Now that I got my RD400 running again, of course I had to do something stupid to screw it up.
On the right side carb, one of the float bowl screw holes was stripped so the screw wasn't tightening fully. Drilled and re-tapped for one size larger to "fix" it. Then thought I might as well do all the screw holes so the same size screw is used. Tried testing it and fuel spilled everywhere. I must've drilled/tapped one or more of the holes crooked, because now the gasket surface of the carb is warped, making it impossible to get a seal on the float bowl - see photo.
Anything I can do to fix this, or did this screw fix screw me? Even if I managed to straighten out the carb again, I'd probably have to drill/tap even larger, and not sure there's enough clearance.
If it's ruined beyond repair, can I run them with the left OEM and the right a new replacement? Or will they not 'match'?
FYI I'm running stock carbs, Dave F modded.
Not much choices anymore for carbs. Go used off ebay and use your new jetting parts.
https://www.ebay.com/itm/Yamaha-RD400-RD-400-1977-Carbs-Carburetors-MIKUNI-Restoration-GREAT-SHAPE-cables/143608049602?hash=item216fb4efc2:g:ExMAAOSwg~lewVGi (https://www.ebay.com/itm/Yamaha-RD400-RD-400-1977-Carbs-Carburetors-MIKUNI-Restoration-GREAT-SHAPE-cables/143608049602?hash=item216fb4efc2:g:ExMAAOSwg~lewVGi)
Or go new and have to make throttle cables.
https://www.ebay.com/itm/MIKUNI-VM-ROUND-SLIDE-CARBURETOR-28MM-VM28-49-1002-0052-13-5007/231584793243?epid=202940934&hash=item35eb87829b:g:6u8AAOSwPoZaq6eu (https://www.ebay.com/itm/MIKUNI-VM-ROUND-SLIDE-CARBURETOR-28MM-VM28-49-1002-0052-13-5007/231584793243?epid=202940934&hash=item35eb87829b:g:6u8AAOSwPoZaq6eu)
Chuck
Ignoring the price difference, and just considering performance, which is better to get:
(A) used OEM carbs
(B) new VMs
Also, for new VMs would a size up from s28mm improve performance with the TSR stage 1 porting?
I believe I have a NOS RD 400 right carb in a box on the shelf. Contact me via email if you are interested in it. vintspclty@aol.com
Lyn Garland
hi,
if it was me, firstly I would try standing the carb on four nuts, one in each corner and give the top a "slight press" whilst protected with wood. you might see it straighted out enough to seal with a good gasket. its bin fodder anyway!.
cheers
les
Quote from: NYSingh on May 18, 2020, 01:53:32 AM
Ignoring the price difference, and just considering performance, which is better to get:
(A) used OEM carbs
(B) new VMs
Also, for new VMs would a size up from s28mm improve performance with the TSR stage 1 porting?
B & Yes.
I checked and I do have a NOS Yamaha RD 400 right hand carb in the YMC box. Part # 1A1-14102-00 is on the tag.
As for needing a larger carb; for your use that is unnecessary. The 28's supply all the fuel/air you will need. I've road raced RD 400's in the Formula RD class with Stage 3 porting, turned cylinder heads, Swarbrick chambers, and PVL ignition systems and never had a problem with insufficient fuel supply. Formula RD required we use production chassis parts (tank, seat, fenders, wheels,etc) and stock carbs with some type of air filter. The VM 28s will also make the bike better behaved around town.
Lyn Garland
Thanks to Lyn for the part! Looks like I'll be back in business sooner than I thought :celebrate:
If anyone has any use for a warped right-hand carb, it's yours to take.
I dont see how drilling could have warped the carb body.
I have drilled a few and installed helicoils after the previous owners had screwed them up and had no issues.
Got a few bikes really cheap because of things like that.