Tell me about the Tillotson 212 and 212r

#4
The 225 is the best engine money can buy. If you think it’s expensive think how much money you have to put into a predator to get it up to the advertised 17hp the 225 puts out. And then the predator is still only 212cc’s. The 225 is the future and the next engine I will be building
 
#7
It seems to be a great block for a HP build. I like that ir is a 72mm bore with enough sleeve diameter to prevent bore distortion. It is reinforced in a lot of key areas and while probably not as robust as a properly welded block it does not have any welding stresses/distortions that some welded blocks have. During my build I had a couple of issues. The first piston I found to fit a arc billet predator rod was a cast piston from NR racing. I had always found in the past that while a forged piston is stronger than a cast one it is usually heavier. I found NR had a cast 72mm piston with rings so I bought one. When I got it it had a wristpin that had the thickest wall I ever saw! Total weight of the piston (piston, pin, sings, locks) as received was 262 grams. I taper ground the wristpin and removed about 18 grams off the wristpin and milled the piston skirt around the wristpin bores to lighten it but it was still over 240 grams. The stock hemi piston total was 200 grams. I asked around and Gary Costanza mentioned the weisco 72mm piston was around 189 grams total. I ordered one for the 72mm bore with 3 rings and the matching predator rod and it was that light. The HD ARC wristpin seems mighty skimpy but we will see. The other issue I had and it was a big one was the dyno 356 cam had issues when I was degreeing in the cam. the exhaust valve would not close till after TDC. Not to drag out a long story but after two cams I realized that the base circle of the 356 dyno cam is smaller than the core diameter. They grind a relief next to the exhaust lobe to clear the tappet but the tillotson block flywheel side cam thrust face is .010 deeper than the hemi block I was comparing it to. I called dyno and they were aware of this issue and sent me another cam with a slightly wider relief but if I pushed the cam back toward the flywheel side I still saw the issue. I fixed it by chucking the cam in my lathe and using a Dremel tool post grinder with a small mill bit relieved the cam more so the lifter could not ride on the core of the shaft. If you are using a cam without a reduced base circle (smaller than the core diameter) then this is a non issue.
 

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MJL

Active Member
#8
Well, I guess I'll be the test subject. Ordered the new version of the 212r and a Juggernaut. Hope they play well together. Figured I needed something to do while we are locked down! Only plans are to swap the intake and exhaust and run it.
 

MJL

Active Member
#9
Got everything in and installed in my Baja. Swapped the intake, and plumbing part hotdog exhaust from my 196 clone. Picked the fattest jet out of my bag of jets. Not quite sure what size it is, but the 196 was too rich with it, probably a .037 or .038. Got lucky and had a perfect plug reading.

Ran it first with the original Comet clutch, just to judge the difference. No doubt it pulled harder. Then I swapped in the Jugger, the difference was night and day, the jugger allows the engine to rev more freely and downshifts quicker when you get off the throttle.

I was worried about losing some of my wheelie/jumping ability with the lighter flywheel on the 212r, but to the contrary, it is pulling better than ever! And I am riding out wheelies farther than ever. I haven't clocked a top speed, but its plenty fast enough for me. I left the governer in. Initially it wasn't set anywhere near right, so I played with the spring just enough to get going well enough. Most of my riding was around 4000 RPM, with a peak of 5100 RPM. Once it breaks in a bit more, I'll mess with it to see if I can get closer to the advertised 5800 RPM.

I really like the Jugger clutch. If it holds up well, I'll be very pleased!

I am getting quite a bit of popping when I let off the throttle. Since the plug reading was good, I'm thinking I need a larger pilot jet. Any thoughts on what size to try? Will I need to back off the main jet with a larger pilot jet?
 
#10
Got everything in and installed in my Baja. Swapped the intake, and plumbing part hotdog exhaust from my 196 clone. Picked the fattest jet out of my bag of jets. Not quite sure what size it is, but the 196 was too rich with it, probably a .037 or .038. Got lucky and had a perfect plug reading.

Ran it first with the original Comet clutch, just to judge the difference. No doubt it pulled harder. Then I swapped in the Jugger, the difference was night and day, the jugger allows the engine to rev more freely and downshifts quicker when you get off the throttle.

I was worried about losing some of my wheelie/jumping ability with the lighter flywheel on the 212r, but to the contrary, it is pulling better than ever! And I am riding out wheelies farther than ever. I haven't clocked a top speed, but its plenty fast enough for me. I left the governer in. Initially it wasn't set anywhere near right, so I played with the spring just enough to get going well enough. Most of my riding was around 4000 RPM, with a peak of 5100 RPM. Once it breaks in a bit more, I'll mess with it to see if I can get closer to the advertised 5800 RPM.

I really like the Jugger clutch. If it holds up well, I'll be very pleased!

I am getting quite a bit of popping when I let off the throttle. Since the plug reading was good, I'm thinking I need a larger pilot jet. Any thoughts on what size to try? Will I need to back off the main jet with a larger pilot jet?
Honestly popping on deceleration is going to happen no matter what if you are reving over about 3500 RPMs. Reason being, if you run a jet that is fat enough that it doesn't pop when you suddenly shut the throttle at 6000 rpm it will be super rich at idle, and will foul plugs constantly. If you are getting good plug readings, I wouldn't worry about playing with Jets.
 

MJL

Active Member
#11
Honestly popping on deceleration is going to happen no matter what if you are reving over about 3500 RPMs. Reason being, if you run a jet that is fat enough that it doesn't pop when you suddenly shut the throttle at 6000 rpm it will be super rich at idle, and will foul plugs constantly. If you are getting good plug readings, I wouldn't worry about playing with Jets.
Thanks. Good to know this is normal. It runs really good as is!
 
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