'87 Honda Magna 700 Carbs - thoughts?

[bwringer]

Greetings, fellow elements of the GSR Hive Mind.

This humble Element has not tangled much with old Hondas, yet one has entered my orbit. And I have questions. And doubts about whether I want to even tackle this.

The patient is a disco-fabulous 1987 Honda Magna 700 (VF700CA, I think). It starts and will idle just dandy (idles fine off choke after warming a little), but dies when you attempt to open the throttle, even a little. The story is a little hazy, but apparently the issue popped up rather suddenly this spring after the bike had been sitting only about a week.

Not having any other ideas, the owner dumped some Sea Foam in the tank and let the bike sit and idle for about 30 minutes. This actually seemed to cure it, and he went for a nice victory ride.

However, the issue returned as soon as the bike cooled down. And a friend of a friend of a friend of a friend put us in touch.


It seems pretty obvious the carbs need to come off and get cleaned out. Is this a legendary epic struggle few have ever conquered, or just a fairly run of the mill pain in the ass?

How available are the parts and such? I'd like to find an o-ring kit like the ones Mr. Barr puts together for us GS-ers. It looks like Honda sells "seal kits" for its carbs that include these, but they're $30 per carb. Obviously, the low-rent aftermarket "rebuild" kits are not an option.

Any other causes or issues that come to mind?

Trying to decide whether this is something I want to take on. I could make a few bucks for the Triumph Fund, but if it promises to turn into a sideways nightmare best avoided by the sane, I may respectfully decline.

Your wisdom is deeply appreciated...

 

[Nessism]

Go for it! Can't be THAT hard. I've owned a VF500 and did valve adjustment and such on it before and don't remember any nightmares surfacing. As for O-rings, Harbor Freight sells an assortment that may help. Worst case take some measurements and order some of the correct sizes. I've got a shoe box full of different O-Rings for all kinds of different carbs and may even be able to help.

 

[fbody_mike]

I do not know this bike, but I had an igniter on my Yamaha act just like this. It would idle, but as soon as you tried to rev it, it would bog until the throttle was released. To my surprise it was the igniter box. Since you said it happened all of the sudden, it makes me think it is more ignition than carb.

 

[storm 64]

I helped a fellow install a set of carboratotors on his Honda 750 Magna. He tried a few times by himself before calling me. It was a two man job putting them on. A pain in the neck but we did it.

 

[Steve]

I have not worked on a Magna. The v-shaped engines that I <have> worked on (and absolutely detest) include: Yamaha Venture Royale (valve adjust and carb rebuild), Honda ST1300 (air filter change and install cruise control), Honda Pacific Coast (install cruise control), Suzuki Intruder 800 (carb clean and valve check).

I think you should take one for the team and take on the job, as long as you do it as objectively as you did your Shinko Tire Torture Test several years ago.

.

 

[robertbarr]

I think step 1 would be finding a good or reasonable forum that covers that bike's engine. A quick Google pulls up a number of fora (plural?); you might find a good vein of info out there. No sense re-inventing the wheel.

Edit: I know that a number of years ago -- maybe a kinda large number -- there was a Honda V-4 equivalent of me, and he carried a much wider array of products.

Edit #2: I knew it was Billy-something. It's Billy C. Good reputation, and seems to be still in business. Check here: We used to send customers to each other.

 

[bwringer]

Thanks, Robert -- that's exactly the sort of meaty slab of useful information I was looking for!

 

[Wingsconsin]

My son and I did a set for one of his friends --

Removal is difficult - but much easier than getting them back on !

