Vs800 surging.

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skunkle121
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Vs800 surging.

Post by skunkle121 »

I seem to be having an issue with surging on an 95 vs800. Surging is about the only way I know how to describe it. It seems to be to pretty consistant when really getting on the throttle at say like a highway on ramp. With costant throttle the bike seems to lose power momentarily then gets it right back and this happens repeatedly till up to speed. Like throwing a switch off then on off then on and only seems to really manifest if given a decent amount of throttle. I cant feel it doing it just meandering around town. Its hard to describe.

Some back story. This is my step fathers bike. He rode in his youth and the bug bit him again so I found him a cheap used vs800. Last summer bike ran pretty good. He had surgery that took him off bike for several months. It probably sat for 6 to 8 months time. After throwing another battery in it and firing it up it ran terribly. Skipping popping and had very little power like it was running on mostly one cylinder. I dreaded it but I pulled the carbs to clean them and they fought me every step of the way out and back in. I cleaned them after dealing with several stripped screws on the carbs. I cleaned the jets and emulsion tubes and put in new pilot/idle screws because one was pretty sticky and the head was pretty chewed up. So I replaced both. I also ordered throttle cables because the rear throttle cable got messed up while trying to get carbs back in at the end where it connects to the rear carb. The shealthing like pulled from the end of cable.

So after much fighting with the carbs I got them back in attempted a carb sync using the cheap blue vacuum gauges that are all over ebay and Amazon. I warmed up the bike and put a temp tach/hour meter on it to get idle about 1000rpm and set the idle sync. It seemed to be pretty close to start with. The throttle sync however was way off. I fought with the adjustment as well. I wish it wasnt so close to the frame. So with the carbs synced at idle of 1000 and throttle done about 2500 2600 the bike is running like its former self now. Much more power idle seems pretty steady but this surging now is really puzzling me. Anyone have any ideas? Or a direction I should be looking. I feel like Im 90 percent there after all this work I am hoping maybe I am just missing something simple.

Lechy
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Re: Vs800 surging.

Post by Lechy »

Bloody Gremlins like this are hard to track down, more so with not being able to be hands on.
So, start off with the simple stuff:
How are the air filters? did you get the boots from the filters to carbs correctly seated, they are a real bitch at times. Did you seat the O-rings correctly from carbs to heads? Did you check the carb diaphragms for pin holes and correct seating ( i don't know how much effect this has but on the front carb the diaphragm cover has a small detente in it, this lines up with the small hole on the carb rim). Did you seat the diaphragm springs correctly, the long one to the front carb, the short one to the rear. Did you re-adjust the AF screws after synch?
Remove both battery cables, give all facing surfaces a good clean, check the earth lead for swellings or stiff spots, if found make up a new one and replace it, fit star washers on the battery fittings ( the reason is that some batteries have fitting screws that are about 1 thread too long and they bottom out before making a secure contact).

Take her out for a good hard spanking and get back to us with your findings.

Herb will probably chip in with a couple of more ideas I may have missed.
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skunkle121
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Re: Vs800 surging.

Post by skunkle121 »

Thanks very much for the quick reply with all those ideas.

Starting with the air filters, they are both brand new when bike was purchased I changed filters, plugs, engine oil and gear oil for shaft drive. I believe I got the boots seated correctly. They are an absolute nightmare to get back on aren't they. I guess after the rain maybe tom I can double check with some carb cleaner or something spray around and see if I get any idle changes eh?

I had the diaphragms out and they seems to look ok with no visible holes in each and I noticed that detent that you are referring to. I didn't realize the front and back carb had different length springs I thought I was careful keeping parts separated between the carbs I dont think I would have switched them but anything is possible I suppose. I could prob check without pulling carbs again right? As for the AF screws yes I did mess with them a bit. A bit before sync and I think I messed with them for a final tweak after to get rid of popping in one cylinder on deceleration. I will check the battery terminals tom as well. If I remember correctly with the new battery I had to put washers in at least one side I think to get the wires tight to the posts.

After what has seemed like endless hours of wrenching and cussing to get carbs out, stripped out screws free, everything clean, put back in I dread the idea of maybe they will have to come back out. I really need to go over everything again I possibly can before to make certain I haven't missed anything. Thanks for the ideas Lechy. Tomorrow I will look again with fresh eyes and get a better grip on when the surging occurs. If its more related to certain speeds or what percent of throttle grip or what have you. To me when I rode it seemed to be when I was on the power maybe 50 percent or more and the surging is quick. Its like no power/normal no power/normal once or twice a sec. Anyway thanks again. Ill keep digging.

