Need advice on a future 212 build

[Wilson_Engine_Shop]

I'm looking into building a Hemi predator soon. I'd like to get a HOT265 cam, 22lb springs, Billet Rod, Billet flywheel, a header and a real Mikuni VM22. I haven't seen anyone else run this combo and i'd like to know if these parts will work together. My goal is to have a motor that will run up to 7,500 rpm for my Explorer so i can rip through fields at top speed and still have down low torque

 

[Smerft85]

From what I understand about the hemi version is that some performance parts that would fit with the normal head won't work for the hemi, personally I have no idea, but I do recall hearing several reasons why the non-hemi carried preference and that was one issue.

 

[jonboy]

Why not build it for a milder more reliable rpm range and set up a torque converter and sprocket combo for what you want?

 

[Wilson_Engine_Shop]

Why not build it for a milder more reliable rpm range and set up a torque converter and sprocket combo for what you want?

The kart already has a TAV with 12t on the jackshaft and 60t on the axle. It took forever to get up to speed before and I couldn't get above 25mph but i think that was because the belt wasnt wide enough. I would have to get a split sprocket to change the one on the axle. I want it to go to at least 6k rpms if 7k isn't possible. I just want to be able to do 40mph but still get out of the hole quickly

---------- Post added at 08:24 AM ---------- Previous post was at 08:22 AM ----------

GPS does make a Hemi and Non-Hemi version of the cam, rod and flywheel I was looking at but i didn't see any reviews

---------- Post added at 08:40 AM ---------- Previous post was at 08:24 AM ----------

The Dyno MOD2 Cam seems like it'll be my best bet here. It has all the specs i'm looking for and I only need 18lb springs instead of 22lb

 

[Flyinhillbilly]

I’d crack it open and measure the deck height before I ordered anything to be sure that I got the right length rod to get the piston flush with the deck. I like zero deck with the .027 mls head gasket. The hemi head has a different installed height for the valve springs which causes coil bind at higher lifts, so make sure you check that. I’d also mill and port the head. I don’t see why 7500 rpm wouldn’t be an attainable goal. I turn my hemi 9000+ rpm every time I pull out on the track with it. You could get a 3.595 ARC rod and matching Wiseco piston for peace of mind.

 

[Karttekk]

What about an engine already built?

https://forums.kartpulse.com/t/new-four-stroke-clone-engines-unveiled-by-tillotson-racing/1804

 

[snowjob]

I installed this kit recently on a hemi predator: http://www.nrracing.com/product-p/stage3hopup-ph.htm

I selected the billet flywheel and Mod2 cam. Other than a wicked recoil on startup, I have been pretty pleased with it. It upped our top speed from ~30mph to between 50-60mph. Still need more tuning time and gauging to test it out further and considering it is now full-on winter, I don't think it will be soon.

 

[Wilson_Engine_Shop]

I’d crack it open and measure the deck height before I ordered anything to be sure that I got the right length rod to get the piston flush with the deck. I like zero deck with the .027 mls head gasket. The hemi head has a different installed height for the valve springs which causes coil bind at higher lifts, so make sure you check that. I’d also mill and port the head. I don’t see why 7500 rpm wouldn’t be an attainable goal. I turn my hemi 9000+ rpm every time I pull out on the track with it. You could get a 3.595 ARC rod and matching Wiseco piston for peace of mind.

Would a Non-Hemi motor be better/easier to upgrade without worrying about coil bind? I planned on running the stock piston(I dont see any reason not to). I don't have any tools to do head work or any place close by so thats a no-go on that

 

[snowjob]

Yes, I believe a non-hemi is a better platform for modification for exactly that reason along with piston clearance. We have one of each (hemi/non-hemi). The only reason we upgraded the hemi is that we had it first and seized it when the actuator arm fell down into the crankcase. For our build, the hemi is adequate and allows us to turn around and sell a low hour non-hemi. No head work needed on our config, running stock piston and +0.020" billet rod. I can't comment on coil bind, but I really don't think we have any. So far there is no indication of any poor running conditions other than starting difficulty which I attribute to the cam and have adapted to.

 

[itsid]

The kart already has a TAV with 12t on the jackshaft and 60t on the axle. It took forever to get up to speed before and I couldn't get above 25mph but i think that was because the belt wasnt wide enough.

