Project My project MC22

Did you say that you have rebuilt the carbs?
I would be pulling the carbs off and going over them very carefully to make sure they are all ok.
Check o rings. Check jets and needles. Check intake rubbers. Check needle valves and seats. Check balance between all carbs (this can be done pretty well on the bench by measuring the butterfly gap).
A mixture distribution issue can foul up plugs pretty quickly and stop them from firing.

 

With the plugs still in the engine, remove the spark plug cap on all cylinders. Using a multimeter on highest meg ohm range, measure the resistance between the contact on each plug and the engine or frame. They should all appear as an open circuit. Anything different from this, you need to ditch the plug.

 

i doubt it is the CDI as one coil drives cylinders 1 and 4 and one coil drives 2 and 3, but I have been proved wrong before.

The spark system on an MC22 is super easy, there is a single pickup coil which is excited as it passes the trigger wheel when the engine is cranked, the pickup coil sends signal to the CDI to tell the ignition coils when to fire. As the Mc22 uses a wasted spark system, cylinders 1 and 4 fire at the same time, hence why they share a coil. That is the same for 2 and 3

A simple test is to remove all 4 coil caps from your plugs ,plug in a spark plug to your coil cap and ground the side of the plug to your frame and turn the bike over using your starter, you should see the end of the plug sparking. Rinse and repeat for all 4 plugs , hopefully you find that you have spark on all 4. Poorly setup carbs will kill plugs quicker than look at them ( mc22 even more than most) , and you cant clean the the ends of plugs , products like Start Ya Bastard kills plugs too, Id grab some spare plugs and ditch the starting fluid.

If cylinder 2 isn't running but the other 3 are then you could have either a compression or fuel issue as that is what is needed for the bike to run. A good set of compression gauges will tell you if each cylinder is creating the required internal cylinder pressure to achieve combustion. On a cold MC22, id hope to see 120-160 psi per pot with all 4 plugs removed and your carbs off the head, with a nicely warmed up engine you should see compression readings of 160-220 psi which is the sign of a good healthy engine.

Conversely if it is a fuel issue, ie your pilot jets are blocked then the cylinder will stay much cooler than the other 3 as it wont allow fuel into the cylinder, pulling the carb off and remove the pilot jet, yould be bale to see a pin ***** of light, if not, then you need to clean that jet . The pilot circuit uses the Air / Fuel mix screw to get the required mix into the cylinder, hence why in previous posts I harped on about the importance of checking your AF screw to check that you have the metal washer and rubber seal in there, I have seen so many bikes where back yarders loose things like those washers or crush them in the housing and the bike wont run anymore, these are super important getting a good mix into the engine. Another possibility is that your balance screw on your butterfly are so far out causing 2 not to sire, google bench syncing to understand that process.



Watch this vid to the end, it explains how a CV carb works



Finally, could be a cylinder head valve issue, but that's rare and Id do the following first.

Once you have confirmed spark on all 4 coil leads by grounding a plug to your frame or engine, a carb clean and check of your pilot jet and AF mix screw should be done on number 2, if that doesn't solve your issue then compression test should be the next step to help you diagnose your issue.

There are some very knowledgeable guys on here who have given you some pearls of wisdom, please use them.

 

Yes there's A LOT more to fuel-flow path than just jets. I compare it to garden-hose sprayer nozzle. When there's problem, most people focus on the nozzle (jets). But what about 30m of hose with golf-balls stuck inside? That contributes to way more problems than just jets.

Once you've removed jets and cleaned them, 1st 5% of job is done, there's more. Here's photo of CVK30/32 carbs that frequently have issues. Yours may have differently shaped passages, but idea is exactly same. Beyond jets, you need to scrub fuel-circuits after the jets with brushes using PEA-based fuel-system cleaner. Follow passages all way through carb-body to venturi. Then scrub from other side starting at carb-throat all way back to float bowls.

Then soak entire carb in ultrasonic cleaner for 4-6 hours using polar solvent. Rinse, dry and micro soda-blast to clean out fuel-circuits. There will be chunks and flakes of dried petrol clogging passages. There's plenty of people who can rebuild entire engine using only their teeth with hands tied behind their backs who've had to remove carbs 4-5x for ever deeper cleaning until they were finally clean enough to run engine smoothly.

Also remove slides and diaphragms and inspect rubbers to make sure they're no holes or rips.

 

Also inspect emulsion-tube and pilot jets very carefully. They may have lateral bleed-holes for vapourising petrol. Be sure to poke through and floss those holes with soft copper wire of matching diameter. Be careful not to scrape of metal from tube and jets.



Also given age, it's best to replace all rubbers, O-rings and seals. O-rings at end of mixture-screws. O-rings in fuel-distribution line. Float-valves. Float-bowl seals.

Idea is to restore carbs to factory-fresh condition. Bike ran great when leaving showroom floor with factory-fresch clean carbs. It will again when carbs are restored back to factory-fresh condition. Fact that it doesn't, means carbs aren't factory-fresh clean.