Your problem is that you bought a Keyster re-build kit. Buy genuine Mikuni float valves and your sticking problem will go away. And I agree that this will also fix your hanging idle and that you shouldn't use 30 pilots.
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BS38 Hanging idle
- Thread starter veedub1955
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- carburetors
veedub1955
XS650 Enthusiast
Cheers ill do that, the floats stuck pre rebuild with the genuine valves which actually looked and felt alright
i think they are cocking over and binding due to wear, now to try and find a decent supplier of floats
in the uk, read the bad reports on here of mikes xs ones
i think they are cocking over and binding due to wear, now to try and find a decent supplier of floats
in the uk, read the bad reports on here of mikes xs ones
veedub1955
XS650 Enthusiast
Forgot to add when one stuck and on sidestand i could hear and audible click shut when i tapped the float
bowl
Also are the bs38 brass floats all the same found an oem supplier one states 70-80 in the year range? Thanks
bowl
Also are the bs38 brass floats all the same found an oem supplier one states 70-80 in the year range? Thanks
That year range is off by one. Yes, all BS38 floats are the same but the year range should be '70-'79. In 1980, the BS34 carb was used. It had a brass float for 1980 (only), but it differs in size from the BS38 float. Yes, there are errors in the factory parts listings. Here's the float for those 1980 BS34 carbs but it is also listed as fitting the '78 and '79 650 Specials, which it will not .....
http://www.boats.net/parts/detail/yamaha/Y-3F7-14985-00-00.html
http://www.boats.net/parts/detail/yamaha/Y-3F7-14985-00-00.html
The OEM floats are expensive, but yes, they are available, part # 256-14985-00-00 -- is that what the supplier is coming up with?
But I honestly don't think there is anything is anything wrong with your floats. The non-mikuni float valves are prone to cocking in their bores. Brand new genuine Mikuni float valves will not do this. Remember, the float valve consists of both a seat and a needle, both get replaced.
If you want to get really picky, tighten up the slop in the float pins by pinching the rolled-over brass that forms hole that the float pin slides into in the float.
But I honestly don't think there is anything is anything wrong with your floats. The non-mikuni float valves are prone to cocking in their bores. Brand new genuine Mikuni float valves will not do this. Remember, the float valve consists of both a seat and a needle, both get replaced.
If you want to get really picky, tighten up the slop in the float pins by pinching the rolled-over brass that forms hole that the float pin slides into in the float.
veedub1955
XS650 Enthusiast
Cheers 5twins im impressed with your depth of knowledge and cant thank you enough for your advice cheers
Hmm ill try that dogbunny as its a no cost option and try lapping the valves as well, they did it with the genuine ones
as well which made me think otherwise, ive some small reems so ill tighten up like u said and reem them out to the pin size,
maybe a couple of thin thrust washers either side might help too if their binding
Oem ones are £18 each here
Hmm ill try that dogbunny as its a no cost option and try lapping the valves as well, they did it with the genuine ones
as well which made me think otherwise, ive some small reems so ill tighten up like u said and reem them out to the pin size,
maybe a couple of thin thrust washers either side might help too if their binding
Oem ones are £18 each here
veedub1955
XS650 Enthusiast
Well found the issue dont know how i missed this, pretty sure its not meant to have this much play!
Click link for video
Click link for video
Last edited:
veedub1955
XS650 Enthusiast
So decided to drill and ream the posts and floats as turning some bushes on the lathe would be too
thin. I used two 3mm (1/8") drills as new pivot pins and drilled the posts and floats out to size, i then
reemed the float holes to perfect size so that it pivots on the pin instead of the posts, just drilling
dosent give enough clearance for it to move, i had one 250 microns bigger than 3mm (1/4 of a mm
dont know equivalent inch size sorry) what i didnt expect was the amount of tang adjustment on
the float for floatheight compared to when i set them last time one of the pics below shows this.
Picture number 3 is the cut down drill in place, you probably have to grind it down if you haven't the
facility to cut hardened steel. No wonder they were sticking
Unfortunately I had a fire service emergency callout to attend to so not got them back on the bike yet
but will report back
thin. I used two 3mm (1/8") drills as new pivot pins and drilled the posts and floats out to size, i then
reemed the float holes to perfect size so that it pivots on the pin instead of the posts, just drilling
dosent give enough clearance for it to move, i had one 250 microns bigger than 3mm (1/4 of a mm
dont know equivalent inch size sorry) what i didnt expect was the amount of tang adjustment on
the float for floatheight compared to when i set them last time one of the pics below shows this.
Picture number 3 is the cut down drill in place, you probably have to grind it down if you haven't the
facility to cut hardened steel. No wonder they were sticking
Unfortunately I had a fire service emergency callout to attend to so not got them back on the bike yet
but will report back
veedub1955
XS650 Enthusiast
Thanks for all your advice 5twins all sorted now, no leaks after putting in new float pivots. Had to go upto 30 pilots and it ticks over so sweet now I keep thinking its going to die at junctions now, been used to hanging idle, but is perfect and sounds great.
So for the record 132.5 mains with 30 pilots, straight through exhaust with baffles mid way, velocity iinlets mesh filter
So for the record 132.5 mains with 30 pilots, straight through exhaust with baffles mid way, velocity iinlets mesh filter
