Tampa_Harrier

My '04 has started firing up thru the front and rear carbs. Like, shooting flames into the airbox. I do have the Factory Pro +4 timing advance, but have not had any problems like this. Seems like under load, about every 20th or 40th firing of the spark plugs take place too early, with the intake valves still open. At least, that's what it sounds/feels like. Anyone ever hear of anything like this?

The symptoms are the same with the TPS connected or not.

If anyone lives in/near Tampa, and would be willing to stop by, I'd like to "borrow" your ICM for about 10 minutes to try to confirm/rule it out. Honda wants $460 for the module.

superbling

Do you have problems in the 2500-3500 rpm range also?

Loco

I'll sell you a module for $150 if that's your problem.

Tampa_Harrier

Under normal idle, it seems ok. But if you snap the throttle, it stumbles, and will very often fire back up both carbs.

If you try to ride it, it just feels like it has no power, really "boggy" and lots of popping back up the carbs, under about 3200, maybe 3500 RPM. When it hits that range, it's like whatever was bogging it went away...the engine wakes up and pulls like it used to.

It has that boggy feel regardless of temp, and regardless of whether the TPS is connected or not. Matter of fact, the TPS doesn't seem to make any change at all. I know the TPS has a 497 ohm correspondence to closed throtte, set it and checked it a dozen times.

If I knew the ICM was failing, I'd take you up on your offer. I can't find a decisive way to test it...the checks in the manual are simply for peak volts, and are fine. There's nothing there about timing drifting around. That's why I'd like to fiind a local who'd be willing to let me swap ICMs for a minute or two...

RickB

If you have a timing light handy it should tell you if you are getting an early or mistimed spark... check it per the manual and if the mark remains steady at teh flsh your timing is pretty much staying fine. I would imagine also if the cam chain tensioner is not doing its job it will cause the timing to jump also.

Rick B
02SH

JamieDaugherty

I've got a spare ECU and ignitor box that you could use if you like. I'll need them back when you are done, but at least it would allow you to see if one of them are bad.

Are you shure it's not something with your carbs? It almost sounds like how mine was running once when a vacuum line blew off (don't ask).

Jamie Daugherty
http://members.iquest.net/~daugherj

superbling

Besides the advancer, do you have airbox or exhaust mods? If so, you need to drop the needles in the carbs a notch or two. BTDT.

Tampa_Harrier

JamieDaugherty, I'll take you up on the loaner parts if you don't mind. Makes it easier to troubleshoot if you can definitely rule something out.

The rest of my mods:
-Erion race slip ons
-Factory Pro +4 degree timing advace wheel (removed today and the stock one is back on...no difference)
-Factory Pro jet kit; #48 pilots, 182F/185R, needles on the 2nd clip from the top (OEM springs, non-drilled OEM slides)
-PAIR valves inverted and blanked
-BMC Street filter, airbox snorkle removed

The bike was bought new last October, and currently has 11.5k miles on it. Anyone have any good knowledge on the factory warranty on these guys?

I put another set of carbs on last weekend...my old DynoJet set, with the drilled slides and half-springs, #45 pilots and 175F/178R (if I recall correctly), and got the same popping and stumbling. Which got me thinking maybe intake air leaks, so ordered the rubber insulator/mounts for both carbs. Those came in Friday, so I installed them and went back to the Factory Pro carbs. No change in the popping and stumbling. Since it showed the same symptoms with either set of carbs, that's got me leaning away from vacuum...the only non-carb vacuum line is the control to the tank petcock, and it looks to be in good shape. I did pull the vacuum plug screw out of the front intake to check it yesterday....looks fine.

Weekend before last I checked valve clearance, thinking maybe an over-tight intake valve. All dead on spec.

The bike has been runing great until about a month ago. Seems like it started running hotter, and when it'd get over 200F, idle was all over the place, and low end was noticably weaker. I do a fair amount of time in stop-and-go commutes, and I was seeing temps routinely get to 217F. That was with abut 60-70F outside temps.

JamieDaugherty

Let me know your address and I'll get them out to you this week.

Jamie Daugherty
http://members.iquest.net/~daugherj

Tampa_Harrier

Thanks, JamieDaugherty
You've got a PM...

EngineNoO9

how exactly are determing that it's coming up through the carbs?? I might have this same problem... Might make sense since ever since I disabled the pair system it's been having issues... let me know... I'm curious as to how you fix it

Tampa_Harrier

Well, in my case, I pulled the tank and airbox, and ran it. And watched flames shoot out the carbs toward the ceiling of my garage...

I can also see scorch marks on the underside of the air filter. And a couple of times it fired so hard out the forward intake, that it kinda skewed the carb slide so that it stuck most of the way open.

The PAIR system is supposed to be exhaust-only. If it's failing, your main symptom should (note I keep saying "supposed" and "should")...should be excessive back-firing out the exhaust pipes. The purpose of the PAIR (as I understand it...I'm certainly no expert) is to introduce clean air into the exhaust stream to reduce emissions. Too much cold air (stuck-open PAIR valve), or more than expected combustion or airflow (from jets/pipes) tend to cause lots of backfiring.

