Hello people. I've always had an issue with the CBR1000f firing on 3. Thought I'd found it as I found one air screw a lot further out than the rest as I had carbs off and was cleaning bowls and jets ( didn't separate ). And this was on number 2 who's down pipe was running cool.

Reset all of them to the correct spec , did valve clearances , ( now runs on 4 , all pipes at same hot temperature) , Balanced carbs. All is good.

Left for a week . Cold start ..great
Changed coolant over the next week which meant frequent starting and running at idle during the process.

All good.

Today , after a 3 week break, difficult to start and now runs on 3 . I know this as number 1 down pipe is a lot cooler than the rest and it sounds wrong.

As all the fairing is back on , I've so far just checked the fuel pump is pumping which it is .

Fairing back off tomorrow . And start process of fault finding again. But just seems odd . Whats happened over those dry stored three weeks ?
So grateful for any ideas ?

 

One possibility would be dirt from the fuel tank getting into the carb.

 

Have you checked the spark plugs ?

These bikes run really rich at idle. You may have a fouled spark plug.... mine would foul plugs all the time with short starts & idle working on the engine.

Try a fresh Sparkplug in the offending cylinder. If this works, take if for a good rip & teach it a lesson

 

Thanks both, Yep that's where I'll start . A new set as I know the carbs are squeaky clean. Might also look into doing the stick coil mod while I'm there as
at first I'm sure, after it started , it sounded like a twin for a bit ( Honda super dream? ) but that could of just been my ears. If it was , maybe it points to a coil pack miss-behaving.

 

I'd do it anyway, doesn't hurt.

I lose the fuel pump and go gravity feed.

 

Typically when you clean carbs due to this issue ( fine dirt clogging up pilot jets) you
need to pull all fuel bowls and clean , all pilot jets and clean as they have microscopic
holes in the sides and a tiny hole on the end - best blown out with an air gun.

Then if fine rust indicated by orange goop is present it's a good sign the tank is rusting
and should be sealed or you'll be doing it all over again.

As TBT said scrapping the electric pump and gravity feeding is a good idea.

I did all of the above with my 87 and fed the carbs from the right side like the mark 2
and 3 also put a filter in line and a pingel inline vacuum fuel valve as sometimes with
gravity fed tanks a sticking carb fuel valve can stick open and you end up flooding
the crankcase with fuel. The Pingel prevents that.

My 2 cents .......having done this to resolve this exact issue

 

Mine did 20 years on gravity feed, never used the vacuum tap setup, but I always shut off the fuel at the main pet ****. Went through three in twenty years from leakage lol. Sprock, is the vac tap more reliable? You still using stock petcock shutoff?

 

I also run an inline plastic auto fuel filter on the gravity system and change it once a year. You can see if there is any crud in there. And there usually is, and my tank is perfect with no rust and running the stock petcock prefilter. Always use good fuel! Although sometimes that doesn't matter lol.....

 

Thanks for the replies, guys. Interesting to know this is a common issue. Not had chance to investigate yet, so just a rambling. It could be another blocked jet,but it's ran only 5-6 times since the carb clean . At first start up things were better , then carbs balanced after valve clearances reset , and she then ran great. Over next few days did they coolant change starting and running 10 mins and draining etc , all great . Until 3 weeks after that. This problem . I think I'll try the inject 'easy start ' down the vacuum inlet again to see if it picks up and so showing a carb fault again . Cheers .

 

Without getting too technical... replace offending sparkplug & the jobs a good'n. Then ride it like you stole it to teach it who's boss