys recommend nowadays?

Maxima 927 at 16:1 should be safe enough. If there’s chips knocked off the rotor though I might be concerned. DSC will turn 19,000+ if you let it.

CHT, I think 160C, but don’t quote me.

In simpler terms, richen the high jet until it starts four stroking at the end of the longest straight, then take the high jet in about 1/8 of a turn in from there. This is not optimal, but safe.

Have you tried hitting the end of puller with a hammer? Sometimes the shock will loosen the hub.

I did use an impact wrench on the puller. That’s when the rotor got chipped when the puller fingers slipped off. I just used a harbor freight puller. I don’t have the nice puller John posted.

Oh, you’ll need the motoplat puller for sure. It’s designed to be pulled by the threads inside it.

I can try. Does anyone know what diameter and thread pitch is needed for this particular motoplat?

27mm dia.x11/4 mm pitch . Right hand thread. That Motoplat ignition was standard on all? European 100cc engines for maybe 15 years until the demise of Motoplat early 90s. “Puller for 100 cc Motoplat” can be bought from www.tal-ko.com or www.kartstore.co.uk in UK and elsewhere.

I had a stubborn clutch shoe on my old Leopard and ended up having to use a torch and shock the crank with a hammer to pop it loose. It was not keyed, but held in place with threadlocker compound on the taper. I think it roasted my bearing seals, because they disintegrated two drives later. If you go that route, make sure you replace the seals.