I have a predator 212 Hemi. Governor is removed, aftermarket carburetor, aftermarket exhaust. Factory cam, Factory flywheel set at 24 BTDC, and everything else Factory. The engine ran fine, a little bit rich, but that's not the issue. I've replaced the flywheel with a Arc Billet aluminum factory set at 32 degreesBTDC, and 20 pound valve springs. I readjusted the valve lash a little tighter because I set when engine was cold. Engine starts if I throttle it up while cranking, but will not stay running if I don't stay on the throttle. Has retarding the timing 8 degrees via the flywheel change it where I may have to replace the cam to get the timing correct again? Or can I stop the flywheel 8 degrees beforeTDC and adjust the valve lash there? Just throwing those out there, I have no real idea. Any help is greatly appreciated.
Valve lash vs timing
- Thread starter gunguru45
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mckutzy
Well-known member
Im too sure about the timing issue.... but If you run new springs without gov installed... you run a great risk of breaking the stock con-rod...
Stock springs allow a valve float that limits the rpm's before the con-rod has a chance to let go....Increasing the strength of the spring pushes that threshold later and thus con-rod dissection occurs....
Stock springs allow a valve float that limits the rpm's before the con-rod has a chance to let go....Increasing the strength of the spring pushes that threshold later and thus con-rod dissection occurs....
The engine is on a drift trike. I understand the need for more upgrades once I begin them I should probably carry them through to the end. Just trying to soup it up a little. Connecting rod and modified cam would be my next project. Kind of new to four stroke engines, have confidence in my abilities just need directions sometimes. Sweet Chopper by the way. Mine is homemade also.
Whitetrashrocker
Inmate #952016
You said it was at 24 btdc then went to 32btdc. But you said retard the 8°
Just making sure you know what your talking about and that was just a typo.
Just making sure you know what your talking about and that was just a typo.
mckutzy
Well-known member
That's cool...
But like I said... It may break sooner than later...
As I understand they won't be as effective with out the new cam anyways...
Here's some ideas that'll help till you get your cam made..
https://affordablegokarts.com/performance_basics.php
But like I said... It may break sooner than later...
As I understand they won't be as effective with out the new cam anyways...
Here's some ideas that'll help till you get your cam made..
https://affordablegokarts.com/performance_basics.php
Whitetrashrocker
Inmate #952016
You adjust the valve lash at the spot where both valves are closed. Not at the 8° btdc.
adjusted the valves at top dead center, both valves should be closed. Correct? The 32°Billet flywheel was purposely made to use the stock timing key. The magnet on it does not line up directly below the coil, it is on the following edge of it at top dead center. Could this be an issue?
---------- Post added at 06:47 PM ---------- Previous post was at 06:41 PM ----------
As the Piston is coming up to top dead center it would pass 32 degrees before it past 24 degrees, wouldn't it?
---------- Post added at 06:47 PM ---------- Previous post was at 06:41 PM ----------
As the Piston is coming up to top dead center it would pass 32 degrees before it past 24 degrees, wouldn't it?
Whitetrashrocker
Inmate #952016
You are correct. Set timing at TDC. Both valves are closed.
And yes 32 btdc would come before 24 btdc.
All that means is where the spark happens. You want the spark to go off Before the Piston gets to the top. This allows for the fuel to ignite and the trick is to get the most pressure and bang at the right time!
A faster spinning engine need this to happen sooner as to allow the fuel to do it thing.
Now there is the compression release mech that opens the exhaust valve a bit to help in starting. Make sure your not setting the valve lash while this is in effect. It would cause incorrect setting.
Your coil and magnet will not alighnment at TDC. They should alighnment at the 32° btdc.
And yes 32 btdc would come before 24 btdc.
All that means is where the spark happens. You want the spark to go off Before the Piston gets to the top. This allows for the fuel to ignite and the trick is to get the most pressure and bang at the right time!
A faster spinning engine need this to happen sooner as to allow the fuel to do it thing.
Now there is the compression release mech that opens the exhaust valve a bit to help in starting. Make sure your not setting the valve lash while this is in effect. It would cause incorrect setting.
Your coil and magnet will not alighnment at TDC. They should alighnment at the 32° btdc.
Okay, I guess that might answer the question I've asked. But still don't have a definite answer as to why it won't run on its own without being on the throttle. so that means the magnet and coil are aligned properly, and the valve lash is set correctly. Maybe I should reinstall the original flywheel and see if it runs without being in the throttle.
