Fuel issues - carb problem or something more serious?

[JohnC]

Hi all, after the problem I had frying my Dyna coils the new coils arrived and I fitted them yesterday.

I charged the battery overnight and tried to fire the bike up earlier.

The bike started OK but the pipes on the left hand side - 1 & 2 don't seem to be heating up as much as the others. It may only even be residual heat from the engine as they are so cool. It doesn't really sound rough but then it doesn't exactly sound right either, revs are a bit wooly to say the least.

The bike was flooding as unburnt fuel was getting through to the pipe, checked all plugs and one was dead, changed all with replacements and all are now sparking OK.

Petrol getting to carbs fine and I drained all the float bowls and tried again after giving the carbs a good tap just in case it was a sticking float etc.

Pots 3 & 4 red hot as they should be.

The carbs are VM29 smoothbores which have all the main parts replaced by new parts from Alens Performance.

Would pots 1 & 2 not firing indicate bent valves? Could I have caused a hydraulic lock while faffing about trying to get the bike started before I found the fried coils?

Checked plug lead firing order and the left coil with the black wire is firing 1 and 4 and the right coil with the green wire is firing 2 and 3.

I'm going to hopefully borrow a compression tester from a m8 but I cant get a hold of him at the moment. From putting my finger over the plug holes the bike seems to have OK compression.

Thanks.

John

[steve bowdler]

Are you running Points or Dyna S , Electrical faults sometimes take out a Dyna S pick up !!

[JohnC]

Hi Steve, it's Dyna S. All plugs are firing OK though.

[ZedHead]

Compression test is always a good idea on these old bikes. Better still a leak down test if you can get one. Have you balanced the carbs recently?

[JohnC]

Hi, no the carbs have only been statically balanced atm. Need to get the bike on the road and to a MOT station, and then get the carbs balanced. I don't own vacuum gauges anymore as someone borrowed them, for good :/

[PAULJAC47]

Do the pipes all get hot when you start engine on full choke? if so fuel is the issue on jets etc

[ZedHead]

Hi, no the carbs have only been statically balanced atm. Need to get the bike on the road and to a MOT station, and then get the carbs balanced. I don't own vacuum gauges anymore as someone borrowed them, for good :/

Static balancing should be fairly close. Some people prefer this method to vacuum gauges.

[JohnC]

Paul, no on full choke just the same.

Until I test the compression it's looking more and more like a carb problem, sticking float or whatever. No 1 cylinder / pipe seems to be kicking into touch, number 2 warm and that's about it. Really black oily fuel still dribbling a fair bit from where the exhaust end can meets the main pipe. Sticking float anyone?

Starts on the button and ticks over no worries, revving out a bit better now as well, poss a testimony to how well these engines handle a bit of bodgery

Can anyone recommend a good place to send smoothbore carbs for a good clean and check / bench setup etc?

John

[ZedHead]

Oily deposits may mean it is burning oil. Is it smoking at all

[PAULJAC47]

If you can get bowls of in situ,as you said check for stuck float(u could use manometer method to check level without taking bowls off)i have known jets to fall off the ends of the emulsification tubes.

Jon just a thought on this,you have fitted new dyna coils?
have you got the proper dyna leads and caps? the lt connections on these coils have a nasty habit of earthing to the frame as they are so close...

[JohnC]

No smoking at all, just the oily fuel that makes me suspect a sticking float and the unburnt fuel is washing the bore.

Paul, the coils use Taylor leads. Had these and the Dyna setup on the bike for a good few years. I'll try and see if I've a stumpy driver small enough to get the suspect carb float bowl off.

If I don't get any joy I'll put my old carbs on while I get the VM's professionally cleaned / setup.

Thanks.

John

[Pigford]

Put a new set of DENSO's in

[JohnC]

What do you mean Pigford, sorry but I need taken by the hand m8 lol. I'm taking it you mean the plugs though. What do you recommended for a Wiceco Z 1075 with the VM 29's?

Update anyway, took the float bowl of No 2 carb and hey ho, pilot jet lying in the bottom of the bowl.

No way to replace it without taking carbs off, so did that and checked every carb, jets, pilots etc etc. All seemed well and I thought I'd cracked it. But........

It's still running like a poor thing, firing on all 4 but 1 & 2 still not getting as hot as 3 & 4 Testimony to the Zed that even with a pilot jet out and replaced it's still running anyhow...... Just not as it should.

The only thing I haven't done is replace all the plugs with completely new ones, but as I'm getting a spark I think I'm really clutching at straws here. Could plugs be the simple problem??

m8 coming over soon to test the compression.

Seems it's only No 1 pot that's not responding fully to the helm.

Next step deff put the Gixxer carbs back on and rule the VM's out :/

John

[JohnC]

Spoke to Steve Debben, he seems to think it might be a shim problem, valves not seating, so not pumping through the fuel, again cant be confirmed without a leak down test or at least a basic compression test. I did check the shims a while back but with my feeble mechanical skills that means nothing

I think I've had one of those multiple fails that it's making diagnosing the problem a right pita :/

[JohnC]

OK compression is 150psi + across the board.

Tried my old (Gixxer) flat slides, no difference.

Took the cam cover off and number 1 intake shim is reading a .20mm gap, or twice what it should be.

Does anyone think this large a gap would seriously affect the engine to the extent I'm having?

It seems only to be number 1 cylinder now that's seriously amiss although number 2 doesn't seem 100% although the clearances seem fine.