backfiring!!!

[88dunerider]

so been messing with my jetting put a 42 pilot in , air screw 2 turns out , got full hmf exhaust but i am noticing alot more backfire on decel , is this okay / normal?? doesnt really bother me just want to see what you guys say

[honda400ex2003]

turn the f/a out until it goes away i guess. that is usually what makes it pop on decel unless your lean everywhere else. Have you been doing any plug chops or readings on new plugs each time you change something? or are you just shooting in the dark with a bb gun trying to hit the target at 100 yrds? lol steve

[88dunerider]

no i have been changing plugs everytime i put a new jet in , the last one i took out was black and then the prong was like a cream color , im used to 2 stroke spark plugs four strokes are kinda hard to tell whether its lean (white) or good ( light gray) , when i had the 200 main in there with the 38 pilot it was to rich , fouled a plug the first 2 rides out , i took the 200 out put a 190 in and put a 48 pilot and it fouled or was fouling then i just put the 42 pilot in with the 190 and only rode it for 10 min and it was popping on decel

[honda400ex2003]

if it is black at the base and the electrode is white your pilot is too lean still. Keep turning the f/a out to 2.5 or 3 and see if your popping stops. then you can work on your main to get that down a bit. go down a size or two on that and see how it is then. I bet you should be close then. white and gray are both on the lean side, you want a cardboard brown color, go down to a 188 leave the needle on the 3rd clip position, leave the 42 pilot in, go 3 turns out, and see how it does then. If it is backfiring still you will need a bigger pilot still, then throw the 48 in there and go to 1.5 turns out on the f/a and see if it stops. steve

[88dunerider]

yeah i will go and turn the air screw to 2.5 but yess that is how my spark plug is , black on the base and whiteish on the electrode, should i go up main jets ??? or down size??

[honda400ex2003]

may have missed or i was still editing it but go down to a 188 and see how it does there. the electrode is white from the lean condition on the pilot. steve

[bkelley]

Since we're on the topic, here's what my plug looks like.

http://img194.imageshack.us/img194/9508/dscf1425l.jpg (http://img194.imageshack.us/i/dscf1425l.jpg/)

[honda400ex2003]

looks like a winner lol. steve

[honda400ex2003]

oh i had the white tip black base last week while i was doing mine. lol. I have it all black now so it is time for the 178 when i get home on thursday. It will be finished up then for sure. lol. I had a 180, 175, 182 but no 178 to put in it so i ordered one a few days ago to put in to finish it up. i ended up going from a 48 to a 52 to get it so it would not pop and have a white electrode. lol. steve

[bkelley]

I'm at 170, 52, 3 clip on the needle and 2 1/4 turns on the f/a.

[honda400ex2003]

That is still the same setup that you were running when we were talking before right? that is a stock bore? steve

[bkelley]

Yeah, that's what's been in it for a few weeks now. I took it out to the dunes last weekend and it ran like a beast. Stock bore with the ESR air box eliminator kit.

[honda400ex2003]

that thing sucks some air to be running a 170 on a stock bore! I was running that with my stock 400 carb in my 416 I will be at the 178 which is a huge jump also. I cant wait to see what kind of mileage i get with that big mongo in there. lol. steve

[bkelley]

I could probably go down to a 168 since that plug looked a tab bit rich when I first pulled it out. I was in the sand all weekend and I usually burn a lot of fuel anyways so I couldn't really tell if it was that big of a difference haha.

[honda400ex2003]

Ill let you know once i finally get to go ride on the trails for a day lol. I would suspect it will be around 25-28 mpg though which still isnt too bad considering the extra hp i gained.:D steve

[bkelley]

Well, let me put it this way. My dad used to beat me by a few lengths on his 350X when we dragged. When we raced last weekend, I blew him out by 4-5 lengths. I'm sure the brand new Skat~Traks also helped, but the carb was definitely the difference maker. Either way, you couldn't wipe the smile off my face haha.

