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post #31 of 39 (permalink) Old 01-09-2011, 05:13 PM
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I believe member Crobins365 has (had?) a bunch of carb pics in her gallery. I just tried to access them and couldn't find them. Maybe you will have better luck!

I'm keepin' all the left over parts. I'm gonna use 'em to build another bike!
_____________________________________________
"Black Beauty"
1989 VN750 acquired December, 2008, 6,711 miles
Currently 23,298 miles

Old Blue
2001 Honda CMX250 Rebel acquired July, 2008

1987 VN750 project bike, acquired August, 2009, 33,000 miles and balancer sticking out of the case, currently awaiting attention and parts
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post #32 of 39 (permalink) Old 01-09-2011, 08:28 PM
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I added a photo album that has a pictures of the left and right views of the carburators when they are mounted on the bike. Hope that helps.

~~C8> Ratt
________________________
'91 VN750 - Cosmic Splendor/Candy Wine
Done: Coastered, .020 ign., Iridiums, VM
Plexistar II, MCCT's, Relocated MOSFET
Next: LED's
Will Do: Horns, Shave(maybe)
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post #33 of 39 (permalink) Old 01-09-2011, 11:18 PM Thread Starter
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Quote:
Originally Posted by VN750Rider/Jerry View Post
To the original poster. Since the carbs are an unknown, I would go ahead and pull them, disassemble them, and clean them out good. Yes it's a real PITA, definitely not an easy job unless you've done it many times, but if you clean them right, it is a one time thing. From then on, use Seafoam every once in a while to keep them clean, and if the bike is going to sit for more than a couple of weeks, use the drain screws to drain all the gas out of the float bowls. If you have a choice, use real gas, rather than the gas/moonshine mix most places are selling.

While you have the carbs off, you can check them and the manifolds (the rubber parts between the carbs and heads) for damage. Sometimes after many years, the manifolds can deteriorate and develop cracks. Look everything over, and put it all back together carefully. The best way I have found to check for air leaks, and the least messy, is to use a propane torch (unlit), open the valve, and hold it around the carbs and manifolds. If there is even a slight leak, the engine will suck in the propane, and idle speed will go way up. Be aware that to affect running to any noticeable degree, the air leak would have to be in the carbs themselves, the manifolds, or manifold connections. An air leak on the air filter side of the carbs will not affect running, though it can let dirt into the engine. In fact, the engine will run just fine without the filters, though it might be a little on the lean side. Check the carb vents, and make sure you are getting gas to the carbs.


I would definitely check the splines, like, right now. That is the biggest weak point of the VN750, and it seems to affect ALL VN750s. The factory never lubed them right in the first place, and if they are damaged, you have a very big (expensive) problem.

Are you sure the pipes were red? The Vulcan 750 has double wall pipes, and for the outside pipes to get red would be almost impossible. I would almost think the aluminum engine would melt first. My pipes never even yellowed, even after 80,000 miles. And it is definitely NOT a good idea to run the engine at high rpm without a load on it, that is, actually riding it. Revving it really high in neutral for more than a second or so can do some serious damage.
Well, let me correct myself, and use the quote button so people know what I'm replying to =). The outside chrome part was not red, just the actual inside pipe. Not the cover. On the right hand side of the bike that exhaust pipe looks like oil does on water, if that makes any sense. And it didn't look like that before. I guess thats me bluing the pipes or some such? I'm planning on getting a different exhaust anyway, thinking of going with this one http://www.amazon.com/Cobra-Boulevar.../dp/B000I592V0 but yeah, when I was revving the engine to try and get the carb cleaner through it ( bad idea i know that now) it was also backfiring some, since it was at night i could actually see small flames coming out. So I have a short series of questions that if someone could answer i think i might be a little closer to figuring this out. Also, i checked on all my boots and hoses, not just for air, but on the entire bike, and every hose is still very flexible, no corrosion or cracking or any wear at all really so I'm kinda doubting it would be a vacuum leak.

1. What causes your pipes to blue or get that strange look on them?
2. Would improperly adjusted air mix screws cause backfiring and poor low rpm/idle running?
3. Would a carb sync fix backfiring or poor idle?
4. Could it possibly be a burnt valve or valve seal? It doesn't even think of dieing at high rpms with the choke off btw. Just wondering (and praying its not)
5. And just out of curiosity, how do i get to the splines and where are they exactly O_o? Once I get there, what do i use to lube them properly? Oil, grease, gear oil like on a manual transmission (still have some from the one i just overhauled) and if its any kind of oil or fluid, is there a particular viscosity?

Anyone got an answer feel free to enlighten me, I'm very eager to figure this out and get my baby running. Then I can move on to the fun part. Cosmetics =)

Last edited by Backlash1818; 01-09-2011 at 11:21 PM.
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post #34 of 39 (permalink) Old 01-10-2011, 10:43 AM
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1. I've heard too lean a fuel mixture leads to blue pipes. Others may know more.

2. Backfiring on decelleration is normal for these bikes. If you ease off the throttle, it doesn't backfire as much. You can "marble" or "coaster" the engine to eliminate or greatly reduce the backfiring. Do a search for these procedures here and it should explain what is needed.

3. If the carbs are clean (many aren't) and it runs rough, it might need to have the carbs synched, but unless someting was done to the carbs, they should be synched already.

