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1983 Honda vt750 Shadow
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Light tan would be OK. But stacks open a new page on CV carb tuning.
You may need to raise the needles and or main jets to get a better mixture at mid range to hard acceleration.
 

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1989 Honda Shadow VT600C
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62 Posts
Discussion Starter · #22 ·
how would i go about doing that? i know absolutely zero about carbs beside what i have watched from tjbrutalcustoms. i know what you are talking about, just don't know how to execute. haha Also how do i know what size jets i would need to buy to rejet? i Want to buy the performance jet kit from tjbrutalcustoms but their a little on the pricey side with all the stuff i have bought for the bike already :ROFLMAO:
 

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1983 Honda vt750 Shadow
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You could go up 1 or 2 sizes on the pilot jests and 2 sizes on the main jets. That may be just about right.
But sometimes it is a learning experience with carbs.
Watch videos on cleaning and that shows how to do the jets and float level.
This is a video of a different engine, but same type carbs.

 
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1999 Shadow 750 ACE VT750CD3 Modified
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My taxes are finally filed and I'm now 30% less grumpy so here is my take on the situation.

That has to be running lean as hell, it must run like cr4p, I'd guess that is at least part of the overheating problem.
Stock is 40 pilots, and 115 main jets.

I'm just guessing here: I'd go to 42 pilots and 130 mains for starters and see how it runs at full throttle.
As a start, I'd probably try a shim or an aluminum pop rivet washer under the needles too. It has been a while since I resorted to such stuff, and prefer decent adjustable needles, but IIRC the small diameter washers for 3/16 rivets work.

Jets: get a few each side of the 130, all the steps say in the range 125 to 138, jets are still cheap, shipping is expensive, their equivalent sized stuff is supposedly OK.


Official Shims:

How to tune a CV Carb

Factory Pro has Keihin jets too and IMHO probably the best Jet kits around. Their website can be a little strange to navigate, but their phone works.
Click on the Cyber Today link and try your luck at navigation.
The do have a Stage 3 kit for the twin carb VT600, which is what I'd buy and use as a proper starting point, even though it is expensive. They use a dyno to develop the kits and the kits have adjustable needles and that is what separates the wheat from the chaff in the kit game.

I would not let a TJBC tuning kit near anything I rode.
 

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1989 Honda Shadow VT600C
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Discussion Starter · #25 ·
My taxes are finally filed and I'm now 30% less grumpy so here is my take on the situation.

That has to be running lean as hell, it must run like cr4p, I'd guess that is at least part of the overheating problem.
Stock is 40 pilots, and 115 main jets.

I'm just guessing here: I'd go to 42 pilots and 130 mains for starters and see how it runs at full throttle.
As a start, I'd probably try a shim or an aluminum pop rivet washer under the needles too. It has been a while since I resorted to such stuff, and prefer decent adjustable needles, but IIRC the small diameter washers for 3/16 rivets work.

Jets: get a few each side of the 130, all the steps say in the range 125 to 138, jets are still cheap, shipping is expensive, their equivalent sized stuff is supposedly OK.


Official Shims:

How to tune a CV Carb

Factory Pro has Keihin jets too and IMHO probably the best Jet kits around. Their website can be a little strange to navigate, but their phone works.
Click on the Cyber Today link and try your luck at navigation.
The do have a Stage 3 kit for the twin carb VT600, which is what I'd buy and use as a proper starting point, even though it is expensive. They use a dyno to develop the kits and the kits have adjustable needles and that is what separates the wheat from the chaff in the kit game.

I would not let a TJBC tuning kit near anything I rode.
Thanks for the feed back and that is great to know!
 

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Could it be a possible tiny hole in a head gasket? So with the new sealed coolant system, some is being forced into the cylinder and causing the sputtering?
 

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Discussion Starter · #27 ·
Could it be a possible tiny hole in a head gasket? So with the new sealed coolant system, some is being forced into the cylinder and causing the sputtering?
I really hope not. i tuned the carb half a turn and still doing it only at high speeds WOT is responsive when this doesnt happen
 

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1989 Honda Shadow VT600C
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Discussion Starter · #28 ·
You could go up 1 or 2 sizes on the pilot jests and 2 sizes on the main jets. That may be just about right.
But sometimes it is a learning experience with carbs.
Watch videos on cleaning and that shows how to do the jets and float level.
This is a video of a different engine, but same type carbs.

Do i have to sync dual carbs ?
 

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1983 Honda vt750 Shadow
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Syncing can't hurt so that you have both throttles opening the same amount. Fine Tuning.
 
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So it’s not all the time, then. Intermittent issues are ‘good‘, but really hard to troubleshoot! Could it be your fuel supply might not be keeping up at WOT?
 

