85 venture dies at 5200

[85 venture]

Had my 25K miles, 85 venture for about 6 years, it never ran right - it would cut out at 6200 rpm, spit, sputter at full throttle on excelleration, I know it needed to have the carbs cleaned but I didn't want to spend the money. I just forked out over 200 bucks to clean the carbs, new plugs, wires, now it hesitates and doesn't go over 5200 rpms at full throttle. If I don't have it wide open I can reach redline in 1st. 2nd gear tops out at about 4500 rpm. Mechanic claims it is not the carbs mainly because it goes great until 5200 rpms ? I'm frustrated - I don't know how to fix the bike myself yet - IF it was a carb problem at 6200, so why not a carb problem at 5200 ?? I've already paid the bill, don't want to invest more money. I feel like I should have just left it alone if this is as good as it gets. Any ideas ?

[Yammer Dan]

Sea-Foam several times. I would do a strong soak first and then run it through several tanks.

[V7Goose]

Whoever you paid to work on those carbs was either a fool or a crook, and probably both. I say he is a crook because he took your money and won't stand by his work. Unless you just took the carbs off yourself and took them to somebody, there is no excuse for any qualified mechanic to work on them and then tell you what he did. If you took the bike in and told him you wanted the symptoms fixed (instead of just saying you wanted the carbs cleaned), then it was his responsibility to find the problem. Frankly, I wouldn't trust someone like that to ever touch my machine.

 

But unfortunately, you still have the problem, and you are going to have to pay somebody to find and fix it. What you describe absolutely CAN be caused by the carbs. Partially plugged main jets will do it, as will holes in the diaphragms. And it doesn't have to be just the jets that are plugged - if there is old varnish built up in any of the passages, partially clogging them, that will work just like dirty jets. Another common cause of sputtering at WOT and high RPM is float levels set too low or dirty fuel filter (including clogged intake screens in the tank) - both of those will cause the engine to starve for gas when it is trying to suck it real fast.

 

Other possible causes are obstructed air intake, extra dirty air filters, or bad TCI module. I would have listed plugs and plug wires too, but you said you just replaced those. Good luck getting it sorted out. I'd start by finding a qualified mechanic based on the recommendation of others who have first hand experience with the person.

Goose

[Venturous Randy]

Could it be a dirty fuel filter that will only supply a limited amount of fuel? It could be some rust in the fuel tank with it having so few miles on it in 26 years that could be causing problems.

It would be good if you could plug up a good TCI and see how it runs with it.

RandyA

[dingy]

One other screen is in the fuel intake port on each carb, it is called a filter net. This should be blown out if the needle valve seat is not replaced. It should be blown from the inside out so dirt doesn't get forced into screen more.

 

Gary

[85 venture]

I replaced the fuel filter last night - No change, still acts up.

[MiCarl]

Whoever you paid to work on those carbs was either a fool or a crook, and probably both. I say he is a crook because he took your money and won't stand by his work. Unless you just took the carbs off yourself and took them to somebody, there is no excuse for any qualified mechanic to work on them and then tell you what he did. If you took the bike in and told him you wanted the symptoms fixed (instead of just saying you wanted the carbs cleaned), then it was his responsibility to find the problem. Frankly, I wouldn't trust someone like that to ever touch my machine.

 

But unfortunately, you still have the problem, and you are going to have to pay somebody to find and fix it. What you describe absolutely CAN be caused by the carbs. Partially plugged main jets will do it, as will holes in the diaphragms. And it doesn't have to be just the jets that are plugged - if there is old varnish built up in any of the passages, partially clogging them, that will work just like dirty jets. Another common cause of sputtering at WOT and high RPM is float levels set too low or dirty fuel filter (including clogged intake screens in the tank) - both of those will cause the engine to starve for gas when it is trying to suck it real fast.

 

Other possible causes are obstructed air intake, extra dirty air filters, or bad TCI module. I would have listed plugs and plug wires too, but you said you just replaced those. Good luck getting it sorted out. I'd start by finding a qualified mechanic based on the recommendation of others who have first hand experience with the person.

Goose

 

Good thoughts. I will disagree on one point: If you can get it to red line at part throttle (even in neutral) it's probably not ignition related.

 

I'll add that a tight valve could also be your culprit.

 

The safe money though says it's fuel system, which includes carburetors.

 

$200 is way too low for the work that is supposed to have been done. It's very unlikely it was done properly.

[93 venture]

I have seen these things run like crap if the air filter box is not hooked back up right,or someone has drilled extra holes in the lid to get more air to them.all the rubber boots have to be seal up to each carb.

[V7Goose]

Good thoughts. I will disagree on one point: If you can get it to red line at part throttle (even in neutral) it's probably not ignition related.

