Honda CBR 250R Idle speed jumping

[Westy_mate]

Hi all,
I own a Honda CBR 250r 1989 and Its idling strange.

In the mornings im having trouble starting it (resulting in me push starting it most mornings) and if it starts and when cold it often idles at around 300rpm then dies and eventually gets above 1000 after a few starts.

Once running and warm the idle jumps up and down from 2000rpm to 2500/3000rpm to 1600rpm.

Ive been told it sounds like it runs of 3 1/2 cylinders when idling low then jumps to 4 again yet at another mechanic store ive been told it sounds like a Air leak.

Any ideas what this could possibly be? Air leak? Carb problem if so what?
I cant afford to send it in to have a complete Carb overhaul.

Thanks in advance!

Dane

[CookMySock]

With the warmed-up engine running, push the carbs gently side to side and nudge the pipework around them and see if you can provoke the irregular idle somewhat.

Try taking one spark plug lead off at a time, and see if the engine behaves the same way every time you do it.

Are the spark plug electrodes all the same colour?

From a dead-cold start, do all of the exhaust header pipes warm simultaneously (check with your hand - not on a hot engine obviously), or is there one particularly cold or hot one?


Steve

[Westy_mate]

Push the carbs? im a new rider and and would rather not touch the carbs (nor can i find them) but i will check the sparkplugs sometime today or tomorrow and get back to you.
where on the bike may i find the exhaust header pipes? cheers for the help mate i really appreciate it.

Dane

[The Pastor]

What dose the bike idle at normally? If you rev the bike is it quick to return to idle or dose it take a while?

I'd recommend a carb clean and balance - this will cost a little bit. give george from motorcycle doctors a call, hes really good, and he WILL fix it.

[Westy_mate]

The bike normally idles around 2000 when warm.
I might add that when i first start it in the morning it Idles at around 3000 to 3250 (with choke on) not sure if that helps but it does feel like a high idle when cold.
after revving It slowly idles back down and begins the funny idle again generally staying around 2000 idling up to 2500 and down to 1700 (generally. sometimes the idle fluctuation is minor and sometimes its major.)

[Westy_mate]

Generally how much is a Carb clean and balance?

[p.dath]

If you don't think all four cyclinders are running, put some spit on the end of your finger, and briefly touch the four header pipes. They should all burn your finger. If one doesn't, then the cylinder it connects to has the issue.

[The Pastor]

Generally how much is a Carb clean and balance?

ring george and ask him mate, hes a good bastard.

[CookMySock]

If you can't find the carbs Dane, you better take it to the shop ay. The older inline four bikes are either mechanics/enthusiasts bikes or money pits.

Steve

[Westy_mate]

I can find the carbs haha just wasnt too keen at looking at the bike today in the rain. will do some checks tomorrow and let you know what i Find. cheers!

[Westy_mate]

Turns out not all cylinders are firing.
3 of the 4 exhaust headers are heating up and the 4th spark plug isnt sparking.
I bought a new sparkplug and even the new spark plug is not sparking.
Any ideas?

[The Pastor]

swap lead 3 and 4 over and see if the problem switches cyclinders

[Westy_mate]

Fixed that problem, turns out it was the Spark plug casing thingy between the sparkplug and cable
still Idleing strange though

[CookMySock]

Fixed that problem, turns out it was the Spark plug casing thingy between the sparkplug and cable
still Idleing strange thoughWell done. If it's been minus a spark plug for a while, it will take a little time for the idle to even out again.

Go for a quick cane and see if it comes right.

Steve

[Westy_mate]

Its been about 2-3 weeks since all four were firing up. Hopefully this fixes my problems... if not ill keep posting on here :)
haha thanks for the help guys :)

[Westy_mate]

So i noticed that when the choke is on the 4th cylinder is either not firing at all or not all the time.
Just wondering if that is normal? once the choke is off its running fine i believe they are all firing although the Idle problem is still there.

[Westy_mate]

So i noticed that when the choke is on the 4th cylinder is either not firing at all or not all the time.
Just wondering if that is normal? once the choke is off its running fine i believe they are all firing although the Idle problem is still there.

[Westy_mate]

excuse my double post

[Westy_mate]

I know this because the Exhaust header is only cold/warmish

[p.dath]

So i noticed that when the choke is on the 4th cylinder is either not firing at all or not all the time.
Just wondering if that is normal? once the choke is off its running fine i believe they are all firing although the Idle problem is still there.

All four cylinders should be firing all the time, weather the choke is on or not.

[CookMySock]

All four cylinders should be firing all the time, weather the choke is on or not.:sunny:

In order, check carb balance,shit in the enrichener jet, hole in enrichener diaphragm, carb clean, compression test.

Steve

[onearmedbandit]

:sunny:

In order, check carb balance,shit in the enrichener jet, hole in enrichener diaphragm, carb clean, compression test.

Steve

I don't think taking a dump in the enrichener jet will help.

[Westy_mate]

plan is to get my carbs cleaned and balanced on sat but i was hoping i could figure this out myself. how would i complete a compression test? or check the the enrichener jet and enrichener diaphragm? once the tank is off where in regards to the carbs are these things? damn carbs take up all the room ha

[CookMySock]

Google images search, keywords - tubing manometer carb balance

Youtube search, keywords - carb balance

Steve

[Westy_mate]

I want to check for air leaks, any idea where to start? fuel lines?

[Westy_mate]

I noticed that when i lowered the Idle to 1800-2000rpm the idle fluctuation was very small compared to when it was idling at 3000rpm. Mean anything?

[CookMySock]

To check for air leaks, warm the bike up, idle it, and gently push the carbs and hoses sideways a bit and see if the revs change.

Steve

[Westy_mate]

Any idea why the 4th Exhaust header only gets warm when the choke is on whilst the others get hot? once i take the choke off it heats up to the other exhaust temps.

[CookMySock]

In order, check carb balance,shit in the enrichener jet, hole in enrichener diaphragm, carb clean, compression test.


Steve

[Gibbo89]

I don't think taking a dump in the enrichener jet will help.

might be worth a go? if DB drops a deuce in his hyosung then it must be good for the bike.

only kiddin BD.

hope your CBR comes right Westy. looks like your gettin some sound advice, put please dont poop in your bike, you'll be spraying stuff all over the road.

[Westy_mate]

Hey guys just a question, Would you rather recommend NGK CR8EH-9 spark plugs or CR9EH-9?

[DrunkenMistake]

Hey man,
I Have the exact same model bike, and I have CR9EH-9 spark plugs in mine, hope that helps you out