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Discussion Starter #1 (Edited)
Afternoon...

For those that have read my previous posts you may recal, however to recap.

My 92 engine is back together and in the bike, had a few electrical issues with the old plug caps but new ones on. Still she's a struggle to start and it seemed like she was running on two cylinders, both 3 & 4 headers seems cold.

The carbs were proper crusty when I stripped them but I've ultrasonic cleaned them and they seem good to go.

I've checked compression, very good at near 200psi (bit higher than spec but the heads been ported so maybe higher compression too?), sparks on all 4 too.

My question is I guess is:

I assume that with the good compression you are bang on with the timing?

Then it must be fueling? When shes running, holding a hand over an inlet the revs rise on 1,3 &4, on 2 it near kills the engine. Headers a lot cooler on 3&4 (like can hold a naked hand on them) at tickover, so must be fueling?

Just checking that the pilot jets are sealed, you can't clean through them 'top to bottom' like the main jet, but only the v small holes across and through to the bottom? I ask this as I have tried and all 4 are solid as in not even giving a little.

Loathed to strip them again without a good direction to look in!!

Any help will be much appreciated!

Cheers
 

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Afternoon...

For those that have read my previous posts you may recal, however to recap.

My 92 engine is back together and in the bike, had a few electrical issues with the old plug caps but new ones on. Still she's a struggle to start and it seemed like she was running on two cylinders, both 3 & 4 headers seems cold.

The carbs were proper crusty when I stripped them but I've ultrasonic cleaned them and they seem good to go.

I've checked compression, very good at near 200psi (bit higher than spec but the heads been ported so maybe higher compression too?), sparks on all 4 too.

My question is I guess is:

I assume that with the good compression you are bang on with the timing?

Then it must be fueling? When shes running, holding a hand over an inlet the revs rise on 1,3 &4, on 2 it near kills the engine. Headers a lot cooler on 3&4 (like can hold a naked hand on them) at tickover, so must be fueling?

Just checking that the pilot jets are sealed, you can't clean through them 'top to bottom' like the main jet, but only the v small holes across and through to the bottom? I ask this as I have tried and all 4 are solid as in not even giving a little.

Loathed to strip them again without a good direction to look in!!

Any help will be much appreciated!

Cheers

Do the other cylinders pic up if you give them a squirt of starter fluid?
Do they pick up when you open the throttle?
When you cleaned the carbs did you make sure all the circuits are flowing carby cleaner?
You did remove the mixture screws and clean the pilot circuits?
I would think the pilot jets would have a hole right through them, but it'll be _very_ small, much smaller than the lateral holes. Did you try a magnifying glass?
The best thing I've found for cleaning them is an old throttle cable. Cut the cable, untwist the wires and cut one single wire off a couple inches long. Although some pilots are even smaller than that.
 

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im having the same issue on my cbr 98rrw it had been sat in my mates garage for 7 long dark years but now i have her,got her running but seems to run a bit rough like on 3 cylinders looking from the front of the bike its the right hand header pipe thats cold, i did strip my carbs and clean them float end and diaphram end but i didnt touch the pilot adjustment screw could it be them thats causing the bike to run rough ??
 

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To avoid removing and replacing carbs multiple times due to rough idle or no idle, it is absolutely imperative that every jet and every screw and every piece that has a hole comes out and is flushed. Then, the carb bodies need to have cleaner prayed through every orifice to verify that all the adjoining passageways are clear. On the 900, that includes: pilot jets, main jets, emulsion tubes, air cut off valves (the units that the choke operates), air/fuel mixture screws, slides, float and needle valves, and needles. Then make sure every brass passageway on the bodies flow fluid. There are some really small orifices as BR mentioned. If they get clogged by the tiniest of debris, idle will be affected.
 

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Just checking that the pilot jets are sealed, you can't clean through them 'top to bottom' like the main jet, but only the v small holes across and through to the bottom? I ask this as I have tried and all 4 are solid as in not even giving a little.


Noooooo!! The pilot jets should have a clear path top to bottom, in addition to the vertical holes. If you can't get a strand of the thinnest wire you can find through there, then that is your problem my friend. They won't get fuel through them.

This is how a proper carb clean should look while in the process, before ultrasonic cleaning.

 

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thanks Ian,,, my carb cleaning was NOT as thorough as that i will have to re strip the bike down and be more thorough anyway a picture of the bike im resorting that was sat in the dark for 7 long years with out being started poor girl :idunno: anyway i managed to get second hand oem body plastics and tank from northern ireland the whole lot for £450
 

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Discussion Starter #7
Ah, thanks for confirming Ian, pilot jets it is then! I had the rather ignorent assumption that the 2 hr ultrasonic clean, would have cleared these tiny holes.. and a rinse through would have done the job.

Happy days..

I'll update tomorrow!
 

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Ah, thanks for confirming Ian, pilot jets it is then! I had the rather ignorent assumption that the 2 hr ultrasonic clean, would have cleared these tiny holes.. and a rinse through would have done the job.

Happy days..

I'll update tomorrow!

Ultrasonic carb cleaning is crap.
 

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thanks Ian,,, my carb cleaning was NOT as thorough as that i will have to re strip the bike down and be more thorough anyway a picture of the bike im resorting that was sat in the dark for 7 long years with out being started poor girl :idunno: anyway i managed to get second hand oem body plastics and tank from northern ireland the whole lot for £450
No problem, and she's a looker. Very nice!
 

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Ah, thanks for confirming Ian, pilot jets it is then! I had the rather ignorent assumption that the 2 hr ultrasonic clean, would have cleared these tiny holes.. and a rinse through would have done the job.

Happy days..

I'll update tomorrow!
Relying on just the ultrasonic is unfortunately not good enough. It suits the carb bodies well for loosening up stuff, but in the end each orifice still needs probing and spray of fluid to confirm no blockages. Basically what BR said, just easier on the ears. lol
 

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Discussion Starter #12
Doohan, Racer

I bow to your experience...

A little slower than hoped, carbs off for the 3rd time, stripped and cleaned as per your comments. Took some doing but got a thin cooper strand through the pilot jets, flushed through with carb cleaner (as well as every other hole I could find!) and back together.

On the bike tonight... And... Boom, starts, runs and idles a treat!

Thanks chaps. Lesson learnt. Take your time. Be thorough, and above all - ultrasonic is (on its own) crap.
 
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