Nope it's the gear ratio being terrible..
5:1 is already a tough ratio with 11-13" wheels
from the rest of your "plan" I assume we talk more like 18-22" wheels in your case

frankly just saying you got 18" wheels
you are now geared for ~ 65 mph which you cannot reach
and thus you robbed yourself low end torque for absolutely no reason!

with 22" wheels you're geared for ~80mph which would be tough even with some serious mods.

If you want 40mph ish top speed
you want a 8:1 ratio on 18" wheels
and 9.7:1 ratio on 22"

you can get away with ~ 7.5:1 on 18" and ~ 9.2:1 on 22"
(roughly 44mph each)
assuming kart/rider combo doesn't weigh more than about 660 lbs
and the 6.5hp original engine is ungoverned and allowed to freely breathe (topping out at roughly 5500 rpms)
[no fancy cam needed! certainly no hefty valve springs... billet parts and mikuni are a good idea anyways [though not required]]

you gear ratio is so far off I wonder if the belt is still at least partly alive...
frankly I'd say you need a new one within the next 45min of ripping through the woods

'sid

 

[Smerft85]

Nope it's the gear ratio being terrible..
5:1 is already a tough ratio with 11-13" wheels
from the rest of your "plan" I assume we talk more like 18-22" wheels in your case

frankly just saying you got 18" wheels
you are now geared for ~ 65 mph which you cannot reach
and thus you robbed yourself low end torque for absolutely no reason!

with 22" wheels you're geared for ~80mph which would be tough even with some serious mods.

If you want 40mph ish top speed
you want a 8:1 ratio on 18" wheels
and 9.7:1 ratio on 22"

you can get away with ~ 7.5:1 on 18" and ~ 9.2:1 on 22"
(roughly 44mph each)
assuming kart/rider combo doesn't weigh more than about 660 lbs
and the 6.5hp original engine is ungoverned and allowed to freely breathe (topping out at roughly 5500 rpms)
[no fancy cam needed! certainly no hefty valve springs... billet parts and mikuni are a good idea anyways [though not required]]

you gear ratio is so far off I wonder if the belt is still at least partly alive...
frankly I'd say you need a new one within the next 45min of ripping through the woods

'sid

He is right you know, my dingo is running a 6.5 clone de-governed with a 6.67:1 ratio, accelerating is no issue, and it does 40mph no sweat, if you can hang on through the rough streets. It's lacking a bit in torque so burnouts/wheelies/ doughnuts aren't realistic, but I catch up with the cars doing 30mph pretty easily.

That is an all original generator engine with one "mod" and it's non-hemi, other than having champion stickers and yellow paint, it is a honda clone just like the predator engines.

 

[Wilson_Engine_Shop]

My Explorer has 18" wheels on the rear. Theres no damage on the old belt either. I havent even driven it yet since i put the new belt on. The old belt was an inch shorter and bottomed out in the driven pulley at idle. Last time i drove it I went down a flat 1/4 mile long driveway and still couldn't go over 25 mph according to my gps. I know for a fact that it DID NOT have the correct drive belt when i bought it. Now it has the correct 37x98 asymmetrical belt which i'm sure will fix my takeoff issue. Before this it would rev really high before it started moving the kart.

 

[itsid]

ah an incorrect belt (cheap automotive V belts mostly)
surely doesn't work..

still the gear ratio is terrible and the reason for the low speed and sluggish acceleration.
And with 18" wheels a 5:1 ratio will likely eat your belt in just a few hours of driving around.

especially on rough terrain and uphills..

there's no point in gearing that high frankly, since you not only cannot reach 65mph
you also do not want to (as you said above)
So there's no reason to Not just gear lower (7.5:1 for example)
and then decide what the next engine should be

'sid

 

[Wilson_Engine_Shop]

So do I put the 10t sprocket back on then? I would still like to drive it before I change it back since it has a new belt but im trying to fix my leaky tire first lol

Edit: i'm going to go ahead and put the 10t back on. If the BMI Calculator is anywhere close then i'll be happy with the gearing. Thanks for your wisdom and gearing math Sid! Its VERY much appreciated!

 

[Wilson_Engine_Shop]

I just watched a video last night by Red Beards Garage and he just so happened to have built a hemi predator with some of the parts that I was looking at with the exeption of the 24mm mikuni, billet side cover, valves, pushrods and head stud kit

https://youtu.be/CvKUFxe1wX4

 

[itsid]

So do I put the 10t sprocket back on then? I would still like to drive it before I change it back since it has a new belt but im trying to fix my leaky tire first lol

Edit: i'm going to go ahead and put the 10t back on. If the BMI Calculator is anywhere close then i'll be happy with the gearing. Thanks for your wisdom and gearing math Sid! Its VERY much appreciated!

