Anti-Grenade thread: billet rod and flywheel install checklist.....

[PhilosophStein]

Hi all!! The 212cc stock predator in my MB200 is still running strong! No signs that it will let me down any time soon and I haven't been easy on the bike either.

I still have the OEM 6.5hp clone that came with the bike lying around....

Before I order the parts and do the install, I just wanted to confirm a few things:

1) The billet rod for the GX200 clone engine has center to center length of 3.303 inches?

2) Do I need to get a new wrist pin and cir-clips?

3) During the rod installation, is the wrist pin force fit into the small end of the rod? I.E., do i need to heat the small end hole before pushing the wrist pin through?

4) When installing a billet flywheel, is my main concern going to be to ensure the correct coil gap? If so, what is the correct gap? 0.030" ?

5) If the flywheel I'm looking at says it has 8 degrees of timing advance built into the key position, will that affect the motor's performance? That is, do I need to replace any other parts to get it to run similar to stock?

Basically, I want to get these 2 parts to make the motor less prone to grenading at higher rpm. Later on, other mods such as valve springs, etc. may be done.

 

[Norcalputput]

Answers:
1. Yes
2. No
3. No
4. Yes (0.030" is the min coil gap)
5. Yes & No

IMO you should install a cam when you take it apart


Sent from my iPhone using Mores code

 

[OND]

Norcalputput is spot on with his answers, and I'm with him why not install a new cam in while you've got it apart. If you don't want to spend $100.00 for a good cam you can get a Dyno CL-1I cam or a BSP 2 or 3 cam for cheap.

 

[davidlamb78]

Dyno CM is cheap and good.

 

[minibikin']

If you're running the ARC billet flywheel with the built in advance, the coil gap is .060-.080".


Sent from my Texas Instruments Speak and Spell...[emoji2]

 

[Commonrail]

Is there an advantage of running .060-.080 gap on the coil with the billet ARC flywheel? Mine came in Monday and it says to set the coil to .030

 

[minibikin']

The magnet is much stronger. It will reduce drag if you increase the gap. That came direct from Hunter at ARC.


Sent from my Texas Instruments Speak and Spell...[emoji2]

 

[Norcalputput]

6619 ARC GX200 & Clone Flywheel - ARC Racing
Conflicting answers

Sent from my iPhone using Mores code

 

[PhilosophStein]

One more question before I attempt to remove the old rod today after work:

Once the rod cap and crankshaft have been removed, can the piston/rod be removed down through the crank side?

Or does the head have to come off to remove said subassembly up through the top?

 

[CarPlayLB]

One more question before I attempt to remove the old rod today after work:

Once the rod cap and crankshaft have been removed, can the piston/rod be removed down through the crank side?

Or does the head have to come off to remove said subassembly up through the top?

It might be able to come out through the bottom, but ya can't put it back in that way. Take the plunge and pull the head! You can thank me later!

 

[ole4]

coil gap info from ARC employee. Copied from bob's


4 Cycle Advanced User

Join Date
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Al it is not about more or less voltage to the coil, because it can only handle so much before they fry. We are accomplishing two things with more coil gap. (One), less magnet drag. The magnets in our flywheels are very strong and will produce some resistance when passing under the coil. This is more beneficial with smaller plate engines. (Two) and the most important is we are trying to time when and how much timing retard we have a high RPM. Every OEM coil no matter if its a Clone, Honda, Predator, Kohler or a Flathead briggs they will retard as the RPMs go up. If you set the timing at 30 deg it will still be at 30 deg while at idle, but as the RPMs rise the timing will begin to retard because the magnet is passing under the coil faster than it can charge and fire. <This is a known fact. Our flywheels have a magnet design that charges and fires the coil much better and more accurately at higher RPMs that does not retard as much as other flywheels, but does still retard. Now factor in that we are running a carb on Gasoline that has a .615 venturi that will reach the point of maximum suckage around 5500 RPM +/-. Because of the cam package and the size of the carb that is where it begins to lean out. We set up these carbs to have a very rich bottom end so they will accelerate quickly and that will require more timing to burn the excess fuel. So we set the timing in the 32-36 deg range to help with the rich bottom end. Now as I stated these little .615 carbs will begin to lean out around 5500 or so RPMs and you do not want to have high timing with a leaned out carb. running pump Gasoline. Therefor we widen the coil gap so the timing will begin to retard a little sooner to try and match the carb leaning out so the engine will continue to make top end power. This is something we worked with for many months while developing our new magnet design and why you can run more gap with the new style design and less with the oil style design. From our testing with the AKRA Clone engines a coil gap of .060-.065 works best on unrestricted engines, .065-.070 works best on blue and purple plates and .070-.075 on green and red. These coil gap numbers not set in stone you may find that more or less will work for you but will require the use of a Dyno, this is what works best for us with our engines on our Dyno. You results may vary...

 

[PhilosophStein]

It might be able to come out through the bottom, but ya can't put it back in that way. Take the plunge and pull the head! You can thank me later!