[honda400ex2003]

mine is a bit on the rich side and put a smile on me last time i was home. it was fun to really get it ripping. i hope getting it a bit closer will help with the low end a bit more. lol. steve

[88dunerider]

so i went and turned the air screw out 2.5 instead of 2 , still has a little rumble and back fire on decel but not as bad , i also pulled the plug before i ran it and it was black base white electrode , so i know its running lean , i put the 200 back in it was gonna ride it around for a bit and pull the plug and check it out , with the 440 kit stage 3 cam and esr air box eliminator and hmf exhaust 200 should be around there with the 42 pilot i see other guys on here running 220s!!! but you are running a 48 and 52 pilot in stock carb???

[honda400ex2003]

mine is a 450r carb. totally different animal. I was running a 38 pilot, 170 main in my stock carb. you should sit down and do some analysis on it before just going willie nilly out there. it is lean from the pilot and will give false readings. I had this issue for two days last week. the white electrode is from the lean pilot. every time you let off the gas it leans it out and burns the tip of the plug up. the black base is from having a rich main. you will have to get the pilot worked out before doing anything else with the jetting. you will never get a correct reading otherwise. you can run a series 26 48 main in your stock 400ex carb if you go to around 1.5 turns out or less, I have done so, with the choke stuff gutted from it. if you have the choke in still the 42 will be plenty or at least should be. take a deep breath, put the 188 in, go to 3.5 turns out or at least get it to quit popping. do a search on correctly setting up the f/a screw and idle. it is buried but you will find it. look under idle adjustment or fuel screw adjustment. if you have a manual look in there for the correct way to set the f/a screw and idle. it will help you out a ton. you first have to get it to the highest possible idle with the f/a screw then go from there to adjust the idle down using the actual idle adjustment screw. you gotta take your time with this or you will fight it for months and months. ask around some guys here have do so because they just throw stuff at it. you have to have a plan to execute before you go out to the garage. it is easy to get it mixed up otherwise. steve

[honda400ex2003]

1) Warm up the engine to full operating temp.

2) Turn up your idle a few hundred RPM using the throttle stop screw (basically you want a fast idle). This will make it easier to hear small changes in RPM. Watch for overheating--pointing a big shop fan at your engine will help it from getting too hot during the fast idling. The whole procedure shouldn't take too long though.

Each time you change the screw setting 1/4 or 1/2 turn or so, wait about 5 seconds to let the idle speed normalize. It usually take the carb and engine a moment to react to the change.

3) Turn the fuel screw IN until the idle starts to drop and miss. The engine should die if you bottom out the screw. Your pilot jet is too big if it doesn't die when the screw is bottomed out--it should die before it gets that far in.

4) Then begin turning the fuel screw OUT. The idle should peak and become smooth. Keep going and look for the idle to begin to drop/miss again.

5) The goal is to find the setting that provides the highest and smoothest idle. If it's unclear exactly were that point is then set to the midpoint between step #3 and step #4. For example, if the idle starts to drop at 1 turn out and starts to drop at 2 1/2 turns out then 1 3/4 of a turn out should be the correct setting.

If the peak/smoothest RPM is reached somewhere between 1-3 turns then your pilot jet is correct (the 1-3 turns applies to most carb types). If you end up less than 1 turn out then your pilot jet is too big and you need a smaller one. If you end up more than three turns out or the fuel screw seems to make little difference as you continue turning it out than you need to go up (bigger) on your pilot jet.

To re-emphisize: If the idle never drops when you're turning the fuel screw in, you need a smaller pilot jet. If the idle never drops when you're turning the fuel screw out, you need a bigger pilot jet.

Typical fuel screw settings are in the 1 1/2 to 2 1/2 range.

6) Once you've got the fuel screw set, re-adjust your throttle stop screw (idle screw) to an appropriate idle speed.

