BS34 jetting with info regarding stock european jetting (Sweden)

[ebb0tk]

Hi. Anyone with good starting points for jetting bs34? Ive red several threads and carbguide which ill follow. Just seeking a Good starting point. And i wanted to Share what i think is stock euro bs34 carb jets/needle/settings.

I have the canadian needle, adjustable and 2nd clip from top and matching needle jet for it.
45 Pilot
132.5 Main
130 air jet

I believe this was stock atleast for the bs34's sold in sweden

Im 3 turns out on mixture screw.
Bike starts easy and idles fine, but dont wanna run it lean during break in.

My setup:
Uni Pod filters with 1.5" exhaust and free flow cans from cone engineering.
700cc
277 rephase with stock rephased cam.
Minor head porting, more like a clean up from casting flaws.

 

[5twins]

Thank you for posting this. I don't think I've ever seen anyone with actual Canadian or "world market" carbs post a jetting list and I've always wondered if/how they may differ from the pollution controlled U.S. version. Thanks to MikesXS, we've learned of the adjustable Canadian needle and needle jet, but they make no mention of other jetting changes that might be used with those parts. The only different jet listing for the BS34 I ever ran across was in the parts manual for the Japanese home market 1980 G model. It is similar to your findings except for the main and pilot sizes .....

With your mods, I think I would start 2 sizes up on the mains. Eventually, to find and verify what is best, you should probably try 1, 2, and 3 sizes up.

 

[ebb0tk]

Thank you 5twins.
Im about to take the carbs off the bike soon, so ill verify every jet in the carb again so i didnt miswrite anything.
Should i just start with focusing getting the main jet about right first?

 

[5twins]

While in your carbs again, could you verify some other jet numbers, specifically the needle and needle jet? The U.S. spec fixed needle is a 5HX12. The Canadian and "world" needle is supposed to be a 5IX11. The U.S. needle jet is a Y-0. The Canadian and "world" version is supposed to be a 336-Y-0. The "Y-0" indicates the size of the metering orifice in the jet. Both appear the same. What makes them different is the number of air bleed holes down the side, the 336-Y-0 has more. The Y-0 has rows of 3 and 4 holes, the 336-Y-0 has rows of 4 and 5. Now, this would seem to indicate that the 336 version is slightly leaner than the plain Y-0, but I guess combined with the much richer adjustable needle, the overall result is still a richer midrange.

Yes, focus on the main jet first. The usual routine is to start with the mains and work your way down. You do this because the mains will affect all the lower settings. Do them 1st and then the mains, and you may have to do them all over again. Remember, the 3 circuits in your carbs overlap the ones next to them a little bit. Larger mains will influence the upper midrange too, making it richer. That may require a leaner needle clip setting to correct. Doing that will influence the upper part of the idle circuit as well, making it leaner. That may call for idle circuit changes (pilot and/or air jet).

 

[ebb0tk]

I can already verify those jet numbers. You are correct. Needle is 5IX11 and Needle Jet is 336-Y-0.
Let me know if theres anything else =)

I'll move onto carb tuning after engine break in.I think the 5IX11 at 2nd clip from top is like a stock US version of BS34 non adjustable needle?

 

[5twins]

Actually, the top notch on the 5IX11 is the same as the fixed clip position on the U.S. 5HX12. Measured from the clip down to the needle tip is 50mm. It makes sense that the factory position for the 5IX11 would be one step down from the top, one step richer than the fixed 5HX12. That would blend in well with the other settings used on the Canadian and "world" BS34s. They were richer in the midrange and low speed circuit, a little leaner on the mains. If you study the jetting specs for the other 650 carb sets, you'll see they were set up in a similar manner. Sets with smaller mains had richer lower jetting, at least in the midrange anyway.

You could raise the needle but that might induce stumbling in the upper midrange with the larger mains. Only test running will show you that for sure, and you'll need to do that testing with big handfuls of throttle, maybe even full throttle. If you test it easy, with the throttle barely open, the "glitches" may not show up. That's the nature of these CV carbs. They're rather forgiving about minor jetting glitches and won't show them unless pushed hard. Obviously, you won't be riding the bike around really hard like this all the time, but it is necessary to push it for carb jet testing.

 

[ebb0tk]

Got it 5twins.

Thanks alot. And let me know if i can be of any more help regarding world bs34's

 

[650Skull]

This is what come out of my Oceania 80SG with Points and BS34's


Also have a Canadian 83SK and the Carbs were set the same.............

 

[ebb0tk]

Not the same setting on needle, your needle is set richer than mine is. Im at second notch (Groove) from the top. Interesting though. I might be wrong about my Main jet. Ill verify as soon as i have the carbs off.

 

[650Skull]

The bike, (80SG), ran well but there is no way i could say the setting was from original. That setting was in the bike when i bought it. 83SK Had the same setup??

 

[ebb0tk]

Richer needle setting than i and larger main jet from what i can remember i had. Ill have another look soon to confirm Good you chimed in here.

 

[ebb0tk]

Did a float level test with a hose. Both carbs equal. Looking good? Or am i on the low side?

 

[ebb0tk]

Sorry guys. Ive updated my first post.
My Main jet is 132.5

 

[5twins]

I think your fuel level looks fine, and according to the '82 manual it's perfect .....

The '81 manual shows a slightly different level, just above the top of the bowl .....

I don't agree with that one and think it might lead to leaks or at the very least, fuel eventually sweating out through the gasket.

It seems both the parts listings don't agree with what you guys found for your mains (132.5). They both list a 130 as stock. Skull, where did you get that listing you posted from? I've never seen it before. Can that parts manual be downloaded somewhere?

 

[650Skull]

That's a one off 5T. Took me close to a day to do that...................There may be mistakes, i did find some when i was cross referencing with Boats.net, files i have from Biker.net and files from the Yamaha Parts Manuals from thexscafe.com..............I think you will appreciate what was involved.

Discrepancies were/are in the Boats.net Parts diagrams/files..............

On the Jets.......The files shows increments of 5 not 2.5 and i guess the question is.........did japan have Parts manuals for the non US BS34's written for the non Japanese market. If not then who knows what the mechanics used in the carb set up for tuning..................And if they did how come there in nothing on any of the European/Oceania club sites........Seems strange that information wasn't poached, borrowed or even written about.................

 

[ebb0tk]

Yeah. We both found same parts but not the same according to the parts listning.

I'll have a look if i can find others in Sweden with bs34's and see if they have fpund similiar stuff or even a Swedish manual/parts list