Bike is still ruining my day.

Well it was 82 degrees today so I went on the longest ride I've been able to for quite a few months. Last season had some problems and shelled out a bunch of money to hopefully alleviate those problems, but it seems a few are sticking with me.

Was having problems with bogging down at low rpm and minor surging at higher rpm once the bike got hot after riding a while.
Carbs were cleaned/synced and given new float needles and seats (supposedly.) I was getting gas in my oil so I payed a shop about $300 for this and an oil change.

Now only a few short months later I have the same symptoms. After bike gets nice and hot, when starting from a stop it starts to die down unless I give it a lot of gas (in which case it then proceeds to quickly rev up after it stops trying to die). And at highway/country road speeds after its hot enough I will feel what seems to be a very slight surging. And throttle response seems very shitty but I'm not an expert on old carbureted bikes. I'm wondering if the mechanics were terrible or if I might have a more serious problem heading my way.
Any thoughts? I think I'm up for a new set of Iridium spark plugs but that won't solve the oil problem.
Also I run 93 octane if that makes any difference.

 

If you let fuel sit in the carbs for months during storage, your carbs are maybe clogged with goo.

Do you see black smoke from exhaust ? Is your air filter clean ??

Symptoms suggest either leaky needle/seat or floats set wrong. If your tank is rusty, flakes may be lodged on the needle, preventing it from closing properly.

You should be able to locate the problem by inspecting plugs.

 

Well, the bike was winterized for the most part and any time it was remotely warm i would run it, so Im pretty sure the problem never actually went away after the carbs were done.
I don't really see any smoke but any time I run my bike it smells like a non environmentally friendly classic car (pretty strong exhaust smell) so i think it might be running rich.
Air filter is a k&n cloth filter still cleaned and oiled.
But as for the plugs last time I checked I think the metal was pretty black butthe porcelain there wasn't much color.

I think I'll tear the carbs open and see if I can't get her fixed, it's just the whole bogging down while hot problem is what got me stranded on a busy street before this winter.

 

You could take it to someone that has an exhaust gas analyzer.

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What squirrelman said.

Did the bike ever run good without those problems? Did you buy it that way?

Just wondering what the history of the carbs are. Were they "rebuilt" at some time.? I just finished a set of carbs for a 83 Goldwing. The owner bought rebuild kits from NAPCO of Japan. I guess they make kits for a lot of bikes.

What I found was the needles supplied w/kit are .005 larger in dia. Which would make the bike run leaner overall. The Idle/cruise jet-emulsion tube holes were way to small. Would be rich at idle/cruise. I enlarged them to stock size. Kit came w/two sets of jets. One the correct size the other smaller. Needle and seats were stock size. If they were rebuilt and nobody checked the new parts. It then becomes a cluster f@#k.

Without knowing if you have stock parts in the carbs it's going to be hard to diagnose and fix your problem. Surging at cruise usually means it's lean at the throttle opening. Lack of power, sluggishness up top usually means to rich. Someone raised needles? Unless it's super lean, then you should hear pinging if that lean. Your richness at idle could be just bad pilot screw adjustment.

So tell us about the carb history, please.

 

The carb history as of now is a mystery to me. I bought it with 11,000 original miles in about the same running condition as it is now. It seems to run and drive fine until it gets really warmed up.

 

Only 11k miles I would assume,yea I know, that the carbs are all stock and no after market parts. Stock paper filter I assume, again.

Then what squirrel mentions is on top of the list to do first. Take a look in side your tank. Super clean or so-so? Take the carbs off and inspect them for debris and float specs are correct and pilot screws are good and circuit is open.. Just for starters. Also make sure the main and idle/cruise jet/emulsifiers are clean.

 

Well the tank isn't perfect but all I can see is some slight rust color and spots but doesn't seem at all serious enough for debris to get through. Besides I have an inline filter and I see absolutely nothing in it.
That's not to say I won't take the tank off and reseal it.
Filter as I said is a NOS 80's K&N cloth reusable filter that I oiled and put in a couple hundred miles ago.
Talked to the shop and they seem to think it might be a fuel pump/relay or something related to the carbs being dirty. He said it might also be a tank venting issue. He suggests going to a gravity feed without a pump and cleaning the carbs to see how things change.

 

I missed the filter part. Most K&N filters I've used or installed for others require a little work to richen carbs at cruise and wot. That very well could explain your surging at cruise. You can check this by raising your needles .020-.040" with tiny .020 thick washers from hardware store. some needed different jetting and different needles which I raised also to get what the motor wanted. This is on my 83 and a couple of others.

Tank venting is not the problem with the richness. Inspect the carbs like what was mentioned before, then we can go from there.

 

Hello rpierce.. If you're doing the work yourself, disregard the following. I put my 94 on a dyno after fitting a K&N filter and a staintune exhaust to see if the carbs needed adjustment(they didn't) and as a benchmark, as I'd just bought the bike. It's a realtime visual tuning aid that identifies most problems.

 

If I'm running lean will it give me shitty throttle response too? I'm not sure if its surging due to lean condition or if it might be fuel starvation?
Also, if it is lean and I shim the needles will that take care of the hesitation at low rpm from a stop? That's the part that really bothers me because I think it's going to die and leave me stranded until it cools down.

 

Fuel starvation is a lean condition. Think about it. Take the carbs off and check what was mentioned before first. Your problems can be anything at this point. But before you do that. Check all the pilot screws and see how far they are turned out.

 

Sorry about that I didn't word that quite right. I meant lean condition from carbs/pilot screws or from petcock/etc low fuel flow

 

Well upon further inspection of the oil it doesn't seem to be ruined with gas. It just seemed extremely thin when it was hot and i feared that it was contaminated.
But I am still concerned about the running problems so I'm going to check the pilot screws.
Is it unanimous that both surging at cruise rpm and bogging down at low rpm once hot are caused by running lean? I would imagine it would do this at any temperature if that were te case.

 

Here's some pictures of the fuel pump and wiring of it. Looks like someone put on a Mitsubishi fuel pump and changed the wiring for it? FSM shows 3 wires on the connector and this one is only 2 wires

 

Checked the plugs and pilot screws today. Plugs looked light chocolate brown, all pilot screws were around 3 1/4 turns out.

Toying with the idea it might be electrical since it happens when there's a lot of heat buildup? Maybe heat makes the fuel pump mess up a little bit?

 

Can you take a picture of one of the plugs?

The fuel pump being different and being spliced in is a bit worrying....the manual has a way of testing the fuel pump flow.

Those screws seem like they are out quite a bit.

I'm having similar idle/low rpm issues that I'm unsure of the reason. I don't know if its a lean or rich issue.

 

Well in the FSM it says the default pilot screw setting is 2 1/2 turns out for 750 and 3 turns out for the 700.

I'll get a picture of the plugs up later today.

I'm pretty sure I'm going to sell the bike due to the fact I don't have a car. When I have enough money for a full restoration or enough to buy a fully restored bike, I'll be back to you guys with a VFkR.

 

Here's one of the plugs, they all look about the same color

Hopefully its readable because it hasn't been run very much since I took a wire brush to the metal of it.

 

The plug looks good.

I know how you feel...I've been having non-stop problems with my VFR since I got it...and even after it's running right I'll still have a shit load of work to do.