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Discussion Starter · #31 ·
So it’s not all the time, then. Intermittent issues are ‘good‘, but really hard to troubleshoot! Could it be your fuel supply might not be keeping up at WOT?
No its not all the time. when its decently hot out it does it but in the morning weather it doesn't. It could be, im not running a fuel pump but the fuel line goes straight down into the carb so i don't see how that would affect anything, but what do i know i've had my bike a month hahahaha There is no filter on the bike as of now tho. when i picked the bike up, the guy told me he just got done cleaning the carb and it wasn't doing it for the first couple days of riding it around, so i'm thinking since no filter jets might be a little clogged? maybe? idk
 

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Discussion Starter · #32 ·
Syncing can't hurt so that you have both throttles opening the same amount. Fine Tuning.
Would i have to take my whole bike in for them to sync or can i just take in my carbs?
 

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Do it yourself for very little money.

 

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1999 Shadow 750 ACE VT750CD3 Modified
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Until you get the main jets right you are just fiddling. With velocity stacks you have no choice, but to face up to it.
The mixture screw on the side of the carb and the pilot circuit has an effect from 0 to 1/4 throttle opening, beyond that it is just a side effect.

If you continue to run it at highway speed in the current lean overheating situation you will burn the exhaust valves and then.........
 

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1989 Honda Shadow VT600C
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Discussion Starter · #35 ·
Until you get the main jets right you are just fiddling. With velocity stacks you have no choice, but to face up to it.
The mixture screw on the side of the carb and the pilot circuit has an effect from 0 to 1/4 throttle opening, beyond that it is just a side effect.

If you continue to run it at highway speed in the current lean overheating situation you will burn the exhaust valves and then.........
i know thats why i really need to get this fixed :cry: so the sputtering is due to a lean condition?
 

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1999 Shadow 750 ACE VT750CD3 Modified
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That is my guess, as soon as you remove the stock inlet snorkel you mess up Honda's designed air flow with the CV carb, it is then a whole different ball game and removal of the rest of air box and replacement with velocity stacks doubles down on that.

I have a fair bit of experience with the similar twin carbed 750 going from stock to Bean box intake and currently with foam UNI clamp on pods.
There are other engine mods so mine maybe an extreme example, but it went from 105 and 110 main jets and currently sits with 148 and 150 mains.
So when in an earlier posting I suggested up sizing the main jets by more than the suggested couple of numbers I wasn't joking.
 

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Discussion Starter · #37 ·
i know thats why i really need to get this fixed :cry: so the sputtering is due to a lean condition?
That is my guess, as soon as you remove the stock inlet snorkel you mess up Honda's designed air flow with the CV carb, it is then a whole different ball game and removal of the rest of air box and replacement with velocity stacks doubles down on that.

I have a fair bit of experience with the similar twin carbed 750 going from stock to Bean box intake and currently with foam UNI clamp on pods.
There are other engine mods so mine maybe an extreme example, but it went from 105 and 110 main jets and currently sits with 148 and 150 mains.
So when in an earlier posting I suggested up sizing the main jets by more than the suggested couple of numbers I wasn't joking.
I bought a couple dynojets on both sides of 130 and 42 when they arrive I will attempt my first carb clean and tune. Wish me luck haha I’ll update you as soon as I finish
 

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Black still sounds like it’s too rich, and colder air is denser air... so more of it, which would lean your mixture out a bit and seem to make it run better. If it were a head gasket leak or something, it would always happen when the engine warmed up, regardless of outside temperature. I can’t remember, are your needles then adjustable type?

Fuel filters are either next to useless, when things are new and clean, to something that can save your engine. Did the PO say that he cleaned the tank out as well as the carbs? If it were junk getting caught in the passages and jets, though, this would happen more often.
 

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Discussion Starter · #40 ·
Black still sounds like it’s too rich, and colder air is denser air... so more of it, which would lean your mixture out a bit and seem to make it run better. If it were a head gasket leak or something, it would always happen when the engine warmed up, regardless of outside temperature. I can’t remember, are your needles then adjustable type?

Fuel filters are either next to useless, when things are new and clean, to something that can save your engine. Did the PO say that he cleaned the tank out as well as the carbs? If it were junk getting caught in the passages and jets, though, this would happen more often.
He didnt say he cleaned out the tank but looks pretty darn clean in there. it seems to be getting worse, last night i pulled the plugs and gapped them to .035 and today took it to work was almost scary on the freeway cause of no acceleration also its doing it at normal street speeds, 1st gear has no go 2nd gear is decently okay and third gear is okay both while cruising at about 40 mph i can feel pushing and pulling its almost to the point of unrideable
 
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