Predator 212cc/Hemi Upgrade ?s

LSCustoms

LSCustoms

Moderator
#61
#61
Boogie Man Ryan said:
I talked to russ about the safe issue regarding the arc adapter. i told him the air bleed on the back of the 390 carb was un able to vent with just the adapter.... you can do two things... One is run a insulator...and you still at a 15 deg angle, or you can jb weld the back of the carb, and drill the air bleed on top/side of carb with a small nipple to vent...this will allow no insulator just gaskets and give the true stock appearing look. If you get nr racings 390 to gx200 adaptor it all ready had the insulators vent areas built in...and will sit at the angle you need... if you go this route the carb is nowhere near as aggressive as the short arc adapter..it feel like a 22mm at best... the first way at the 15 angle did idle and surge...but as soon as you got full throttle it was like warp speed:laugh:...just food for thought.
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thanks for this post! is this the stock insulator, or 390 insulator to add back in? im thinking the 390 (and would need an additional 390 gasket)? if I have this issue...

I had ordered the short adapter shortly after picking the carb, because after research, learned it was apparently better performing than the longer one... and figured it was $13 more at NRRacing for a reason... was making an order (5th or 6th) through ARC and threw it in the kart... when talked to Russell he asked me if i had one, i told him yes the arc and he told me what to do if i had the issue... your post clears this info up, as i forgot exactly what he said...
 
LSCustoms

LSCustoms

Moderator
#63
#63
wont have the rest of my parts until, Monday... Happy Holidays everyone!

and still waiting on Cam and extra springs (springs/stock piston will be shipped out to the new owner, soon as i get them)...

other than that, ready to move forward... and put this together. cant wait to test it with the manual clutch... and the new brakes, without the wheelie bars (need to be made)... once bars go on can work the kids up to riding it...
 
The Restore Kid

The Restore Kid

New Member
#64
#64
With the price you guys spend on these motors, I don't see why ya don't just drop a 4 cylinder Ford in there and get some REAL power.. :laugh: Whats a 2.0 Escort engine running these days?

Hell, a grand will probably still buy ya a Pinto engine.. :drool:
 
LSCustoms

LSCustoms

Moderator
#65
#65
The Restore Kid said:
With the price you guys spend on these motors, I don't see why ya don't just drop a 4 cylinder Ford in there and get some REAL power.. :laugh: Whats a 2.0 Escort engine running these days?

Hell, a grand will probably still buy ya a Pinto engine.. :drool:
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lol... no matter what is done to a mini bike, it wouldnt be fast enough for me... but hopefully fun enough... unfortunately, i will be looking for a kart soon after i call this project done... if this can get down the 1/8 at a decent speed, with one of the kids on it, I will be extremely happy. my daughter loves the race track and is inspired by Nicole Lyons... hoping this is fun enough for her, where I dont have to find and fund a jr dragster... she is 11, wish i would have known she was into this stuff alot sooner... i still havent gotten my car to the track yet and already thinking about putting it off longer to help start her early... this mini bike project gives me time to think, while still allowing me some sort of "fix"/challenge for completing a goal...
 
H

Havasu Dave

Moderator
#66
#66
LSCustoms said:
my daughter loves the race track and is inspired by Nicole Lyons... hoping this is fun enough for her, where I dont have to find and fund a jr dragster... she is 11, wish i would have known she was into this stuff alot sooner.....
Click to expand...
Hey, great idea getting her into a Jr Dragster! Definitely chocked FULL of cool parts to spend money on! PLUS you can ride your "pit bike" all around the pits and stuff. Win/win right there! :thumbsup:
 
LSCustoms

LSCustoms

Moderator
#67
#67
Havasu Dave said:
Hey, great idea getting her into a Jr Dragster! Definitely chocked FULL of cool parts to spend money on! PLUS you can ride your "pit bike" all around the pits and stuff. Win/win right there! :thumbsup:
Click to expand...
She is working hard toward that goal, but she just about likes anything having to do with motors, building something, doing the work, etc. more so than my son (so if i get her everything she is into, i couldnt afford to support the family)... i am careful with jumping right in though, as i would want to make sure she is focused on it enough to spend the money, investment and sacrifice on it... she has some work to do in school, before I even think about it... the racing/car would be the reward and not the plan... but id def like to find one someone who has to get out of one, where i could better afford to get into it... im not really sure im into mini bikes just yet! lol.

if she does what she is supposed to, she will be racing (id sell my harley for that, if i had to).
 
LSCustoms

LSCustoms

Moderator
#68
#68
LSCustoms said:
for this project... no rules to follow, just want a nice running engine/performing bike... the current old style predator in the bike, performs well, but would like to get more outta this motor...



14t clutch sprocket/54t axle sprocket, 13.11" ish rear tire height
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still making changes to the bike too...