Whitetrashrocker
Inmate #952016
If it runs the timing should be satisfactory.
I'd go for a carb cleaning now....
I'd go for a carb cleaning now....
Uhm...
have you reset your coil gap properly or at least CHECKED?
IIRC the ARC flywheels are a hair smaller in diameter..
so the coilgap needs to be adjusted as soon as you swap the flywheel...
ALso.. drift trike being even WORSE for your engine setup than a regular kart/minibike..
simple reason: if the wheels lost traction (which is intended) you have nearly no load on the engine itself, thus it can rev up even higher... increasing the likelyness of catastrophic failure!
IIWY I'd get rid of those stiffer valve springs until I have a billet conrod to install
'sid
have you reset your coil gap properly or at least CHECKED?
IIRC the ARC flywheels are a hair smaller in diameter..
so the coilgap needs to be adjusted as soon as you swap the flywheel...
ALso.. drift trike being even WORSE for your engine setup than a regular kart/minibike..
simple reason: if the wheels lost traction (which is intended) you have nearly no load on the engine itself, thus it can rev up even higher... increasing the likelyness of catastrophic failure!
IIWY I'd get rid of those stiffer valve springs until I have a billet conrod to install
'sid
Thanks for everyone's input it has been very helpful. Upon further research I've found that I do need to use a modified cam to compensate for the timing adjustment of the flywheel. I've known for some time that the connecting rod should be replaced when the governor is removed. I installed a tachometer too kind of monitor my RPMs, have kept it around 5500. The thing about it being a drift trike is you don't stay in the gas all the time, so I'm not keeping it at high RPM constantly. Although I do drive it at higher speeds routinely for short periods. It's just a grown up toy to have fun on from time to time, and yes I'll probably blow it up one day. But until then I am ordering a Billet connecting rod and cam.
bob58o
SuckSqueezeBangBlow
I don't know about that.
Stage 1 modifications involve air filter, exhaust, carb jet, and advanced timing key.
https://www.ombwarehouse.com/predator-212cc-go-kart-kit-stage-1-hemi.html
Show me where you found those springs you have.
I've seen 18 and 22, not 20.
65ShelbyClone
Active member
That was bad information then. What you have is functionally no different than advancing the stock flywheel, which is done routinely. The ARC might have stronger magnets and may need the coil gap to be adjusted, but that's it. If you have strong cranking spark, then it's unlikely the ignition system is related to your running problem.
While I'd be first one to say that RPM stands for Ruins Peoples' Motors, cycling load and RPM up and down constantly is taxing on an engine too, particularly the ones that have finite limits on cyclic fatigue(like aluminum). Some turbochargers have to use titanium compressor wheels because the application (like city buses) would stress cycle an aluminum one so many times that the wheel would burst and destroy the turbo. That is also why drag racers replace aluminum connecting rods at regular intervals for preventive maintenance.
The performance level of the engine has a large bearing on this and utility engines are not exactly highly stressed, so don't take the above as fear-mongering. Your engine will probably last a fair while as-is, but you've got enough valve spring to take it into rod-breaking territory, so proceed with caution until you get that billet one.
Denny
Canned Monster
Is any one going to tell him to recheck his valve lash? Maybe he closed it up too tight?
Denny
Denny
bob58o
SuckSqueezeBangBlow
You ADVANCED the IGNITION/SPARK TIMING 8 degrees with the flywheel change (assuming you are using the stock key). The CAMSHAFT TIMING is related to the spark timing, but even with a stock camshaft 8 degrees advanced ignition timing shouldn't prevent the engine from running.
You should tune the ignition timing to be optimized for the camshaft, compression, octane rating,... but setting the lash at a different point in the rotation isn't the correct way to do so.
A higher RPM cam will generally like a more advanced ignition timing, but you have to consider the carb, the jetting, and other things affecting the burn rate inside the chamber. I think some stocker engines that Jody from ARC builds use up to 36 degrees BTDC. Higher RPM engines (using Stock Carbs) will tend to lean out at higher (7000+) RPMs so less timing is used (30-32 BTDC).
I'll paste this again....
While pulling the cord slowly with the spark plug out and the valve cover off, watch the valves and the piston (through the spark plug hole).
Piston Moves Down while intake rocker/spring/valve is moving = intake stroke
Piston Moves Up while both valves are still = compression stroke
Piston Moves Down while both valves are still = power stroke
Piston Moves Up while exhaust rocker/spring/valve is moving = exhaust stroke
Turn the engine over a bunch of times until you identify each stroke.
