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Posted by: terd
If you want an easy fix for that throttle. Get rid of your oil injector pump and get the single cable only $20.00 for that. We did and it is great on the kids little thumbs. Do a search on this forum for "Oil Inection removal" in the kids forum. You will be happy you did. The system is easy to get out. You will have to premix but it is well worth it in my opinion. Goodluck
Posted by: terd
Goto wrhracing.com you can get the cable from them. We have the predator also and it worked out great. Fast service.
Posted by: terd
We are mixing at 32:1
Posted by: spike99
mikehops43,
To me, the back firing is probably caused from carbon build-up on your Spark Plug. This sometimes happens when young riders don't keep their 2 stroke engine reved very high or give it those up/down revs to keep it cleaner. Yes, those "put - put" drivers who learn for the first time. With low revs, the injection or pre-mix oil becomes "gummed up". With higher revs, the engine is hotter, has more air flow through its system thus it flushes the burnt carbon out.
A few suggestions are:
- Run with a little warmer spark plug and one that contains the "P" code. The "P" code is for Protruding and is much better on low rpm engines - because it tends to burn more carbon away. A little warmer plug helps as well.
- Removing the Oil Injection and going Pre-Mix at 30:1 -> 36:1 (average at 32:1) also helps. By going pre-mix, you can then tweak the best oil mix ratio for your unique riding conditions. To find your best mix ratio, you'll need to read your spark plug many times. If you stay with the same brand of pre-mix oil, it takes approx 4 plug readings to find your most optiminal pre-mix ratio. For our riding condition and brand of oil, we're running 35:1 Removing the Oil Injection system and its "pull spring" also removes 50% of its pressure from its thumb control lever. With less pressure, your kid will probably do more riding (re: no sore thumb within a few minutes). Besides that, your young rider will have better control of his mini. re: I don't control my quad with extreme sore fingers / thumb very well either.
- If your engine is running higher revs, as your kids brings up his/her speed, remove the "P" plug and replace with a normal non-P plug. "P" plugs can damage a high reving engine if used over a long period of time. As described to me, "P" plugs are great for city stop / go type driving but they make the engine too hot on the hiway type high revs".
To read your spark plug, surf: -Press Here-
Also, I'm assuming you've removed the CDI Jumper and are only using the Throttle Thumb Control Screw. If you have the CDI Jumper installed and us the throttle control screw as well, the jumper "may" make it back fire as well. The reason is.... The CDI is telling its engine NOT to rev any higher but if your throttle control is set above that, your rider is giving it more gas then it can burn. Much behavior if running with its choke partially on. Hence back fires may happen. If you remove its CDI jumper and only use its throttle control screw, it should eliminate this "accidentaly choking" condition...
Hope this helps...
.
Posted by: spike99
To me, there's no such thing as a "dumb question". As some would say, "its better to ask where to put oil in an engine then to NOT ask this type of question at all".
The CDI on the Pred-90 has a little jumper within its CDI box. Its actually a piece of steel that allows its electrical current through a different set of circuts, whick keeps is RPM "equivelant speed" down to around 15 MPH. If you want the unit to go above 15 (15-30 range), then you need to remove its jumper. For illustration of this jumper, see item 12 within: -press here-
If an Operators Manual came with your Pred-90, the CDI Jumper details is also within it.
When we purchased our Pred-90, my dealer would NOT remove its jumper. He loosened its screws, I was asked to remove the jumper, then he tighten its screws tight again. For liability reasons, most dealers will NOT remove the CDI jumper. My dealer "recommended" I remove its jumper and only use its gas throttle screw to restricts its speed. This damatically reduces "accidental flooding" behavior and allows more "fine tuning" of its ground speed (based on gas flow control). This inturn also reduces the amount of "returns for tweaking" to the dealer. win-win condition for everyone.
Note: Ensure you test your Pred-90s thumb control speed setting before and during long rides. For us, we left it a very low for flat ground and moved it out a little for little rolling hills and soft sand type conditions.
Hope this helps...
.
Posted by: spike99
For your thumb control hardness question..... The cable going into the carb has one compression spring. The cabine going into your Oil Injection system has another spring. Combine the compression strength of these 2 springs together and its factory thumb control lever is stiff. A little too still for hands that aren't conditioned to it. By removing the Oil Injection system, you also remove one of these "compression" springs. Thus, the hardness on the thrumb control system is approx 1/2 its stiffness.
If your unit is new, I'd wait until its warranty period is over. This isn't a risky change. Some dealers blame a broken xx on anything that "we the people" changed. For example, all warranty is void on its back tire because we install different hand grips. Not trying to sound negative but some dealers (minis, autos, houses, etc.) are like that. By the book and only by the book. If you don't mind doing the work yourself and aren't too worried about "possible" future warranty claims during its warranty period, then it might be worth removing the Oil Injection system now.
Also, you may want to investigate thumb control extensions / extenders. Some people love them and some people don't. This idea many work for your young rider (and you) much better. Well worthin investigating extenders with this forum's search engine.
Hope this helps as well.
Posted by: mikehops43
My son and I were out riding the other day, I was following behind him and his 04 Preditor 90 started to backfire, We took him back to the truck and changed spark plugs which resolved the backfire, However, after it started to backfire & for a few minutes after we changed the plug the throttle was SUPER sensitive, you would barely touch the throttle and that bike would take off, I jumped on it to test it after I changed the plug and was able to spin the tires pretty easily in the dirt and Im 200lbs. Shortly after my son got back on, it was back to normal.
Anyone ever heard of this before? I have the throttle jumper off and the throttle limiter screw about half way out.
The throttle was great for the few moments it was Super sensitive, How can I get that back?
Posted by: mikehops43
Thanks A.D.D. I'll look into that, What ratio do you premix at?
Posted by: mikehops43
Dogg,
Here ya go pics of the cdi jumper location. This is on a 2004 Predator 90.
http://community.webshots.com/album/138877496afNSrY
Predator 90 cdi jumper location
Posted by: dogg
Spike99,
Dumb question, BUT where is the CDI jumper on the Predator 90? I have been looking for it, but could not find it. Do you or anyone else have pictures of where it is or where I should look? Also, what does removing the oil injection have to do with thumb fatigue?
Thanks,
Posted by: dogg
mikehops43,
Thanks very much. You're the greatest!!!!!
Posted by: dogg
Now I am really concerned. I looked under the wheel well and what do you know, the CDI? box was hanging. There was no jumper in site. A while back, it Predator was sputtering and I took it back to the dealer. Do you think they took it out? I now need to unscrew the limiter and see what I got. That was a little strange. So I should be looking at speeds of 25 mph+? I will keep you posted.