And that's it! Your pilot circuit is now VERY close to ideal. From here you can experiment with how small adjustments affect low-end (i.e. small throttle openings) response and make adjustments for weather. The hardest part is usually gaining access to the screw while the engine is running. Also, you may really have to listen carefully to detect the rpm changes in the idle. 100 or 200 rpm differences can be tough to detect when the change happens over several seconds.

steve

[honda400ex2003]

http://www.exriders.com/vbb/showthread.php?s=&threadid=413556&highlight=fuel+screw+adjustment

3rd post will get you started to adjust it also. im off to home for the night, Ill check in tomorrow and see how operation jet 88's 440 with a stock carb is going lol. steve

[88dunerider]

so i went out there to do this procedure and i turned on the bike to let her warm up while im finding some device i can reach the air screw with and turn around after a couple min of idleing and bam headers are red hot , shut the bike off , i see that that means they it is running lean!! i put the 42 pilot in there which i think should be fine after i get the air screw adjusted right??? or should i go up to a 45 pilot??? i think my main is way to big like you said but i want to get this pilot thing figured out before anything, oh and does anybody have any special creations they have came up with to adjust the air screw while the bikes running??

[88dunerider]

another question is how come i never had any problems with the stock pilot ??? bike ran good , no glowing heads no back firing , did foul a couple plugs but thats about it

[honda400ex2003]

when did you have the 38 pilot in there? before or after the big bore and such? I still think the 42 should be good but if you have a 45 put it in and see how it does. I just use a small flat head screw driver to turn my screw. If it is glowing you are probably still lean. I have never had that issue. It may always glow you may just never notice it during the day. lol. steve

[88dunerider]

yeah i had the 38 in there with the big bore and never had any of these problems no glowing nothing , when i got the bike the guys said it was a 450r carb so the reason i went to change the pilot was to go up to a 52 thinking it was a 450 carb , take the carb out find out its a 400ex carb stock 38 pilot and all , then i see some people running the 42 pilot in there so i figured i throw it in there while i had the carb out and now i run into all these problems , but the headers were glowing bright red, i do alot of night ridin and would have noticed it before , im goin to adjust the air screw this morning for the 42 pilot but if im still having issues should i just put the 38 back in there and go 3 turns out like how it was when i got it and just run a big main??

[honda400ex2003]

if it ran fine then put it back in there why did you mess with it in the first place? Put the 188 in there and do some plug chops on it with new plugs. steve

[88dunerider]

i messed with it because after riding for about 15 min if i kill it let it sit for 3 min and turn it back on it craps out until i give it some revs to clear the carb , its always done this even before i got the full hmf , so i figured i would throw a 42 pilot in there to see if it did anything , but i had a 185 in there with that stock 38 pilot before i did all this and it was running to lean , black base on the spark plug , white electrode , when i had a 200 in there it was full black , i never ran the 190 in there with the 38 pilot

[honda400ex2003]

oh yeah thats right that was the issue last week lol. What do you have done again with everything. You have the 440, slip on, choke out of the carb, 11:1 comp, stage 2 correct? steve

[88dunerider]

i have 440 kit stage 3 cam . full hmf bill ballance , choke is still on carb , and i have a esr air box eliminator and k and n filter

[honda400ex2003]

see now we are talking. put the 45 in 2.5 turns out, leave the needle alone for now. put in the 190 warm it up and do some chops on it. see how it looks after 5 or 6 chops on it each 20-30 seconds long. leave it in first or second if you have to to get a good reading at each section. I bet you would be suprised once you start to run it a bit. take some pics of the and see how it goes. do at least one plug at each section. main, needle, and the pilot. also try turning the choke on and see if it runs better or worse. if it starts chugging it is close if it starts to run better it is too lean. steve

[88dunerider]

alright i will do that tomorrow , nearest atv shop is 45 min away , but for now i stuck the 38 back in 3 turns out of the air , and no popping/backfiring and the headers dont seem to be glowing but yet you cant really tell , idle seems to be alright but i havent checked the plug probably still running lean but got rid of the other problems , but you think the 45 is the answer?? 2.5 turns out??? the 48 was to big bogged when you went to give it gas , and back fired alot .

