I have two 06 pred 90's. and two daughters. my oldest can handle more power and speed, so I tried some miner modifications. but to my disappointment they were not worth the time , money or effort.

I replaced the air filter with a k&N air filter and had to rejet it. so I had to buy a bunch of jets. this ended up being more of a hassel then it was worth. but I do ride in the desert only so it is a must to upgrade the filter one that suites an outer wear. but it opened the intake so much that I had to go from an 82.5 to a 105 then back down to a 100 then pinch the intake like with a few zip ties. it finally worked , I guess the K&N is just to good for the bike. but it did sound nice. but then I realized that it was not as responsive as my other daughters stock bike. nor did it start up as quickly when it was cold.
next I bought this so called adjustable cdi box. I was thinking how this would help out alot since she did need more rpms for the sand dunes. well sure it is adjustable but only to limit it. I had to max it out in order to get it to be as fast as my other daughters stock bike. once again a waste of time and money and effort. the stock cdi did just fine. but I guess If I did want it to go slower it would be easier then a adjustment screw on the throttle.

the few modification that I did fine usefull were upgrading the light bulbs. that was about two dollars, at the auto parts store. then I ran a light up the flag pole for night riding. using the same bulbs as in the headlight and hooking up a toggle switch near the back of the leg area.

but after all this I still need my oldest daughters bike to run a bit faster. I plan on shrinking the intake hose a bit more and see if I could create more of a vacuum because I have to keep the K&N with the outerwear on for the sand dunes. I have been thinking of a pipe but I hate to just make it sound cool have the stock bike still be as fast if not faster.
I tested both bikes using a hand held gps. using several passes and testing. not to mention using a local steap sand dune to test the power I lost compared to the stock bike.

oh and the stock tires seem to work just as good as paddles.

I think what it comes down to is the stock bike is as good as it gets with out changing the carb, boring and putting a new motor in the old bike , in that case I am better off buying a bigger bike.

but if anyone has any suggestion I would love to hear them.

 

I think I would tend to agree about the simple mods you did. But I disagree that in stock form is as good as it gets. First off are we talking about the 2 stroke 90 or the new 4 stroke?

The 2 stroke really wakes up with a pipe, K&N filter and clutching. If you want to go further porting is the best power upgrade you can do to a 2 stroke next to a pipe. All of these mods work great together. I have done some clutch work, carb mod and pipe mod to my sons DC90 (same as the pred90) and it was like night and day. He is 9yo and can pull wheelies from a dead stop. Prior to mods it was actually kinda sluggish on take off but would go pretty good in top end. I would not give up just yet. Kids all ver the country race these 90cc 2 strokes and they kick butt. There are tons of mods you can do to the 90cc to make them very quick. I just dont think you have found the right combination yet.

 

yes I agree if you bore out any motor you will see an increase and then you have to mess with the carbs and jeting as well.
and like I said at that point you are just better off buying a new bigger bike and teaching them how to use a clutch.

I will get the pipe but not sure witch one yet since I am not after making it as loud as I could but more after getting this so called better performace out of this 06 pred 90 and yes it is a 2 stroke. they just started making the 4 strokes in 07. or so I believe so.

so any suggestion on a pipe? once again I dont want some banchee sounding little 90 riding around my camp site. hehe!!!

 

I think you are confused about boring and porting. Boring a cylinder does not gain much but porting will add a crap load of hp and performance. Hetrick racing has all kinds of mods for these. He builds them to race.

 

I added a clutch kit, jet kit,pipe and filter but would like a better launch. Anybody mess with the springs (add or remove some) and find a good setup? I wounder if there is an air/fuel mixture screw to mess with after jetting also.

 

To make modifications work they must be mated together properly......Adding fuel or air into an engine that can't use or get rid of it, is not going to give the results you desire.

It all has to work together.....

If you added an exhaust to these mods I bet you would be much happier....


Personally I am a big fan of the DRR lineup of quads....Their stock set up is hard to be beat for the cost....44" wide and HP matched engine and tranny in stock form.

http://www.drrinc.com

 

Have you looked at a different ignition? They make a DC igniton that gives a stronger spark and retards the timing for a better launch...


The kits that you have added also have to match...I have met local racers that have bought kits and the performance was not as expected due to issues like unmatched roller weights etc.....They had too heavy of weights and the motor couldn't rev to where the power range was etc....

The air/fuel screw will have a huge impact on the bottom end, so you should definately start there....Little changes at a time.....Jetting properly will make or break the performance as well

 

I bought a whole setup off some jokers on the web, they helped me pick it out. I think It just needs some fine tuning to make it a whole new animal.I will try taking out a few roller weights and if that helps, I'll buy lighter ones. Also try the air/fuel screw when I find it.

 

I would think that 5.5 to 6 gram rollers would be a good starting point for most slightly modded 90cc 2 strokes


Good luck with the fine tuning....

 

The most important performance part to a 2-stroke is its pipe. This is largely what sets the "power band". The porting also helps to determine this as well. When these two are set up to work together, this is where you will see the most gains. Other things of course will play a major part in adding performance like clutch kits, bigger carbs, CDI box, etc. but all these things need done so that they will compliment each other instead of fighting each other. When built up properly, these little 90's will out drag a stock 400ex in a hundred yard drag. So their is alot of performance to be had out these but to get it, you have to do right.

If you want to add noticable performance then your best bet is to get a GOOD pipe. In doing this though, you will also need to get the right clutch kit. This way the clutch will work with in the power band of the pipe. You will also need to get a GOOD unlimited CDI box. As you found out already, the adjustable ones are not it. With these three things you will add about 30 percent or more performance to the machine and you would be happy with the results. This will probably set you back a little over $400. And yes, the pipe will be louder. It will sound like a performance 2-stroke.

Like to 2manytoys said, Hetrick Racing is a good source for these parts and they are extremely knowledgable. Their web site has all the parts listed if you want to check them out.