212 Predator sputtering

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mudboat_josh

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My predator has been sputtering at mid to high rpm, my guess is the main jet needs to be bigger. What do you guys think?

Mods are:
governor removed
arc rod
mod 2 cam
arc flywheel
18lb springs
1.3 ratio rockers
mudboat pipe
hi-flow filter
 

rocketkart

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idk but thats what i use in all my 212 Predator i had one that was not starting so i got a new plug and it runs alot better than new the stock spark plug are crap so i got that spark plug in all my Predator engines now. thay is them on all honda gx200.
 

OzFab

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Not that that's a bad idea but, in the list of mods there's nothing about the jet so, I'm assuming it's stock. If so, you probably need to go bigger.

Speaking of the spark plug, what does yours look like? It will tell you if it's running lean or not...
 

mudboat_josh

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I drilled the main jet out some but didnt measure how much it was drilled out and didnt touch the low speed jet.

This is what the plug looks like.
 

OzFab

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Yeah, it looks new...

Try doing a high speed test; take it for a run at WOT & kill the engine while still at WOT (I think that's correct) Then show us what the plug looks like...

If I had to judge from that pic, I'd say it was a bit lean but, it's hard to tell
 

mudboat_josh

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Here is a video of it running, i checked the plug and it looked white suggesting it was running lean. I drilled out the main jet some more but not the low speed jet since it seemed to be running fine at low speed. Im guessing ill need to drill out the main jet some more?

 

OzFab

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Either it's still running a bit lean so, drill out the jet a bit more OR the valves are bouncing, that a few thousand RPM it's putting out...
 

mudboat_josh

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I have a tiny tach hooked up to it and it never revved up over about 6500. Is 6500 revving too high or normal?

Ill try drilling out the jet a bit more.
 

OzFab

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Well, considering that engine, in it's stock form, is governed to 3600rpm, I'd say that's high...

Since the plug is showing white, go ahead & drill the jet & see what happens. If you then get a good colour on the plug & it still tops out, put it down to valve bounce...
 

mudboat_josh

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Thanks for the help Fabro, hypothetically speaking if it is valve bounce what woild the cure be? Heavier springs?
 

OzFab

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Thanks for the help Fabro, hypothetically speaking if it is valve bounce what woild the cure be? Heavier springs?

You already have 18lbs springs. That should be enough

For 6500rpm, I don't think so; standart are 10lb, super heavy are 26lb putting 18s right in the middle.

Since you have all the other necessary mods in place, it should be safe to go to heavier springs IF that's what it needs...
 

itsid

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When you say arc wheel, you talk about just billet instead of casted fly wheel, or you talk about the variable timing wheel?

and what is your ignition timing? have you set it to let's say 4° earlier already?

'sid
 

danssoslow

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When you say arc wheel, you talk about just billet instead of casted fly wheel, or you talk about the variable timing wheel?

and what is your ignition timing? have you set it to let's say 4° earlier already?

'sid


This guy is onto something! Very good observation! While the OP is at it, he might want to get in touch with ARC, as there was a model change on the static flywheel; they now have advanced timing built in.
 

mudboat_josh

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When you say arc wheel, you talk about just billet instead of casted fly wheel, or you talk about the variable timing wheel?

and what is your ignition timing? have you set it to let's say 4° earlier already?

'sid

The flywheel is just the standard flywheel non adjustable timing. The timing key is stock as well.
 

itsid

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This guy is onto something! Very good observation! While the OP is at it, he might want to get in touch with ARC, as there was a model change on the static flywheel; they now have advanced timing built in.
they did?.. didn't know that, I thought it's still the same as stock..
good to know.

The flywheel is just the standard flywheel non adjustable timing. The timing key is stock as well.

In that case, maybe a small timing advantage will help;
that is if you fixed your gas issues, and made sure this is not valve flutter already.

At one point it is necessary to advance your timing a little to raise the rpm, (I'd suggest a small number 4° maybe 6°)
too much and it's more likely to shear the timing key and you loose too much torque on lower rpms.


on a clone the mod2 cam is supposed to be run with 26lbs springs AFAIR, and since the predator is basically a clone, I think you can apply the same rule here.
This is where I would start to make sure it's not valve flutter,
if that doesn't help to raise the rpm, get a timing key.

[EDIT]

Looking at the ARC website, the std flywheel now comes with 8° advanced timing,
so if you bought the flywheel just recently (I don't know when they changed that) there is no need for a timing key,
quite the opposite, I wouldn't recommend using one!!


'sid
 

danssoslow

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It's easy to overlook the fact that the rate at which gas ignites does not change. At some point, advancing is necessary to keep engine events in sync. 8K would seem appropriate here, as that is twisting these engines at a pretty rapid pace.

If the op is going to go this route, it's important that he takes the time to lap the flywheel and yoke. Along with correct torque specs, this will insure that the mechanical lock will lessen any chances of flywheel movement and possibly shearing the key.
 

itsid

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If the op is going to go this route, it's important that he takes the time to lap the flywheel and yoke. Along with correct torque specs, this will insure that the mechanical lock will lessen any chances of flywheel movement and possibly shearing the key.

Again, if OP has an 8° timed flywheel already I would NOT suggest the use of a timing key at all!
(not even a 4° one)
I can't tell if it is a "timed flywheel", I don't think I would be able to spot it on a picture either.


So Josh,
if you're in doubt, please ask ARC send them an email, tell them what you got and when you bought it, and ask if they can tell you if it has an advanced timing or not, and/or how to spot the difference.
(hopefully they changed the ID or something)


Dan, do you know when they changed the timing on the flywheel by any chance?
that might help here.

'sid
 
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