Using a ratchet strap actually helped create enough leverage to get them to seat in the boots. (NOT-pro tip?) {worked for me?}

The actual carb internals are typical and usual for someone with your experience

In my experience - not worth the effort - but it was a pro bono project

 

[Guest]

If you're going to tackle this be very careful of the fuel tubes. They are fragile after that age. My Interceptor tubes were shot and OEM tubes are unobtainable. I would up finding a guy on one of the forums that made CNC alloy replacements. It looks as though someone has made a cheaper version for $70, I think I paid double that for the CNC version. :encouragement: https://www.ebay.com/i/202717604776...8pIgo0dSkkYKmkMpdN5XqGbYX6k9mrT0aAjMNEALw_wcB

 

[chuck hahn]

I just did a set on my buddies 85 Magna. Remove carbs WITH the plenum on and install them with it on. I strongly suggest you remove the jets and have them done in a BIG BIG ultrasonic cleaner. Be aware of the sporings for the sync adjustments..they fly off regualrly. If you break them down put the carbs onto the plenum and then put the springs in otherwise as the carbs twist and move the springs come out.

And they go in rather easy actually. Heres the video of how to reinstall them without much fuss.
https://www.youtube.com/watch?v=BFGTAYog0_Q

And the ratchet strap trick....

https://www.youtube.com/watch?v=2JxDcWqYhyA

 

[Guest]

Using a ratchet strap actually helped create enough leverage to get them to seat in the boots. (pro tip)

This is NOT a pro-tip and NOT the right way to put the carbs back on. You just have to have the boots in the right position and limbered up, there's actually a guy on the V4 MuscleBike forum that created a concoction of stuff (wintergreen???) to soak them in to make them soft, then it's not that bad at all, or buy new ones if you can find them. Using a strap has, will and can result in a broken plenum and then your up $hiit creek.

 

[GregT]

All the Honda V4's are difficult to replace the carbs. Yes, keep them on the plenum, it causes too many problems if they're removed from it.
Yes, the rubbers must be lubricated. Specialist rubbergrease is available and should be used.

The 400 V4's are particularly difficult. I had a customer who used to stand on the plenum while hanging onto a rafter in his workshop...
His girlfriend told me what he was doing so I gave them a pot of rubbergrease as a present.

 

[Wingsconsin]

This is NOT a pro-tip and NOT the right way to put the carbs back on. You just have to have the boots in the right position and limbered up, there's actually a guy on the V4 MuscleBike forum that created a concoction of stuff (wintergreen???) to soak them in to make them soft, then it's not that bad at all, or buy new ones if you can find them. Using a strap has, will and can result in a broken plenum and then your up $hiit creek.

All I know is it worked for me -
I will also NEVER do another nor own one .

 

[Guest]

All I know is it worked for me -
I will also NEVER do another nor own one .

Well, it's been reported many times throughout the years of guys who "thought" the wratchet trick was a good idea, only to end up with broken plenums and broken hearts after attempting it. V4 carbs are pretty bad, but big Eliminator carbs are not easy to reinstall either, the VMAX is 10 times easier to get the carbs on and off!

 

[Steve]

..., the VMAX is 10 times easier to get the carbs on and off!

"10 time easier" is still WAY too hard for me. :-\\\

.

 

[bwringer]

Well, the patient is on the slab...

Overall, if this bike were a dog, I'd dig a hole and take the mangy beast to the vet for the big pink shot.

75,000 miles, banged up and rough shape all around, absolutely nothing is straight, uncorroded, or un-scraped, ancient front tire, leaky fork seals, seat a mess of duct tape, turn signals all busted, radiator fan switch failed and jumpered to leave the fan on all the time, janky melted K&N air filter and airbox lid totally mangled and letting filth into the engine for who knows how long, headlight connector melted, 1/4" bolts here and there, missing and chowdered fasteners everywhere, oil pan leaking, something leaking down by the secondary gears, battery damn near expired (but I did get it to charge after a couple of attempts) etc. and so on.


Anyway, I haven't removed the carbs yet, just the airbox, but three out of the four vacuum diaphragms are bad and oh yeah, there's a coolant leak from one of the many coolant lines underneath the carbs. I drained the float bowls and nothing horrible came out. Gas is very "off", but not terribly deteriorated.