[88dunerider]

oh and also wanted to add , when i had the 42 in there , i turned the air screw all the way in and it didnt die . usually means jet is to big right??? ill still try the 45 but just wanted to throw that out there , and on sparkplug chops , i know there is the pilot the main and the needle , what is what on the plug

[bkelley]

http://www.4strokes.com/tech/sparkplg.asp

[88dunerider]

so just went and did the chop thing with the 38 pilot 3 turns out and a 200 main , when i pulled the plug it was all black , not black base with a white tip , all black. im thinking now i need to back off the main , 180 is to lean ive tried it before so im goin with a 195 and a 190

[honda400ex2003]

make sure you use new plugs. do some chops and go from there tomorrow. steve

[hjsmith00843]

Little off topic but is it ok to reuse the plugs after you get your reading on a chop. Secondly how many plugs do you think is a good number of plugs to have on hand.

1 more rookie question

What plug do you use. Or what plug would you use for the setup in my sig. s

[88dunerider]

i run dpr9z which is a cooler plug , stock is dpr8z , and you can run dpr7z if you want to run hotter

[88dunerider]

for steve: i ran the 195 with the same pilot set up (38 3 turns out) pulled the plug and its all black except the top of the electrode is a whitish grey?? im gonna get some pics up tomorrow of it but do i need to go down to a 190??? thanks

[honda400ex2003]

no you cant reuse them after they have already been used. I guess if you went richer you could use it again but it is not really recommended. I used around 4-5 plugs when i was doing mine last weekend. I am going to use one more when i get home and put my 178 in there to see how it is after that. My plug is all black at the moment but i had some cold starts and such on it. I plan to drop the main a bit and see how it does and tune my f/a screw according to the info given earlier in the post. I ran out of time last weekend to finish it completely. I run a dpr8z that is the normal plug to use the extended high speed running plug is dpr9z it is a colder temp range plug but i would not suggest using that one. have a good night, I am heading home. Come back tomorrow with the results from your chops in the morning 88! I should be at school again around 11 est. lol. steve

[honda400ex2003]

Originally posted by 88dunerider
for steve: i ran the 195 with the same pilot set up (38 3 turns out) pulled the plug and its all black except the top of the electrode is a whitish grey?? im gonna get some pics up tomorrow of it but do i need to go down to a 190??? thanks

sorry missed it last night, I would suggest going to it and see how it looks. We are back at the beginning again with the white top and the black base. I still think it is too lean on the pilot, but i guess it is up to you to decide base on your plug. I would get it all black first then start dropping jets until it is where it needs to be. lol. steve

[88dunerider]

yeah i got it back to all black , and yes im using new plugs with the chop . its back to all black with the 195 main, goin to go to the 190 and see how it looks , like i said before the 180 is to lean i think . how much are you suspost to jet up for exhaust , when i got the bike it had no air box , k and n filter , and the 440 kit, stock exhaust , with that set up it had a 165 main, then i threw the new full hmf on there and im still trying to jet it so just wondering how much you usually jet up for exhaust

[honda400ex2003]

you shouldnt have to go up too much, on a stock machine you go up about 1 jet size lol. the 440s pump more air though, see how it is with the 190 with a new plug and chop. then go to a 185 again, and see how it looks after doing this same thing. pick the best one of the 3. steve

[honda400ex2003]

any updates? steve

[88dunerider]

i stuck the 190 main in there and is still rich , i might work my way back down to a 180 , figured with the 440 and cam with no air box and stock exhaust it had a 165 in there and all i have done is added exhaust since then i should only have to bump it up and jet size or two like you said so a 175 should be about right but im workin my way down , ill see how the 185 works out tomorro

[honda400ex2003]

how did it come out for you? I think the whiter tip is fine, the bottom that is black on the plug is where it shows that it is running rich. I would try to move your needle down by moving the clip up if you havent done so already. steve