So it wasnt the plugs

[vtryorks]

Neither of us are having much luck lately.

This might be a very silly suggestion, I dont know. Anyway, why not sit down and document what happened in the two "bike" days prior to this issue, as precisely as you can remember. Any work carried out, riding, weather conditions, everything. Fact is, it was running fine, then suddenly not. Whilst every fault has to manifest at a point in time, it does seem a little odd.

It might help to establish a time line. When I am diagnosing a computer, if the fault is not obvious, I often ask clients about their usage pattern immediately prior to the issue. It really helps sometimes.

There might be one small detail you have missed which could make all the difference.

Just a suggestion, but I have to agree it sounds like fuelling. The fact that you are getting deposits on the spark plugs is a good indicator. Determining the type of deposit might well give further clues.

[tattoo]

you can check the coil on the bike..

warm the bike up to normal temp then disconnect the wiring plug to the coil

primary circuit....set a multi meter to OHMS X 1 scale and measure the resistance between the terminals on the coil..it should be between 0.4-0.8 ohms...

secondary circuit....set meter to k ohm scale and push one probe into the spark plug cap and the other probe onto the green terminal wire(negative)...the reading should be between 17.0-19.0 ohms with cap...if not remove the cap and retest,it should now read between 12.0-14.0 ohms without cap....if the reading is now correct your caps defective as the plug cap should be 5 ohms...if the reading isn't correct remove the lead and retest...if this reading is correct your lead is defective and if not your coil is defective and needs replacing

this takes about 10mins from start to finish

[benny hedges]

[quote="Miztaziggy] - The interesting bit is that the problem feels much worse with full open throttle. If you wind on gently in 1st gear up to 1/2 or 3/4 throttle, it accelerates almost flat out all the way without much problem. If you whack open full throttle at low revs, the revs climb and then stutter after 6k.

[/quote]

busted carb diaphragm / sticking slide

[Miztaziggy]

[quote="Miztaziggy] - The interesting bit is that the problem feels much worse with full open throttle. If you wind on gently in 1st gear up to 1/2 or 3/4 throttle, it accelerates almost flat out all the way without much problem. If you whack open full throttle at low revs, the revs climb and then stutter after 6k.

busted carb diaphragm / sticking slide [/quote][/quote][/quote]

Thanks Benny

Another update

Changed coils today and still no difference.

Took off the airbox lid and sprayed carb cleaner in the trumpets but noticed when I revved it, it was making a really odd sucking noise but I couldnt tell which cylinder it was coming from. It wasnt firing properly in one of the cylinders and spitting petrol back up through both of the trumpets. No idea if this was normal, but it got worse when you opened the throttle fully. The guy next door had a look and said that it was banging and popping when I revved it and said that it must be either not firing or out of time.

When you open throttle fully, it still looks to be spraying fuel into carbs and the gold plate things open right up as they should, but engine sounds as though it is running out of fuel.

Could the things you said Benny be the cause of these things?

What is the diaphragm and where is it? How hard is it to change?
And what is the slide and how hard is it to unstick or do I need a new one?

I assume these things are things that can suddenly go wrong rather than building up over time...eg why I thought it wasnt the air filter as one day it was fine, next it was broken

[tattoo]

the diaphragm is under the black top cover...unscrew the 3 screws and lift off,watch for the spring underneith the cover,gently pull the diaphragm and piston out...when you've inspected/replaced it make sure you put it back with the CARB UP facing out (towards the carb)....as for the sticking slide...i'm sure someone will advice you on that as i've not touched mine so far...sorry

[tinysmall]

If the stuff Benny suggested was going to go wrong, it would just happen. There would be no build up to it. If it's spitting fuel up the trumpets, it's sounding like torn diaphragm(s). When you take the tops off the carbs, they are the big rubber skirts. They can perish and tear very easily. This is a job you can do at home, though getting the springs back in can be a bit fiddly.

[Miztaziggy]

Ok got the air box off and the back cap off the carb to inspect the diaphragm. It looks to be ok, with no tears or holes.

As for front one, Can't get it back together, but same story, no tears or holes, it looks good.

So...what is the slide thing that might be sticking?

Failing that, what else might it be? I'm nearly at my wits end now :-(

[stormingjoe]

You will lose a little coolant, from the carb preheaters, you can do a basic check on the diaphragm, push up the black slider, should hiss and release should come down in a dampened manner, if it shoots back quick it is shot, now for refitting, hold top in one hand-slide in the other, now feed spring into slider with other end in the lid, until you can put top onto top of slider, then hold together holding complete thing in one hand, feed slider into carb, with your free hand inside carb throat, slowly lower into carb locating the needle in the jet, once that is done lower in keeping control of slider until the lid stops ontop of carb the put screws in, the gasket most of the time will self locate, you can lift lid a little to check, a lot easier than writing it down!!

[Miztaziggy]

Thank you...all refitted now.

Could this misfire be caused by incorrect timing?

Could my timing chain have slipped? Im thinking that maybe the tensioners are too loose and a sudden jolt on the engine has caused the chain to slip?

Or how about too much oil when I did the oil change? The oil is much higher in the window than it was before I did the change. It used to be on the minimum line when on the level, now it is at the maximum line and sometimes higher, but hard to tell when it is level

[AMCQ46]

Not going to be the oil level, even if above the sent glass it will be fine.

Cam timing is also unlikely cause, for the CCT to be so slack they could jump, you would be able to hear them rattling over your exhaust noise, so very much doubt that it has slipped a tooth.

When benny says a sticking slide he is talking about the throttle slides that you can see when you look down the carb trumpets. You can generally feel if the move up and down ok, and in the previous post storminjoe described what they should feel like as they go up and down.

[Miztaziggy]

Not going to be the oil level, even if above the sent glass it will be fine. ok, I already emptied a bit out, but I agree, very unlikely to be the cause

Cam timing is also unlikely cause, for the CCT to be so slack they could jump, you would be able to hear them rattling over your exhaust noise, so very much doubt that it has slipped a tooth. Agreed...while it is in bits I took off the rear and checked that one anyway and it is fine

When benny says a sticking slide he is talking about the throttle slides that you can see when you look down the carb trumpets. You can generally feel if the move up and down ok, and in the previous post storminjoe described what they should feel like as they go up and down.Ok so the black things are the slides? They are both fine. Both move quite easily and dont stick open or closed or anything

I have uploaded this video to youtube. The bike runs with a sort of chu chu chu steam engine noise which sounds as though it is coming from back cylinder. You can see when I cover the back cylinder it goes quiet, but is still there when I cover the front. So which one is abnormal? Should they both make that noise, or should neither make that noise?

[youtube][/youtube]

Also, at the very start, you can see some sort of white smoke come from back cylinder. I turned off the engine about 5 seconds before video starts and it is some sort of smoke from that. Doesnt come out of the front though, so is that some sort of exhaust gas coming through back carb?

Also, you can see when I rev it, how it seems to die, when I rev gently it is fine, when I pull throttle full open it dies quite easily. It didnt actually do this before I took off the tank and air box, so maybe that is just normal for when the carbs are exposed? When the bike is running, the misfire isnt as bad as it seems to be right now without the air box on etc.

[stormingjoe]

Did you take the nipples of the top off the plugs when you fitted them

[Miztaziggy]

Did you take the nipples of the top off the plugs when you fitted them

The little things that go over the screw threads?

Yes...took them off as they wouldnt fit into leads with them on

[stormingjoe]

Good .
What did you remove to gain access to plugs

[Miztaziggy]

Good .
What did you remove to gain access to plugs

Nothing...front one just pulled off lead. Back one, just lifted tank by removing front bolts.