Author Topic: Main nozzle BS38 carbs  (Read 629 times)

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Offline Joffa1

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Main nozzle BS38 carbs
« on: February 22, 2019, 08:10:50 AM »
Hi there I have recently ordered rebuild kits for BS38 CV carbs in my 76 XS500C

What Iím trying to determine is the following:

the Main Nozzle is the push in type with O Ring. The existing one in my carb is a ďY6Ē. Im trying to replace it as itís ovalled. All Iíve been able to find is the ďz6Ē which is the part for the 76 XS650 with the same BS38 carburetors. 

It looks almost identical but if a different part number.

Does anyone know if this part is a direct swap or know where I can find a ďy6Ē?

Thanks so much.

Offline Joffa1

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Re: Main nozzle BS38 carbs
« Reply #1 on: February 22, 2019, 11:05:32 PM »
So this is the part I have and then the replacement part Iím looking at buying...


Offline Joffa1

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Re: Main nozzle BS38 carbs
« Reply #2 on: February 22, 2019, 11:12:48 PM »
Part number 4 on this diagram

Offline guylr

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Re: Main nozzle BS38 carbs
« Reply #3 on: February 23, 2019, 03:28:09 AM »
The Z6 is a full size richer than the Y6 main nozzle so you would likely need to lower the needle to lean the off idle and mid range up mixture. Now because fuel these days has 10 or 15% ethanol in it the mixture can stand to be slightly richer than it was in 1976. So if you can't find the original 341-14941-96-00 part I think the Z6 might work fine.

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

Offline Joffa1

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Re: Main nozzle BS38 carbs
« Reply #4 on: February 23, 2019, 04:23:38 AM »
Thanks so much Guy. Iíd rather find a Y6 but I donít know where? If I do end up having to use a Z6 I would assume they both need to be Z6 in each carb?

Offline Joffa1

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Re: Main nozzle BS38 carbs
« Reply #5 on: February 23, 2019, 05:15:32 AM »
And just one other thing could you identify the bottom right jet there for me ?

I couldnít find on my parts diagram. Is it removable because one of mine looks damaged like itís tried to be pryed out.

Offline Joffa1

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Re: Main nozzle BS38 carbs
« Reply #6 on: February 24, 2019, 10:18:26 AM »
Choke jet maybe?

Offline Joffa1

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Re: Main nozzle BS38 carbs
« Reply #7 on: March 27, 2019, 09:29:33 AM »
So back to my Y6/Z6 issue. I actually ordered some Z6 from Heiden Tuning as I could not find Y6 anywhere.

Theyíve arrived and actually look quite different to the original Y6 but am assuming they will still work (see pic)

Alternatively I was thinking of putting my original Y6 back into service. I donít know if you can see in the photo but the top has been ovalled when attempting removal.

My question is will it still function ok in this shape or would it be worth trying to re round it carefully? I doubt Iíd be able to get it perfect but close to original.

Let me know your thoughts. Thanks again.

Offline guylr

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Re: Main nozzle BS38 carbs
« Reply #8 on: March 27, 2019, 09:28:36 PM »
Hard to tell. If they fit the carb bodies I'd  try them as is. Otherwise I'd put the old ones back in.

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

Offline Joffa1

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Re: Main nozzle BS38 carbs
« Reply #9 on: March 28, 2019, 08:09:45 AM »
Ok so here is a slightly better picture of the differences between the Y6 and the z6 (XS650 part).

You can see in the last pic that the z6 extends further into the carb. Also it is not a snug fit like the Y6 is. I havenít fitted the new o rings yet but I donít think that will make much difference as the Y6 is snug without the o ring and the Z6 is not. I knew the Z6 was going to be richer but I didnít think it was actually different dimensions.

I donít understand - is the actual BS38 carb body different in the XS650 than it is to the XS500? I mean I know there is differences in jet sizes settings etc but I would have thought the orifice that takes the Y6/Z6 would be identical?

Very annoying spent a fair bit on getting these z6 jets from Europe to Australia.

Offline Joffa1

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Re: Main nozzle BS38 carbs
« Reply #10 on: March 28, 2019, 08:40:17 AM »
So the outside diameter of the part that slides into the carb on the  z6 is 5mm and the Y6 is 6mm  - no wonder itís not snug. These carbs are really starting to annoy me. Wasting a lot of time and money trying to rebuild them.

Think Iíll go to a 2 into 1 manifold and just run a single brand new VM 36.

I just canít believe that itís impossible to source original Y6.

Offline Joffa1

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Re: Main nozzle BS38 carbs
« Reply #11 on: March 28, 2019, 08:30:13 PM »
They sent me the xs-1 part not the XS650c part. Problem solved

Offline guylr

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Re: Main nozzle BS38 carbs
« Reply #12 on: March 29, 2019, 03:38:16 AM »
Well, those carbs have been out of production for 42 years  ;)

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

Offline Joffa1

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Re: Main nozzle BS38 carbs
« Reply #13 on: March 29, 2019, 05:12:17 AM »
Yeah I get it... just thought thereíd be more support given how popular vintage bikes and builds have become.

All good Iíve solved my problem now so will pursue with the original setup 🙄

Offline guylr

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Re: Main nozzle BS38 carbs
« Reply #14 on: March 29, 2019, 10:42:04 PM »
Yamaha sold over a quarter million 650s in 14 years and a lot of them are still around and being worked on. Not all had BS38s but a bunch did and that's probably why they are much better supported than the XS500 which only used them for 2 model years and I believe less than 25,000 total units.

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