*non-toyota* CBR250R misfiring

**skiddz** · 21-02-2009, 04:52 PM

hey everyone i know this is not a toyota topic but i thought i would ask anyway

my cbr250r is experienceing some difficulties, it broke down on the freeway last night

now it cuts out like its a fuel issue, then restarts in say 5 minutes where some fuel has made it through the pump via gravity, runs for a bit then dies.

at times it cuts out completely, loss of power/ignition tacho stops reading, even when the engine being forced over via pushing/rolling.

at times has heavy misfire, and i mean huge misfires possibly 2 or 3 cyl at a time then other times runs with all 4 and cuts back to 2 or 3 for a bit then dies

all that in italics were the intial symptoms, i have replaced the CDI box and it ran sweet as ya nanna, but after a while the tacho stopped and it started a heavy miss again, so i pulled over, and the fuse is blown, replace fuse and continue, i get about 4 k's from home and it starts missing again, i pull over and check the fuse, not blown. also had the tendency to want to die.

so now im home it has been suggested that the regulator/rectifier be checked and check the charging voltage, i do that, idle it was 13.3v, 6k rpm was 14.3-4v, 8k rpm-15k rpm were 14.5v.

all good, it also ran cleanly with no missing. check coils 3.2 ohm on both on the primary side = fine. leads all ~5k ohm resistance, plugs are freakin perfect, #1 slightly oily but its a 20yo sport bike im not particilarly worried there. the other 3 as said before were perfect, infact it looks like they have only done ~5000k's. when really they have done 15k+km

so my question is what else would cause a miss under load, idle or any conditions

also what would casue the fuse to blow but not regularly, its more random, a short to the frame perhaps?

**Billzilla** · 21-02-2009, 07:50 PM

Not sure mate, but I've got a copy of the CBR250RR workshop manual in PDF format that you're welcome to have. Or just search around and you should be able to find one I guess .... I did.

**RAd28** · 21-02-2009, 07:58 PM

First question is... did you REALLY check all 4 plugs? trend with these things is that the outer 2 get checked and changed, but the inner 2 don't... My younger brother has been through the sorting out misfire issue on his RR, and it ended up being that the middle 2 plugs didn't get changed, despite Poo-Honda telling him they did...

If all else fails, take it to "Startline Racing" in slacks creek... they ended up fixing his bike for a lot less then quoted (a little over $200 vs the $600 at Pro-Honda)... I'll be taking my TRX there soon...

**skiddz** · 22-02-2009, 01:54 AM

i have all 4 plug on my desk, so yeah i really did check all plugs its a massive cnut to get all the plugs out, gotta pull the fuel tank and airbox off, and pull radiator off bike is basically bare frame + motor atm

thanks for the offer bill but i have a manual in PDF most un helpful though, nothing like a toyota one.

**Vios-GT_07** · 22-02-2009, 02:49 AM

erm probably a silly question but is your fuel line from tank to filter to carbie ok? no kinks in the line, filter not blocked? also if the fuel line is activated via a vacuum from the carbie, i'd suggest not using that.. do you have a fuel tap? if the tap is dodgy it might not allow all the fuel in?

hm.. just trying to rule out a fueling issue as if no fuel gets to the engine, it cuts out and tacho doesn't work..

**ONETEN** · 22-02-2009, 02:53 AM

So looks like you have checked everything on Ignition side of things, what about fuel?

Blocked/poorly flowing filter?
Clogged line?
Shithouse Fuel?

Id say carby probs IE blocked jets are out of the equation if its intermittent, and effecting different cylinders each time it happens.

Start checking fuel supply from the tap downwards, and even try draining it all (even from the carby bowls) and go with some fresh fuel from a non-independant servo.

Good luck.

**ONETEN** · 22-02-2009, 02:54 AM

LOL @ Vios, posted @ same time! Great minds think at the same time eh? oh wait, that think alike isnt it....

**skiddz** · 22-02-2009, 02:59 AM

Originally Posted by Vios-GT_07

erm probably a silly question but is your fuel line from tank to filter to carbie ok? no kinks in the line, filter not blocked? also if the fuel line is activated via a vacuum from the carbie, i'd suggest not using that.. do you have a fuel tap? if the tap is dodgy it might not allow all the fuel in?

hm.. just trying to rule out a fueling issue as if no fuel gets to the engine, it cuts out and tacho doesn't work..

its pump, have checked fuel tap filter and lines all good, i dont think fuel isnt the issue cos it would be more constant, same with bad fuel, wouldnt cause electrical issues or a constant (yet intermittent) heavy miss, but rather a few random small ones

had the problem with bp ultimate as well.

edit: the tach should still operate even if the engine is gettin no fuel, the engine is either decelerating or being forced over

**ONETEN** · 22-02-2009, 03:31 AM

You would be suprised what sorts of problem shitty fuel can cause, i have seen a couple of interesting ones.

Checked the battery yet?
Also the terminals, and main power feed lines for corrosion?

**skiddz** · 22-02-2009, 04:11 PM

the battery is not in great health but it is doing fine, i have pulled the reg/rec and found it has melted the insulation off a few wires leaving them bare, that may have been the problem, but i will investigate further

**allencr** · 22-02-2009, 04:11 PM

Have a manual choke? Does it cure or hurt when it's used during the 'misfiring'?

'replaced the CDI box... sweet'... and then getting a blown fuse sure looks like a wiring problem.

**allencr** · 22-02-2009, 04:14 PM

Originally Posted by skiddz

i will investigate further

**skiddz** · 22-02-2009, 04:18 PM

i do have a manual choke havent ever touched it

**StuC** · 22-02-2009, 04:24 PM

check the wiring mate. As it is an RR it will probs have been sitting around the docks for a while and have some corrosion. Check all earth points, stator wiring/pickup, all connections etc. Had the same prob with a few NSRs. Was pretty much the stator pickup every time

**RGHilux** · 22-02-2009, 04:50 PM

Originally Posted by skiddz

the battery is not in great health but it is doing fine, i have pulled the reg/rec and found it has melted the insulation off a few wires leaving them bare, that may have been the problem, but i will investigate further

If it is blowing the fuse, then you have too high of current draw for the circuit. Either you have a severely corroded wire or one that is shorted to ground. One of those bare wares is probably shorting against the frame or other metallic object in the general vicinity.

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