still backfiring...te450.

ok, so 2004 te450. jetted as per jd jetting with a fcr41. no intake leaks. exhaust leaks - probably the head pipe and mid pipe move quite a bit when i go wot.

it's not valves. or valve timing. or bad gas, or bad plug.

i'm to the point where it's gotta be an exhaust leak.

how do you cure the exhaust leak? more springs? ultra copper? what actually works? this is not just popping back. it's a definitive bang and a nice blue flame every time i go from wot to idle. it's jetted close....(180 main, 42 pilot, red needle 5th, 70 leak, accel pump squirts mildly and is timed properly...fuel screw 1.5 turns out. etc....)

oh yeah, the muffler has no baffle just the screen.. so that probably ain't helping.

it runs pretty good, aside from the most annoying bang everytime. i can deal with popping back. backfiring is a whole nother deal.

any suggestions would be appreciated!

Definately sounds like exhaust valve leaking/tight guide or a small crack in exhaust valve....

does it do it only when its really hot ??

new exhaust valves today. so that ain't it.

it does it cold/hot/all the time/everytime. it is consistent to say the least.

whats the deal with your muffler......the packing is removed
but the spark screen is still there...???

there is a screen that's covered with some fabric of some kind and the end cap.. there is no tube inside of it... it's been shortened a few inches also. ..i don't know why the previous owner did it, but it's defintiely not helping.

i put ultra copper on all the joints, let sit 24 hours.
i went through the carb once again - the only anomaly i found was a 72 starter jet (i think it should be 85?) which i would assume would just make it a bit harder to start - does the small starter jet have any affect when i come from wot to idle? i thought the pilot jet circuit was open at idle... my pilot is 42, my main is 180...

anyways, the ultra copper seals did not work, as soon as it got hot (30 seconds or so) the exhaust moved enough when i wack it or when a backfire occurs to to break all the silicone at midpipe and head pipe to exhaust flange connections... and it still backfires. i noticed the headpipes get light cherry red at idle with choke off, which i know is semi-common on many modern 4 strokes (my yzf426 did the same thing..) but i think it's still lean.. all exhaust joints fit tight... but when i get to wot, i can see the headpipes move away from the exhaust flange..............

i've had the muffler apart, i think the internal baffle tube (which is non existent) may help the exhaust a bit, but i don't think it is the total fix.

i can go to wot, and back to closed throttle slowly and it won't backfire, just minor popping back. it only backfires when i really wack it and let throttle return fast.

another thing i noticed is when i got the new head gasket after doing valves, the original head gasket was cardboard style, and the new one is a 3 piece metal assembly...head nuts torque spec in the book is 27.5 ftlbs - i assumed the torque specs are the same for the new head gasket.

so i'm still stumped. i was thinking maybe i could retard the exhaust cam timing one tooth and see if that affected the backfire. i dunno where else to go..

on another note, i found a new complete exhaust system for cheap, so when that shows up i'll try that too. i was intending on purchasing one anyways, but i hate throwing money at a problem with a bike that still is not running right.....

Mine from new has always had a slight Pop on decel from WOT. I am running a JD kit with 45 pilot and 180 main. I also have the exhaust mod. I sealed the pipes as soon as i got it. Its not a huge pop. Just low burbles with an occasional small pop. I will be trying to work it out in the next few weeks with minor needle clip position, needle and fuel screw positions. I thought mine was running lean before also so i threw in a 45 pilot and it bogged so much that a whack of throttle and it would flood and die. that was with the fuel screw all the way in. Take off was horrible. re-enstalled the 42, pop returned and and would run like no tomorrow. If the minor changes dont fix it for me, im leaving it. I like the way it rides.

mike

hah, if it was just minor popping i'd be happy, it's a definitive bang - complete with pipe movement from the bang...and it's not occasional, it does it every single time i go from wot to closed throttle...

If valves are verified (I did have bad backfiring caused by new valves seating in on a previous bike), if no exhaust leaks found, then my personal guess would still be way too lean on off throttle.....maybe a problem w/fuel screw?

Just another thought, and area I don't know much about on these bikes.....but can timing be off??

(Dieselox4: 45 and fuel screw all the way in?....really?)

