Carb synch problem

[mralex714]

Well, if not the TCI, then as suggested replace the plug caps, or for that matter all the wires and caps! I would also look at the coil secondary inside where the plug wire inserts for the dreaded green crud!! Also, when you replace the plug wires after looking do not forget to cut off about a 1/4" so the tang in the coil makes a good connection with the wire and make sure you have the rubber o ring on the coil wire as well so the wire will not vibrate out...

 

I did trim the wires, but I will change the later. I am also in the process of changing the coils. If this dosen't fix my problem the I'll pull the carbs again

[van avery]

I did not see that you sprayed starter fluid etc around the carb and intake boots to check for vacuum leaks. There are orings under the bottom carb boots that caused problems on my 87.

[yamagrl]

Got another issue. The tach, temp and volt gauges all quit working. Where is their common failure point?

 

 

Temp and volts go through the 9 pin connector in the dash. And the tach goes through the 4 pin connector. There may be other things that are effected

 

Edited December 13, 2016 by yamagrl

[yamagrl]

I'm also wondering if the exhaust is plugged. Make sure you have good exhaust flow. These old exhaust chambers (collector) and mufflers can can come apart inside and I'm sure could cause a restriction.

[mralex714]

I did not see that you sprayed starter fluid etc around the carb and intake boots to check for vacuum leaks. There are orings under the bottom carb boots that caused problems on my 87.

 

Yes I did do this with no change in RPMs.

[garyS-NJ]

I would think with 2 & 1/8 to 2 & 1/4 turns on mixture screws and a bench sync and cleaned carbs with fluttery sliders and no vacuum leaks and a good supply of clean fuel (feed the carbs direct for now) & no water in the bowls (drain periodically to make. Sure no float stick and clean fuel in carbs until you are sure) that your problem is spark. Put a known good ignition in there and test the resistance of primary, secondary, and pick ups. And clean reseat the connector going to the pickups. And get a new set of plugs in there and measure resistance in the plug caps else replace them.. I don't think the coil wires go bad but the plug caps do. Did the bike die when you lost the gauges?

 

Sent from my VS987 using Tapatalk

[snyper316]

I would think with 2 & 1/8 to 2 & 1/4 turns on mixture screws and a bench sync and cleaned carbs with fluttery sliders and no vacuum leaks and a good supply of clean fuel (feed the carbs direct for now) & no water in the bowls (drain periodically to make. Sure no float stick and clean fuel in carbs until you are sure) that your problem is spark. Put a known good ignition in there and test the resistance of primary, secondary, and pick ups. And clean reseat the connector going to the pickups. And get a new set of plugs in there and measure resistance in the plug caps else replace them.. I don't think the coil wires go bad but the plug caps do. Did the bike die when you lost the gauges?

 

Sent from my VS987 using Tapatalk

 

I think the wires would depend on whether the bike is in Humid area, Mine went bad With corrosion cut them open after I went ahead and replaced them and towards the middle the wire was so green It was a wonder it even fired.

[garyS-NJ]

The copper wires oxidize green and yes that's a great point because conduction is on the surface and oxidation wouldn't conduct like clean copper. Over time oxidation does have a way of creeping up an insulated wire but the wire resistance is way low compared to the secondary winding. I wonder if a wire could oxidize that bad... The connection to plug cap definitely goes bad.

 

Sent from my VS987 using Tapatalk

[snyper316]

Don't know but over the past year I have a mag light that the batteries have literally welded with corrosion. My spices get hard from a month or to. I live in very humid area I guess

 

Living life one curve after the other. Vroom scooting, thru the countryside.

[mralex714]

I did a compression check today and got 120 psi on each cylinder. Should I continue or call this a loss?

[MiCarl]

I did a compression check today and got 120 psi on each cylinder. Should I continue or call this a loss?

 

I wouldn't give up. I think It should run better than it is with even only 120PSI compression. If it's been sitting rings can stick in their grooves and valves can get some surface rust. After it runs awhile the compression might come up. Also, with them all being the same and low I'd wonder if the compression gauge was reading correctly.

 

From my first post:

.....

2) Compression test. Spec is somewhere in the range of 170 but if they're above 120 you probably have another problem.

...

 

At 120PSI you might not get the full 10" of vacuum. Until you get to 8 or 9 though I'd still be looking for other issues.

[mralex714]

Now the fuel pump is not working. Which one is the fuel pump relay? Tomorrow I will connect the pump directly to the battery to be sure

[jasonm.]

2.5 turns is the average of my carbs after total go thru. My richness was need of NEW floats and float needles. Setting the floats is NOT simple. Should be done with the left and right pair separated. Many do it quickly and not "leveling" the carbs on the bench. You have the manual I hope... it's a process....to get it perfect. ... and lots of patience.

[Matt_P]

Im vary new to Ventures and motorcycles in general, is it possible to replace the carbs with EFI?

[bongobobny]

If you want to spend big bucks you can...

 

http://roadstercycle.com/yamaha_vmax_fuel_injector_cv_car.htm

[Flyinfool]

While there is nothing that I am aware of that is in the form of a plug and play kit, it certainly can be done.

There is the method that Bob mentioned above.

OR

There are several people making a manifold to put a single automotive carb on our engines, I do not see why you could not put a small automotive TBI on that same manifold.