Imagine those backfires...but instead of hearing/feeling them out the back of the bike, they originate and stay down between your knees...and the bike has power-loss and extremely erratic idle. That's what I have.

EngineNoO9

that's kinda what I have.... but idle is fine. just between there and 3k part throttle going like 25 does is mess up

Tampa_Harrier

Pull the harness to the TPS (throttle position sensor) and ride it and see what you think. It's under the tank, on the right side of the bike, behind the PAIR actuator, a 3-lead wire going to the rear carb...if you've never seen it, it'll be a fun chore to get to, but once you've done it couple of times it's a piece o' cake ('specially if the PAIR stuff is gone!).

The Ignition Control Module (ICM) uses inputs from the TPS and engine coolant temperature to decide when to advance spark timing. The TPS input is most noticable above 3k RPM, IF the TPS is set right. There seems to be a lot of dabate about that, but as best I can tell, at idle it should read about 500 ohms, and goes up as you open the throttle. In some bikes, the factory settings are too high, so spark is too far advanced low in the RPM band, or advance comes on too early. (The TPS reads too high, so the ICM "thinks" you're trying to go faster than idle, so it advances the spark too soon, and the bike pops early until you get to the 3k RPM point where advanced spark is needed...)

Below about 3k RPM, "normal" (un-advanced) timing will run the bike fine, so if testing with the TPS unplugged gives better results below 3k, you need to adjust (or maybe replace) the TPS. If you find that's the case, let me know and I'll tell you how to adjust a "non-adjustable" TPS.

EngineNoO9

yeah I've seen it and had it unplugged when I did some tank off work over break. I'm not sure if it's that or maybe if I'm over jetted (owner before me told me it had a stage 3 jet kit). I'll try it out tomorrow

Tampa_Harrier

Well, after much hair-pulling, and no success...I dropped the bike off with my local dealership <shiver> to have it diagnosed. I should hear back today about what's wrong.

Tampa_Harrier

They called yesterday to ask if they had permission to replace the plugs.

They also said the battery was weak and they repalced it under warranty.

And they said the BMC Street filter looked clean, but a bit dry. Told them I was aware that it was on the dry side, cuz with flames shooting out of the carbs I was a bit leary to put too much oil on it...

Still placing my bet on the ICM.

superhawk22

Don't worry they'll just keep replacing parts 'till they figure it out. Good luck and I hope you found a good dealer to work with.

Tampa_Harrier

I have no problem with them replacing things until it runs better, as long as they don't change my jet kit, or sprockets, or Evo shift star, or Erion pipes.....

I was kinda hoping they'd call me up and tell me they thought it needed a good wax job to help diagnose the sputtering...

Tampa_Harrier

This dealership is pretty good. I know a lot of them, and they are actually riders. Matter of fact, when I traded the 919 in for the Hawk, the service manager bought the 919. And after a week of dyno tuning, he was only able to get another 3 HP out of it.

superhawk22

Good to have a dealer you can trust...some are just clueless.

Tampa_Harrier

Well, just off the phone with them again. They ordered a "throttle position set", which I assume is the TPS. It should be in today.

Doesn't make sense that the TPS is the fault...I ohmed it out to 5k across the outer terminals (in spec per the book), and it was adjusted for 497 ohm across the position sensor leads with closed throttle, and increased according to throttle input (also per spec). And the bike had the same symptoms with it unplugged as plugged in.

However, since about 3200 RPM is the "break over point", and the bike became "normal" around that RPM range...maybe there's more to testing it than the 3 simple checks in the manual.....?

Tampa_Harrier

Still leads me back to the ICM, though. With proper feed from the TPS (as indicated by my ohmmeter), the ICM is supposed to retard ignition for slow speeds...and at around 3200 RPM the TPS is "pegged" and the ICM goes to full advance.

If the TPS is good but the ICM is reading or responding incorrectly to TPS input, then ignition would be over advanced at slow speeds, and the bike would fire too early (through the open intake valves)...but above 3200 RPM it would run fine. And the bike would run the same way with the ICM plugged in or unplugged. Exactly what I'm seeing.

Time will tell.

shayne

Electrical gremlins can be hard to find. Keep us posted.

Tampa_Harrier

OK, got the bike back this weekend. Total cost, $23.00 for 2 iridium plugs. The battery and TPS were replaced too, but covered by the warranty.

Of course, the bike still runs like crap. The dealer said they swapped the ICM to test, no success, so put my original back in.

They were wanting to go into the carbs next...suddenly they aren't convinced it's timing, but now fuel. Of course, the carbs aren't covered under warrantly and they estimated $300 to diagnose.

Sooo...anyone got a spare ICM I can borrow for an afternoon? Call me hardheaded (I've certainly been called worse!), but I want to confirm/rule it out for myself. I'm still not convinced, can you tell?

I did spend the last 2 days swapping jets and needle positions, and have yet to make any noticable difference in the pre-firing. I think tonight I'm gonna put the old Dynojetted carbs back on again to see what that does. I know I did that before, but it was so long ago now (seems like ages since I've ridden!) that I'm not certain I'm accurately remembering the symptoms.

shayne

Perhaps the pulse generator doohickey in the clutch cover is at fault?

Just a wild guess, but strange things happen.