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running bad...please help.

10K views 86 replies 14 participants last post by  foxfire 
#1 ·
I'll try to cover all the details here...

2002, 34k miles, staintunes, pc3, bypassed fuel filter. Ran great until about 1k miles into my last trip (mostly gravel/dirt).

It started rough one morning...sputtering and clunking. I managed to ride it home, but it did it again the next time. It also has a definate miss in lower rpms. I cleaned the air filter (air compressor), checked the boots, and did a tb sync...a little better but still no good. Had a really hard time nailing down the sync with it running so bad.

Next I put in fresh iridium plugs. Still no improvement. Unplugged pc3 and did yet another sync...still crappy. It's bad enough it's almost not rideable.

I did notice something new today...when I disconnected the fuel line there was a lot of pressure and a lot of gas behind it. Is that normal (never had it happen before)...maybe the bypassed filter is plugged?

I know the air filter is dirty (I blew it out good, but didn't wash). What else can I check? I'm leaving for a 10 day event I'm 3 days and I'm about to pull my hair out.
 
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#2 ·
#5 ·
High rpms are the usual place a problem is first noticed with the usual clogged high pressure filter problem. You shouldn't have pressure in the fuel line you mentioned and it's possible something else happened in the fuel pump. I think it's worth a check. Throttle body air leak is one instance that is different.


Also check to make sure the throttle bodies are secure on the engine intakes. The rear one especially likes to get blown off. Rear Throttle Body Out of Boot (manifold)

Oil on the air filter can come from the breather tubes, especially if the bike has been on its side. Oiled sections of the paper air filter won't pass air. That could be your problem too.
 
#6 ·
I'll have to track down a suitable container...I know I don't have anything that can hold 1200ml.

I just checked the boots (again). Actually pulled the box and reinstalled. All snug.

Couple more symptoms to note...there is a significant clacking coming from the front cylinder. A buddy says it's the loose tip of the cam chain tensioner banging around. What I hadn't noticed before is when it does clack, the idle goes rough. I also noticed the secondary valves move. Again, I have no idea if this is normal.

Also, the last couple times I started it the rpms ran up to 2000 and didn't come back down for a while.

I've been leaving the manometer connected through all this and every time I start it, it reads different.

Not sure if any of this is related.
 
#8 ·
Make sure the warm idle is set between 1100-1300rpm. All that low rpm trouble is beginning to sound like a TPS problem. It's probably time to replace it.
 
#9 ·
I set idle a bit above 1k. When I start it up ig goes back to 2k or so, then drops down after quite some time.

Are the secondary valves supposed to move a lot? Every couple seconds I see them moving around.

TPS...replace, not adjust?
 
#11 ·
You can get infrared thermometers quite cheap, get one and check that both cylinders show the same temperature at the exhaust header.

If one is cooler that is the problem one and a good place to start.
 
#13 ·
The TPS on your 2002 is 14 yrs. old? A notorious FAIL.

Signals from that Throttle Position Sensor inform the ECM which controls fuel injection. And air supply, using the upper throttle plates you noticed fluttering about.

Mine went bad around 40K miles. The new replacement not only solved my starting / idling problems. It let me eliminate the surging at around 2800rpm steady throttle w/ an upper throttle plate synch.

If you get a replacement, be sure to remove the old vacuum seal gasket before attempting to install w/ the new one.
 
#14 ·
Just did some reading on tps failures...sounds promising. Well, I'm leaving in 3 days. Is it worth trying to test or simply adjust? Or do I pay big dollars to try and have the dealer overnight it? I have the bike torn down to the throttle bodies anyway.
 
#16 ·
#18 ·
Since you have it apart down to the throttle bodies, why not CAREFULLY remove the upper throttle plates? I used capital letters because you don't want to loose those tiny screws down the intakes. Magnetized screwdriver? I assume they are steel screws.

Premise: If those upper plates aren't there to control, signals from a bad TPS to the ECM become irrelevant (with regards to them). They are merely a fine tuning, top speed limiting solution from Suzuki. Install a new TPS later and replace the plates then.

You'd rather have them (properly synched) in my experience. But there are plenty of Stromtroopers who have simply removed them and claim their worst effects were a snatchy throttle and somewhat decreased fuel mileage. Free to try. If it gets you on the road...?
 
#21 ·
No. The TPS has nothing to do with the secondaries. They are controlled by the STPS and a stepper motor.
 
#26 ·
Hotter exhaust from the left pipe is normal until the engine is completely warmed up. Hot Idle s/b 1100-1300rpm. My Hot Idle sweet spot is 1200+ rpm.

Started fine cold but 2000rpm? 1800rpm normal. Cold start circuit supplies a rich mixture. Cold start idle, depending on temp, 1500 - 2400rpm. The TPS influences this too.

I wasn't suggesting that removing the Secondary, upper throttle plates would compensate completely for a TPS that's starting to give false signals to the ECM that controls them.

Most of the wear on the little reostat inside the TPS happens at the most used throttle positions - closed or slightly open throttle. The throttle positions of the starting, low rpm running problems.

When my TPS started to fail, a half dozen full twists of the throttle with the key OFF, to scuff the TPS contacts, would enable normal starting and low rpm runing. Only worked for a few weeks.

I would remove the STV's (upper, secondary throttle plates), set idle to 1200 rpm (hot, 2-3 bars), and take a ride. Can't hurt and then you will know whether to order a new TPS for delivery while you're gone. Just my opinion based on experience with my Vee.
 
#27 ·
I'll try to cover all the details here...

2002, 34k miles, staintunes, pc3, bypassed fuel filter. Ran great until about 1k miles into my last trip (mostly gravel/dirt).

It started rough one morning...sputtering and clunking.

I did notice something new today...when I disconnected the fuel line there was a lot of pressure and a lot of gas behind it. Is that normal (never had it happen before)...maybe the bypassed filter is plugged?
.
I bet it's the bypassed fuel filter. Average fuels are dirty and then add dirt roads with dust and debris.

a plugged up fuel filter that has been bypassed would not affect anything. The fact that it has been bypassed and not able to filter the fuel of debris sounds like your culprit.
 
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