Carb Options...

[LIVINtheLIFE]

Hey everyone so new member here I've be in the process of a restore/build on a '77 XS650D model, so far everything has been going well except for parts options. Specifically speaking the carbs, the bike has been in storage for 15 years since I rode it last. I replaced my intake boots and put new pod filters on the stock BS38's, carb rebuild kit, cleaned and re-lined the tank and rebuilt the petcocks. When I was rebuilding the carbs one of the M4x0.7 carb bowl holes stripped. I hoped for the best though and got the bike running again, but then a week later noticed the bowl was leaking. My biggest question is has anyone tried repairing the threads on BS38's with a Helicoil/thread repair kit? I have a feeling there is not enough meat on the carb to drill and tap to a bigger size or use a thread repair kit, I wanted to ask first before I spend the money on a kit to find out it wont work.

And if by chance it doesn't work what's the recommended carb option for a daily driver/street bike over the BS38's? I'm in Canada so options are limited and the search function on the site is overwhelming. But I can buy the Keihin PWK kit from XS650direct which looks to be the same as MikesXS kit. Is it worth even trying to repair the BS38's or should I just save some money and order the PWK kit? Thanks.

 

[willis]

Try the search function in the top right of the screen. I just typed carb helicoil and came up with several threads that should help answer your question on repairing it. Good Luck !

 

[member28833]

BS38's get my vote.

Is there a chance that the float bowl screw hole is still usable with a longer screw ?
-R

 

[bikefreakjon]

Helicoil, or tap to 5mm for sure.

Shade tree hack is a nut on a longer bolt or jb weld.

Proper fix is tig weld/retap or replace carb body

 

[member28833]

noticed the bowl was leaking. My biggest

question..
Bowl thread

 

[Mailman]

Helicoil carb repair Post #485

http://www.xs650.com/threads/mailman’s-xs2-a-full-on-restoration.51520/page-25#post-546624

 

[willis]

There it is. I was looking for that, but saw something shiny instead...

 

[5twins]

I've repaired a few myself, both bowl and carb top holes. A delicate operation for sure, but it can be done.

As far as longer bowl screws go, you can use them in 3 of the 4 holes. The one you can't is under the choke assembly. There's very little space above the hole. Too long of a screw will butt against the choke housing before tightening the bowl down. Keep turning it and you strip the hole.

 

[LIVINtheLIFE]

Thanks for all the replies everyone. Glad to hear they have been repaired. I’m fortunately a welder for a living but it would be some incredibly delicate work to plug weld and drill/tap. I looked up the M4x0.7 HeliCoil kit and it requires a 11/64 hole to install the new threads, which is just about the same drill size needed to Tap an M5 as a last resort(0.0065 larger). I got some stainless allenhead M4 machine screws to replace the original philips heads so I’d like to keep them all M4 as much as possible.

 

[5twins]

Yes, I've switched all mine to stainless Allens as well but you have to learn to be more careful with them. It's easier to over-tighten and strip them, and also, the threads seem like they're cut sharper so are more prone to stripping the holes. I put split ring lock washers on all the screws. When I tighten them, I watch for the lock washer to get flat then just go a hair tighter.

 

[grizld1]

LtL, be sure to do your homework before you throw money at aftermarket carburetors, especially PWK or PWK knockoff. Those are dedicated 2-stroke carburetors. The most I can say about positive reviews of them on the XS650 is that some folks are easily satisfied. If you want Keihin 4-stroke carburetors, you have a choice between a pair of used CVK carbs from a Kawasaki Ninja 500, a custom pair of CR roundslide carbs (expensive), or a custom pair of FCR flat slide pumper carbs (very, very expensive). IMO a pair of used CVKs is a good way to go. If you want the most bang for the buck in a new carburetor, it's the Mikuni VM32 or VM34. There's plenty of information on them available here. Use the Tech button and the search window, the search function here works great. A tip: it's a mistake to buy the cheapest offer. Michael Morse at 650 Central and Gary Hoos at Hoos Racing are both accomplished tuners, provide tech support after the sale, and answer their own phones.

 

[650trader]

Grizld you don't know what your talking about or probably you just think you do. The Keihin
Taiwan PWK carbs are what the builder of the 6 cylinder RC374 uses ( See classic motorcycle mechanics
Nov. 2018 ). This guy ( Allan Milyard ) is also the builder of the V8 from 2 KZ1000.s, the V12 from 2 KZ1300's, the H type Kawasaki 4's and sixes
and a couple of dozen other similar specials. Here in the USA the seller (Mikesxs.net ) has not followed thru on the
last few changes specified by Heiden Tuning when he dyno developed these carbs ( these special changes were made
after they left they left the factory) as he wanted his work to be secret. Heiden was a top Yamaha world
cup mechanic so he just doesn't do a bad job on anything. Too bad he is gradually retiring . Do you know that one
of Heidens special engines is even in a museum in Japan. Do you know Heiden won a best new idea contest by winning
with an XS650 he converted to a steam engine ? Yes the original use for the PWK was for 2-strokes
but that does not mean anything. Even Peter Mclean uses the PWK on his 650 and reported they ran great.
But once again you seemed to seldom agree with even Pamco. Now take your beloved VM carbs - they were
originally a failed AMAL design. Yor opinion is just that - YOUR Opinion ! Why don't you build something great
like the pro's do. ?

 

[5twins]

All that being said, I have to say I've always been perfectly happy with the stock carbs. And that '77 set you have is considered one of the better sets, well worth saving in my opinion.

 

[grizld1]

Ah, my favorite shill speaks again, full of bluff and guff. I know what Pete McLean reported. After mrriggs did his expose thread on those carbs on this site, Pete gave his excuse for not mentioning sticking slides: he claimed he'd thought of it as a "minor issue" (right; just a minor issue that could cause a minor fatality). The original XS Performance carbs (with Keihin castings, later dropped) were the same bored out PWK28 pirated clones that JRC Engineering had been selling for years for old Triumph and BSA twins. I've had both in my hands. From materials to machining, they were junk, and if you want to call me a liar, have at it. I was also very underimpressed by Mr. Heiden's Taiwanese "billet" clone of the Megacycle 250-00 grind. I bought and installed one. The sprocket mounted on two 7 mm. fasteners and could be secured either on two holes, so that it could be dialed in only by fiddling with deck height, or on two slots. Since standard construction for adjustable camshaft sprockets entails 3-point mounting, I timed by deck height. Performance was fine, but the sprocket bolts mounted in two heavy lugs that switched position every 360* and turned the motor into a paint shaker. I reinstalled my Shell #1 and gave the XS Performance cam away to Jack; I considered it so bad that I wouldn't take a dime for it. Question: if Heiden applies the creative genius that he has demonstrated on many showboat projects to every product he sells, why did he knock off Megacycle's cam specs? Re. "beloved" VM carbs, I've written many times that they're not the best, just the best for the dollar. I don't use VMs anymore. Right now I'm using a pair of Mikuni 33 mm. flat slide 4-stroke pumpers that deliver over 50 mpg in mixed riding on a cammed and ported engine. Of course I'd go for a pair of those stone beautiful Keihin FCRs, but they're a little rich for my blood.