You said "probably" not ignition related, so I can't jump on you too hard, but I'm gonna disagree with your disagreement anyway. The OP specifically used exact RPM numbers in his post - not "around" 5200, but "at" 5200. If he really meant to be that specific, then I think it strongly implicates the ignition system on an engine with a TCI. I do not know if the 1st gens have a fixed pickup coil and electronic ignition advance like the 2nd gens do, but if so, then that REALLY opens the possibility of a bad TPS or TCI.

 

Actually, the more I think about it, I think the throttle position sensor (if there is one on that bike) is a prime suspect right now. That even fits with the idea that the carbs were cleaned, thus the idle point on the throttle was probably set lower to compensate for more fuel through the pilot circuits, and that would change the exact RPM point for a throttle position issue with the advance curve in the TCI.

Goose

[bkuhr]

You said "probably" not ignition related, so I can't jump on you too hard, but I'm gonna disagree with your disagreement anyway. The OP specifically used exact RPM numbers in his post - not "around" 5200, but "at" 5200. If he really meant to be that specific, then I think it strongly implicates the ignition system on an engine with a TCI. I do not know if the 1st gens have a fixed pickup coil and electronic ignition advance like the 2nd gens do, but if so, then that REALLY opens the possibility of a bad TPS or TCI.

 

Actually, the more I think about it, I think the throttle position sensor (if there is one on that bike) is a prime suspect right now. That even fits with the idea that the carbs were cleaned, thus the idle point on the throttle was probably set lower to compensate for more fuel through the pilot circuits, and that would change the exact RPM point for a throttle position issue with the advance curve in the TCI.

Goose

 

I dont think the 85 have a TPS, but does have a vacum sensor used by the TCI for ignition advance. Going along with your thinking, I would first make sure someone has not placed 83 carbs on an 85. Vac port below butterfly on 83 #2, above butterfly on 85 #2.

 

Second, I think I would disconnect vac hose and plug port and see if failure to reach afore mentioned RPM's. If so then vac sensor is advancing when installed, if not then a possible problem with vac sensor/vac tubing. As Op stated he can reach redline in first, so sound to me like ign is advancing, and fuel/air mix is not keeping up.

 

In my opinon, I would suspect an air leak, maybe the bottom boots folded during carb reinstall. Maybe sync plug missing/worn. Would suggest spray carb cleaner.... under carbs during idle listening for rpm change, if so pinpoint leak with carb cleaner. Keep fire ext nearby.

[MiCarl]

No TPS on 1st gen.

 

My reasoning is that he can get it to go past 5200 rpm with low load, it just tops out on him when he's into the throttle. Only ignition component that "sees" anything about load is the pressure sensor (who's proper name is currently escaping me). Coils, Pick up coils (4 of them) ignition wires etc don't "know" what the throttle position or load is.

 

Spark plugs will see the higher pressures and temperatures and the TCI gets an input from the pressure sensor so any of these might be the problem but they'd be low on my list given the symptoms.

 

Since the float bowls store some fuel problems with the vents, lines, filter etc. usually exhibit as stumbling after the throttle is applied. In other words, it initially gets going but then falls down. So I wouldn't start there either.

 

Air delivery is a likely cause. I'd look really closely at the filter, air box and carburetor-air box joints first. Need to get that stuff out to get to the carbs anyhow.

 

Usually gummed up/dirty carburetors exhibit problems at idle first. I did recently have a Virago in the shop that had high speed carburetor issues. Apparently someone had previously cleaned the carbs but couldn't get one main jet out. The needle jet (emulsion tube) behind that jet was all plugged up.

 

If I were doing this job and got past the air box I'd be looking very closely at the needle jets and the slides (sticking?) and slide diaphragms.

[MiCarl]

As Op stated he can reach redline in first, so sound to me like ign is advancing, and fuel/air mix is not keeping up.

 

Your post got me thinking.......

 

You can get an engine to rev under low/no load without normal spark advance. That would be a possibility. When that happens the intake noise makes a rather deep "BWAAAA" sound. I really can't describe it any better but once you've heard it you never forget.

 

Of course if the advance was failing on only some of the cylinders the sound might not be that noticeable......

[dingy]

$200 is way too low for the work that is supposed to have been done. It's very unlikely it was done properly.

A complete rebuild is around $600 for parts only in carbs.

 

A minimum amount of around $140 which would consist of the 4 basic carb kits for about $100, 4 pilot jets about $20, 4 enrichment gaskets about $20.

 

Chances are slim that the diaphragms are good in an 85, about $80.

 

This is parts only, if you pulled carbs & took them to someone, at minimum, there has to be 4 hours labor, with someone that is good at this, may be more.

 

Picture below shows what a disassembled set of carbs looks like, many parts.

 

Gary

[GaryZ]

A bad Vacuum Sensor

. . . would not allow ignition advance causing the engine to not pull RPM with a load.