I know this doesn't help the back firing, but for reference, currently on my bike ('05 TE510, FCR41MX) I run 180 main, stock needle clip at 3 dn, just upped pilot to 48, Kouba brass extended fuel screw at +/-1.5 out, 45 leak jet, AP arm adjusted to 2.75mm, pipes not sealed, but do have wrapped in header tape.

I ride anywhere from 2500ft to over 8000ft, mostly 3500-6500 in temps from mid 50's to low 90'sF.
Once tried a 42 pilot briefly and felt to me that was too lean. I had been running a 45 most the time w/fuel screw out 2 - 2.5 turns out (adjusted for elevation/conditions).
I installed a 48 pilot before a ride this last Saturday. During the ride, found best idle w/fuel screw about 1.5 turns out. The bike ran really well, but still did have some popcorn popping on fast decel (temps 50-60F, +/-3500-4000ft)......and pop/died on a friend once while he was trying out my new suspension work. (still haven't figured that occasional pop/die crap out)

also - the previous owner cut the muffler down in length - the end of the end cap/cone only goes to the end of the side cover on that side.. the entire muffler is only 13" long - it looks like he took maybe 6" off of it? i don't know how long the stock pipe should be...

this could be a major cause of it too i would think.... suggestions? no amounts of jetting has fixed this problem. so i'm down to exhaust hopefully...

RLW, with the 45 yes i had the fuel screw turned all the way in and there was no stumble or rpm hunting. It purred pretty well until i cracked the throttle and it would either bog or die. I screwed it 1.5 turns out and it would just die. lots of gas smell like it was flooded. Once i took out the plug and had to clean it, disconnect the fuel line and turn over the starter to get all the gas out. It was bad. This was all while running a STEATH Titanium Fuel Screw. Im going to give it another try and put in my Zip-ty fuel screw to see if there is a difference.

I did this as part of my muffler mod. It is on TT. I dont remember anyone doing it before that. Maybe someothers that have been on there longer would know. I did it to loose weight and for the muffler to flow better. It helps out more in the mid to top end. I wanted the performance of an aftermarket pipe without having to buy one. Which the Arrow is. I dont know if he copied my post. It didnt make it Pop more. it actually pops less than it did before the mod. My bike bictures are posted in the "Pictures of your bike" thread on here. You can see my muffler even with the end of the number plate. If that is where yours is then the previouse owner cut 4" off. But non of that will contribute to the probles you are noticing. I havent heard of anyone having issues after that.

Mike

woohoo. i think i figured it out. the oring mod had kinda jammed. 1 oring broke, and the other kinda was sitting against the pump timing screw. i removed the o-ring mod, turned the timing screw in a turn or 2. bam. no more backfire. or at least way way less. i could make it backfire if i really tried to , but i think under normal riding conditions this will not be a problem.. now i gotta put it all back together, go for a ride and see what happens...

now for a new question..

so i ran it kinda hard on the stand, and i started to get some minor dripping out of the raditor cap overflow tube. maybe a thimble full. i'm assuming this is normal - i did fill the system with engine ice after i rebuilt the head. maybe i overfilled it (if that's even possible..) ..

so now i ran it till it got hot, and i get a consistent drip out of the radiator overflow tube.....

good..........hopefully that o-ring jam was causing the problem.

It might be possible to get a little too much coolant in there and have it bump out the excess, but watch it for a while.

FYI on fuel screws: My first extended fuel screw on my TE was an aluminum MSR Fuel screw (same as Zip-Tie) I picked up when I got the bike.
Kept having trouble getting it to fine tune right, so thought I was having issues w/not getting pilot right or, maybe the AP tuning (which I was very green on).
Things were not making sense to me and I was getting very frustrated. I've used Kouba brass T-Handle fuel screw before and trust it, so when I saw one at another dealer, bought it and yanked the aluminum piece out. "My" fuel screw tuning problem went away.......not saying this is an issue or fix for everyone, but I'm not using anything but brass again.

http://www.jdjetting.com/xcart/home.php?cat=4
The "T" handle that Kouba or Scotts extended fuel screw have is easier IMO to adjust on a ride w/gloves too.

i have the r&d flexjet - i'm not a huge fan, but it is brass. i had it on another bike that couldn't use a regular t-handle one - so i just moved it over to this bike... so it works fine for what it is....