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Recently bought a 2006 ltr450 and need help getting it fully figured out. First off ill start with what mods are done to it (that im fully aware of):
  1. Hot cams intake cam.
  2. Pro circuit T-4 slip on. (assuming stock header)
  3. Moto Works cherry bomb? (see pic attached)
  4. Aftermarket air box with lid removed.
  5. Swirl filter delete w/ inline filter replacement.
Now for the issues i am having....the quad will bump start fine (had weak battery so decided to bump start) and it seems to idle well when it wants, but if I give it any sort of throttle it will kill itself immediately. It also seems to like it better when the choke lever is in the full down position (unaware if that is considered choke ON or OFF). Last night after idling for about 2-3 minutes the header began to glow red. I had the head apart to inspect cylinder, piston, etc. Everything looked perfect and seemed to have very low hours on the engine (noticed it has a vertex piston in it). Putting head back on, I ensured timing was correct (it was perfect) and all valves were well within specification (after a little adjustment). I made sure that the hose coming off of the throttle body was connected to the sensor on the sub-frame.​
I have a couple theories as I have owned one in the past and fully rebuilt the whole thing:​
  1. Air fuel ratio? Maybe the idle air screw is turned way out or in too much? I read on a forum here that it should be set roughly 1 5/8 turns out? (I know manual calls for a vacuum gauge to be applied and set it to a certain r/min but I do not own one to do it that way.)
  2. Could it be starving for fuel? Maybe dirty injector? I also thought that maybe the inline filter that was installed to replace the swirl filter could be the incorrect size? (which in return would restrict fuel flow)
I have videos of it idling and being bump started behind the truck from last night if you would wish to see them just let me know. Any help would be greatly appreciated as I am eager to get riding more before winter appears...​
 

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The fuel systems on on these bikes are very sensitive, if you weren't the one that put the inline fuel filter on I would replace it, then I would move down the line, your injector could be dirty. You can clean it out with a 9v battery and some brake clean (you can find information on here on how to clean your injector) and you might also want to look into checking your fuel pressure regulator. There is also a fuel filter on the bottom of the fuel pump that you can clean out. As for the head pipe glowing red, there might be more done to the bike like a high compression piston so you might want to look into a programmer and not just that cherry bomb. Good luck.
 

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Going through the exact same thing on my sons 08. Bought the quad a couple months ago supposed to be bored to a 47?, has cherry bomb, Dasa exhaust, not sure about cams but were supposed to be new, basically "rebulit motor". Ran fine, pulled strong especilly with my 300#+ ass on it. After 1st good ride we found an oil leak on Stator cover. previous mechanic had welded i assume a crack on the cover so we have replaced it. Then discovered previous owner hacked on wiring harness some. Have repaired (soldered&heat shrink) several wire splices where they just scratched insulation back and wrapped wire around bare spot (smdh). They bypassed clutch position switch by wrapping tape around plunger on switch and stuffing under plastics (smdh). Discovered it had 7 of the 14 teeth called for on the front sprocket (lol replaced chain and sprockets). Cotter pin on rear axle nut was way too small and just barely stuck thru the nut (SMDH). Really just a piss poor attempt at tryin to be a mechanic.
So it started running crappy after a bath (we do tip it up on its tail so maybe we sloshed up some trash in tank?). Since machine is older and we have no idea what all has been maintained we basically have started from scratch. Pulled all Plastics and going over everything. Swirl filter was already deleted with an inline filter replacement. Inline filter was dirty (on the outside) so we changed it out. We checked fuel pressure at Fuel Pressure Regulator and had 42 psi but it dropped pretty quick after key off. So we rebuilt/replaced guts in the FPR (Fuel Pressure Reg.) and discovered they don't sell the o-ring for the FPR cover but measured it (30mm id x 35mm od x 1.5mm thick) and got a 6pk from amazon for $5. Removed, inspected, cleaned, and blew out all fuel lines and tank. Removed and disassembled fuel pump and blew carb cleaner and compressed air thru screen. We are replacing the o-rings on fuel rail/pipe at the injector. Replacing mounting screws at the injector because previous owner/mechanic was a buffoon with a phillips screwdriver. Think we've narrowed it down to a dirty injector so we're replacing with non OEM. Yes non OEM because OEM is +/-$200. Non OEM +/-$30. If the new injector works we will buy a better aftermarket as replacement/spare.
Any input as to what else we should inspect and or test? If injector isn't it we'll have to start testing sensors. but it sure seems like a fuel delivery issue.
GLOWING exhaust is typically a Lean Fuel mixture sign.
 

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A glowing exhaust header is completely normal for the LTR.

The fact that it was running good might not help with this thought, but with being bored over, dasa exhaust, possible aftermarket cams, and only using a cherry bomb might be the issue.
 
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