Possible Test = Rev engine from idle, slow to rev

 

If all Diaphragms are split open

. . .would not allow engine to run up past 4 - 5k

Possible Test = remove air cleaner cover and see if slides are moving equally when throttle twisted

 

No air cleaner; clogged fuel filter

. . . allows mixture to lean out to fuel starvation

 

 

 

My 2 cents

Edited July 12, 2011 by GaryZ

[Yammer Dan]

Diaphragms would have to be totaled. Lot of ways to go but I would still be looking at starving for fuel some way. Something still plugged.

Fuel filter? Could be.

I haven't had any of the air box problems that seem so common to these things but worth looking at.

[85 venture]

---

Initially - Mechanic thought it might have something to do with restricted exhaust - like a mouse got in and filled the pipe equalizer, under the kick stand, with Fiberglass insulation. Sounds empty, appears to be lots of air coming out, plug one side the other side increases. If this was the case, I think, it wouldn't red line without load ? ? I CAN red line it w/out load

 

I havn't gone back yet - I wanted to have lots of ideas from you guys, thanks, I'll check in with him in a couple of days........... thanks again, I'll keep you posted.

[Ndiaz]

So, your Venture died at 5200. That's one helluvan old Venture!

 

Nick Diaz

Middletown, MD

[MiCarl]

Could still be restricted exhaust. The exhaust has to clear way more air when the engine is loaded vs. revving without a load.

 

This is the same reason it could be the intake side as well. A loaded engine at 5200rpm is pumping a lot more air than an unloaded one.

[85 venture]

A bad Vacuum Sensor

. . . would not allow ignition advance causing the engine to not pull RPM with a load.

Possible Test = Rev engine from idle, slow to rev

 

My 2 cents

 

Yes I can red line my bike without a load.

Vacuum Sensor, same as Boost Sensor, under the battery Box ? ** So just remove the battery box and it's under there ??

This is something I could buy and try - wouldn't cost me a ton of money. Is the sensor the same for all the years ?

[V7Goose]

Make sure you check the timing advance before you tear into anything. Even if it is not adjustable (the 2nd gens are not), it is very easy to check and will mostly rule out any possibility of an ignition problem. Note that the shop manual only tell you to check it at idle, but you are particularly interested in seeing if the timing advances as you open the throttle. Your ignition timing is controlled by a "pressure sensor" from an intake vacuum port, so if you have a cracked or cut vacuum hose there, that could be your problem. Looks pretty easy to check from a quick scan of the shop manual. If you do not have a timing light, most auto parts stores these days will actually loan you one.

Goose

[GaryZ]

Yes I can red line my bike without a load.

Vacuum Sensor, same as Boost Sensor, under the battery Box ? ** So just remove the battery box and it's under there ??

This is something I could buy and try - wouldn't cost me a ton of money. Is the sensor the same for all the years ?

 

Yes, vacuum sensor = boost sensor.

I am not sure where the thing is located.

And, if there is a problem I would also be looking for a vacuum leak.

As Goose said, it's best checked with a timing light.

Timing should advance as RPM increases.

 

[Squidley]

The boost sensor is under the battery box area, on the left side of the bike (when sitting on it) right next to the TCI. You can check it while it's in position as it sucks to get it out. It operates off #2 cylinders vacuum (left front) and electronically tells the TCI to advance the timing when throttle is applied due to the vacuum fluxuation. You can take the hose off the carb intake and try to pull a vacuum on it with a mighty vac. If it holds vacuum then that portion of it is working, if it wont hold a vac it's absolutely bad. I just replaced one on my '86 although I didn't have the issue you are having as mine would still ramp up to redline without the boost sensor working

[dingy]

Another check for the boost sensor is to disconnect hose from the L.F. carb intake. While it is running at a steady rpm's, apply vacuum to the hose that was disconnected. The RPMs should change some if it is working. You can use a mighty vac or do it the old fashioned way and suck on it, I mean this in a good way.

 

I don't think a bad boost sensor will keep it from revving up though, it will certainly hurt overall performance, but not cripple it like this.

 

Check all your cylinders & verify they are heating up at exhaust flange. These things will run decent on three cylinders, but you might be down to two.

 

Since plug wires were replaced, check and verify they haven't been swapped. This would be at coil end, coils are positioned in same pattern as cylinders.

 

Gary

[MiCarl]

When you check for timing advance you need to check the timing of all four coils. I've seen TCIs where some advanced and some didn't.

 

I suspect the boost sensor tells the TCI to advance the timing a bit more when the intake pressure is high (light load). I cannot imagine it could cause the engine to fall on its face.

 

Older Goldwings used a vacuum advance on the pick up coil plate to accomplish the same thing. It's quite common to just disconnect them when the actuator starts to leak.

[V7Goose]

When you check for timing advance you need to check the timing of all four coils. I've seen TCIs where some advanced and some didn't.

THAT's interesting - I would have never guessed that. But it just highlights how many strange things you can find with a TCI. Simple lack of advance is not going to cause misfire or sputtering, just loss of power, but if the TCI is getting an erratic or incorrect timing signal at a particular RPM (or vacuum level, in this case), then it can go all wonky with unpredictable results.

Goose