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Discussion Starter · #1 ·
I have recently purchased a 91 mc22.
As it was purchased from a wrecker in vic it had numerous problems that had to been seen to, so I just started to replace everything so I then knew it should run fine; not, Or as it seems.
These are all parts that have been replaced new;
CDI , rect/ regulator , coils, plugs , plug lead caps , stator, both handle bar block switches, new battery, key ignition, indicator relay.
it should have started and purred.
Before I tried to start it, I checked timing , too dead centre, timing chain alignment, plug fires , fuel flow, carb adjustments ( being air screws and idles), I’ve pretty much covered it, or I thought so.
So I fired her up. It for some reason it feels like 2&3 aren’t firing right. The exhaust on 2&3 aren’t as hot as 1&4.
But here’s the strange bit. To make sure all pots were firing, I used an aerosol starter can., and thusly it started no worries and all pots were firing, and it idled fine and sounded great.
But then after reconnecting the fuel line and air draw line from pot 1;( and used the right ring clamps for those lines), it didn’t run very well, 2&3 weren’t firing.
Therefore; my own diagnosis is this:
There must be some sort of fuel line blockage in fuel distribution tube to 2&3,,,, or,,, carbies idle or main jets are blocked again in 2&3.,,,,,or,,, the ignition pulse coil isn’t working properly.
About to strip it down again and start again, but it is perplexing me a bit, and tearing out the carbs on these things is really tight to do.
It’s all really weird, could have sworn I had it all right.
Any help would be good.
 

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Buying from wreckers is always suspect. Don't know real history, so assume the worst.

Since it runs fine on starter spray, we can assume carbs aren't delivering sufficient petrol. Mains aren't even concern, it's choke and idle circuits you want to focus on. Most likely need complete restoration with tear down to every last nut, bolt and individual component. Keep on disassembling until no further pieces can be separated:

1. scrub everything with brushes using PEA-based fuel-system cleaner. Scrub secret hidden passages in carb-body. Scrub entire path of petrol flow from tank to intake valves, including petcock and all hoses

2. poke out all bleed holes in jets, emulsion tube, carb venturis with matching gauge soft copper wire. Especially the lateral bleed holes in pilot jet and emulsion tubes. You'll find they poke out dried plastic petrol plugs like little grains of sand.

3. ultrasonic soak everything for days on end

4. micro soda-blast everything

5. scrub everything again with brushes and solvent

6. re-assemble and replace all rubbers: fuel-rail O-rings, float-valves, pilot-jet O-rings, float-bowl seals, even slide diaphragms if necessary

7: adjust float-levels and sync carb

Idea is to restore carbs back to factory-fresh clean. Bike will run like brand-new off
showroom floor. Fact that it doesn't means carbs aren't factory fresh clean.
 

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Discussion Starter · #3 ·
Okay great., this will be fun.
I did suspect it was a fuel flow problem if not carbies rebuild. I came to this conclusion as things I did electronically should have done it as certain order of procedures canceled others out. Your recommendations are of value.
Like I said, this will be fun.
Will return with results after carbs rebuild with verdict. Some how , me thinks you are on it.
Thankyou for your knowledge, very helpful,, cheers from down-unda.👍
 

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Here's some images and resources that helped me refurbish my MC19 carbs. From different bike, but all Keihin CV carbs tend to be similar. Split carbs and disassemble down to individual components. Scrub everything thoroughly with PEA-based fuel-system cleaner since modern carb-cleaner sprays no longer work due to removal of chlorinated compounds.



This site illustrates secret hidden passages in carb body needing lots of scrubbing end-to-end. Secret Ninja 250 Carburetor Passages

There are numerous bleed holes in pilot jets and emulsion tubes that remain clogged regardless of scrubbing efforts. That's due to dried petrol deposits turning to plastic and cannot be dissolved. Must be mechanically poked out with soft copper wire. Be sure to re-assemble needle-jet/collar with bevel facing needle.


Bend 5mm tip of wire 90-degrees and use to poke out bleed holes in carb-venturi back towards jets. These holes tend to get clogged from inside out. Pushing debris backwards is only way to clear out holes.

Also test petcock, then clean & rebuild as necessary.


Good luck! :)
 

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Discussion Starter · #5 ·
Here's some images and resources that helped me refurbish my MC19 carbs. From different bike, but all Keihin CV carbs tend to be similar. Split carbs and disassemble down to individual components. Scrub everything thoroughly with PEA-based fuel-system cleaner since modern carb-cleaner sprays no longer work due to removal of chlorinated compounds.



This site illustrates secret hidden passages in carb body needing lots of scrubbing end-to-end. Secret Ninja 250 Carburetor Passages

There are numerous bleed holes in pilot jets and emulsion tubes that remain clogged regardless of scrubbing efforts. That's due to dried petrol deposits turning to plastic and cannot be dissolved. Must be mechanically poked out with soft copper wire. Be sure to re-assemble needle-jet/collar with bevel facing needle.


Bend 5mm tip of wire 90-degrees and use to poke out bleed holes in carb-venturi back towards jets. These holes tend to get clogged from inside out. Pushing debris backwards is only way to clear out holes.

Also test petcock, then clean & rebuild as necessary.


Good luck! :)
Good value mate, cheers.
It’ll take a while, but will be worth it.
 
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