VS800 front/rear carbs using different main jets?

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B_Roost450f
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VS800 front/rear carbs using different main jets?

Post by B_Roost450f »

Why are the main jets in the carbs on a VS800 different sizes? And should that same size difference be kept when re-jetting?

A Hayne's manual is telling me: (Rear carb main jet is 5 units larger)

Front Carb:
Main Jet: 127.5
Pilot Jet: 40

Read Carb:
Main Jet: 132.5
Pilot Jet: 45

This Website: https://www.jetsrus.com/a_jet_kit_stree ... truder.htm is telling me: (Rear carb main jet is 37.5 units larger!? Doesn't seem right....)

Front Carb:
Main Jet: 90

Rear Carb:
Main Jet: 127.5

Slow Jet: 40


So what I'm getting at here...
When I go to re-jet my bike, do I keep the front main jet a bit smaller?
If I re-jet to say, a 165 in the front, should my rear be the same 5 units larger? so 170?

My bike has airboxes removed, K&N pod filters, and Jardine slip ons (LONG ONES) pics of the pipes can be seen in this thread: http://www.intruders-alert.com/viewtopi ... =19&t=4757
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enforcer
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Re: VS800 front/rear carbs using different main jets?

Post by enforcer »

Rear is larger to compensate for lack of air flow. Also, side draft vs down draft. 165 is way too big. The service manual sizes are correct. Pilots stay the same. What you are really compensating for is lack of vacuum to lift the slides. You could simply get restrictive material to block air flow slightly into the pods to create more negative pressure. No rejet required, just adjust your air fuel mixture.

If you insist, start by shiming the needle and moving up a few jet sizes at a time. I think the sweet spot consensus on the other site was 145 and 150, IIRC.
Current rides: 03 HD FLHT & 01 Yamaha XVS650(BIP)
Former: 87 Suzuki VS700, 94 BMW K1100LT & 91 Honda CB250

I don't want to own them all, just ride them all.
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wally w
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Re: VS800 front/rear carbs using different main jets?

Post by wally w »

On mine I had Vance & Hines exhaust with K&N pods and factory pro jet kit if I remember correctly I Had 142.5 Main in the front carb and 145 in the rear and it was a tad rich but topped out at 118mph.

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