Is there value in using an offset timing key with my setup? Predator 212 hemi with stage 1 intake/exhaust kit, governor removed, billet flywheel, centrifugal clutch. The engine internals are stock. It will see some short flat track race use. I may make other improvements later, but for now it is what it is. Using the search feature led me to a few mentions of the offset timing key, but no clear answer if there's any benefit when used with stock cam timing, etc.
Offset Timing Key Question
- Thread starter Tom S.
- Start date
tom if you really want to take advantage of your timing and billet rod, you will want to install a stiffer spring. I would think 16 pound would work or even a 18 pound. just don't go over that. you might chew up the stock cam. I believe they are not harden very well? and make sure the bike is geared correct so it is pulling about 5000+ right before you let up on it when going back into the corner. you did say you want to run it on a short track. I don't think it will pull much more power beyond that with a stock cam. I'm sure other people will chem in and start to tell you buy a race cam...etc... but that's not what your asking really.
just stick with the basic's first and see how you like it and you can always go back and do more improvements if want?
sounds like fun......
just stick with the basic's first and see how you like it and you can always go back and do more improvements if want?
sounds like fun......
@CarPlayLB has talked about this on his show. Maybe he can give you a answer.
that is kind of weird you got a off set keyway with a billet flywheel. unless you have one of the old ones. need to check your flywheel and see if it is engrave with 32 degrees on it. if so do not use that off set keyway. pull your stock keyway out of your engine and use that one and don't forget to lap your flywheel to your crank with little valve lapping compound. that is a must to do...
Some damn good info in here! Way to go folks! I think Tom is setting up a younger guy 14 years old, to run one of his bikes in this upcoming event.
be cautious when purchasing valve springs for a hemi. like ole4 said the spring height on a hemi is shorter. if you put a regular clone spring in it.... your done. my first choice of spring would be a 16 pound on a stock cam. long as you don't have any coil bind with them you will be good to go and at 5000+ rpm's you won't float the valve. stock spring you might get little valve bounce? also i'm just going to throw this out at you too since you have to take the head off. maybe little porting in the bowls only and it won't hurt to mill just little off the head(option) and that will not affect your push rod length. it's all free extra power.
still sounds like a lot fun....
still sounds like a lot fun....
ok,from what I understand from arc racing the hemi exhaust valve spring height can be little shorter from factory(china) and with you installing a 18 pound spring , you now have created a much stiffer spring. if I am correct the honda cam is not harden very well either. you might want to look at your spring heights one more time? also that spring looks to be a animal spring. maybe something else to think about is purchasing a 16 pound animal spring. if indeed the spring heights are correct. sorry I don't know off hand what the hemi is from factory? .800+ or so? help me out ole4 not a hemi guy. actually i'm chevy guy that's a whole nother story...lol
I know in the pass when I have purchase animal springs from dynocams they had a animal spring they say it was only rates at about 15+. that might be the stock briggs animal spring they are talking about? I run that on a stock Tecumseh cam and that turn's about 5000 rpm's. all day and no problems....yet 3years+...lol also that only has a 200 lift and the stock honda/clone cam is about 230-240 lift.
I have also seen a spring that they use in a gokart class that's rated at 10.5 don't know much about that spring? might be another option?
I know in the pass when I have purchase animal springs from dynocams they had a animal spring they say it was only rates at about 15+. that might be the stock briggs animal spring they are talking about? I run that on a stock Tecumseh cam and that turn's about 5000 rpm's. all day and no problems....yet 3years+...lol also that only has a 200 lift and the stock honda/clone cam is about 230-240 lift.
I have also seen a spring that they use in a gokart class that's rated at 10.5 don't know much about that spring? might be another option?
that is kind of weird you got a off set keyway with a billet flywheel. unless you have one of the old ones. need to check your flywheel and see if it is engrave with 32 degrees on it. if so do not use that off set keyway. pull your stock keyway out of your engine and use that one and don't forget to lap your flywheel to your crank with little valve lapping compound. that is a must to do...
The local indoor flat track is having a big event on Feb. 8/9, and there will be a class for pull-start mini bikes. There is only one rule, it must be pull-start. Because there is normally almost no minibike racing in this area and none at this track, it will be a fresh start for everyone. My plan for success is to put a fast, light rider on the bike and give him the benefit of total throttle control via governor removal w/billet flywheel for safety. The stage I kit was just a little icing on the cake. I'm not motivated right now to dig deeper w/billet connecting rod, cam, springs, porting, etc.
The track is big for an indoor circuit, wide, and banked at each end. They also race cage carts and dwarf cars here. 220 yards? Maybe, but most likely a bit smaller than that. I have 12/60 gearing and 6" wheels.
The young man whom I've engaged to ride it is no beginner. He's very experienced and really fast on 85cc and 250cc flat track bikes.
The races will be televised live nationwide on fanschoice.tv on Saturday, Feb. 9, 6-9 pm, PST.
fanschoice.tv
