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Discussion Starter · #1 ·
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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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

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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.
 

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Discussion Starter · #5 ·
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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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.
 

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Discussion Starter · #7 ·
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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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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Discussion Starter · #9 ·
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
 

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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.
 

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Discussion Starter · #13 ·
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.
 
G

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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.
 
G

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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.
 

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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!
 

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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.
 
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