Author Topic: Pod friendly carb replacement for BS38s ?  (Read 2113 times)

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Offline mrEJ

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Pod friendly carb replacement for BS38s ?
« on: April 28, 2016, 09:11:02 PM »
Hi,

I 've been searching the forum for a while but can't find the answer I'm looking for.
I know from reading pages and pages on rejetting, that switching to pods can be a daunting task. However, what I can't find an answer for is; which carbs will be good replacements for the BS38s presuming that the new carbs at the same time will work with pods? Surely, there must be some options of carb/pod combos that can replace the BS38s. Regardless whether your desire was power gains, or just the pods look - has anyone gone down this road?

Cheers!
Eivind, Drammen, Norway

Offline guylr

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Re: Pod friendly carb replacement for BS38s ?
« Reply #1 on: April 28, 2016, 11:34:37 PM »
VM34s. See Mike's XS for the ones that go on XS650s. Those can be made to work with pods. Don't ask me for jetting because I have no idea what to recommend. Someone has probably used them on a 500 and can chime in.

Guy
Now Retired Yamaha guy. Cut me and I bleed "Cinquasia Red"

Offline mrEJ

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Re: Pod friendly carb replacement for BS38s ?
« Reply #2 on: May 11, 2016, 07:37:37 PM »
Thanks for your reply Guy. Haven't had the time to read up on the VM34s yet though.

If anyone else have other suggestions please join in!
The ideal answer to this topic would be carbs suitable to our bikes, delivered as a kit with pods and correctly jetted out of the box.

For the interest of conversation; lets assume money is no object here  :)
Eivind, Drammen, Norway

Offline Jewbacca

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Re: Pod friendly carb replacement for BS38s ?
« Reply #3 on: May 12, 2016, 08:48:46 PM »
Not sure you're gonna find an out of the box solution. The 500 wasn't popular enough to warrant companies really spending time researching carb options. Vm32s or vm34 are your best bet, mechanical slides and super easy to both find and swap out jets and parts for. They're also less expensive for the Jets and easier to tune after the fact.
1974 TX500A
I'm unique, just like everyone else.

Offline Patavanmax

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Re: Pod friendly carb replacement for BS38s ?
« Reply #4 on: July 13, 2016, 12:55:17 AM »
Hello mrEJ, don't know if this will help you but I just recently put on a set of VM34'so on mine because those outdated keihins were not working for me. I completely rebuilt a stuck everything 74 TX500. The air box was gone and not usable and the exhaust was completely rotted off. So got a set of good pods and custom made 2 into 1 exhaust and could not get a tune on the carbs as they leaked from every orifice. Did some digging around and found a new XS650 kit that had billet flanges, cables, carbs, filters and some jets. Had to mock up the cable as it was not entirely the same but other than that and crinkling the filters to fit they worked beautifully. I am currently riding it as a daily driver. You will need to tune it as the carbs are not pre jetted for a 500. I hope that aided in your search for a solution.

Offline djxs500

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Re: Pod friendly carb replacement for BS38s ?
« Reply #5 on: March 19, 2017, 05:44:28 AM »
Anyone on here who has swapped the 38's for 34's what manifolds did you use? I have an opportunity to use a mint set of bs34's off my friends xs650 but I read on another thread that the stock manifolds are too large which makes sense. Would a stock xs650 manifold bolt up or would I need to look elsewhere?

Offline ken01

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Re: Pod friendly carb replacement for BS38s ?
« Reply #6 on: March 28, 2017, 09:05:48 AM »
I fitted a set of BS34 II's which I purchased from an alleged reputable shop which advertised them as reconditioned and ready to fit onto an XS500E (after a great deal of mucking about and swearing, I discovered they had the wrong needles, float heights were out and one float leaked, but that's a story for another day). I fitted them to my TX500 by using the inlet manifolds off an XS500E. Although those manifold bolted straight up, it wasnít quite that simple. The XS500E has vacuum petcocks which hook up to spigots on the top of the inlet manifolds. Much against what I had earlier planned, I discovered the vacuum petcocks donít fit the TX500 (from memory they donít fit the tank and there isnít enough room under the tank to take them). 