 

Either way you still need to come up with all of the sensors and computer to make it all work and may need to generate your own fuel maps. IF you were to go with something like the Micro Squirt system for the EFI, it also can handle the job of ignition to replace your ancient one you have on the bike now, it will even handle going to COP if you were so inclined.

 

Dang it, I almost talked myself into doing this again....................

[BlueSky]

I did a compression check today and got 120 psi on each cylinder. Should I continue or call this a loss?

 

I realize it's been a few days since you posted this. Did you have the throttle plates open when you checked the compression? That may make a difference.

[mralex714]

I realize it's been a few days since you posted this. Did you have the throttle plates open when you checked the compression? That may make a difference.

 

Yes I did.

[CaseyJ955]

I realize it's been a few days since you posted this. Did you have the throttle plates open when you checked the compression? That may make a difference.

 

I have had less expensive gauges that were somewhat south accurate. Any muck or any flaw on the hose or o-ring can skew numbers also. 120 on all four pots is pretty damn fine consistency indeed. In my experience it would be strange (although not unheard of) for a tired engine to have so little variance between cylinders. I hope the issue is something less menacing.

[mralex714]

I have had less expensive gauges that were somewhat south accurate. Any muck or any flaw on the hose or o-ring can skew numbers also. 120 on all four pots is pretty damn fine consistency indeed. In my experience it would be strange (although not unheard of) for a tired engine to have so little variance between cylinders. I hope the issue is something less menacing.

 

I'm using a gauge I bought from Harbor Freight. I will borrow one from a parts store that loans tools and see if I get different readings.

I will also be going thru the carbs again. The left front cylinder is very slow heating up and never as high as the other 3.

[CaseyJ955]

I'm using a gauge I bought from Harbor Freight. I will borrow one from a parts store that loans tools and see if I get different readings.

I will also be going thru the carbs again. The left front cylinder is very slow heating up and never as high as the other 3.

. I wonder how the mew readings will be, im guessing it wont be dramatically different. If one cyl is taking its sweet time reaching op temp I wonder if its firing at all. The Yammy v4 runs deceptively well on only 3 lungs. Hows the ignition system looking, plug caps and HT leads going into the coils. When I found a bad coil on my max I used the mom-and-dad-are-first-cousins spit sizzle test on each downpipe to find one not pulling its weight. I think the decades old ign sys is at least as vulnerable as the carbs and really easy to rule out. I hope the troubleshooting nets something. I might have missed this but was the engine warm when comp tested?

[BlueSky]

I'm using a gauge I bought from Harbor Freight. I will borrow one from a parts store that loans tools and see if I get different readings.

I will also be going thru the carbs again. The left front cylinder is very slow heating up and never as high as the other 3.

 

When mine was running ragged, I removed about 3/4" from the end of one of the spark plug wires and screwed the cap back on. Then measuring the exhaust headers temps with an infrared themometer, that cylinders exhaust was much hotter than the others. So, make sure there is no corrosion on or in the wires at the plugs and at the coils, TCI, etc.

[yamagrl]

I'm using a gauge I bought from Harbor Freight. I will borrow one from a parts store that loans tools and see if I get different readings.

I will also be going thru the carbs again. The left front cylinder is very slow heating up and never as high as the other 3.

I have a Morgan Carbtune and a near complete 86 parts bike and even offer assistance... that is if you don't mind having a "girl wrench" help out.

 

Edited January 5, 2017 by yamagrl

[yamagrl]

I think I'd start troubleshooting like this...

 

Left front (#2) seems to be the problem child.

 

First, lets determine if the fault is ignition or something else.

 

I presume that by now you have the left side fairings off. If not then it's probably a good thing to do about now.

 

You will need a "known good" TCI, spark plug and wire. If you are not certain about any of those components don't worry, I have all of them.

 

Next, we're going to flip-flop the #2 & #1 coils. This is no big deal... just switch out the coil wires on the coils. Don't mess with the spark plug ends. Now swap the 2-wire connectors going to the coils... just unplug them and plug them in to the other coil. Now the coil that used to power the #2 plug is rerouted to the #1 cylinder and the #1 coil now powers the #2 cylinder.

 

If the problem is the ignition coil then the rear cylinder (#1) will become the problem child. If the coil is the bad... I have one.

 

Frankly, I would not mess with the carbs anymore, at all until I have done the above swap/test.

 

[mralex714]

I think I'd start troubleshooting like this...

 

Left front (#2) seems to be the problem child.

 

First, lets determine if the fault is ignition or something else.

 

I presume that by now you have the left side fairings off. If not then it's probably a good thing to do about now.

 

You will need a "known good" TCI, spark plug and wire. If you are not certain about any of those components don't worry, I have all of them.

 

Next, we're going to flip-flop the #2 & #1 coils. This is no big deal... just switch out the coil wires on the coils. Don't mess with the spark plug ends. Now swap the 2-wire connectors going to the coils... just unplug them and plug them in to the other coil. Now the coil that used to power the #2 plug is rerouted to the #1 cylinder and the #1 coil now powers the #2 cylinder.

 

If the problem is the ignition coil then the rear cylinder (#1) will become the problem child. If the coil is the bad... I have one.

 

Frankly, I would not mess with the carbs anymore, at all until I have done the above swap/test.

 

 

I did end up replacing the coils, and it appears I have continuous spark on all 4 cylinders, but still had the same issue. I already have the carbs out and there was an issue in that carb. I ended up changing the jet block and the float in that carb and I also rechecked all the float levels. I'll reinstall them tomorrow, fingers crossed.