Hemi Predator Build #2

[bob58o]

Here is the cap for draining and accessing the jets without removing the bowl.

 

[Denny]

Wow Bob! You got me? Strange stuff there. Sorry for bad info.

Denny

 

[bob58o]

Wow Bob! You got me? Strange stuff there. Sorry for bad info.

Denny

No problem. There isn't really too much info on these. It's a knockoff Keihin PWK. Keihin's smallest is a 28mm. OKO makes this 24mm. I actually think this is a knockoff of an OKO. Knocking off the knockoff. I think the real OKO carbs have the hex style main jet, not this round one (but not really sure). The bigger 26-30mm OKO PWK carbs come with the powerjet circuit as an option. For some reason the 24mm has it as the standard. I've read people like to block it off and not use it.

Most people have been using VM22 with the types of engines we deal with here. Only a few threads I've come across with people using these on karts and such.

Here's a decent thread about the 24mm OKO powerjet carb...
http://www.scootercentral.net/forums/viewtopic.php?t=12265

servicing and tuning tips oko carbs
http://www.mid-atlantictrials.com/Instal.html

 

[bob58o]

So about this power jet.

Most of the reading I found was on scooter engines.
They say the power jet is too big. So if attempting to use it, you must use a smaller main jet. They say if you get the main jet right for WOT, then it has a trickle down where you're lean in the mid range. If you go bigger on the main, trying to richen up the midrange... then you're too rich at WOT.

I can't seem to find replacements for the actual jet that is too big.

Seems like the midrange would be more of the needle, and not the main and powerjet, but I've read a thread (more like a fight) where someone (never used the carb) says, it's just not tuned properly and the others (who have and like the carb) say that NOBODY has been able to tune it while using the power jet.

 

[Kentucky Boy]

A $25 Mikuni would be easier.

 

[bob58o]

I'm just studying up on it. No need to complain about how hard it is to tune, until I try to tune it.

I still need to figure out how I'm going to hold the piston at a 12 degree angle while trying to cut with my drill press. 12 degrees off of perpendicular is what I measured the the angle of the canted valves to be

 

[KartFab]

Just a trick I learned last month (you may already know it) but if you go wide open throttle and let off the throttle a tiny bit, it will richen the mixture momentarily. If you are running lean at WOT, the kart will lurch forward slightly when you let off the throttle. Not sure if this is the same for your carb or not, but that helped me tune my jet just right at higher rpms when everything else seemed just fine at the low end.

 

[Kentucky Boy]

I'm just studying up on it. No need to complain about how hard it is to tune, until I try to tune it.

I still need to figure out how I'm going to hold the piston at a 12 degree angle while trying to cut with my drill press. 12 degrees off of perpendicular is what I measured the the angle of the canted valves to be

Could you make some kind of jig out of wood to hold the correct angle while you're grinding?

---------- Post added at 04:19 PM ---------- Previous post was at 04:07 PM ----------

Cut a couple 2x4 very short with 12degree angles. Screw them together and fasten the piston on top. Should hold it at the correct angle while you grind the relief in the top with your drill press.

 

[Kentucky Boy]

Like this.

 

[bob58o]

So I didn't have my drill press with me. I was having trouble picturing how to clamp it to the table. It's the little Harbor Freight one in this pic. It tilts 45 degrees.

How about an eyebolt around the wrist pin going through the center hole in the table with a washer and nut on the bolt under the table?

Or two metal straps (1/2" each wide, leaving room for the cut) across the top with 4 longs bolts or some threaded rod.

With the piston at TDC, I'll mark the center of valve with a drill bit (13/64") through the valve guide. TDC is probably not exactly when the valve is closest, but it'll do for me. Then I'll use clay and mark the edge where the valve is the closest. I'll mark the center of the clay impression too.

Clamp the piston. Rotate the table 12 degrees. Find the center with a drill bit, then switch to the cutting/grinding tool and make sure the orientation is so that the edge of the tool matches the edge I marked.
I don't know how to describe it.... Make sure the center of the relief, the spot where the valve came the closest to the piston, and the cutting tool are all aligned.

It might be easier to use the two metal straps so that the cut can be in the center of the table so I wouldn't have to worry about how rotating the table would change approach to the piston.

Maybe I should just go to bed and wait until I have the piston and the drill table together.

 

[Whitetrashrocker]

Your on the right track.
Make sure you hold piston and it can't move. The wrist pin obviously won't protrude outside the pison to hang on to so put a dowel through it.

Mark the piston at TDC and put some prussion blue on the rocker end of the valve and slide it in the guide backwards.
Then set up on your makeshift mill. Use a drill bit to get your alighnment on center then switch to the cutting wheel.

---------- Post added at 08:56 AM ---------- Previous post was at 08:54 AM ----------

It's not like your trying to match 8 pistons.
In this case close will suffice.
But your also losing CR by removing a relief.

 

[bob58o]

Your on the right track.
Make sure you hold piston and it can't move. The wrist pin obviously won't protrude outside the pison to hang on to so put a dowel through it.

Mark the piston at TDC and put some prussion blue on the rocker end of the valve and slide it in the guide backwards.
Then set up on your makeshift mill. Use a drill bit to get your alighnment on center then switch to the cutting wheel.

---------- Post added at 08:56 AM ---------- Previous post was at 08:54 AM ----------

It's not like your trying to match 8 pistons.
In this case close will suffice.
But your also losing CR by removing a relief.

I'm Hoping it will be less than 1/4cc Thanks guys.

 

[bob58o]

Thanks I was originally thinking about using only one eye bolt in the center (inside the piston), but a dowel with two eye bolts (using the two slots in the table, instead of the center hole) makes much more sense to me. It would give me the x, y movement I need to center the cut on the table.

Thanks again.

 

[bob58o]

5/8" Round Bar
(2) 5/16" x 4" Eye Bolts w/nuts
(6) 1/2" Washers
(2) 5/16" Washers

Allows all the x-y movement I need without moving the table.

 

[bob58o]

Mark the piston at TDC and put some prussion blue on the rocker end of the valve and slide it in the guide backwards.

Where can you buy this stuff in the land of brick and mortar?
Can only order it. Prussian Blue, Dykem, .... can't find the stuff without ordering it. I checked grainger and the local auto parts stores. I'll try Eastwood when they open. I can do without it, but it bugs me when I can't find something I feel I should be able to find.

 

[Whitetrashrocker]

It's by the rtv and other permatex stuff.
Just don't ask the part monkey.

 

[bob58o]

It's by the rtv and other permatex stuff.
Just don't ask the part monkey.

LOL I searched the permatex section at a couple stores. Even gave the monkey the part no. Not in stock anywhere by me.

 

[Noseoil]

Just use lipstick if you can't find what you're looking for. I've used lamp black for inletting gun stocks & it works well enough also for marking.

 

[bob58o]

OK I found it at Car Quest - which I guess is part of Advanced Auto Parts now... I was on the AAP site and am picking it up from a CarQuest like 12 miles away.

 

[bob58o]

This is an $8 brake spring tool from advanced auto parts. It sells for $32 or something on NR as a valve spring compressor. Not sure it will help with the 37lb springs. I could do 26 lb with my thumbs, but these.... fuggettaboutit.

Scared to remove the valves on the head with the 37 lb springs. Not sure I'll get em back in. I remember the hours the first time I did the 26 lb ones.

And I don't want to center my piston relief using a head that wasn't milled the same 0.040".

Guess I'm pulling the valves?