Makes sense! I guess that means I need to order a few head gaskets (which i did not order in my recent billet rod/flywheel list hehe) too. It is more than likely that the head gasket can't be re-used? Anyway I can still take the stuff apart at least because my new parts haven't shipped yet...

 

[CarPlayLB]

You may want to take the head off before ordering your rod. Some of the clone pistons are 0.020 in the hole, or more, and you can get a zero deck with a longer rod. ...and with all the other expense, a head gasket is the least of your worries!

 

[PhilosophStein]

You may want to take the head off before ordering your rod. Some of the clone pistons are 0.020 in the hole, or more, and you can get a zero deck with a longer rod. ...and with all the other expense, a head gasket is the least of your worries!

too late! parts were shipped yesterday... Anyway, info gained for next time! I mainly just want to make this motor safer.

 

[SnakePliscan]

coil gap info from ARC employee. Copied from bob's


4 Cycle Advanced User

Join Date
Oct 2013
Location
ARC Racing / arcracing.com
Posts
377

Al it is not about more or less voltage to the coil, because it can only handle so much before they fry. We are accomplishing two things with more coil gap. (One), less magnet drag. The magnets in our flywheels are very strong and will produce some resistance when passing under the coil. This is more beneficial with smaller plate engines. (Two) and the most important is we are trying to time when and how much timing retard we have a high RPM. Every OEM coil no matter if its a Clone, Honda, Predator, Kohler or a Flathead briggs they will retard as the RPMs go up. If you set the timing at 30 deg it will still be at 30 deg while at idle, but as the RPMs rise the timing will begin to retard because the magnet is passing under the coil faster than it can charge and fire. <This is a known fact. Our flywheels have a magnet design that charges and fires the coil much better and more accurately at higher RPMs that does not retard as much as other flywheels, but does still retard. Now factor in that we are running a carb on Gasoline that has a .615 venturi that will reach the point of maximum suckage around 5500 RPM +/-. Because of the cam package and the size of the carb that is where it begins to lean out. We set up these carbs to have a very rich bottom end so they will accelerate quickly and that will require more timing to burn the excess fuel. So we set the timing in the 32-36 deg range to help with the rich bottom end. Now as I stated these little .615 carbs will begin to lean out around 5500 or so RPMs and you do not want to have high timing with a leaned out carb. running pump Gasoline. Therefor we widen the coil gap so the timing will begin to retard a little sooner to try and match the carb leaning out so the engine will continue to make top end power. This is something we worked with for many months while developing our new magnet design and why you can run more gap with the new style design and less with the oil style design. From our testing with the AKRA Clone engines a coil gap of .060-.065 works best on unrestricted engines, .065-.070 works best on blue and purple plates and .070-.075 on green and red. These coil gap numbers not set in stone you may find that more or less will work for you but will require the use of a Dyno, this is what works best for us with our engines on our Dyno. You results may vary...

Intersting, A properly jetted small carb dosnt go lean on the top end, it just simply cant move enough air and fuel to keep filling the cylinder and power noses over, i can see fattening the bottom if your trying to run compression and timing if your not allowed to add octane booster, but retarding timing on the top end because your running out of air and then seeing power on the dyno, whats going on there?

 

[ole4]

I posted that for the part about the coil gap but did not pay attention to the carb leaning out stuff. I have never played around with the OEM carbs and always run tillys or mikuni's but you sure can have a tilly that is rich on the bottom and runs lean later on if drill patterns are too low. but a regular carb if main jet is right should not lean out but again I am not familiar with those carbs.

 

[Commonrail]

im getting around 7500-7700 RPM's out of my stage 4 kit on the hemi. Is it the carb keeping it from going further?

 

[Prowler08]

If or when you try a bigger carb with your build you will know that a larger carb. Makes a big difference... Just going from a stock engine to a S/A engine was a nice boost... Cam, bigger valves, P&P the head boost comp to 12-1 was a nice kick... But when I put a 390 carb on with Alky it was a whole different animal...

 

[PhilosophStein]

Well, I removed everything just fine. I will keep the OE rod and flywheel as backups.

I have 2 more questions (1 stupid one and 1 smart one):

1) Which way does the ARC billet rod install?
That is, I'm fairly certain that the oil dipper on the rod cap points toward the right (toward the valves) when looking into the case from the PTO side. However, which side of the rod faces the PTO side of the engine?

2) I ordered several parts for this build and another project from an online vendor (not OldMiniBikes Warehouse). However when I checked the contents of the box against the packing list, I only had 3/4 items.... What recourse do I have? I haven't tried called the vendor yet since they were closed.

 

[Commonrail]

The rod will only go one way. It's machined with teeth to line up one way so it's not to confuse you. Just be careful installing the rod bolts. I snapped one off doing the torque sequence per the instructions. Also YOU NEED A 12pt 1/4 socket. The rod bolts are a 12pt. Find one before you start b/c you need to torque them down per instructions. You can use a boxed end wrench but you won't know what the torque rated is.. Good luck.