There were a few other issues and the aforementioned spigot for the vacuum petcocks is but one of them. They fits at the top of the inlet manifolds. On the XS500E you remove the tube form the vacuum petcocks and connect them to your vacuum gauges when balancing the carburettors (The BS34 II doesnít have a vacuum port as its predecessor the BS38 did). There was something about the cam-box shape or rocker cover of the TX500 that precluded the existing spigot on the BS34 II from being used. I seem to recall experiencing the problem of if wanting to use them of having to leave the tubes attached to the spigots, which then meant without a vacuum petcocks on the other end, the tube hang free and open, which obviously creates a vacuum leak. Top resolve this and keep the spigot in place, means a need block the tubes when not in use, but be able to free them when wanting to balance the carburettors. Either way, i didn't find that to be very satisfactory. The location of the hole for the spigot, being on the top of the manifold precludes it from being removed and replacing it with a threaded plug that could in turn be removed and replaced with a threaded tube for balancing purposes (The cam-box and or rocker cover preclude this).

The aforementioned caused a great deal of consternation for me and the only solution I could see was to turn the inlet manifolds upside down and swap left for right and vice versa.  This left the problem of the spigot on each manifold now facing inwards and being unaccessable.  So, I removed the plastic spigot, drilled and tapped the holes in each and turned up a stainless steel threaded plug, which I screwed in with a little Hylomar to ensure I had a good seal (I used either a fine metric or imperial thread).  From there, where the bottom of each inlet manifold now was, I drilled and tapped a hole, once again using a fine thread. I  turned up some threaded plugs out stainless hex with a head length of about an 1Ē so when on the bike I can get a 5/16 AF spanner onto them to get them in and out. I also turned up a little more stainless with thread on one end, a small amount of hex in the middle to take a spanner and the rest be round with a small hole right through the middle. This was so, with the plugs out, I can screw these in and get some rubber tube on to them to connect to my vacuum gauges to balance the carburettors. The only other thing I had to do with this was to cut away part of the metal cage that goes around the manifold to make allowance for the new plugs/vacuum gauge fittings.

Next issue was, with the manifolds upside down the profile didnít match the inlet ports. Having said that they didnít match in the first place, but I  upside down the issue was a little more exaggerated. The profile from the manifolds for the BS38 manifolds doesnít match the inlet ports on my TX500 either. With the BS34 II inlet manifolds upside down there was a large chunk of metal sitting up at the base of the inlet port creating a small wall. So I marked it off and gently ground the wall upwards to give a smooth flow effect inwards towards the valves (itís now more like a 30 degree angle going from the bottom of where the inlet manifold meets the head towards the inlet valves as opposed to a 90 degree obstacle).

I see the original thread is about using pods, I didn't do that, I just wanted to jet the same way as the XS500E and avoid all the hassle (I also quite like the standard look) The XS500E fiited up to the air filter in a complete different way to the earlier bikes and the later fittings don't translate across to the TX500. I needed to fit the BS34 II's up to a the plenum on my bike. I canít remember which of the rubbers I used with the plenum, they were either the ones that went with the Keihins or the BS38ís. I have a sneaky feeling that I had to expand the holes in the plenum I used to take the rubbers. I reckon I used the  rubbers that fit the BS38ís, but donít quote me, if goping this way youíll need to measure up. The rubbers I used were still a little tight to get onto the BS34 II's, but it was achievable.

I canít remember if I had to fit up a spacer between my inlet manifolds and head to take up room to push the BS34 IIís back so they fitted up to the plenum, but I do remember measuring the inlet manifolds and BS34 II carburettors and comparing it with the measurements for the inlet manifolds and Keihin carburettors (which obviously gave the required combined distance). Something tells me the BS34 IIís with manifolds required a spacer of about 1/16 to 1/8Ē. AsI said, if you go this way, you'll need to measure up yourself.

Iím planning to take my carburettors off again in a few weeks to fix a couple of issues and If you like I can take some photos of some of the bits (donít hold me to that couple of weeks thing though, Iíve been planning to take them off for a fare while now Ė Iím in desperate need of a shot of motivation)

I hope that is helpful to you in determining which way to go.

Offline Joffa1

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Re: Pod friendly carb replacement for BS38s ?
« Reply #7 on: May 26, 2018, 11:56:24 PM »
I know this is old but 34mm Dellortos from Euro Carb are a great performance upgrade. Run really well with great throttle response. Go on their recommendation for jetting and slides and youíll be sorted!