I would also bet a considerable sum that the valves have never been checked once in 75,000 miles. And who knows how much dirt the engine has swallowed through the cabbaged airbox and filter.

IMnsHO, this bike is used up and ain't remotely worth saving. Part it out or sell the carcass and start over with something with a better foundation. Yes, it would probably be possible to get it running again. Maybe. But it would take a ridiculous amount of money and time, and even more (or just be impossible) to get it remotely safe and reliable.

So now I have to find a way to convince the owner of that...

Feh.

 

[RichDesmond]

Well, the patient is on the slab...

Overall, if this bike were a dog, I'd dig a hole and take the mangy beast to the vet for the big pink shot.

75,000 miles, banged up and rough shape all around, absolutely nothing is straight, uncorroded, or un-scraped, ancient front tire, leaky fork seals, seat a mess of duct tape, turn signals all busted, radiator fan switch failed and jumpered to leave the fan on all the time, janky melted K&N air filter and airbox lid totally mangled and letting filth into the engine for who knows how long, headlight connector melted, 1/4" bolts here and there, missing and chowdered fasteners everywhere, oil pan leaking, something leaking down by the secondary gears, battery damn near expired (but I did get it to charge after a couple of attempts) etc. and so on.


Anyway, I haven't removed the carbs yet, just the airbox, but three out of the four vacuum diaphragms are bad and oh yeah, there's a coolant leak from one of the many coolant lines underneath the carbs. I drained the float bowls and nothing horrible came out. Gas is very "off", but not terribly deteriorated.

I would also bet a considerable sum that the valves have never been checked once in 75,000 miles. And who knows how much dirt the engine has swallowed through the cabbaged airbox and filter.

IMnsHO, this bike is used up and ain't remotely worth saving. Part it out or sell the carcass and start over with something with a better foundation. Yes, it would probably be possible to get it running again. Maybe. But it would take a ridiculous amount of money and time, and even more (or just be impossible) to get it remotely safe and reliable.

So now I have to find a way to convince the owner of that...

Feh.

Some years back, a buddy who owned an independent bike shop had a guy come in with a bike in about that kind of shape and want to sell it to him. Buddy and I go out and look at it, he walks around it slowly a couple of times and tells the guy:

Buddy: "Hey, this is OK, it just needs a little Ronson treatment."

The Guy: "Really, what's a Ronson treatment"

Buddy (pointing at the Walgreens next door): "Just go in there and buy a can of Ronson lighter fluid, hose this pig down with it and light it on fire."

And then we walked back inside. Funniest damn thing I ever saw.

So, tell the guy the Ronson treatment is the only thing that makes sense for bike he has, and if he wants you'll be happy to administer it. Otherwise, come get his pile out of your garage...

 

[chuck hahn]

DO NOT remove the plenum when removing carbs. Do it and youll know why you leave them bolted up.

 

[Guest]

DO NOT remove the plenum when removing carbs. Do it and youll know why you leave them bolted up.

Agreed, and 700 Magna's aren't worth $hit to start with, not worth much at all. In other words, you could sink $500 plus into this turd and still be over your head, you can buy a pretty darn nice one in the $500-$1000 dollar range. Hell, the V65 Magnas (which I have restored 50 of), have lost value over the past 3 or 4 years. Not worth messing with, a losing proposition any way you look at it, and heck. You aren't going to sell many parts off of it either. Maybe the tank and side covers and maybe the mufflers if they are mint, nothing else will sell quickly if ever.

 

[robertbarr]

you can buy a pretty darn nice one in the $500-$1000 dollar range. Hell, the V65 Magnas (which I have restored 50 of), have lost value over the past 3 or 4 years. Not worth messing with, a losing proposition any way you look at it, and heck.

Interesting. There was a period of time when I had a pretty serious itch for a V65 Sabre, the 1984 vintage, and they'll still turn my head. I suppose I'm glad I didn't learn this first-hand. In my case, I kept hearing about trans problems -- don't recall the exact malfunction. That's mainly what kept me from buying one.