knocking

[killer400ex]

when i first bought my ex i noticed that it was wicked snappy when you first started it up and as it warmed up it seemed to loose some of its snap and overall power, but the loss was only on bottom end power, and after the fresh rebuild it is starting to do the same thing again, it will hesitate or stutter when you tap the throttle ( when your letting out the clutch, not allready moving) and it will make like a real loud tapping noise that sounds like its coming from either the cam or valves, like when its about to stall out, im not positive but i think it might either be that the pilot jet needs to go up one size or the fact that the timing chain was never replaced and im sure that by now after it warms up it is stretching too far. just thought i would throw that out there to see what everyone els thinks

[TRXRacer1]

Sounds like detonation. Have you tried a higher octane fuel yet? What is your current jetting?

[killer400ex]

i dont think its detonation because it only hesitates when i first tap the throttle, and it would be dooing it all throught the rpms, its not as violent as detonation, it just like coughs, hesitates and tries to stall out if you just tap the throttle when its just idling, and it only does it after like 15 mins of riding, when i first start it its fine

[mcgrath]

Whats your pilot jet? Sounds like it might be running lean. Does it pop when you get off the throttle when your riding?

[TRXRacer1]

Originally posted by killer400ex
i dont think its detonation because it only hesitates when i first tap the throttle, and it would be dooing it all throught the rpms, its not as violent as detonation, it just like coughs, hesitates and tries to stall out if you just tap the throttle when its just idling, and it only does it after like 15 mins of riding, when i first start it its fine That's detonation. It's most noticable when you first get on the RPMs, not throughout the RPM range. Also detonation is a heat issue and you're saying the pinging isn't starting until the motor is well warmed up. The truth is detonation can be so subtle that many don't even know it's happening. After 15min it's just getting bad enough for you to hear.

That leads into the jetting specs, if you're too lean that can be the icing on the cake causing the heat issue that is causing the detonation. What is your carb set at?

[killer400ex]

i think its a 40 or a 42 pilot, and i think it has a 160- 165 main, like i said it has insaine power at higher rpms now, at first i thought it was my new cam or something cause it sounds like its clapping, i have been running just regular 87 gas, i had nothing els but i am getting the 93 today so i will let you know how it works out, it makes the same noise when its almost out of gas or it is out of gas right before it stalls or dies

[killer400ex]

allright finally got the time to get 93 octane and go riding, well i was extremely dissapointed to find out that even after changing the gas it still gave me problems after warming up, i am slightly positive that i have to adjust the air fule mix screw because it runs best when i first start it, after it warms up it is choppy and lacks power and is also acting weird throught the throttle range, but when i went riding i also think that there was enough of an elevation change to affect it because around my house it will run decent, not great but better than it was running today, but i am also not sure if changing the gas might have affected it because it didnt act like that before i switched over, i am slightly confused and i do this for a living

[MtnEX]

Adjust your fuel screw after it warms up.

Start by checking your turns out before starting. Set it back.

Then start it, get it to the point where it is running bad. Then adjust the fuel screw. What you are looking for is the point of highest idle, or the point dead between the two (in/out) points where you hear a change.


Report back and we will go from there.


(you might also want to check for intake leaks)

[killer400ex]

set it back to what, 2 1/2 turns out from the seated position?

[Punkmaster Flex]

That's definely bad jetting. This combined with poor gaz ( Common are you really able to afford a quad yet still buy the cheapest gaz available? ) is what causes your knocking.

Just start by completely cleaning your carb and flush your mixed 93 / 87 octane tank and get FRESH gaz. Then go one and jet your quad the right way. If it's still knocking well atleast you will have an idea of what your problem isnt.

[tri5ron]

Originally posted by Punkmaster Flex
That's definely bad jetting. This combined with poor gaz ( Common are you really able to afford a quad yet still buy the cheapest gaz available? ) is what causes your knocking.

