Carb Icing?

[WR6133]

At speed while accelerating, getting sudden lumpiness/surges. I suck at describing things so best to see the video, if you watch the tacho the revs nose dive then bounce about briefly. I didn't notice at the time but watching the video noticed a high pitch noise comes from the bike when it happens.

It's only happening at speed. Can anyone confirm this is carb icing? or do I need to start tearing stuff apart.

https://www.youtube.com/watch?v=OAb7DrgguyY&feature=youtu.be

[wheelers]

what bike?
possibly not icing as intermittent I would expect it to die for longer.

carb heater/s fitted? water cooled bike? could have air lock and warm coolant not getting to carbs.

could be a coil breaking down. faired bike? try some hose from the front of the bike to direct the air flow over the coil to cool down.
maybe plug leads breaking down.
so many possibilities with fuel and electrics involved.

[WR6133]

ZZR400, no carb heaters (that combined with the weather made me think icing).

If it persists I think I have a set of coils I can swap out to see if that is to fault. So far that today is the 1st time it's happened.

[8_ball]

it could be the carb diaphrames ?? or fuel related its hard to diagrose a issue without ripping into stuff to eliminate... could be battery earthing out high revs= high voltage could be arcing across something ????

[wheelers]

ZZR's did suffer from carb icing. mainly the bigger ones. it was the vacuum created from the fairings sucking the heat away from the carbs.
being water cooled you could tap off a small hose and run around the carbs to keep them warm if there isnt water circuit allready round the carbs.
but as I said I would think it would die until they heared up again. which is [possibly not icing that you have.
check terminals, may even be a loose battery terminal or battery going down.

ZZR also known as ZX

another possibility,dirty fuel or water in the fuel .
doubt it would be diaphragms as would happen more often, but could allways be if neer changed.

[WR6133]

I think you guys may be right with something electrical, I just took it over some speed bumps somewhat faster than one is meant to go over speed bumps and with each bump I got (air :p ) a small amount of the stutter.... it felt like multiple misfires. This bike's electrics are 99% gaffer tape, 0.5% prayers and 0.5% prior owners strange ideas of DIY.

Luckily I've got a mostly empty day tomorrow so it'll be tank, fairings, airbox off and have a dig about....... :( was hoping to not need to do anything to this bike till I gut it in the summer for project parts.

edit to add - Mine is a zx400k (zzr400) jap import so no carb heaters. I think the UK model 600's had them though.

[Dan]

Definitely electrical. I had issues with the coils as mentioned when you took it - replaced one of the coils and made up new HT leads for each one IIRC. Never had this issue though as it would just run on two or not rev at all. I'm not sure if I threw the faulty one back into the spares or chucked it out, but I do remember it was breaking down under load and read ok out of circuit.

[8_ball]

one thing i have learned and that is never ......never overlook an unknown issue, could be this could be that ??? what does it start like ??? on the button or a fair few turns 5 , 10 turns to go ?????
Id go with your instinct but never rule out anything when diagnosing issues.......could be ice could be electrical could be fuel could be rider error (sorry no offence) could be the **** up fairies ????? who knows. dig around and if you dont find something dig deeper.... its fustrating but the reward comes from finding the gremlin....
I own a triumph believe me Ive had a few lol

[WR6133]

Well I've given up for tonight, working on the roadside via headtorch got irritating. The rear subframe (steel) gave me multiple electrical shocks with the engine running and revving at about 5k so I guess tomorrow I'm tearing through the electrics.

Dan - I think there were a couple of coils in the parts from you. I've since got hold of a few more of unknown condition. All tested ok a while back on the table but may be duff under load. All the HT leads are recent (yours). The loom as you must have seen is mind boggling, I think prior owners tried to wire up their house to the bike or something, the amount of added bits and connections that just don't make sense are baffling. I've almost finished rebuilding the spare loom for the project, though it still needs heatshrinking and a few new connectors.

[wheelers]

if you are getting an electric shock from the subframe then defo electrical, if its a small shock you have a wire touching earth somewhere or a loose connection. if its a heavy shock could be a coil going down and earthing out.

[Jed]

If you're getting a shock from the sub frame it has to be HT, so check coils and leads. I had a ZZR1100 and it iced up coming off the Pyrenees into Andorra; it missed, stuttered, popped and banged all the way down. It never became unrideable or 'failed to proceed' but once at lower altitude (warmer temperature) and after a coffee stop all was well for the rest of the trip.

[WR6133]

Had a "fun" morning.

I warmed it up this morning, then once warm gave it some beans in neutral. It happily revved to the redline a couple of times then it began to stutter toward it and do the bouncy revs things.

Pulled tank, airbox, all fairings/panels. Various wires in the loom are damaged, I applied the ultimate fix of tape to the damaged areas. The loom is so old the plastic coating on some wires just crumbles/disintegrates. It's also a law unto itself there are random bits and bits in the wrong place, routed all over the shop, its as if someone had planned to wire in everything bar the kitchen sink at some point.

Close inspection showed some damage on HT lead 1. I don't think it was bad enough to be an issue but as I had a bit of new lead and these leads will get used in the project build I replaced it. Still had the stuttery, hesitant misfire.

Coils. I had a pile of unknown provenance after checking them on the table with a multimeter 2 showed as in spec. Swapped them both with my current coils....... bingo, ragged it round the block a few times and the initial problem was gone. New problem these coils are buggered too, once hot they leave it running on 2 pots.

So I know I need new coils..... wish it had been carb icing, at least that's free! ;)

[Dan]

Only one of the coils will be failing under load, leaving it on two pots. I'd also be surprised if BOTH coils were faulty originally, maybe swap and change until you find a good set?

Nevermind, just read the above message properly showing you tested the rest and they were duff. Shame!

[Nigel B]

Dan was talking about this tonight. Electric shocks from the frame are not good.

I personally know your bike and the wiring loom. Dan parked (abandoned😱) it in my garage for several months. The bag of spare coils that you received had the good and bad mixed in. Or that at least the way I gave them back to Dan.

Since then Dan persuaded me to get back on a bike do i have bought a zzr600 it runs well but one coil sparks from the attachment points to the frame.

One thing to check on the 400 is the main earthing point on the engine. ( above gearbox under carbs) it was clean and tight the last time I saw it, that was some time ago. If it's loose it could explain the shocks.

[WR6133]

Hi Nigel, I cleaned the earth yesterday. I think the rear subframe going live may have been related to one of the leads that had split slightly, I replaced it and the subrame no longer shocks.

The coils currently, I have the ones that go crazy at high revs and the 2 from the spare lot that work, which work ok till they get hot then 1&3 stop firing.

They'll do for now, new coils cost more than I can fork out currently. It only needs to last a few more months till I gut it for parts.

[Trev]

How about trading it for a GSXR750K1, I know where there's a nice one going and, for you, I'm sure there's a good price ; )

[WR6133]

How about trading it for a GSXR750K1, I know where there's a nice one going and, for you, I'm sure there's a good price ; )

Unless the price is £7.98 it's a bit out of my league ;)