Predator 212cc free mods

cxbra

New Member
#1
I have a few idea's for free'ing up some power on my engine (bone stock Predator, NO mods yet). Power isnt the problem, i'm running 12/72 gearing with a 13" rear tire. The front comes up when I need it. The problem is my throttle response is pretty bad. When I roll off the throttle, there is a lag before the power comes on again and its pretty abrupt (mainly due to the high gear ratio). I have looked at the stock intake box and I see no air flow vents anywhere! That must be why my throttle responce is horrible when im out of the gas all the way and get back in it. If I keep the throttle open a bit instead of closing it all the way it remedies that issue but I think that the stock airbox is too restrictive.
Mods:

1) Holes in the airbox. Im thinking of the top/back of the airbox mainly so it still has good dirt protection. That should free up the restrictive feeling a lot!
2)Open header. I modified the stock 2 piece muffler/header to run outboard because it wasnt going to fit with it mounted regularly (thats what she said...). The internal diameter of the stock 2" long header looks to be about 5/8". A lot of guys are running a 7/8" to 1" diameter open header with a 6"-10" length and they perform great. I guess i'll just have to give it a test..
3) This is a mod that I will not talk about due to fear of being stoned to dea... I mean "talked to". No it does not involve tampering/removing the governor in any way, but it does involve removing "something" that I wont talk about haha.
 
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GustoGuy

Well-Known Member
#2
I have a few idea's for free'ing up some power on my engine (bone stock Predator, NO mods yet). Power isnt the problem, i'm running 12/72 gearing with a 13" rear tire. The front comes up when I need it. The problem is my throttle response is pretty bad. When I roll off the throttle, there is a lag before the power comes on again and its pretty abrupt (mainly due to the high gear ratio). I have looked at the stock intake box and I see no air flow vents anywhere! That must be why my throttle responce is horrible when im out of the gas all the way and get back in it. If I keep the throttle open a bit instead of closing it all the way it remedies that issue but I think that the stock airbox is too restrictive.
Mods:

1) Holes in the airbox. Im thinking of the top/back of the airbox mainly so it still has good dirt protection. That should free up the restrictive feeling a lot!
2)Open header. I modified the stock 2 piece muffler/header to run outboard because it wasnt going to fit with it mounted regularly (thats what she said...). The internal diameter of the stock 2" long header looks to be about 5/8". A lot of guys are running a 7/8" to 1" diameter open header with a 6"-10" length and they perform great. I guess i'll just have to give it a test..
3) This is a mod that I will not talk about due to fear of being stoned to dea... I mean "talked to". No it does not involve tampering/removing the governor in any way, but it does involve removing "something" that I wont talk about haha.
From the factory these engines are jetted lean for emission reasons. Jetting a bit richer will usually improve engine response like it did in mine. After doing this mod it became a wheelie machine and my step daughters boy friend wheelie it right over even though I told him to lean forward. I fixed the wheelie problem with three 6lb pieces of mild flat steel mounted over the front wheel and down low on the frame in front of the engine.

The opening right under the foam is restricted some and I enlarged the hole and sanded it smooth with the inside of the opening and it was enough of an air increase that I needed to jet it richer since it bogged out and would only run right with the choke on. I used super floss and polishing compound and I increased the size of the main jet until the engine ran really nice. I then checked the spark plug to see if I am running lean or running rich. The sparkplug ended up having a nice dark tan color to it after running it for a bit and there is no hesitation when acelerating. I also drilled a hole on the air cleaner assembly to draw some more fresh air as well. From the outside the cover looks totaly stock except the engine breaths better now. I may get a new exhaust off OldMiniBikes website too to help it produce even more power since I heard the stock exhaust can be restrictive too. After doing this I noticed it had a bit more umph off the bottom and acelerated even better. Here are some pictures of what I did.
 
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cxbra

New Member
#3
Thanks a lot for the advice :thumbsup:. I opened up the hole that you were talking about, about twice the size as stock. I also realized that the opening of the intake is at the bottom of the intake assembly, and it draws air in along the side of the intake filter cover and into the open area of the intake. I noticed that there were 4 "runners" that draw air in, but at the filter cover the outside 2 runners were blocked off. I widened it so that all 4 runners are drawing air in . I also realized my plug gap was down to .025", so I re-gapped it to .032". All I know is that the throttle response couldnt be any better! I know that part of it was the spark plug gap, but the engine even sounds a lot more "tuned" now that its breathing much more air. I thought it was beast before, but it realllly free'd up some free hp! I will have to do some runs around the neighborhood later to really give her a test and check the plug. Thanks a lot!
 
#4
Free mods are great, but there some cheap mods too. Jet and infusion tube kit is about $15. I like my air cleaner and exhaust. Those were fairly cheap too. New valve springs are cheap, but you won't need them with the gov. I bet you can find a cam for a decent price. I have a CM cam that I'm not using. I don't know if it would give you any more get up and go or not.
 

cxbra

New Member
#6
Free mods are great, but there some cheap mods too. Jet and infusion tube kit is about $15. I like my air cleaner and exhaust. Those were fairly cheap too. New valve springs are cheap, but you won't need them with the gov. I bet you can find a cam for a decent price. I have a CM cam that I'm not using. I don't know if it would give you any more get up and go or not.
Thanks for the info man. Im going to stick with the stock cam for a while, it makes good torque all around which I like. Im going to focus on getting another nice vintage roller to put my spare 5.5 clone on, then i'll start modding the Predator out :wink:.

And GustoGuy, thanks. My goal for my "stage 1" mods is to keep it around $100 and with the stock governor/rod/flywheel. Im going to go for a header, intake filter, timing advance key, 140 emulsion tube, jetting and a 14t clutch sprocket. I want to gear for 40mph and still have the same acceleration as my stock engine did geared for 30mph :). I have bills (dont we all..) so i'm just going to keep it how it is until I get another roller to put my spare 5.5 clone on :001_cool:
 
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