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'78 XS400 Idle/Mix Screw Tip Broken Off In Carb


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I've got a '78 XS400 that I am trying to get running. I was cleaning the carbs today and got through the first one great. When it came time for the second, as i went to remove the idle/mix screw I found out that a previous owner had tightened the mix screw in too far and the tip is stuck in the hole. It is broken off from the screw and jamed in there. Any ideas on how i could remove the tip? It seems very stuck. The whole carb is soaking in carb cleaner right now. Where might I find a set of carbs? I checked ebay. No '78 xs400 carbs. What other years or models will fit? Or is there another alternative if I have to buy new carbs. I'm not looking to spend a whole bunch.

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I've got a '78 XS400 that I am trying to get running. I was cleaning the carbs today and got through the first one great. When it came time for the second, as i went to remove the idle/mix screw I found out that a previous owner had tightened the mix screw in too far and the tip is stuck in the hole. It is broken off from the screw and jamed in there. Any ideas on how i could remove the tip? It seems very stuck. The whole carb is soaking in carb cleaner right now. Where might I find a set of carbs? I checked ebay. No '78 xs400 carbs. What other years or models will fit? Or is there another alternative if I have to buy new carbs. I'm not looking to spend a whole bunch.

Oh dear .... you are in the poo !!! :icon_eek: if the point is broken as you state you are better off looking for a new set of carbs or split the bank & just fit another carb to replace the faulty one ! Most sohc XS400 carbs will fit & run ok and in the past I managed to get a 400 to run on 360 carbs, it wasn't too good but at least it idled fine ! When I fitted the 360 carbs a customer brought them in as replacement for his 400 carbs with broken mix screws .... he was on a budget so I did no jetting or tuning work ... I just did as instructed fitted um ! and it ran ok but not as good as it would run on 400 carbs so perhaps with a bit of playing about you may get it to run on 360 carbs, but dont forget you will need the inlet manifolds also.

Regards Jim

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you can push the tips through into the carb.

this will obviously widen the hole, so you may find that you only need to take 1 full turn from bottom when tuning the pilot system.

this happened to both carbs and one of those carbs twice!! (that's another story)

so all is not lost

drewps

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you can push the tips through into the carb.

this will obviously widen the hole, so you may find that you only need to take 1 full turn from bottom when tuning the pilot system.

this happened to both carbs and one of those carbs twice!! (that's another story)

so all is not lost

drewps

great to hear, thanks a million. I will try that and let you guys know!

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you can push the tips through into the carb.

this will obviously widen the hole, so you may find that you only need to take 1 full turn from bottom when tuning the pilot system.

this happened to both carbs and one of those carbs twice!! (that's another story)

so all is not lost

drewps

any suggestions on what to us to puch it through?

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you can push the tips through into the carb.

this will obviously widen the hole, so you may find that you only need to take 1 full turn from bottom when tuning the pilot system.

this happened to both carbs and one of those carbs twice!! (that's another story)

so all is not lost

drewps

also, where can i find new mixture screws?

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also, where can i find new mixture screws?

Hi,

you hit the same problem I did in the 80's when the customer supplied the 360 set, If the points are pushed back through the carb body from the venturi as suggested there may be damage to the carb bodies which may just mean the bike idles like a bag of poo (as this only has effect on that part of the running of the bike) and does the XS400 hang at 5k thing. but is it worth having good idle on a bike that is now 30 years old or so ?

Regards Jim

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hmm Drewps,

if the body is ruined by removing the old screw there would be little point putting a new one in the old body ? But at my point when people did this my response was "buy new carbs" it made the dealership more money ! so can you point out how the screw can be removed with no damage to the body and a new screw seat down to the body ?

Regards Jim

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hmm Drewps,

if the body is ruined by removing the old screw there would be little point putting a new one in the old body ? But at my point when people did this my response was "buy new carbs" it made the dealership more money ! so can you point out how the screw can be removed with no damage to the body and a new screw seat down to the body ?

Regards Jim

I am riding my bike with it done that way, is that not proof enough!!!

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Will carbs off of an '81 xs400 work?

if it is a dohc carbs, they can be modified but its a lot of work to get it right. the dohc carbs are too narrow and a new mounts need to be fabricated as well as the carb linkage. the carbs also have their throttle cable on the right side as opposed to the middle on the sohc bike!

drewps

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I am riding my bike with it done that way, is that not proof enough!!!

Well i have successfully pushed the tip through! hopefully I did not damage the hole too much. I guess I will have to buy a carb kit for for that pilot screw and see what happens.

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I am riding my bike with it done that way, is that not proof enough!!!

Hi Drewps,

never seen the bike run :lol: but if you say it idles fine it must be a sound repair

Regards Jim

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  • 2 weeks later...

Hi Drewps,

never seen the bike run :lol: but if you say it idles fine it must be a sound repair

Regards Jim

SHE'S ALIVE! I can also say that pushing the tip through the carb and using a new needle can work. I recieved my carb kits yestarday and installed thim this afternoon. She's running pretty nicely considering the filters aren't on yet. Starts up easy. I don't want to run very long without filters and having that much air getting to it, so I will be installing the airbox tomorrow. Thanks for all the help guys! Especially Drewpy for his idea!

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SHE'S ALIVE! I can also say that pushing the tip through the carb and using a new needle can work. I recieved my carb kits yestarday and installed thim this afternoon. She's running pretty nicely considering the filters aren't on yet. Starts up easy. I don't want to run very long without filters and having that much air getting to it, so I will be installing the airbox tomorrow. Thanks for all the help guys! Especially Drewpy for his idea!

no problem,

just had an "accident " with my carb so having to use my own advice and pushed out the broken tip off. now I'm baking soda blasting the bugger and ultrasonic/dishwasher cleaning it at the mo (wife is at work) :lol:

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no problem,

just had an "accident " with my carb so having to use my own advice and pushed out the broken tip off. now I'm baking soda blasting the bugger and ultrasonic/dishwasher cleaning it at the mo (wife is at work) :lol:

I'm a fan of the carb cleaner that comes in the bucket with a strainer

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no problem,

just had an "accident " with my carb so having to use my own advice and pushed out the broken tip off. now I'm baking soda blasting the bugger and ultrasonic/dishwasher cleaning it at the mo (wife is at work) :lol:

I'l trade you a needle screw for 2 main jet washers

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I'l trade you a needle screw for 2 main jet washers

i haven't any spare, but you can get them from ciriusconinc in canada, they also operate on ebay

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