Bultaco 350 Carburettor settings 199A

[Adam Bulty]

Hi new to he fold just bought a Bultaco 350 Sherpa 199A from a friend, it 95% complete lots of new parts including a fresh out the box Mikuni that needs settings altering bike runs and ticks over but when you open throttle 1st quarter bogs down 2nd quarter power is there last half bogs down and will cut out if you hold open. Thanks Adam.

[fourex]

41 minutes ago, Adam Bulty said:

Hi new to he fold just bought a Bultaco 350 Sherpa 199A from a friend, it 95% complete lots of new parts including a fresh out the box Mikuni that needs settings altering bike runs and ticks over but when you open throttle 1st quarter bogs down 2nd quarter power is there last half bogs down and will cut out if you hold open. Thanks Adam.

Hi Adam, I'm of little help here, but you'll need to be more specific with your type of Mikuni to get some replies I think. Is it a round slide VM 26 or 28mm for starters, even then there is variations of these models. A picture of your carb would help also. Cheers.

[Adam Bulty]

Hi mate,been fettling the bike today have stripped the Mikuni carb it is a VM I have a suspicion it too small so my mate may bought the wrong one.the sizes of the inlet of carb to engine are 35mm..airbox side 44mm those are the external measurement..Main jet is 130...

Pilot jet 30...needle has 5 notch and clip is set on middle notch...he also gave me a Bing carb.. he felt it made the bike run woolly... which I think is standard fitment he said he been told that one is worn so he bought the Mikuni..but I've just fitted the bing and it running 100% better than the Mikuni so will ride it before I do anything else...Thanks Adam.

[scifi]

You have probably got the slow end too rich, and the top end too weak.  

But I can't understand what you mean by 'bogs down and cuts out' at high revs..   Bogging down means too rich ( four stroking.) and cutting out means too weak...  take your pick.

Just for reference, a TY175 uses a 240 main jet.   If you need to measure your jets, see how far a thin tapered needle enters the jet, and compare it with the Bing jet.

[Adam Bulty]

Hi mate,by bogging down when you pull away and give it more than half throttle it just dies down almost as if you had turned an ignition off..if you roll off on the throttle it picks up..the Mikuni carb seems a long way off especially you say 240 main jet for a Ty 175 and this Sherpa 350..just rode it up and down the road with the Bing carb and loads better ..it a pphysically bigger carb both inlets couple of mm bigger actually fits both rubbers better so I think Mikini is wrong one..only got back from Germany with it last night so all new to me.

Thanks  Adam.

[carl ekblom]

I don´t have  my own computer now (with all data), but I think this is correct

Sherpa 325; Mikuni 26mm

Main 160 (or 150?)

Idle 25

Needle 5C23, top notch

Needle Jet O3

Throttle Valve 2,0

May not be perfect but engine runs well.

After Mikuni-Dellorto-OKO I am now back with Mikuni. All have their pros and cons

With Mikuni must tap the float chamber with a small hammer to get fuel into the carb after a week stand still

Carl

 

 

 

 

[Adam Bulty]

Hi Carl as I suspected all the jets are wrong to what you're saying, when you say 26mm what is that measurement I.m measuring the internal of carb engine side and got 28mm and it fits in rubber manifold easy but tightens up well as very flexible rubber.perhaps I could get some jets and experiment now you given me something to work off once Ive ridden it with the Bing carb it starting 1st or 2nd kick now just will see how it rides..

      Cheers Adam.

[carl ekblom]

26mm is internally engine side. 26mm is Mikuni common practice on these engines. I think this carb came from francetrialclassic.com. I bought it unused together with an 199A.

No problem with starting. Once started it starts first kick. I think there is something with the float valve hanging after a week stand still.

Carl

[metisse]

Quote

Puma Racing the Spanish trials bike builder of the highest reputation uses Del Orto carbs on his Bultacos.. and he knows his Paella . I have a 199a built by him and goes very very well.

 

 

[fourex]

16 hours ago, Adam Bulty said:

Hi Carl as I suspected all the jets are wrong to what you're saying, when you say 26mm what is that measurement I.m measuring the internal of carb engine side and got 28mm and it fits in rubber manifold easy but tightens up well as very flexible rubber.perhaps I could get some jets and experiment now you given me something to work off once Ive ridden it with the Bing carb it starting 1st or 2nd kick now just will see how it rides..

      Cheers Adam.

Maybe just see if you can get the bits to re-furb the 28mm Bing, they do work well when not worn, have a look here.....http://bingcarburetor.com/index.html

Too many variations on Mikunis over the years and they all use different types of jets, yours looks like it could be a VM26-8074 or VM28-49, but who knows for sure?

[Adam Bulty]

16 minutes ago, fourex said:

Maybe just see if you can get the bits to re-furb the 28mm Bing, they do work well when not worn, have a look here.....http://bingcarburetor.com/index.html

Too many variations on Mikunis over the years and they all use different types of jets, yours looks like it could be a VM26-8074 or VM28-49, but who knows for sure?

Think its a VM 28-49 it came with a booklet thats not a lot of use..Yes that's a good idea will look into that the Bing looks a quality carb,the Mikuni seems the wrong hand as well the air mixture screw is on the right side so the exhaust blocks access when on the bike you can get them on the left so another reason I think they sold my mate the wrong carb he did specify the bike when buying that carb.Shame if it is as its brand new and could be of no use,might be worth getting in touch with them to ask..

Cheers Adam.

[woody]

28mm is the correct size carb for the 199a (all Sherpas in fact with the 'new type' 325 motor from model 159 onwards as they have bigger inlet and exhaust ports than the original 325 engine)

Mikunis are really difficult to jet from scratch, as someone else said, so many variables of carb type, needle jets, needles, all of which have to match as you can't just fit any needle to any needle jet. It probably is the right type for the bike but as they weren't standard fitment there is no base setting for jets etc. You rely on someone else having one on the same bike that works properly and using the same.  They all have the air screw on the right hand side which is another pain in the a*** feature about them when you have a bike with a right hand exhaust like the Sherpa. Then there's the flooding...

The Bing works fine as long as it isn't worn, as with any carb

For the jetting you have, 130 is a bit small and you probably need a 150 / 160.  The TY main jet size of 240 is misleading as they are sized differently. Put a 240 VM jet in your carb and you'll pour more fuel in to the motor than it can burn, it'll be flowing out of the exhaust

OKO 28mm carb works very well and runs pretty well straight out of the box with maybe just a drop of one notch on the needle and pilot jet change. They cost about £65 from Scooter Assassins in Taiwan (ebay) and a set of 10 pilot jets is about £18 - free post. There are cheaper available but they're copies and useless. Or you could buy one from Mid Atlantic trials in USA for about £100 ready jetted, but to be honest they are an easy carb to set up, unlike a Mikuni.

I see you're in Hednesford. I'm running a trial (Stafford Auto club) at Milwaich on Sunday a few miles north of Rugeley. Bring your bike up there and we can have a look, if time you can try the OKO off my Sherpa

[Adam Bulty]

Hi mate that's great got a whole bunch of info there, I am considering refurbing the Bing.I'm working on it now as bike isnt quite a finished project one thing lead to another since I got back from Germany with it on Sunday and I.ve been working on it since gone mad taking apart checking everything.I am familiar with Milwich sounds a brill idea.  Cheers Adam.