 
LSCustoms

LSCustoms

Moderator
#70
#70
in another thread, a new member asked a question related to push rod length... I directed him here, in case it is answered here first and to help keep info in one spot (for future people searching for info on this motor)... here is an article from car craft, which closely matches information from comp cams...
Setting Pushrods Length, Quick and Easy- Car Craft Magazine

with normal larger car and race engines, i know this is a very critical thing to get right (esp with roller rockers etc)... is there a simple way to figure out the correct push rod length for my motor, without buying a special tool?

through research I have found that the length (for my motor and valve train) should be between 5.35-5.45"

what is the correct way to cut and properly fit the "cut to fit" push rods that are on their way to my doorstep?
 
ole4

ole4

#71
#71
Funny you should ask! As I always cut mine to length and press in the end. However the first time I did it the interference was so tight I bent the chrome moly pushrod!. Now after I figure what the correct length should be I have a tiny tapered ream that fits in the end of the pushrod and it ream it ever so slightly to get rid of any burrs from the cutting and also open it up just a hair. Next time I will get a solid rod of aluminum and drill it so the pushrod fits in it for 5 inches so when I press in the end it cant bend in the middle. You can also use red Loctite stud and bearing it you ream a bit too much.
 
LSCustoms

LSCustoms

Moderator
#72
#72
ole4 said:
Funny you should ask! As I always cut mine to length and press in the end. However the first time I did it the interference was so tight I bent the chrome moly pushrod!. Now after I figure what the correct length should be I have a tiny tapered ream that fits in the end of the pushrod and it ream it ever so slightly to get rid of any burrs from the cutting and also open it up just a hair. Next time I will get a solid rod of aluminum and drill it so the pushrod fits in it for 5 inches so when I press in the end it cant bend in the middle. You can also use red Loctite stud and bearing it you ream a bit too much.
Click to expand...
i wish i could have bought the rods cut to length and ends pressed on! lol... how did you/do you determine the length. i understand the principal and goal, but would like to understand the process better... with no specialty tools...

the head and carb arrived today, once engine is torn down will post pics of both stock and ported...
 
ole4

ole4

#73
#73
The motor I made up my own pushrods used raceseng 1.3 rockers and isky billet lifters. The isky lifters were .180 different (I think they were shorter than stock but I am not certain) and the pushrods come with one end in. using Prussian blue you want the roller or tip slightly further out at mid lift to start then you cycle the motor and you want to find that the mark it leaves is more or less centered on the lash cap. If it goes to one end or off the end that is a problem With the racesend rockers you can also get various shims to aid in case you mess up with pushrod length. I added the length ot the tip as if it were installed and used the rod without the tip but now cut to about the correct length. I started with the length that tim states fur using his lifters. In the end I think I still had to go a little shorter. Every setup is different if the head is milled or different gasket thicknesses. Ithere is a little leeway befote you get too close to one end but if you can get the contact as close to centered that is the best. This is how I do it but it is more complex in that you really want the distance that the roller travels to be at a minimum and that has to do with the alignment at mid lift. I don't really do that. Here is a comprehensive article on it and if you have the patience to read it all you will uncerstand it better.
http://www.sbintl.com/tech_library/articles/rocker_arm_geometry.pdf
 
LSCustoms

LSCustoms

Moderator
#74
#74
ole4 said:
http://www.sbintl.com/tech_library/articles/rocker_arm_geometry.pdf
Click to expand...
After reading the entire article, while I do have a better understanding of push rod geometry, i still want to get this correct... would these adjustable push rods work with this motor and should I grab the billet lifters while at it? i feel that the adj push rods would be easier for me to get the proper geometry rather than an attempt to creep up on the right measurement? I am still under my budget and I do not mind spending a little extra to ensure this is done correctly and with the right parts...

Raceseng PUSH ROD - ADJUSTABLE - S2

Raceseng Billet Lifters
 
Last edited:
ole4

ole4

#75
#75
Let go measure the hemi pushrod compared to the stock ones. If the length is close it should work. If not ask them what the max length is and see if it can go a bit longer than the stocker just in case. I should have the two compared within the hour.
 
ole4

ole4

#76
#76
Ok looks like hemi pushrod is a lot longer than stock. (.325 more or less) and the build your own without any cutting is just a bit longer. Here are some photos with measurements
Stock:


Hemi:

Comparison:


Build your own vs hemi
 
LSCustoms

LSCustoms

Moderator
#78
#78
ole4 said:
Ok looks like hemi pushrod is a lot longer than stock. (.325 more or less) and the build your own without any cutting is just a bit longer. Here are some photos with measurements
Stock:


Hemi:

Comparison:


Build your own vs hemi
Click to expand...
the raceseng is adjustable from 5-5.5"... is the width of the push rod (hemi vs reg) the same? where that adjustable will fit properly in the predator hemi... it shows it works for a honda/clone/predator (normally when it wont work for the hemi, it states that it will not work, it doesnt say)... sent an inquiry to raceseng, but more than likely wont be getting a response for a few days, as they are closed during the weekend...
 
LSCustoms

LSCustoms

Moderator
#80
#80
ole4 said:
Just realized I posted the wrong hemi pic the lengths are as follows:
HEMI = 5.557"
Stock clone = 5.225

Sorry for the confusion.
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no prob... the new push rod length should be shorter right? between the 5.35 and 5.45"? which would allow the use of the adjustable rods? this way i can just adjust it to the shorter length 5.35, check it and re adjust if necessary... without having to cut (and fit) and press in the ends, like in this vid, only, after the geometry is correct, just lock the push rod at that length then done?
https://www.youtube.com/watch?v=Cqx8Cs6O6Vo

thanks for all your answers, it really does help... with the big motors, race car stuff, things are more common and more bolt on parts are available... i dont mind trying to cut fit and press the ends on, but id rather have someone else do this correctly, or just spend the extra on the adj.
 
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