Proper way to rebuild carbs?

VMAX  Forum

Help Support VMAX Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Joe Planter

Active Member
Joined
Jul 12, 2020
Messages
42
Reaction score
4
Location
Alameda, California
Hello, I just bought my 1994 VMAX for $2300. After having some issues with it idling (which i figured out and solved) I tore apart the carbs and rebuilt them and in the process damaged them by pounding out the brass pieces that the float valves sit in. Long story short I ordered new carbs and am looking for anyone that can send me a link to a forum that has already been made or that knows how to properly rebuild and reject the carbs. As in, what exactly I need to replace in the carbs/what to do/not do. I have a cobra exhaust so I’m also wondering how I rejet the carbs properly for that type of exhaust. I have drilled the diaphrams and put new needles in but I’m confused as to what size Jets go where for that type of exhaust. Any help would be greatly appreciated, thanks.
 
...what exactly I need to replace in the carbs/what to do/not do. I have a cobra exhaust so I’m also wondering how I re-jet the carbs properly for that type of exhaust. I have drilled the diaphragms and put new needles in but I’m confused as to what size Jets go where for that type of exhaust.

I hope that you have realised that going at it gung-ho is not the way forward.
What to replace will depend very much on the condition of the carbs.
Have you run the bike yet and if so how did it feel?
IMO the worst thing you can do is to guess at what needs to be done.

Base any decisions you make on facts, either by inspecting the components or establishing how the motor is fuelling either by seat of the pants, doing plug chops or putting it on a dyno. DO NOT GUESS!
The first two assume (and no insult intended) that you have the experience to understand what is going on whereas the latter will give you hard facts and may possibly work out cheaper in the long run.
You will be inspecting for wear in the main jets/ needles and the integrity of the diaphragms. A dyno run will indicate if you need to alter the mixture which should take care of the mains if they need to be changed.

Hopefully those who have a Cobra exhaust and have set the it up will be able to offer more advice.

The old adage of 'If it ain't broke don't fix it' should be near the top of all our mantra's list.
 
Sell the Cobras. A stock exhaust makes more power.

At this stage send the carburetors to member (screen name, use the PM function to contact him) Dannymax or to [email protected] Sean Morley for rebuilding. You already ruined one set. Get it running well & did I mention get rid of the Cobras? Really. The Cobras are looks-only. They cost you performance and drivability. You don't believe me read past threads & posts. From your desire to re-jet & etc, I assume you have the full set Cobras, the 4-into-4 system.

Riding a VMax with a Cobra 4-into-4 full exhaust is like using .38 Special cartridges in a .357 Ruger GP-100. You can do it, but the equipment is capable of so-much more! If you don't believe me, spend some time reading the Cobra exhaust comments in the many threads. The Cobras are pretty, they are impressive to anyone who doesn't know the cost they take on performance, but for someone who bought a VMax for what a VMax-stock- is capable-of (to say nothing of modified rides), you can't get-rid of them fast-enough.

I'd rather have a scraped-up set of OEM Yamaha full exhaust on my bike than a perfect-condition Cobra 4-into-4's. Take those off, and get whatever you can for them, and regain the horsepower and throttle response that your motorcycle was designed to give-you. I guarantee that if you rode two VMax'es back-to-back, one with a brand-new Cobra 4-into-4, and the other with a scabbed-up OEM Yamaha exhaust, you wouldn't care what the OEM exhausts looked-like, given the difference in performance. It's that-big of a difference.

You got onto that bike for a decent price, now return it to the level of performance it was designed to deliver! You will never get there with a set of Cobras, don't waste your time and money. Of course a properly-operating set of carbs is an essential component in enjoying a trouble-free ride. If you decide to go with a Dynojet Stage 7 kit for use with a full exhaust where the system has the scavenging which the Cobras do not, you don't have to eliminate the VBoost system as the Dynojet Stage 7 directions tell you to do. That will help you to properly synchronize the carburetors. Under the left scoop, is a round electrical M-F plug for the stepper motor which controls the VBoost. You can expose the plug, and when you turn-on the ignition and the VBoost cycles to an 'opened' position, unplug that connector. Now your VBoost will be always-open, which changes your exhaust note to a nasty one, sure to get people's attention as you idle through the crowd of people parked at your local bike night. Personally, I like the VBoost operation. The advantage to keeping it is that you have a much-easier time of it to synchronize your carburetors, and you do not need to buy a special tool to do it, if you already have a carb synch tool for 4 cyl bikes.

Sean Morley has a Morley's Muscle intake kit, jets, air filter in a modded airbox lid, and his instructions, instead of the Dynojet Stage 7, and did I mention, he often has used exhausts of various types and prices, as-well-as being a dealer for new ones?

