Mikuni jet misprint

Jack Rutherford /

Just installed Malossi top end on qt50. Was running an 85 jet but could tell that I needed to upjet. I put in a 90 jet and took it for a ride. In the middle of the ride at maybe 3/4 throttle, temperature starts shooting up beyond anything before - 396F. Hottest it had been with 85 jet was 381F. So I slowed and let it cool down and brought it home. this left me scratching my head, wtf, right? I'm thinking I misread the number on the jet. Did I put in a 60 jet? No. I remove the jet and it reads 90. I check it several times. Still reads 90. I take out my drill bits and try to stick an 85 drill bit in it - no go . I try an 80 bit - it goes in barely. Check the jet again, it still reads 90. Good thing I had a temp gauge. Anyone else ever run into mistakenly marked jets? I'm thinking this should be an 80 jet.

Re: Mikuni jet misprint

#CrazyWane rocks # Crazy Wayne /

Who was the vendor on the jet.

What was the brand name of the jet

Re: Mikuni jet misprint

yeah it happens, i always eyeball for a second like an astronemer and if in doubt do the go no go thing with bits.

Re: Mikuni jet misprint

Jack Rutherford /

I thought I had bought all my mikuni large hex jets 4/042 from treats. But I have no record of buying a 90 or 95 jet from them. Perhaps I bought them off ebay.

Re: Mikuni jet misprint

A mikuni carb and dellorto main jet numbers are totally different when it comes to jetting them. I run a 43/94 in one bike with a phbg 19.5 and a 17.5/140 in another bike set up identical but with a vm20. With that being said what carb and filter are you running would help also.

Re: Mikuni jet misprint

Jack Rutherford /

these are all mikuni large hex jets 4/042 for the vm18

Re: Mikuni jet misprint

Jack Rutherford /

Which made me wonder - does a Mikuni round jet for the qt50 correspond to the Dellorto SHA 15.15 jet? Enquiring minds want to know. I pulled a 70 Dellorto jet and a 70 Mikuni jet. 65 drill bit went through both about the same. 70 drill bit met a fraction more resistance in the SHA jet than in the Mikuni. I didn't test other sizes but based on that I would saythe 70 SHA jet was maybe 1 size away from the Mikuni. So if the Mikuni was a 70 the Dellorto would have been a 69.

Re: Mikuni jet misprint

#CrazyWane rocks # Crazy Wayne /

> Jack Rutherford Wrote:

> -------------------------------------------------------

> Which made me wonder - does a Mikuni round jet for the qt50 correspond

> to the Dellorto SHA 15.15 jet? Enquiring minds want to know. I pulled

> a 70 Dellorto jet and a 70 Mikuni jet. 65 drill bit went through both

> about the same. 70 drill bit met a fraction more resistance in the SHA

> jet than in the Mikuni. I didn't test other sizes but based on that I

> would saythe 70 SHA jet was maybe 1 size away from the Mikuni. So if

> the Mikuni was a 70 the Dellorto would have been a 69.

You're joking right.

Re: Mikuni jet misprint

Yes sha jets work on stock mikuni for qt50, and knock off mikuni jets are worthless..

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