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Discussion Starter · #1 ·
ok 2002 vt1100 30 k miles all stock has no power over 50 mph it's all it can do to get to 60 mph... the bike did sit for almost a year .ok that being said; I have done compression test good 165 both cyl. new plugs clean fuel , plugs look good ,slite brownish,( on old clugs) found the front carb slide not pulling up.it moves free by hand pulled the carbs cleaned , checked both slide diaphragms both look good can blow air into the black elbow rear carb slide moves up front does not where does it get its vacuum signal from I had the carbs apart and blew air and cleaner though every port. WHAT AN i MISSING ?? eng runs great down low.
 

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1983 Honda vt750 Shadow
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Engine off, twist the throttle full throttle and look down at the throttle drum on the carb to make sure it is wide open also.
A carb sync may be a good thing to do if one throttle is not opening full like the other.
 

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It's an internal passage in the carb I believe. The diaphragm should have an ear that sticks out to seal the vacuum passage. See #15 here:
2002 Honda VT1100C A CARBURETOR COMPONENTS | Ron Ayers.

Verify that passage is not plugged. Also hold the diaphragm up to the light and gently stretch it, looking for vertical
splits. On the one on the right, there's 1 just to the left of the ear that seals the vacuum passage. another further around, shown in the 2nd pic. note the assembly sequence in the parts diagram also.

295834
295835
 

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Discussion Starter · #4 ·
Thank you !! the diaphragm is good . I checked it I have done a lot of cv carbs over the years ( xs650 bs38's and bs34's ) the throttle plates open all the way and close the the same as each other. I'll pull them again and recheck that passage
 

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I usually stick a screwdriver handle in the throttle bore to hold the slide up while I put the cap on, seems to make it easier to get seated properly.
 
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Discussion Starter · #6 ·
ok I got the carbs working both slides fluter and onen on throttle opening. put all backtogether test ride great power up till 1/2 throttle falls on its face and backfires acts lean. it has V&H long shots exhaust coud it be way too lean on the mains.as far as I know it's all stock jetting and air filter. what am I missing
 

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'83 VT750C
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Could still be a blocked passage. Undersized jets would probably cause you to run lean, but not experience the issues you are… Are you testing with the carb intakes open for you to watch? If the choke isn’t helping, it’s either part of the blockage… or lack of fuel isn’t exactly the issue.
 

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Discussion Starter · #9 ·
checked the slides with air intake off they both pull up now reinstalled everything test rode runs like **** above 1/2 throttle, runs great low rpm up till about 50 pmh then fall flat over 1/2 throttle
 

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Hard to test high throttle operation while its apart on the Center stand… The cylinders are opening, but that still screams the needles aren’t letting fuel through, or the high speed jets are clogged.
 
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