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Re: Vs800 surging.

Post by Forge »

Good luck and keep us posted.
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WintrSol
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Re: Vs800 surging.

Post by WintrSol »

Is the tank nearly full when this happens?

Electrical problems can behave like fueling problems, so the wiring check suggestions should be followed; also, you may want to re-seat all the fuses, and check the run/stop switch. That switch has been known to lose spring pressure with age, and become intermittent; a good cleaning couldn't hurt, just look out for bounding parts.
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MarineScott
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Re: Vs800 surging.

Post by MarineScott »

Check your battery, make sure it is up to par.

skunkle121
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Re: Vs800 surging.

Post by skunkle121 »

So an update for everyone. My stepfather decided to take bike out today for about 45 min or so. He said he filled the tank put saddlebags back on it and went out for a jaunt. He told me the bike wasn't displaying any surging that he could feel. I was very surprised to hear this because to me it was very obvious, although I am a bit harder on the throttle than he is. He did tell me though that there was quite a bit of popping on deceleration. I came by after work with no time to mess with bike outside a few min drive myself.

So I take the bike out myself and once warmed up hit a few onramps where I can get up to speed quick with copious amounts of throttle and you know what....I felt no surging anymore but deceleration pop can be bad at times. I'm really, really confused more than I was Sunday now. Sunday I messed with the AF screws when bike was warm and eliminated any popping and had the surge issues. Today, nothing changed outside topping off the tank and its back to popping with no really noticeable surging. I feel like I'm chasing my tail in circles.

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WintrSol
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Re: Vs800 surging.

Post by WintrSol »

You may have bits of small stuff passing through the jets, like the fuel line crumbling on the inside.
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Lechy
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Re: Vs800 surging.

Post by Lechy »

Like I said. take her out and give her a real good spanking to blow the cobwebs away then re adjust the AF settings.
I put inline paper filters on mine, the ethanol gas destroyed the cement inside holding the filter to the casing causing bits to get through into the carbs. the float valve filter caught most but not all of the fine debris causing the rear carb to act up quite a bit. I disposes of the filter and replaced the fuel lines, took her out and hammered the dog crap out of her, working just fine now.

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skunkle121
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Re: Vs800 surging.

Post by skunkle121 »

Went over to step dads and took her out for a bit before work. Popping pretty good so I let it warm up while driving around the neighborhood. I then got off and turned in the AF screws to lightly seated and worked my way out to the strongest idle for both cylinders. Pop is now gone and no longer seems to surge either. Only issue left I think is the choke cable.

I have noticed that the choke cable has about no effect on rising the idle on the first 75% or 80% of the choke pull. Its all in the last little bit of the choke pull does the rpms start to move up like it should. That is no biggie as far as I'm concerned but the issue lies in the cable pulling itself back in. You pretty much have to pull it pretty hard and hold it there to get the bike warmed up on initial start.

skunkle121
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Re: Vs800 surging.

Post by skunkle121 »

So I'm starting to think this darn bike is cursed. Step father took bike out tonight several hours after I rode it with no exhaust popping at all. He said it was popping on him a bit but not bad and the speedometer decided to stop working. I think I might just have to set this bike on fire :hellfire: :bang: :bang: :bang:

Lechy
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Re: Vs800 surging.

Post by Lechy »

Have you considered an exorcism?
The choke is not a conventional choke as it does not restrict the intake to enrichen the mix, it opens a small fuel enrichment valve in the slow running circuit. The cable lock is and always was a useless piece of crap, some folks use a small plastic clothes peg to keep it open.
Check the header manifold bolts. if they have come loose you could be drawing air into the headers causing a pop.

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skunkle121
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Re: Vs800 surging.

Post by skunkle121 »

Nice tips once again. I think with the bike being so old I really should consider breaking down and ordering new fuel lines throughout and order and a new speedo cable. Today when I had it out with no popping and no surging it was really running quite good and man it likes the higher revs. For a cruiser it really seems to haul pretty good. I am a sportbike guy but can really see the appeal of this bike.

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Re: Vs800 surging.

Post by WintrSol »

The speedo drive unit should point towards the head pipe, where it exits the cylinder, to reduce the curve in the cable; the tighter the curve, the sooner the cable fails. Also, sometimes you think you have the cable seated in the drive unit, but don't really; it works for a while, then jumps around, then stops - personal experience on this one :bonk:.
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