[fixed!] running on 3 Cylinders

13518 Views 22 Replies 12 Participants Last post by aj26, Jan 28, 2013

xotoby

Discussion Starter · Jul 11, 2010

sup "peepz"

having a bit of an annoying issue of my 91 cbr250RR running on 3 cylinders.

originally was an issue of it not starting, and mechanic found that ignition switch/wiring was burnt out. +replaced it.

bike now starts.. but it looks as if he's forgotten to plug something back in, because my dash doesn't light up, and my neutral and sidestand lights don't light back up either.

HOWEVER, the guy also did a service on the bike, pulled carbs apart, cleaned them etc.
after this the bike was running on 3 cylinders.
he did a 'compression test' thing on the cylinders and found that one had less than normal compression (i believe).
he simply suggested to buy a new cdi and left it at that.

can tell by spraying water on the headerpipes, 1 has no heat.
checked the plug for that cylinder, looked fine, tested the lead with a screwdriver to make sure power is getting to it. it is.
swapped the coils. no change.

my question now is, what should I check NEXT.
(it would be good if I could fix this easily and not have this mechanics worthless hands on my bike again).

ps. I just read this from an old post of someone else having a cylinder not firing.

"do you have the speedo/dash hooked up?

If you haven't, you'll be chasing that miss for ever." -- Studricho.

my dash doesnt light up? is that related? anyway.

any help would be appreciated.

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1 - 20 of 23 Posts

Nathan89

· #2 · Jul 11, 2010

RE: running on 3 Cylinders

Check the fuses on the left hand side of the fairing between the tank and handlebars properly be better to remove the left fairing and kinda look up towards the handle bars there in a little black box.

all so check the battery condition there is very good post in the maitnence ( can't spell lol ).

G

· #3 · Jul 11, 2010

RE: running on 3 Cylinders

I normally add some start ya bastard down the throat of the carby on the miss firing cylinder.

If the revs go up, then it's a lack of fuel issue. If they die, then it's possibly a spark issue.

That is a rough guide that I use to help me.

banana.logic

· #4 · Jul 11, 2010

RE: running on 3 Cylinders

does it still miss fire when you rev above 8,000 - 10,000 rpm?

xotoby

Discussion Starter · #5 · Jul 11, 2010

RE: running on 3 Cylinders

yeh. from 4k up to 20k it would seem, rumbly grumbly and weak.

none of the fuses are blown.

would nulon carby cleaner work the same as this 'start ya bastard' stuff.
else i'll have to buy that and give that a go,

is there some kind of link between the dash and cylinders, as per that post I quoted of you stud from a few years ago.
as something in my dash is unplugged at the moment.

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banana.logic

· #6 · Jul 11, 2010

RE: running on 3 Cylinders

So it misses from 4k to redline? what about below 4k

if you are getting a spark in that cylinder then it is possibly a fuel issue. might be worth having a look at your carbs, if it's missing above 4k then have a look to see if the main jet is clogged in the corrisponding carb, if it is missing below 4k have a look at the pilot jet.

my 2c.

xotoby

Discussion Starter · #7 · Jul 11, 2010

RE: running on 3 Cylinders

ah jets hey. thanks. hmm il check em tomorrow.
yeh up to 4k it seems to be smooth then suddenly shit afterwards.

mechanic pulled carbs apart and "cleaned" them though so I don't understand why it would be clogged.
however perhaps didnt put something together properly..
either way he has fucked something somewhere.

anyone have any input on this "something from the dash being unplugged can cause a cylinder not to fire" theory which i've seen suggested in a few threads around the place.

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Johnnie5

· #8 · Jul 11, 2010

RE: running on 3 Cylinders

wtf ????

if one cylinder has fuck all compression then there is nothing NEXT to check bikes dont work without compression

fuses, start ya bastard and all that other shit is going to do FUCK ALL

5 hours, $900 and the suggestion of trying a new CDI ???

you need to work out why you have no compression in 1 cylinder

leaking valve, blown head gasket

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xotoby

Discussion Starter · #9 · Jul 11, 2010

RE: running on 3 Cylinders

Johnnie5 said:
wtf ????

if one cylinder has fuck all compression then there is nothing NEXT to check bikes dont work without compression

fuses, start ya bastard and all that other shit is going to do FUCK ALL

5 hours, $900 and the suggestion of trying a new CDI ???

you need to work out why you have no compression in 1 cylinder

leaking valve, blown head gasket

that's not very comforting..

can I check these things myself easily or is it for a workshop.
i dont think it was 'no' compression, i think it was 'less than normal' compression..
and um.. what could the mech have done to cause it..
coz bike was 100% power before he did his service on it

Matt

· #10 · Jul 11, 2010

RE: running on 3 Cylinders

another story of a clusterfuck...

who did you take it to, out of interest?

aj26

· #11 · Jul 11, 2010

RE: running on 3 Cylinders

My bike decided not fire on the 3rd cylinder, I had CR8 plugs before because the MCA guy said its good to use in winter but change in summer. OK... not good well I changed back to CR9CEH9? i think and the bike fires better and idles better.

xotoby

Discussion Starter · #12 · Jul 13, 2010

RE: running on 3 Cylinders

where can i get a cheap pressure metere thing to check each cylinders compression?
if thats a problem it should be the first thing to be fixed right?

xotoby

Discussion Starter · #13 · Jul 15, 2010

RE: running on 3 Cylinders

fixed.

Running on 3 cylinders.
Cable behind dash (also responsible for the dash lighting) was unplugged.

Plugged it back in, and all 4 cylinders up and running again.

Who can explain this please, as I'm interested in knowing why a dash plug for the lighting can stop a cylinder from firing.

The Dwarf

· #14 · Jul 17, 2010

There's a restrictor in the clocks.

G

· #15 · Jul 17, 2010

ps. I just read this from an old post of someone else having a cylinder not firing.

"do you have the speedo/dash hooked up?

If you haven't, you'll be chasing that miss for ever." -- Studricho.

All the run around and the answer was there from the start.

xotoby

Discussion Starter · #16 · Jul 18, 2010

haha yeah but it didnt make sense to me so i never checked it.
any idea how that causes it?

G

· #17 · Jul 18, 2010

Yes, the MC22 has a speed restrictor built into it. When you reach 180 klm/h it drops the spark on a few cylinders.

Without the dash hooked up the bike thinks that your doing 180 klm/h therefore it cuts the cylinders.

pawn0

· #18 · Dec 7, 2010

Hey lads,

Just a question about this, when it stopped firing was it the spark or did it disable something in the carburettor?

I have the same problem, same bike. Spark is going strong but cylinder is dry.

[hr]
oh, i missed the bit about "drops the spark", nevermind, thanks!

Shadow

· #19 · Dec 7, 2010

Speed cut is a spark thing...
If you've got no fuel, check your fuel bowl has petrol, if not, probably a blocked fuel in line/needle and seat to/on that carb...

p4ndor4

· #20 · Jan 28, 2013

So which cylinder does the restrictor affect? I'm having this '3-cylinder' problem too...

studricho said:
Yes, the MC22 has a speed restrictor built into it. When you reach 180 klm/h it drops the spark on a few cylinders.

Without the dash hooked up the bike thinks that your doing 180 klm/h therefore it cuts the cylinders.

1 - 20 of 23 Posts

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