4. More than likely, the carbs need cleaning. Here's a good place to have it done at a good price if you don't want to tackle it yourself: http://www.carbworx.com/

5. Click on the Search button on the tool bar toward the top of this page. Type in Fergy under Member Search. Go to one of his posts and click on the spline lube procedure in his signature. Use a grease/paste with at least 60% moly content, such as Honda Moly 60 or Guard Dog Moly.

I'm keepin' all the left over parts. I'm gonna use 'em to build another bike!
_____________________________________________
"Black Beauty"
1989 VN750 acquired December, 2008, 6,711 miles
Currently 23,298 miles

Old Blue
2001 Honda CMX250 Rebel acquired July, 2008

1987 VN750 project bike, acquired August, 2009, 33,000 miles and balancer sticking out of the case, currently awaiting attention and parts
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post #35 of 39 (permalink) Old 01-10-2011, 12:08 PM
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Excessive heat is what 'blues' the pipes. There's combustion in the pipe. If the bike has not been 'marbled/coastered', by design, there is fresh air being delivered to the exhaust through the stock emission equipment. This fresh air can mix with the unspent fuel and burn in the pipe. As FliteControl said, coastering, and setting the fuel mix slightly richer will mostly eliminate this occurrence. Secondly, I would definitely check compression for a valve timing or closure problem. Excessive heat is one thing, but glowing red is an entirely different level.

Any time you remove the carbs, you should sync them as soon as the bike is running again. My 2 cents.

~~C8> Ratt
________________________
'91 VN750 - Cosmic Splendor/Candy Wine
Done: Coastered, .020 ign., Iridiums, VM
Plexistar II, MCCT's, Relocated MOSFET
Next: LED's
Will Do: Horns, Shave(maybe)
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post #36 of 39 (permalink) Old 01-10-2011, 03:20 PM Thread Starter
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Quote:
Originally Posted by flitecontrol View Post
1. I've heard too lean a fuel mixture leads to blue pipes. Others may know more.

2. Backfiring on decelleration is normal for these bikes. If you ease off the throttle, it doesn't backfire as much. You can "marble" or "coaster" the engine to eliminate or greatly reduce the backfiring. Do a search for these procedures here and it should explain what is needed.

3. If the carbs are clean (many aren't) and it runs rough, it might need to have the carbs synched, but unless someting was done to the carbs, they should be synched already.

4. More than likely, the carbs need cleaning. Here's a good place to have it done at a good price if you don't want to tackle it yourself: http://www.carbworx.com/

5. Click on the Search button on the tool bar toward the top of this page. Type in Fergy under Member Search. Go to one of his posts and click on the spline lube procedure in his signature. Use a grease/paste with at least 60% moly content, such as Honda Moly 60 or Guard Dog Moly.
I already cleaned the carb I'm in the process of putting it back in but it was pristine whew I took it apart so I'm not sure if the problem was fixed guesse I'll find out soon lol
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post #37 of 39 (permalink) Old 01-10-2011, 06:04 PM
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If you still have problems, try starting a new thread in the applicable section of the forum. You'll probably get more responses there.

I'm keepin' all the left over parts. I'm gonna use 'em to build another bike!
_____________________________________________
"Black Beauty"
1989 VN750 acquired December, 2008, 6,711 miles
Currently 23,298 miles

Old Blue
2001 Honda CMX250 Rebel acquired July, 2008

1987 VN750 project bike, acquired August, 2009, 33,000 miles and balancer sticking out of the case, currently awaiting attention and parts
flitecontrol is online now  
post #38 of 39 (permalink) Old 01-10-2011, 07:41 PM
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Here is the link to Crobins external carb pics from the stickey thread at the top of the *Carbs and Fuel* forum.
https://www.vn750.com/photopost/showgallery.php?cat=548

"Marbleing" or "coastering" the exhaust header cuts off fresh air which causes unspent fuel to burn in the pipes. This is the source of the popping upon deceleration. You probably still need to richen the air/fuel mixture to eliminate/reduce further the popping, as the factory setting is only 1 5/8 turns of the screw out from the seat. See picture above for location. The a/f mixture screw is covered by a metal cap or plug, which needs to be removed in order to adjust the screw out further. Usual a/f adjustment fix seems to be from 2 1/2- 3 1/2 turns out maximum. Only 5 turns until screw falls out, so seal screw in place with dab of silicone sealant to retain setting and avoid loss of screw.

Link to fergy`s spline lube write-up and pics.
http://pages.tstar.net/~fergy/writeu...al_drive1.html

Gordon

1991 VN 750 -"Cosmic Lady" or "Bad Girl"?
Purchased May 16, 2008
Approx.19,300km (12,000 miles)

H-D windshield
Relocated R/R
MF-AGM battery
Fiamm Freeway Blaster horns
F&S luggage rack and engine guard
Kury Offset Hiway pegs
July 13, 2016, Riding on the DARKSIDE now, Classic Radial 165/80-15


TOP TEN THINGS A NEW RIDER/OWNER SHOULD DO. Click on link.
https://www.vn750.com/forum/11-vn750-general-discussion/9127-top-ten-items-you-would-suggest-new-owner-do-his-new-ride.html
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post #39 of 39 (permalink) Old 01-10-2011, 08:41 PM Thread Starter
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Quote:
Originally Posted by flitecontrol View Post
If you still have problems, try starting a new thread in the ok applicable section of the forum. You'll probably get more responses there.
Ok will do thank your advice and sharing your knowledge and experience, along with everyone else, its given me a much better idea of what to do.I'll move this to the appropriate section and list everything I've fine so far may even be able to include a sound clip of what its doing
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