Turbo YZ


350 replies to this topic
  • hondacrf250rrr

Posted May 03, 2009 - 05:43 AM


thats a sick bike

  • yz480doinwork

Posted May 03, 2009 - 06:15 PM


pluging the accel. pump jet helped a little. but it was still studdering bad. i took a T and put a small jet in one of the barbes and put it in the line from my charge tube to my carb to let some of the air bleed off. helped a bit more. still kinda studdors. wide open in 5th gear (studdoring only pulling 2 pounds) i can slip the clutch and it will rev up and boost like 7 pounds. i can slowly let the clutch back out and it will hold that 7 pounds for a few seconds. it was enought to make me happy for a little! it was haulen. still not working correctly. anyone have any tuning ideas?

  • grayracer513

Posted May 03, 2009 - 06:47 PM


I get the impression that for whatever reason, an excess of pressure is being fed into the float bowl, creating the reverse of the imbalance one expects to see when no pressure is fed in at all. In other words, the pressure within the bowl is rising to a level higher than in the venturi, pushing an excess of fuel into the air stream.

Unless you can figure out why this is so, If in fact it's the case, the two most complete solutions are an old fashioned pressure box for the carb, or move the carb to the atmosphere side of the turbo.

  • yz480doinwork

Posted May 03, 2009 - 07:18 PM


if the needle and seat wouldnt hold the 2 pounds of pressure my regulator is letting out, wouldnt the idel be screwie? i dont see anyother way the bowl would be pressurized tooo much.

  • grayracer513

Posted May 03, 2009 - 09:21 PM


You are feeding air pressure into the bowl vents to balance boost pressure, are you not?

  • DRX350

Posted May 04, 2009 - 08:25 AM


I get the impression that for whatever reason, an excess of pressure is being fed into the float bowl, creating the reverse of the imbalance one expects to see when no pressure is fed in at all. In other words, the pressure within the bowl is rising to a level higher than in the venturi, pushing an excess of fuel into the air stream.

Unless you can figure out why this is so, If in fact it's the case, the two most complete solutions are an old fashioned pressure box for the carb, or move the carb to the atmosphere side of the turbo.


+1^^^

I am a fan of pull through turbo systems. They're easy to tune, usually run better (to a point). Most of all, they don't need a fancy pressure box for the carb.

They do have 2 problems, 1 minor, 1 not so minor;
1. Carburetor icing
2. Pretty much limited to 10 PSI

  • grayracer513

Posted May 04, 2009 - 11:14 AM


I have been involved with about 10 turbo installations on a variety of vehicles, including motorcycles, and the 3 with carbs were each a fairly large PITA. The 3 EFI installations I was most involved with were a piece of cake. None of the carb jobs were downstream from the turbo, and I would not frankly consider placing one there. Note that the carbureted turbo cars from Detroit in the 70's and 80's universally had the carb upstream.

EFI simplifies every detail of the whole concept.

  • gbalias

Posted May 04, 2009 - 02:20 PM


i love EFI.


thats why i program em. :excuseme:

  • diegox450

Posted May 04, 2009 - 02:29 PM


I've worked on blow-thru turbo carbs setups and worked flawless... Did you balance the pressure in the bowl, presurizing the vents lines, connecting them to downstream the turbo? As Gray asked to you... If you do so, your float and needle wouldn't have problems in maintaining the correct fuel level in the bowl.

Don't move the carb to the atm side of the turbo... old and quick way of making it work... but it will give you starting problems, fuel puddling in the intake or inside the compressor side, turbo seals problems....

Also, TOTALLY agreed with Gray, that the BEST solution for turbocharging an engine, is the EFI

Good luck !!

  • yz480doinwork

Posted May 04, 2009 - 03:11 PM


i know EFI is the best thing ever! my supercharged snowmobile is FI. i love it. but i dont see EFI being plasuable on a yz as of right now. yes, all vents on the carb are boosted. also i dont see a suck-through carb/turbo set up to be plasuable either, because of space reasons.

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  • JamesNad

Posted May 04, 2009 - 03:51 PM


have you talked to anyone that built turbo 450's or anything??

i was doing alittle searching and found http://www.tysonracing.com/ it looks like in there pictures they are running a carb,

or in this article they say they are running electronic fuel injection,
http://atv.off-road....l.jsp?id=191321

i know these are for quads but isent the yfz 450 motor pretty identical to the yzf450???

  • yz480doinwork

Posted May 04, 2009 - 04:16 PM


i have been talking to a turbo YFZ guy over on YFZ tech fourms. he hasnt been able to help my tuning issue but he's told me alot.

  • gbalias

Posted May 05, 2009 - 04:55 PM


why dont you hook up a wideband to see what the fuel is doing? you never know, it might be an ignition issue. im assuming the gap on the plug hasnt changed even though youre building a lot more pressure in the chamber.

  • yz480doinwork

Posted May 05, 2009 - 06:33 PM


"hooking up a wideband" isnt that easy, or cheap. its to rich, i know that. i dont believe its a ignition problem because i can slip the hell outa the clutch (removing alot of load) and it will get past the blubbery stage and build boost.

  • BC3

Posted May 05, 2009 - 09:16 PM


[COLOR="Blue"]Hmmmmmmmmm I think before I went to all that trouble I would have installed a nitrous kit (they make them ) NOS sells kits for most dirt bike and street bike apps. Turbo on a dirt bike........Waste of time IMO....too much stuff to fit on a dirt bike chassis....I have experience with nitrous bikes and they are trouble free if you set them up right......

[/COLOR]


  • TIG88

Posted May 06, 2009 - 01:20 PM


"hooking up a wideband" isnt that easy, or cheap. its to rich, i know that. i dont believe its a ignition problem because i can slip the hell outa the clutch (removing alot of load) and it will get past the blubbery stage and build boost.


It would tell you how rich you are running.

Difficult and expensive....YOUR BUILDING A TURBO YZ450!!!

:excuseme: :smirk:

  • qwik12beat

Posted May 06, 2009 - 04:33 PM


Try closing the gap on the plug. Takes 2 minutes, and is worth a try. I have seen many turbo applications clear up when you feather the clutch, but the real problem was sparkplug blowout. Check it out it may help you

  • sirceo26

Posted May 06, 2009 - 05:21 PM


[COLOR="Blue"]Hmmmmmmmmm I think before I went to all that trouble I would have installed a nitrous kit (they make them ) NOS sells kits for most dirt bike and street bike apps. Turbo on a dirt bike........Waste of time IMO....too much stuff to fit on a dirt bike chassis....I have experience with nitrous bikes and they are trouble free if you set them up right......

[/COLOR]



where would the fun in that be?

  • gbalias

Posted May 06, 2009 - 05:53 PM


"hooking up a wideband" isnt that easy, or cheap. its to rich, i know that.



all that time and money put into it and you dont wanna spend another $200 to tune it properly?


:excuseme:


then, you can use the sensor on tuning anything after that. money very well spent.

  • BC3

Posted May 06, 2009 - 06:17 PM


where would the fun in that be?


Not sure Bro....I kinda like RIDING my bikes and not working on them all the time.....:excuseme: :smirk: :ride: :cry: :cry:

Posted Image



[COLOR="Blue"]NOS Nitrous equipped....... [/COLOR]





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