z400 bogging/backfiring problem

[zukirder93]

i have a 2006 ltz400 with a full system yoshimura pipe and ONLY the main jet is jetted to 150 with the fuel screw 2 1/2 turns out. it has always bogged and lacked power when you pinned it in 2nd, 3rd, 4th, and 5th gear. today while i was riding it began to cut out and back fire and have no power when you tried to go past half throttle. Do I need to rejet the carb or is there another cause to this problem

[John Noftsinger]

Did you get new needle with jetkit? that was my problem changed main jet not needle and pilot jet might need changing.Call Yoshy on this, they can tell you what jets to run.

[zukirder93]

i just bought a main jet from my local suzuki shop. i will probably buy a jet kit though.

[John Noftsinger]

Did same ,then learned you need the needle that the jet kit come,s with hope this gets you riding again.

[zukirder93]

did you change the fuel screw at all?

[John Noftsinger]

only turned screw out 2 1/2-3/4 didnt need to replace. are you running aftermaket filter?

[zukirder93]

no stock and cleaned the carb and now it wont start so im going to check the plug tomorrow and if its not that then im going to check my kill switch connections and if that doesnt work i guess ill just take it to the shop

[Minndave13]

Whoa, replace the stock air filter with an aftermarket air filter (k&n, etc.). Remember for a engine to run it has to breath, you opened up the exhaust now you have to open up the flow to the carb. Usually one will do one with out the other and then place blame on something that doesn't have anything to do with what is going on. Do some investigating on this forum and learn your quad, It can be intimidating but there is some really good posts here. Besides when talking about your quad to your buddies would you rather tell them how you fixed your problem or tell them how your dealer fixed your problem at 80.00 an hour.

[zukirder93]

ive put off going to a dealer for just that reason. i plan on getting an aftermarket filter soon and today i took my quad to my friends dad, who has worked on quads for the past 20 years and he said to clean out the carb or check the wires

[Minndave13]

Remember start with simple or KISS (Keep It Simple Stupid). Keep in mind that a engine needs three things to run-air, fuel, and spark. Start with making sure you have spark, take the spark plug out make sure it touches the engine somehow (metal to metal) and turn over the engine fast enough to start it if the spark plug was installed. See if the spark plug has a spark between the electrode, if not use another spark plug to see if it is a bad spark plug (sometimes I will test the spark plug on another engine, lawnmower that you know runs, works well). While you have the spark plug out now would be the time to do a quick compression test, put a finger on the spark plug hole and turn over the engine fast enough to start, as if it had the spark plug installed. The excapeing air should blow your finger off the spark plug hole, Note if you have spark make sure you don't get shocked-make sure the wire is not near any metal when turning over. Now if you have spark and you have good compression now check for fuel. 1st, turn off the gas on the fuel tank, now slowly take off the screw on the bottom of the carb. Remove slowly-some gas should come out, now with the screw removed turn the gas back on breifly- a good amount of gas should come out of the hole on the bottom of the carb. Note-another quick way to see if it is a gas problem is to put a small amount of fuel in the spark plug hole, quickly put the spark plug back in and try to start. If it starts but stops running again then you know it's a fuel problem. Just some ideas.

[zukirder93]

ok its getting fuel and spark and has good compression. i got it back together and took it down the road and it doesnt backfire anymore however it lost all the snap and wont even pull a wheelie or hit the rev limiter even in neutral.

[Minndave13]

now the real work begins, you got it running, good job! now you have to start checking other things. I would check your timing to start with ( I have seen motors slip a tooth on timing and run poorly). Read your SERVICE manual or ask your local dealer on how to do this-better yet research the web it should be here somewhere. If timing is ok check your wiring, maybe you have a loose wire somewhere. Remember KISS.

[zukirder93]

a friend told me it was the throttle position sensor. how do you adjust the tps? i got 5.31 as my first number so i need 4.04 (because thats 76% of the first number) for the second and it only got to 3.8. i touched the black ohm stick to the black tps connector and the red ohm stick to the blue tps connector for the first number. i did the same for the 2nd one only i touched the red ohm stick to the yellow tps connector.