Misfire at 5000RPM

[tony.mon]

You could try seeing if it's fuel or electrics by the following:

Open airbox, take off air filter.

Start engine, open throttle.
Get it to 5000, and it starts to misfire- hold the throttle open then spray easy-start down the carb throats.
This will probably make it rev it's nuts off!

If it does, it's a fuel problem, if it doesn't rev any higher, it's a sparks problem.

A bit drastic, but we're not getting anywhere any other way.....

(BTW, there's a rev limiter at about 10,000, so it won't go much above that- you can't do any damage as long as you don't hold it open more than a few seconds).

Then let us know what's the result

[Gerrit]

Hi Bennie!

It's worth a check again, but the wierd thing is that the bike has been flying the past few weeks, temp is quite cool here now, and it really goes like a raped ape.

Then last week Wednesday I noticed the headlight dead when I got home.

Replaced the light & on my way to work next day, it started with the 5000rpm misfire.

Thats why I assumed it is electrical, some relation to the headlight popping.

But I will have the carbs off again on the weekend, and double check.

Also going to drain all the fuel out the tank, and fill it with fuel from the race car, it's been known that there can be contaminated fuel at our filling stations from time to time.

It is a real tricky one.

Gerrit

[Gerrit]

Hi Tony!

yeah that is a good idea.

When I got home today, I opened the airbox, removed filter & started the bike to see if the slides move ok, and it is all fine, so yeah, I will do this tomorrow, blast some quick-start past the slides & see what happens.

Mind U I will take some quick-start myself too, it'l put a jump in my step.

Gerrit

[Gerrit]

Hi Tony!

I did the trick with Quick start and it makes no difference at 5000rpm.

I would have thought that if it would pickup, once the quick start is sprayed down the throats, it would be indicative that the catbs are where the problem is.

I tried it a few times, and no diffs.

Gerrit

[benny hedges]

wondering if the ignition advance gear is fkt but can't see how it could break as it's on splines, not a key???
it's highly unlikely the valve tming has slipped 180 degrees overnight.
wonder if the rev limiter is fkt???
i'll have a look into that ^ see if it's possible???
it should only limit the revs over 10k... not sure if it does that mechanically or of the tacho pulse?
just out of curiosity, try it with the tacho unplugged, see what happens
i would guess the tacho pulse is fed back to the cdi unit and backs off the ignition over 10k>??
suppose it is possible that could be the problem, if you've ruled out everything mechanical.

[Gerrit]

Hi Benny, I will try that tonite. I undid the headlight, no difference.

It can not be the coils, as a coil either works or does not work.

I saw someting in the manual about the ignition pulser or generator?

Gerrit

[Gerrit]

Hi Bennie!

Tried it with the dash disconnected tonite, problem still there.

Maybe there is a relationship here with the bike cutting out in the wet.

Whenever it is wet, the slightest of drizzles, and the bike will go onto One Cyl. and then finally it cuts out. After a few mins though the bike will fire up again, and a short while later the same sequence of events will happen, ...in the slightest drizzle.

I have never managed to solve this, and the weird thing is I have had the bike on the main stand, running, and I will flood it with the garden hose, and it will not cut out, but then as soon as I ride in the slightest drizzle it cuts out.....It has almost become a joke now.

But maybe this problem has escalated to the point where it now has an effect from 5000rpm onwards?

I dunno, open to suggestions.

Gerrit

[tony.mon]

TPS, maybe?
Meter it out to see.
At least we know it's electrical now....

[Gerrit]

Hi Tony, if u say "meter it out" exactly what do I do?

Gerrit

[tony.mon]

Engine off, disconnect connector beside carbs.
Start engine, hold at 3500 or above and reconnect. Engine speed should increase.

If not, meter between yellow/black and green/black wires, resistance should be between 4 and 6K ohms.

Then meter resistance while engine off, opening and closing throttle.
Resistance should increase when throttle opened.

Then set TPS by following instructions in workshop section.

That should keep you busy for an hour or two.....

[benny hedges]

Maybe there is a relationship here with the bike cutting out in the wet.

Whenever it is wet, the slightest of drizzles, and the bike will go onto One Cyl. and then finally it cuts out. After a few mins though the bike will fire up again, and a short while later the same sequence of events will happen, ...in the slightest drizzle.

I have never managed to solve this, and the weird thing is I have had the bike on the main stand, running, and I will flood it with the garden hose, and it will not cut out, but then as soon as I ride in the slightest drizzle it cuts out.....It has almost become a joke now.



Gerrit

had a suzi used to run like sh1t in the rain, couldnt get my head round it.
ended up calling aa out one day and took him 5 mins to sort....
took tank of and painted the ht leads with nail varnish,
(yes, i also wondered why he had a make-up bag...)
did the trick. it was tracking along the frame & under the tank - could see like tiny faint track marks like lightning drawn in pencil.

tip - dont feel for it lol.
start the bike in a dark garage with tank up, see if you see any sparking?

[Gerrit]

Hi Tony!

When I read the ohms from the wiring I get no results. I removed the TPS and reading from the actual connectors, the TPS seems fine. So it seems that the problem is somewhere in the TPS wiring.

I started tracing the TPS wire, but it seems to end up inside the main wiring loom.

Any suggestions?

Gerrit

[tony.mon]

Wiring diagram, check all likely wires for continuity.

[Gerrit]

Hi Tony, think I found the problem.

The TPS is fine. Whe I measured yellow/black and green/black wires, I got no result. On my bike those wires are top & bottom, when I tested top & middle, it is fine and the TPS is at 510

I did the test in the manual, section 17.6. The min, voltage at the ICM must be .7v and I get zero.

The follow up test is at the ignition pulse generator connector ( I found it the right side radiator) when I do this test I get 12.5v.

The manual reckons if that is the case I need to find a loose wire or loose easrth somewhere in the wiring harness.

Been searching the whole morning, no luck yet.

Gerrit

[benny hedges]

loose wire could be a dodgy connector / bullet connector.
might be worth unplugging everything and inspecting for corrosion on the connectors & where the wire is crimped into the connectors.
sounds like you're getting somewhere