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Low compression

A cable or zip tie down plug hole works to do shim changes. Look for zip tie method in search bar. Carb O rings etc can be supplied by Brian McCall at Centurion motorcycles in Hexham, he has an Ebay shop.
 
Reply to Kiwialfa156 Thanks for the pilot system info (where is this from?) I didnt remove the pilot screw when cleaning carbs. What do you use to plug the threaded hole and the pilot jet as per the instructions? Can you just use your finger? Ill have to check again if header is hot just while idling on choke or also when giving some throttle. I think it was both. I think I will again clean carbs with this additional info as my next task aswell as recheck the sparks.Then go onto valve clearances. I previously had weak sparks to all cylinders before I replaced the coils leads caps RR and stator but didnt recheck after this work. Atleast it was charging which it hadnt been before? Do you have any further instructions for cleaning all the mikuni vm carbs? Thanks alot Chris
 
There is a link to a VM carb cleaning tutorial on BikeCliff's website. under the the Wiring diagrams, right column, third link down. Or just click on THIS.
 
Reply to Kiwialfa156 Thanks for the pilot system info (where is this from?) I didnt remove the pilot screw when cleaning carbs. What do you use to plug the threaded hole and the pilot jet as per the instructions? Can you just use your finger? Ill have to check again if header is hot just while idling on choke or also when giving some throttle. I think it was both. I think I will again clean carbs with this additional info as my next task aswell as recheck the sparks.Then go onto valve clearances. I previously had weak sparks to all cylinders before I replaced the coils leads caps RR and stator but didnt recheck after this work. Atleast it was charging which it hadnt been before? Do you have any further instructions for cleaning all the mikuni vm carbs? Thanks alot Chris

Hi Chris, using your finger to plug thing is fine. Whatever works for you. Each of carb circuits (choke, idle/pilot, needle/main), mix air and fuel and THEN let this mix into the carb bore through their outlets to mix with the air coming through the bore. This froth or emulsion forms smaller, more easily combustible, droplets when entering the main air flow. The holes on the side of the pilot and on the emulsion tube (which is either part of, or feeds the needle jet) is there to do this 'pre-mixing'. All the holes in the jets, all the outlet orifices all the internal passages in the carb need to be clean and clear for the carburettor to work as intended. So generally a full strip down and scrupulous cleaning is the only way to guarantee this.

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Having a plastic organiser box is an easy way to keep the pieces sorted during disassembly, cleaning and reassembly.

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You can clean the bits manually, taking care to to scratch the interaction. I used plastic cleaning implements.

You can can also soak the parts if you have access to carb dip. Or use a ultrasonic cleaner, if you have access to one of those. A YouTube search will show you what these things are.

If stripping carbs you might take the opportunity to replace the nitrile orings that seal the various parts of the carb. They're 40+ years old now, so liable to leak after being disturbed. One of the guys on the forum sells kits.

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Christopher;n1726592. said:
I will retest the compression with all plugs removed to get a more accurate reading.

Forget about the compression. It's fine.
 
Ive been intimidated to separate carbs and do a complete strip down that I might get stuck screws and problems doing correct reassembly. Ok Im going to go for it and see if I can get all the cylinders running nicely. Do you guys recommend buying an ultrasonic cleaner and any recommendations? Also where is best place to buy replacement O rings? I tried a member website but it was removed. Thanks guys
 
I have O-ring kits. Send me a PM for info. It takes a little while to get to the UK, but I've sent kits to UK before without issue.

You may need an impact driver to get off the large # 3 screws that hold the carbs to the joining plate. Other than that, it's just normal hand tools stuff. Just take your time and take photos as you go.
 
You may need an impact driver to get off the large # 3 screws that hold the carbs to the joining plate. Other than that, it's just normal hand tools stuff. Just take your time and take photos as you go.

Good bit of advice. Buying a $10 set of made in Japan JIS bits in the #1/#2/#3 size has saved me many stripped screw heads and much frustration over the last few years
 
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