Help a starfish out with your psychic powers of engine diagnostics

[Captain Starfish]

So, before I get started, I know this is a long shot and I should probably just take the bike to Kamahl and get him to ride it. This may well end up happening.

Before I do though, just in case this tweaks someone's memory, I'm hoping for a clue here.

A while ago (10,000km or so?) I replaced the timing chain and clutch plates (EBC kevlars) amongst other things. I also ripped out the TRE I installed ages ago. The engine became a bad mofo again after getting into a bit of a tired grandad rut. Annoying because from 2500 - 3500 RPM it would hunt and surge, and burbled popped and BANGed the zorst on overrun despite a very lean map on the PCIII. Annoying because the clutch is now really heavy and grabs until it gets some oil through it - clutch lever fully in and the bike will still take off forward if I start it in 1st when it's cold.

Still, plenty of power, really good fuel efficiency, a little bit bitey and lacking smoothness but otherwise a huge improvement.

Fast forward a few months. The busa had a bit of a hissy fit one night last week.

After getting a fresh tank of juice and riding for an hour or so, then getting a bit of air off a couple of speed humps (they are such good fun) and then some more fairly sedate riding I may or may not have attempted a little powpow 1st gear wheelie. It came up, revs started climbing, got to something well short of the limiter and I experienced a lurching lack of power combined with a God-awful "clack - clack - bump" noise from somewhere under me. Every time, every gear I powered out for the rest of the night the bike would hesitate and generally be reluctant.

I got home and discovered a woefully loose chain which I've since tightened, I'm thinking from the sudden reverse spike in torque from an airborne free wheeling rear wheel to suddenly back to relatively low speeds on landing. Meh. Is okay now.

But that surging and shit is still there as always from 2500-3500 and, now, from about 4000RPM up a hesitancy comes in. Almost like it's misfiring or only partly misfiring, but the engine still sounds pretty smooth. Almost like you're hitting tight/not tight bits in the chain but it's a little more random and is definitely related to RPM and throttle - the more I ask, the more it sulks.

This ringing any bells?

Otherwise my next steps are to check the timing with a light, check the valve clearances again, change the plugs (just in case, they probably have 20,000 on them), change the fuel and flush the tank and pump/filter, detergent soak the K&N filter and then, finally, spit the dummy and throw it at Kamahl.

[Desmo]

You've knocked something loose in your airborne antics and it's breaking down under load?

[Captain Starfish]

Hmmm

Connector check time too. Good thunking. But I would expect that kind of fault to present as an intermittent thing, you know, that annoying bug where the front right indicator randomly drops out every now and then. Or the engine drops a cylinder sometimes.

I wouldn't expect a repeatable, hit-4000RPM-and-get-lurchy-stuttering-hesitation behaviour.

[darkfibre]

Is there any on board diagnostics to be had?

[Captain Starfish]

Yes, didn't think of them but will put that (easy) at the top of the list for tomorrow afternoon

To add to the list of symptoms - idle speed has dropped steadily since the service, it's now sitting around 800-900rpm warm. Rather than fuck with the idle screw when other things may also need doing, I've been using the fast idle control to keep it up around 1200 where it should be.

There's also a ticking noise coming from the head on the LHS, but I'm reasonably sure it's just a slight leak at the exhaust header.

the things you get used to...

[agrid]

I remember from the Dreamtime that "hunting" was a common result of an air leak on the intake side. Any chance something came loose when you anded the speed-hump-jump?

[Captain Starfish]

Another thing to check - quite possible that the throttle bodies have popped from the rubber interconnects.

[giet]

get a new bike

[jme]

could it be some crap in your injectors, i had a k2 once that got some crap from a fuel up or from the tank made it run like a dog and not let me load it up, had the injectors prof cleaned and found 1 was dripping not spraying.

[smeghead]

.. check for a bad earth, prob to do with ECU or ignition circuit.

This could manifest itself as corrosion but more likely a wire crimp that has fatigued over time & is almost completely broken; mainly a symptom of older, high mileage bikes.

Never hurts to check the earths occasionally as they can be the cause of many a weird prob.

I have been there & done that with this type of prob myself & it can be a bastard to sort.

[robocop]

sucking air and/or valve adjustment wrong but sounds more like sucking air.
try keeping constant revs at the specific area it "breaks down" at then spray some CRC or wd 40 around areas such as pipes and inlets and see if it makes a difference.
sometimes a tiny leak can cause a major problem

[robocop]

ps without actually hearing it makes it hard to diagnose but above is a starting point then maybe check plug leads and plugs

[Ozboy]

I think you two need to have a chat. >> http://www.perthstreetbikes.com/foru...d-96-a-127751/

A bike landing hard from speedhump jumps could very well create the same symtoms as a bike that has crashed. Not saying that Aidens bike has crashed, but he seems to be experiencing very similar problems Capt.

Checked the throttle position sensor?

[Captain Starfish]

Good point Ozboy - the TPS calibration on the zooks is what comes up as part of the "all's well" ECU diagnostic so I'll check that as part of this afternoon's festivities, together with looking for leaks, checking wiring and plugs and timing.

jme - that's what it feels like, hoping not but otherwise I'll have to set up the test rig and have a look. Bitch if that's it, I only u/s cleaned the bastards a year ago.

giet - you buy a new bike and we can swap.

I understand that it's nearly impossible to diagnose something like this without being on the bike, appreciate the efforts guys!

[Veefore]

Annoying because from 2500 - 3500 RPM it would hunt and surge, and burbled popped and BANGed the zorst on overrun despite a very lean map.

Banging in the exhaust on overrun is a sign of a too lean mixture.
Hunting & surging would also suggest the same.