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Blood Sweat Tears and Grease => Engines => Topic started by: 860go on Jun 01, 2019, 19:13:20

Title: Vm32 help!!!!
Post by: 860go on Jun 01, 2019, 19:13:20
Hey guys, Iím pulling my hair out here; I know Iím desperate when I hit the forums haha.

  Xs400, ignition timing is checked and rechecked, compression is good, Spark is great, canít get fuel into this engine.

  Iím running brand new Vm32ís ball park jetted from DCC for 400ccís, fuel supply is flowing great, battery power is great, fuel is in the bowls, I can not even get the plugs wet with fuel on either side. The engine runs on starter fluid but only spits and coughs occasionally without it.

Iíve never worked with Mikunis before, am I missing something?

Thanks, clayton
Title: Re: Vm32 help!!!!
Post by: Nebr_Rex on Jun 01, 2019, 22:50:43
Idle mixture screw?

Oh and vm32s are to big for 400cc.


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Title: Re: Vm32 help!!!!
Post by: teazer on Jun 02, 2019, 00:43:55
They are a little large and that will make it hard to jet at small throttle openings and/or low revs.  As Nebr-rex suggested, try to screw the air screw in to see if that richens it up enough to start and idle, but you will probably need larger pilot jets.

Most re-jetted carbs are jetted all wrong for a 4 stroke motor and need changes to air jet, needle jet and needles to get them close, but maybe DCC are jetting them for a 4 stroke.  I suspect they came with 159 series needle jets and 2.0 air jets which are fine for a 2 stroke and not much use on a 4 stroke. You can make them work, but better off with suitable needle jets and 0.5 air jets. 

But for now try a larger pilot jet and see if you can get it to start and idle.
Title: Re: Vm32 help!!!!
Post by: 860go on Jun 02, 2019, 11:51:22
Thank you for your reply and time. You are spot on with your assumptions.

185 main, 35 pilot, 6dh7 jet needle, 2.0 air jet, 159 p-5 needle jet.  I went with these because they specifically mentioned the xs400 in their production description.

I will try some different pilot jets first and go from there just to try and get some headway.

I have gone in and out with the air screws to not much avail. I suppose I fell ignorant to the hope that DCC jetting would be pretty close out of the box. The only thing that makes sense from here is to go down that road.

Thanks again, Clayton
Title: Re: Vm32 help!!!!
Post by: irk miller on Jun 02, 2019, 19:21:46
Donít overlook the cutout on your slides.


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Title: Re: Vm32 help!!!!
Post by: Nebr_Rex on Jun 02, 2019, 21:06:35
Thank you for your reply and time. You are spot on with your assumptions.

185 main, 35 pilot, 6dh7 jet needle, 2.0 air jet, 159 p-5 needle jet.  I went with these because they specifically mentioned the xs400 in their production description.

I will try some different pilot jets first and go from there just to try and get some headway.

I have gone in and out with the air screws to not much avail. I suppose I fell ignorant to the hope that DCC jetting would be pretty close out of the box. The only thing that makes sense from here is to go down that road.

Thanks again, Clayton

Not a bad looking bike, and I'm not a Yamaha fan.


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Title: Re: Vm32 help!!!!
Post by: 860go on Jun 06, 2019, 19:18:34
Thank you, still a bit to go the get it wrapped up but hopefully this is the year it gets finished haha.

 After a crazy busy week at work I pulled the pilots and found 25ís. I just placed an order for 37ís and 50ís. Fingers crossed
Title: Re: Vm32 help!!!!
Post by: 860go on Jun 12, 2019, 07:20:05
I am humbled by embarrassment haha. I doubled the size of the pilot jets and it fired up.
Title: Re: Vm32 help!!!!
Post by: teazer on Jun 12, 2019, 16:47:07
Don't be.  Some of us have tons of jets in boxes after years of this sort of trials and tribulations. We just have a (slightly) better idea of where to start looking.