Call them out as you see them.
Intake, Compression, Power, Exhaust, Intake Compression, Power, Exhaust,.....
In between the compression and power stroke, when the piston is as high in the cylinder as it will go (TDC, Top Dead Center), THIS IS WHERE TO SET THE LASH.
The other time the piston is at TDC is when the exhaust stroke turns into the intake stroke.
Both valves will be moving around TDC and you cannot set lash here. The lifters need to be on the base circle (NOT THE CAM LOBES)
During the compression stroke, the camshaft decompression mechanism bumps the exhaust valve open slightly. You will notice it, but it is quick. Much shorter and smaller in magnitude than the movement of the exhaust valve during the exhaust stroke. Don't let the decompression mechanism confuse you while you watch for valve movement.
If you happen to have the side cover off, the timing marks on the camshaft and crankshaft gear are aligned at TDC of the compression stroke. At TDC of the exhaust stroke, the marks are 180 degrees out. But you should put the side cover back on before setting the lash
bob58o
SuckSqueezeBangBlow
Stock Cam is basically a CL1 grind cam.
Recommended ignition timing for that cam is 32BTDC (at least when used for racing).
A CL3 Cam is a very similar profile, but retarded 5.5 degrees. This is cam timing. Retarding the camshaft timing moves the power band to higher RPMs. In this case about 1000 RPMs higher than the CL1. The recommend timing is still 32 BTDC
https://www.dynocams.com/item/cl1/
Description
Designed in 2010, this cam was the Original power house for clone engines. The CL1 Original has a wide power band and is a strong cam in restricted clases.
The DynoCams CL-1 Original is legal for the current profile rules for stock classes.
The lobes are hardened for extra durability, extending the life of this cam.
Specs
Engine: 196cc OHV Clone, 212cc Hemi Predator
Recommended Class: Restricted
Target (MAX) RPM: 5200-5800
Spring Pressure (In / Ex): 10.8 lbs
Valve Lash (IN/EX): .003"
Ignition Timing: 32 Deg BTDC
https://www.dynocams.com/item/cl3-pred/
Description
The CL3 utilizes the -5 duration check, in the AKRA rule package, by allowing a softer ramp rate on the nose of the cam. This design has shown gains in the 6200+ RPM range with minimal loss in peak horsepower.
The lobes are hardened for extra durability, extending the life of this cam.
This cam is for 212cc OHV Non-Hemi Predator engines, and has a journal size of .5575".
Specs
Engine: 212cc Non-Hemi Predator
Recommended Class: Unrestricted Stock Classes
Target (MAX) RPM: 6400-6900
Spring Pressure (In / Ex): 10.8 lbs
Valve Lash (In/Ex): .003"
Ignition Timining: 32 Deg BTDC
Recommended ignition timing for that cam is 32BTDC (at least when used for racing).
A CL3 Cam is a very similar profile, but retarded 5.5 degrees. This is cam timing. Retarding the camshaft timing moves the power band to higher RPMs. In this case about 1000 RPMs higher than the CL1. The recommend timing is still 32 BTDC
https://www.dynocams.com/item/cl1/
Description
Designed in 2010, this cam was the Original power house for clone engines. The CL1 Original has a wide power band and is a strong cam in restricted clases.
The DynoCams CL-1 Original is legal for the current profile rules for stock classes.
The lobes are hardened for extra durability, extending the life of this cam.
Specs
Engine: 196cc OHV Clone, 212cc Hemi Predator
Recommended Class: Restricted
Target (MAX) RPM: 5200-5800
Spring Pressure (In / Ex): 10.8 lbs
Valve Lash (IN/EX): .003"
Ignition Timing: 32 Deg BTDC
https://www.dynocams.com/item/cl3-pred/
Description
The CL3 utilizes the -5 duration check, in the AKRA rule package, by allowing a softer ramp rate on the nose of the cam. This design has shown gains in the 6200+ RPM range with minimal loss in peak horsepower.
The lobes are hardened for extra durability, extending the life of this cam.
This cam is for 212cc OHV Non-Hemi Predator engines, and has a journal size of .5575".
Specs
Engine: 212cc Non-Hemi Predator
Recommended Class: Unrestricted Stock Classes
Target (MAX) RPM: 6400-6900
Spring Pressure (In / Ex): 10.8 lbs
Valve Lash (In/Ex): .003"
Ignition Timining: 32 Deg BTDC
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