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Discussion Starter #1
Hello everyone!

I just picked up a trx 300ex and it came with quite a few extras. One being an FMF pipe- I don't know what type or anything. I was wondering if this does anything for performance.

Also, where can I go from here? What should I upgrade next?

Looking forward to riding and I'm sure I'll have plenty of questions for you guys. Thanks
 

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Welcome to the Forums.

I have a FMF powercore 4 and I love it they sound really good and yes it does add to the performance over stock. if you don't have a good aftermarket filter i would suggest that as well either K&N or UNI also you will need to rejet the carb if it hasn't been done already for the exhaust and filter. That's a good start it really depends on your riding style and what you are looking to get out of your quad.
 

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Discussion Starter #4
thanks for the response guys.

Right now im just trail riding but I hope to build some light jumps soon, and see where it takes me from there.


I've looked into some re-jetting guides and I've never had much experience with engines in general, so I would absolutely not want to try this. Can most motorcycle shops rejet for me, and how much would that cost approx?


As for the filter, I will give that a shot.

Thank you guys for your help! I've been reading everything I can on these forums and y'all seem very knowledgeable.
 

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Re jetting the carb isn't that hard. You can do it if you are the least bit mechanically incline. Just have a clean area and watch how you take every thing apart and some jet kits come with instructions to were and how to set every thing.
 

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Welcome to the forums.
 

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welcome to the formus..yeah..re-jeting is so easy..a caveman can do it..well..you get the idea..lol..as stated..work in a well lit..clean area..take your time..it should go very good for you..just tell your dealer what you got..carb name..size..and they should know what the next size jets you can get, you don't want to go to big on the jets..or you will get alot of engine trouble from them..oh..i didn't see anyone say what rejetting is..soo..it's just going to a higher jet number..bigger hole in the center of the jets..at least i think thats what it is ?.lol..don't quote me on this..i always stick with stock.
 

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Yep shadetree is right about the jet (hole) being bigger. When you get a K&N or UNI filter the air to fuel ratio changes so you have more air with the aftermarket filter. So you need more fuel to bring the mix of the two back to a good combustable state i.e. a bigger jet. Now you have more air and more fuel thus greater performance from the engine. ........... Hope this helps.
 

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Discussion Starter #9
Thanks for the replies guys, really helpful stuff!
So if I get a K&N, do I HAVE TO jet? or can I still ride until I get bored and want to jet?

Will the K&N + FMF give any performance without re-jetting?

Also, if I jet, doesn't that put more strain on the engine? Which would mean more frequent oil changes/oil filter/general wear & tear?

I know it hasn't been said much, but it seems common sense that if my engine is performing better = it works harder = life expectancy decrease?

Thanks again
 

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If you make any modification over stock you need to compesate the air/fuel ratio. ie. if you add an aftermarket filter system that = more air which in turn will cause a lean state = not good add in the aftermarket exhaust = even worse jet the carb it's really easy and an inexpensive upgrade if you install the filter and pipe I suggest. this is directly from dynojet
3. Install Dynojet needle on groove# 4 for applications below 5000 feet,
groove# 3 for above 5000 feet, using all stock spacers. Install the Dynojet
washer above the E-clip.
4. Remove stock main jet. Replace with the Dynojet Main Jet Adapter
(DJA001). Screw the Dynojet main provided into the Main Jet Adapter. If
you are running the stock exhaust use the DJ124 below 3000 feet, DJ120
from 3000 to 6000 feet and DJ116 above 6000Feet. If you are running an
aftermarket exhaust, use the DJ128 below 3000 feet, DJ124 from 3000 to
6000 feet and DJ120 above 6000 feet. Be sure that the jet you are changing
is the main jet.
5. Locate the Fuel Mixture Screw (Fig.B). Using a flat blade screwdriver,
turn the mixture screw clockwise until it seats, then turn out 3 turns below
5000 feet or 21/2 above 5000 feet.
 

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Discussion Starter #11
Hi all. Just picked up my bike over the weekend. turns out it came with a K&N filter, FMF pipe, and is already jetted.

I didn't have much time or space to ride this weekend (We just got 2 ft of snow) so i took it on the street for a little bit.

When I got into high 3rd, 4th & 5th it would start bogging down. But first and second would rev all the way. The filter was disgustingly dirty so I bought a K&N recharge kit. I haven't tested it with the cleaned filter yet.

I was thinking the bogging could be caused by low air mix (so i cleaned the filter) or spark plug... any other ideas?
 

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You may need to go through the carb and give it a good cleaning. Check the fuel lines for fuel filter it may be clogged some and clean the pit cock also..
 

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Discussion Starter #13
Thanks mud.

Are there any guides on how to clean the carb? preferably with pics/videos since I am oblivious to mechanics of an engine. I couldn't tell you where the carb is lol. But one of the reasons I got the bike is to hopefully learn a thing or two about this type of stuff.

Thanks a bunch guys you've been a great help so far.
 

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That is the symptoms of a filthy air filter...
 

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Sound like not enough air to me too.Is the airbox lid on or off?It's the thing with the air filter in it
 

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Sound like not enough air to me too.Is the airbox lid on or off?It's the thing with the air filter in it
lol I got that.

I havent had a chance to test it without the box on it. I just cleaned the air filter and now i have to wait for it to dry so i can add oil to it.

I'm gonna drill holes in the air box soon too
 

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Good idea.It needs air to run corectly.
 

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if you jet bigger thats more fuel, i say get a uni air filter, thats more air flow, which keeps air/fuel in check
 
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