To Yost or not to YOst

[HotRodSporty]

:tour I am wanting to know about the Yost tubes. I have SE bolt in cams and a Mikuni 42 , also have a Forcewinder, and SE II's. I am going to buy Bassani Pro Streets next week and Hopefully if I can sell some welding equipment I will be doing stage 2 to my heads.
So is the Yost tube worth the money? I understand the logic behind it but can one of you wise people tell me if they work or if I should just go with a Dyno Jet or if I should just not spend the money on either. :frownthre
And also its a 2003 1200C, if that matters or not.

[chaserband]

Well I don’t know about wise,
I had a Yost Tube put in my 2003 XL1200C after 1000 mile checks up. It really made a difference with the low rpm carb farts. I also noticed fewer nosebleeds with the stock breather. I can’t tell you about high rpm advantages because before I had the tube installed my bike ran like crap! It could have also been just the carb being adjusted wrong after the dealer installed the SEII pipes & A/C. I Hate Stealers!!!!!

[HotRodSporty]

I have minor carb farts at times also. And I also hate Stealers. So so far you do not have any complaints about the yost tube? Can you tell me more as you ride your bike more? Like hoe the response is in all ranges and anything else that might be useful. PLEASE :rolleyes:

[chaserband]

I don't really know about how it will work on a Mikuni 42. On the stock CV it has been good ( mid power is better than my buddies 1200 )....but I really don't know how the bike was supposed to run before I had my carb man work on the bike. The Yost tube was one of the projects he did to my bike when I brought it to him fed up with the dealer service people.

[gwcrim]

I can't imagine why you'd put one in a Mikuni. They're very tunable as is.

[HotRodSporty]

I was hoping you would chim in gwcrim :clap Your knowledge always pleases me. But they do make them especially for the mikuni's. So I have tried to get the pdf from mikuni on how to tune them but it always makes my computer stop.
I wont waste the money if it wont help. Does the same go for dyno jets with the mikuni? :wonderlan
Also gwcrim. What jets sizes do you think I should have in it right now with the mods that are listed below?
I am going to check and see whats in there sometime this week. I do get carb farts at times and it seems to be a little lean. I say this because the back in my pipes.
Would be nice to know what should be in there so I can get the right ones when I take it apart to check. :tour

[gwcrim]

Here's a place to start:

Pilot jet: 25
Accelerator squirter: 50
Needle: 97
Main: 160

You might be able to lean it out even more if you like to tinker. And don't miss that accelerator squirter. It will improve you fuel mileage immensely.

[Mechano]

:tour
So is the Yost tube worth the money? I understand the logic behind it but can one of you wise people tell me if they work or if I should just go with a Dyno Jet or if I should just not spend the money on either. :frownthre
And also its a 2003 1200C, if that matters or not.

The role of the emulsion tube is to start a fine air/fuel mixture into the needle hose before this comes out into the venturi and get sucked by the engine.

The emulsion tube is important for overall efficiency of the engine because it has to prepare the mixture for a good burning.

The same is done by high turbolence roughish intake.

Because at high rpm there's no time (and no needs) for the mixture to get fine emulsionated, the emulsion tube and a roughish intake will affect only low end power, but expecially the torque.

Yosh tube is a good improvements for low end torque but it's really overpriced!!!
A metal tube with calibrated holes doesn't cost so much, and maybe the Yosh tube is a standard emulsion tube produced by the carb factory but used in different applications (other motorcycles?). They buy in stock for few buck, tell you'll improve performance a lot and ask you for lot of $$.

--
Mr. Mechano

[HotRodSporty]

Here's a place to start:

Pilot jet: 25
Accelerator squirter: 50
Needle: 97
Main: 160

You might be able to lean it out even more if you like to tinker. And don't miss that accelerator squirter. It will improve you fuel mileage immensely.

Does your tuning manual tell me about all this? Do I have to take the carb off to check all this out? Where the hell do I find this stuff in it? And where do I buy the right numbers at? Also do these numbers still aply to my bike with the Bassani pro streets? or do any of these numbers change?

[gwcrim]

The tuning manual won't specifically tell you all that. It will tell you how to determine what jets are appropriate. That basic set up was passed on to me by a fella who knew a fella....

And yes, you'll have to remove the carb and look at the jets to know for sure what's in there. There may be a way to contact Mikuni USA. They ought to know. Try a Google search. You can buy Mikuni jets at any reputable motorsickle shop in the US. But get good at carb R&R if you want to really jet it right. It's a trial and error process.

As for running that set up with Bassani pipes, that's getting pretty specific. Bassani pipes and aftermarket cams can sometimes produce funny pressure waves at the carb. A Mikuni is the best piece for that set up. But it all depends on how precise you want the jetting to be. It's not necessarily something you can do in an afternoon. The needle is the biggest bitch to play with. I always have a hard time getting it out. But if you want to get it right, you have to feel very comfortable inside a carb. (Yes, I know they're small.) The manual sort of walks you through the different circuits as they take the engine from idle to WOT. It's basically, idle set up, needle set up, and main jet.

[HotRodSporty]

Thank you so much for the help.

[xl1200r]

I have a yost in my bike...never knew what it was or what it did...thank you.