What's up with the bike? - take two

[Loo Kahs]

Having had more time with the bike, I'll note down the symptoms that I've noticed in no particular order.

Generally speaking they happen all in conjunction with one another and tend to have a range of 'badness'. There have been times where I've done 100 miles without any issues, or even had entire week perfectly fine. Other times, I will have the problem come up on daily basis.

1. When the bike runs fine, the pitch of the exhaust sound is pleasant. When it goes bad, it becomes lower and duller - sounding like a helicopter in distance. When it runs particularly bad, it will also start to backfire, and do loud popping sounds.
2. I will start hearing and feelings knocks from under the fuel tank (carb farts of unburnt fuel?). Sometimes it may be one every so often, other times it might be a number one after another.
3. Loss of responsiveness to throttle. At better end of the spectrum, it will not feel as responsive as it should be, but with a good twist of the throttle it will 'kick' through the problem and accelerate as nothing ever happened (or so it feels).

At the worse end of the problem, you can be in 2nd gear and you will not go past 30mph despite turning the throttle all the way up. When stationary it can become a bit of a struggle to keep idle high enough to stop engine from cutting off.

// Today I had the worse end of the problem. There were several instances I had to stop just because I could no longer keep up with the traffic, or the speed had become so erratic that I did not want to cause any trouble behind me.

What I keep on noticing, is that it seems to consistently get better after having been stationary for a while (with the engine on). Just before pulling at home, the bike was not running ok - it was sort of halfway in the 'bad' scale.


Thanks again,
L

[Wicky]

Raise idle to 1250–1500, get the carbs balanced, set TPS clean accumulated dead things out of airfilter, check for airleaks in exhaust and carb intake manifold rubbers and wait till things properly warm up in Spring. Carb farts are quite normalish...

[8541Hawk]

I still think you need to check out the pulse generator.
If you pull out your handy service manual and turn to the "trouble shooting" section you will find that for all poor engine performance and running issue it suggests that the pulse generator can be the issue.

So you should at least do the tests on it as until you do, you can not rule it out.

[tony.mon]

Also consider a blocked tank breather.
Next time it does it, open the filler cap.
If you hear a rush of air going in you have a blocked breather.

[Loo Kahs]

Also consider a blocked tank breather.
Next time it does it, open the filler cap.
If you hear a rush of air going in you have a blocked breather.

I've tried that and sadly no change.

I'll look into the other things suggested.

[alanfjones1411]

You should bring it to Grainstorm in May.Somebody there will probably be able to sort it out.

[fabiostar]

i had similar problems or at least some of them when i got the blue one.. i stripped,checked cleaned and stood on my head. i did find out the bike was timed 180 out, once that was sorted still much the same on certain days and in the end the only thing that sorted it was changing the entire carbs for another set..

the only thing i could find after stripping the carbs many times was the chokes or rather the bore in the carbs were the chokes fit into looked worn.. so from my bikes id check
180 timing and try another set of carbs, at least it rules them both out.

ps,,, just another little one. your large ignition box, check there is no stick goo around were the loom plugs into it. if it has what looks like goo leaking out of it your big box is on its way out.

[kenmoore]

In the video at the start as you give the bike a few revs it appears that your throttle housing is rotating on the clip on ! Is the housing loose ?

Tighten it up and stop it rotating as this causes the cables to work against each other . Also check that the cables are locked in place at the carbs.

Are your choke fittings the original plastic ones ? if so they could have a crack in one.

Clutching at straws I know .

One last thing, I have remote vacuuam lines and one day when I was out for a ride my bike started behaving like yours and one of the lines had come off. Even if you don't have remote vacuuam lines make sure the plugs in the inlet manifolds are tight and sealing correctly.

Good luck .

[Loo Kahs]

You should bring it to Grainstorm in May.Somebody there will probably be able to sort it out.

Problem this year is that my insurance is about to run out in three weeks time, so now I am thinking whether I will bother to renew it. Question is then if I will attempt to fix the problem myself (although would be unable to ride to check if anything's improved) or if I ought to rid of it to someone who has the time and space for fiddling with it.

[Cadbury64]

I'd go back and take another look at the fuel supply through the vacuum petcock. Maybe you have a damaged vacuum hose? If you don't get a good vacuum to the tap, or the tap has some issues, you will lose fuel flow and get the running out of fuel symptoms (which is what I think you described). When you stop running there may be enough fuel flow to refill the bowls so the bike runs well until the next outage.

I think if you had an electrical or ignition fault, this would happen all the time.