[Graham B]

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Here we go again, my 1500 is stumbling badly coming off idle. But this time it's different.

After a good friend in the GWOCB breathed on it, almost all of my problems had gone. The only real issue being that, as you settled down to a cruising speed the bike would "cut" for a split second - almost like it lost all it's sparks and then come back. After that she would cruise and give me at least 140 miles to the tank. Bear in mind I kept well away from the empty end of the scale as the low fuel light has never worked.

Then things changed. The revs on idle dropped a bit but it was still steady. When you rev it sounds like (and is) running on three (Right bank). After 2000 - 2500 rpm the left bank cuts in, the bike kicks you up the backside and you're off! Not safe.

I know she is idling on the right three by the simple test of pulling off the left three plug caps while she is idling - no change. Pull just one of the right plug caps (Any one) and she dies.

With just one of the left three plugcaps off the bike will not rev so I know they are all firing.

Having taken it to the local meet, it was pointed out that there is a smell of unburnt fuel on the left side on idle so perhaps it may be ignition. The carbs have been out countless times, tubes changed, carbs balanced. I've even reversed the gauges in case they were reading wrong. The gauges being Davida so they're reasonable.

I should also say I've measured the ignition coils and pulse generator resistances and they check with the manual. I've also changed the ignition coils simply because I had a spare set.

The good friend mentioned above is lending me a set of pulse generator coils to try even though he still thinks it's a fuel problem. I have three questions for here;

1. Any thoughts?

2. Can anyone in the UK lend me an ECU? All postage costs will be met and ECU returned without argument should not not wish to sell if it fixes the problem.

3. Can the TW sensor be checked without removing it?
Now, where's that wall?

 

[DaveO430]

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It is almost impossible for it to be an ignition problem since each coil fires a cylinder on each bank.
Have you checked the cam timing?

 

[Rudy]

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So the exhaust on the dead side stays cold? I agree with the ECU swap to test it with. At least to start with.

I would also check connectors all over for corrosion.

 

[Graham B]

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It doesn't stay cold so there has to be some ignition going on - probably at the wrong time and certainly when the choke is applied or the throttle is open.



All connectors checked. Some corrosion found and cleaned with something nasty that gave me a headache - or was that the wall again?



Cam timing not checked with a light but all the cam belt marks have been checked and they line up.



I forgot to say. HT voltage all checked with a super tester that I don't understand. What I do understand is that the voltages on each side was consistent across all the leads on that side.

 

[Graham B]

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Just bumping this back up. Can anyone in the UK lend an ECU?

Please?

 

[Graham B]

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Update.

Bike stripped and pulse generators removed ready for when the test set arrive in the post later this week.

Existing generators had very dirty pole faces. Not sure if that has any effect.

All timing marks line up.

Left hand spark plugs white - no blistering.

Right hand spark plugs had white electrodes, dark (nicely) around the end of the thread.

Still hoping for a loan ECU.

 

[Rudy]

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Those dirty pole faces can make a difference.
I'd clean them up and take it back out again since you are waiting for delivery anyway.

 

[Graham B]

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I won't be able to work on her today. Hope to give things a try tomorrow.



Thanks.

 

[abnormal 1]

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Hello,

Had similar experience with trigger rotor. Measure distance on gap . filed mine to specks and now the bike preforms like a new one. No stumble anywhere

 

[sandiegobrass]

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Surprised no one has mentioned carb sync.. if one side ismore closed, it will idle on the other... sorry.. reread post... ignore... :?

 

[Graham B]

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Update,

Test pulse generators arrived, fitted and bike tested. No change. I guess that puts me back down the fuel route.



However, I forgot to mention one bit of luck(?), when I took the belt covers off I found some red dust and the left hand belt a little looser than it should be. Closer inspection shows the belt tensioners are on their way out.



Something else to add to the list before she goes back out on the road.



Now back to tubes and carbs.........................

 

[jemj]

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Hi graham have you tried checking the carbs are set up and balanced correctly?

Sorry Graham just reread the post and seen that carbs have been balanced. It might pay you to try and chage some of the settings for the carbs (the correct ones obviously do not work) and see if you get any improvement.