6:1 is better.. but still too high!
BMI is also incorrect on the result (discarding the fact that you do not have a std cent clutch but a series 30 TC
it also lacks the ability to throw errors on stupid values


And albeit the recent ios13 trouble.. mine is still better

KartInfo by kartcalc.net:

[FONT="Verdana"]
[B][U]KART[/U][/B]
[INDENT][I]RW diameter[/I]: [B] 45.72 cm | 18 in[/B]
[I]Total weight[/I]: [B] 255 kg | 562.18 lbs[/B]
[/INDENT]
[B][U]ENGINE[/U][/B]
[INDENT][I]Original HP[/I]: [B] 6.5[/B]
[I]Asummed HP[/I]: [B] ~6.5[/B]
[I]Torque[/I]: [B] 7.71 Nm | 5.69 ft lbf[/B]
[I]RPM[/I]: [B] 6000[/B]
[/INDENT]
[B][U]TRANSMISSION[/U][/B]
[INDENT][I]Final ratio[/I]: [B] 6:1[/B]
[I]TC type[/I]: [B]  series 30 6" driven[/B]
[I]Lowest ratio[/I]: [B] 16.2:1[/B]
[I]Highest ratio[/I]: [B] 5.4:1[/B]
[/INDENT]
[B][U]PERFORMANCE[/U][/B]
[INDENT][I]Max Wheel Torque[/I]: [B] 124.9 Nm | 92.12 ft lbf[/B]
[I]Min Wheel Torque[/I]: [B] 41.63 Nm | 30.7 ft lbf[/B]
[I]Acceleration[/I]: [B] 1.22 m/s² | 4 ft/s²[/B]
[I]Top Speed[/I]: [B] 95.76 km/h | 59.5 mph[/B]
[/INDENT]
[B][U]PROBLEMS[/U][/B]
[INDENT][B]Max-speed cannot be reached![/B]
[I]Max Speed[/I]: [B] 82.66 km/h achievable | 51.36 mph[/B]
[B]Gear ratio too high![/B]
[I]Suggested final ratio[/I]: [B] at least 8.9:1[/B]
[B]Min-Torque not sufficient![/B]
[I]Min Wheel Torque needed[/I]: [B] 58.29 Nm | 42.99 ft lbf[/B]
[B]You might burn your clutch/belt![/B]
[/INDENT]
[/FONT]

'sid

 

[Wilson_Engine_Shop]

So should I go to a smaller jackshaft sprocket or a bigger axle sprocket to get the right ratio?

 

[itsid]

bigger axle sprocket is less aggressive on the chain than smaller jackshaft sprocket.
So as long as you have the clearance for a larger axle sprocket that's what I'd suggest.

I know some disagree since smaller sprockets are usually cheaper than big ones,
but frankly they wear down quicker and once worn, they eat on the chain much earlier..
so in the long run the price difference isn't working in your favour I'd say

(rule of thumb: 10% less teeth means 10% increased overall wear.. 10% shorter replacement cycles for sprocket AND chain.. and worse a worn chain then eats on the otherwise good large axle sprocket and at worst you need to replace that as well)

'sid

 

[karl]

(rule of thumb: 10% less teeth means 10% increased overall wear.. 10% shorter replacement cycles for sprocket AND chain.. and worse a worn chain then eats on the otherwise good large axle sprocket and at worst you need to replace that as well)

'sid

This is very true, but ground clearance is also a factor, smack something while drifting ect , and the sprocket is tacoed and a total loss , So wear would be irrelevant.

And the chain is lower to the ground picking up more dirt, dew ect.

Always a tradeoff.

 

[Wilson_Engine_Shop]

I cant find any sprockets bigger than 66t which would make my ratio 6.6:1 but i'm looking for a 72t live axle sprocket or split sprocket for #40/420 chain. I'm still looking though. What classifies a chain as worn out? Thats something I need to know about. My current #40 chain was locked up when i got it but i soaked it in evaporust for 2 days then soaked it in good oil for half a day. I spray it with chain lube after riding it everytime and its a night and day difference in the way the chain works now