FYI, it's usually not-necessary to replace the float needle seat, it's the needle valve piece, with its rubber/viton tip, which usually wears. Maybe after 100,000 miles, you need to-think about replacing them. I normally just replace the needle valves, and don't touch the seats. I use an ultrasonic cleaner to 'scrub' the carb bodies clean. Use a jeweler's loupe, or a magnifying glass to inspect the seat if you wish, for deposits (possible) or wear (less-likely). When disassembling the carbs, I leave them in a 'front' pair, and a 'rear' pair, unless I know there's a need to replace some piece requiring further disassembly.
 
Last edited:
What MM said.

It sounds like you've read about 50 different pages on the internet and are combining it all into one huge soon-to-be cluster.
 
Sell the Cobras. A stock exhaust makes more power.

At this stage send the carburetors to member (screen name, use the PM function to contact him) Dannymax or to [email protected] Sean Morley for rebuilding. You already ruined one set. Get it running well & did I mention get rid of the Cobras? Really. The Cobras are looks-only. They cost you performance and drivability. You don't believe me read past threads & posts. From your desire to re-jet & etc, I assume you have the full set Cobras, the 4-into-4 system.

Riding a VMax with a Cobra 4-into-4 full exhaust is like using .38 Special cartridges in a .357 Ruger GP-100. You can do it, but the equipment is capable of so-much more! If you don't believe me, spend some time reading the Cobra exhaust comments in the many threads. The Cobras are pretty, they are impressive to anyone who doesn't know the cost they take on performance, but for someone who bought a VMax for what a VMax-stock- is capable-of (to say nothing of modified rides), you can't get-rid of them fast-enough.

I'd rather have a scraped-up set of OEM Yamaha full exhaust on my bike than a perfect-condition Cobra 4-into-4's. Take those off, and get whatever you can for them, and regain the horsepower and throttle response that your motorcycle was designed to give-you. I guarantee that if you rode two VMax'es back-to-back, one with a brand-new Cobra 4-into-4, and the other with a scabbed-up OEM Yamaha exhaust, you wouldn't care what the OEM exhausts looked-like, given the difference in performance. It's that-big of a difference.

You got onto that bike for a decent price, now return it to the level of performance it was designed to deliver! You will never get there with a set of Cobras, don't waste your time and money. Of course a properly-operating set of carbs is an essential component in enjoying a trouble-free ride. If you decide to go with a Dynojet Stage 7 kit for use with a full exhaust where the system has the scavenging which the Cobras do not, you don't have to eliminate the VBoost system as the Dynojet Stage 7 directions tell you to do. That will help you to properly synchronize the carburetors. Under the left scoop, is a round electrical M-F plug for the stepper motor which controls the VBoost. You can expose the plug, and when you turn-on the ignition and the VBoost cycles to an 'opened' position, unplug that connector. Now your VBoost will be always-open, which changes your exhaust note to a nasty one, sure to get people's attention as you idle through the crowd of people parked at your local bike night. Personally, I like the VBoost operation. The advantage to keeping it is that you have a much-easier time of it to synchronize your carburetors, and you do not need to buy a special tool to do it, if you already have a carb synch tool for 4 cyl bikes.

Sean Morley has a Morley's Muscle intake kit, jets, air filter in a modded airbox lid, and his instructions, instead of the Dynojet Stage 7, and did I mention, he often has used exhausts of various types and prices, as-well-as being a dealer for new ones?

FYI, it's usually not-necessary to replace the float needle seat, it's the needle valve piece, with its rubber/viton tip, which usually wears. Maybe after 100,000 miles, you need to-think about replacing them. I normally just replace the needle valves, and don't touch the seats. I use an ultrasonic cleaner to 'scrub' the carb bodies clean. Use a jeweler's loupe, or a magnifying glass to inspect the seat if you wish, for deposits (possible) or wear (less-likely). When disassembling the carbs, I leave them in a 'front' pair, and a 'rear' pair, unless I know there's a need to replace some piece requiring further disassembly.
First off thank all of you for the brutally honest responses you have given me. I really appreciate it. Before I even messed with the carbs, the bike would not idle without the choke. I assumed it was that the carbs were dirty. Tore into the carbs and they were actually pretty clean, turns out the thumb idle screw was down too far therefore it wasn’t idling without choke. So now I’ve made a way bigger problem than there was to begin with, but I’m determined to have an excellent running VMAX by the end of all this. At this point I’ve spent so much money and I’ve actually made things worse for the bike. So where I’m at now is from here on out I want to do things correctly with this bike and stop wasting my money. Basically what I’ve gotten out of it is that I need to send the carbs to DannyMax to get properly rebuilt/rejetted, and that I need to get rid of the Cobras ASAP. Going off of that, what aftermarket exhaust would you recommend then? I’ll probably just put the stock exhaust back on it until I end up getting a better pair of aftermarket. Also I’ve already PMd Danny, how can I get ahold of Sean Morley for a used exhaust and/or any other help he may be able to provide? Thank you all again
 

Latest posts

Back
Top