Just start by completely cleaning your carb and flush your mixed 93 / 87 octane tank and get FRESH gaz. Then go one and jet your quad the right way. If it's still knocking well atleast you will have an idea of what your problem isnt. make that 2 Aspirins :huh

[killer400ex]

yeah well like i said, i completely rebuilt the motor and carb so everything is fresh, and i had dynojet give me there recommendations for jetting at my elevation and seasonal changes, i just never had time to get the stupid air/fuel mix right cause in order to adjust it you have to basically twist the carb cause everything is in the way, i dont have one of the knobs i have the stupid screw you need a 90 degree screwdriver for, and yeah i wasnt the smartest person for putting 87 in the tank but i had nothing els and i had to move it so yeah, and i did drain the tank b4 i put the 93 in it.

[MtnEX]

Originally posted by killer400ex
set it back to what, 2 1/2 turns out from the seated position?

Keep track going in...

Then set it back to where it is now.

Then ride and get it acting up.
Then start adjusting on the screw.




A way to make this easier to get at is to remove the bolt holding the idle adjuster.

(heck yeah the fuel screw should be set up the same way!)


Once that is out of the way, it helps and you can get at it with a craftsman bit ratchet and a small straight bit.

[killer400ex]

k well i set it to about 2 1/2 turns out and i rode it and it had no balls, like it would hesitate on the throttle and had no mid-top end power like it should, so i brought it out to about 2 3/4 to almost 3 turns out and it seemed ok, im just wondering if that sounds about right, im going to go ride it and try adjusting it again and yeah i did wind up just taking off that stupid idle adjuster bracket

[killer400ex]

well i was able to bring the air/fuel screw all the way in and still have the quad running half decent, i slowly brought the screw out but it seemed like basically nothing was changing , idk after a while i got a case of the f-its and called it a day, soo im not sure at this point, i am running a 170 main and a 38-40 pilot, and all my mods are listed, i believe i am around 400 ft above sea level but im not positive, and today was a relatively cool day, im stumped, and i need to know alittle more of what "running like crap" should sound like, i did notice that when i brought the screw in to its seat that the idle went down a hair but nothing drastic soo yeah any input would help because i am trying to sell it before winter hits and we usally have a few inches of snow around thanks giving so time is of the essence, i am debating on taking it into a shop and having them do it for me, not because i cant but just because they have more time to do it, where i have school and neighbors who like to call the cops after 20 mins of riding

[MtnEX]

If you have a 38 pilot, that thing needs to be changed. It needs a larger pilot.


Go ahead and take the carb off to change it, and don't drain the bowl before you do.

Once you have it off, before you do anything, get in a good place and "work" the carb.

What you are looking for is the spray from the accelerator pump... watch out, it's a good spray.

Make sure it is squirting good, and make sure it is going straight through with zero obstruction.

Then drain and pump it on out so you can visually inspect the slide/butterfly timing.

[killer400ex]

i know the accelerator pump is fine cause its new and i cleaned the whole carb out a few weeks ago, and i contacted dynojet a few weeks back after i rebuilt the motor and they told me to use a 40 pilot with a 170 main

[MtnEX]

Originally posted by killer400ex
i know the accelerator pump is fine cause its new and i cleaned the whole carb out a few weeks ago, and i contacted dynojet a few weeks back after i rebuilt the motor and they told me to use a 40 pilot with a 170 main

You have in-person seen is squirt?
And checked the slide-butterfly timing?


Don't tell me you are using dynojet parts.

The guy who did mine screwed me up the same way with RD Precision parts/jets.

As a result, it runs, but is impossible to tune properly.... and is now down waiting on me to order some genuine carb parts.

Only put carb brand parts in your carbs.
Check out Jets R Us, etc...

[killer400ex]

im not positive but the guy i got it from said it might have dynojet jets in it, and there deff not stock, i ran it again today and it seemed alright but it is still its snappiest when its cold, when its cold she snapps like a two stroke and had no problem pullin up the front end in 3rd gear with ease, idk im selling it anyway, it was just bugging me for a while but since it should be gone before winter i guess ill just let someone els screw with it, thanx for all the info and help bro