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Discussion Starter · #1 ·
So i came across some aftermarket carbs on ebay and i wanted to know if anyone has used them? I know that the stock ones on mine are 38 year old technology so it couldnt hurt! Anyone have anythoughts on this?
 

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Carbs, all carbs, aside from some bells and whistles, are pretty much the same as they were 75+ years ago. The carbs that came with the CX from the factory are just as good if not better (they are, after all, made and fitted by the factory for our bikes.) Finding a replacement would be a worthy endeavor if OEM carbs were hard to find, but they're not, and once rebuilt the correct way, with normal care they'll go a decade+ before the next rebuild is necessary.



After mounting accelerator pump equipped later carbs on my 1978, I'm going back to the originals, the originals perform better IMHO. Nothing I can point to on a graph or chart, but I know what my "pou pou" (butt) meter tells me, and it seldom errs.
 

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I think Jim was using similar on his salt flat bikes but that's about all I know.



Anything can be made to work but work perfectly is anther question.
 

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Discussion Starter · #6 ·
thank you for the advice i dont know to much about motorcycles but i work on cars for a living and i know on car or any engine for that matter it how everything works together as a whole. You can put on some kickin carbs but the intake or exhaust isnt very good with the setup and get less hp out of it. Im just looking for a way to get more umph from this 500cc motor and if i cant then i think i will be doing some sort of motor swap to a 650 or see what all is different about the motors.
 

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thank you for the advice i dont know to much about motorcycles but i work on cars for a living and i know on car or any engine for that matter it how everything works together as a whole. You can put on some kickin carbs but the intake or exhaust isnt very good with the setup and get less hp out of it. Im just looking for a way to get more umph from this 500cc motor and if i cant then i think i will be doing some sort of motor swap to a 650 or see what all is different about the motors.
Even the production racers at Bonneville have to run the stock carbs and they run 113 mph (at altitude). Unless you are planning to add a camshaft, headwork, pistons, and a trick exhaust, I wouldn't waste the time or money. If the carbs are in bad shape, buy some of Larry's or have him do yours. Getting more "umph" out of the CX gets real expensive because of the lack of parts (ie no demand). Good luck.

Ed
 
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I put on the 38mm Mikuni flatslides. Just bought another set (2) for $75 plus shipping. They work great and are far superior to the stock carbs. Some issues that you will encounter;

1 Air filter fitment, needs to be 64mm. I use a modified car filter that is made to fit.

2 My filters are bolted together so they need to be spaced properly. Lots of machining nas measuring

3 Jeting needs to be sorted but all the jeting can be modified while the carbs are in frame

4 My carbs only use one cable that had to be custom made and I use an extra spring to make sure that the slides close.

It takes about 4-8 hours to convert this set of carbs to the CX. My Mikuni carbs have no accelerator pumps so you cannot whack the throttle open. Some other mods to my bike are: exhaust system where the pipe diameters are almost 100% larger in volume to the stock (1.42" vs 1.1"). They also weigh in at least half as much as the stock system. Copper head gaskets that are .020" thinner than stock at .040". The bike runs good with these mods but it will never be considered fast. They look way cool and have a ticking rattle at idle.
 

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Scudman, good for you I love the American ''can do'' spirit ha ha. If you don't mind what model Mikuni flat slides?

What are the from originally? OEM or aftermarket? Are they the TM or RS?

My first thought was that's too much carburetor for a 500cc motor?

Did you have any fitment problems to the carb holders and height? I have my two into one headers

that start out the same as your's then step up two more times .125" each step to the merge collector.

Bonneville Jim has a cam and then some porting work would make that engine come alive I'd guess?

Cheers, 50gary
 

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Scudman, good for you I love the American ''can do'' spirit ha ha. If you don't mind what model Mikuni flat slides?

What are the from originally? OEM or aftermarket? Are they the TM or RS?

My first thought was that's too much carburetor for a 500cc motor?

Did you have any fitment problems to the carb holders and height? I have my two into one headers

that start out the same as your's then step up two more times .125" each step to the merge collector.

Bonneville Jim has a cam and then some porting work would make that engine come alive I'd guess?

Cheers, 50gary
The carbs are from a Polaris snowmobile. Not sure of the model. They foul the frame bracket but since I am using the GL rear case that is not an issue any more. Originally I just lightly modified the brackets. The original carbs are 38mm but they are not smoothbores and the difference is abot 2mm as a rule of thumb due to no restrictions in the ventury. The new set ($75) is from a Artic Cat and even though the carbs are similar there are differences such as the cable facing the rear of the bike. This will be overcome with a round directional cable pulley to provide 90-180 degrees of cable rotation. This conversion is not for novices as there is tons of work to make them fit. They need to be spaced properly and the air filters are a royal PITA to fit. Just got 2 air filters for $30. The exhaust has been modified again and placed on my steam punk project in full swing at this time. I made another for the cafe racer and used a Ducati 848 muffler to keep the bike quiet for my early morning Saturday departures. The steampunk is sporting a 600rr UPS front end and it will be a fine ride when finished. Tis project is for my friend who got the second CX that was in my garage as a parts bike. The porting and higher compression does help with the output but since I have never ridden a stock CX it is hard to judge. There was a difference between the stock motor with the new headers and the modified motor. It sounded much louder.
 

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Update;

Finally got the CX to run right. Took the bike out for a ride this morning (70F and sunny, go ahead and hate me). I have been chasing an elusive engine miss at 7K rpm. Tried every single jetting/needle position known to mankind to no awail. Then it hit me, it was an electrical issue as one cylinder ran fine while the other was misbehaving. Anyhoo I replaced the coils, Dyna high performance, and the bike howls up to redline with no issues. Carbs need to be sorted again as it runs lean in low to midrange but that will be rectified with the needle positioned one clip higher. With all the other mods this thing likes to rev as the real power comes on between 7-9K rpm. Sounds great with the Ducati muffler but the shorty megaphone was a better sound if too loud. I would recomend this carb setup as a performance mod but it would be expensive. If anyone want a more detailed DIY on this setup just contact me as I am willing to share any info.
 

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Discussion Starter · #13 ·
thank you so much this is exactly what i wanted to hear and see! I love my cx500, its no ducati (my other bike) but its fun. thanks alot again everyone.
 

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thank you so much this is exactly what i wanted to hear and see! I love my cx500, its no ducati (my other bike) but its fun. thanks alot again everyone.


Which Duck do you have?



The Honda requires less upkeep than the Duck ... right???
 

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Even the production racers at Bonneville have to run the stock carbs and they run 113 mph (at altitude). Unless you are planning to add a camshaft, headwork, pistons, and a trick exhaust, I wouldn't waste the time or money. If the carbs are in bad shape, buy some of Larry's or have him do yours. Getting more "umph" out of the CX gets real expensive because of the lack of parts

Ed
Who's Larry and how much are his carbs?
 

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You can find Larry in search. It cost me $240.00 to rebuild a pair fro my GL650 and he polished them up to look like a brand new pair. Well worth the investment. He even tried them and tuned & balanced them on his own bike.
 
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