Devil is in the details - Carburetors!

[desert_max]

You guys may have been half heartedly paying attention to my “New” 86 thread with multiple issues. As noted and as usual, carburetors were at the top of the list. I found multiple issues. Last person in those carbs was a few bricks shy of a full load:

- One idle mixture screw jammed all the way down in the bore and stripped.

- Two Jet block washers missing

- No float heights were correct and no two were the same!

- three of four pilot jets plugged.

So, I got the carbs back together, synced them up and hit the road. The bike ran well but was really weak in the mid range. Strong down low and screamed on the top end, but was pretty wimpy in the middle. I didn’t bring it up here because I was embarrassed to admit I didn’t know what the problem was.

Since the first thing that springs to mind with regard to mid range power are needles, I went back in and took a look at them. All stock and everything seemingly OK until I noticed one was quite a bit lower than the other three. Pulled it out of there and I found that the plastic spacer under that needle was gone! It was almost an eighth of an inch down! I don’t know how I missed that the first time through. Didn’t wanna buy a kit just for that piece, so I just used a couple of washers that equaled that height.

I wasn’t sure how much effect one horribly out of adjustment needle was going to have on that performance issue, but let’s just say I was astounded when I got back on the road. OMG!

This ‘86 is a real, honest-to-goodness, fully mature Vmax now.

I guess the point of this note is that folks who struggle with carburetors should not be reluctant to dive back into them and recheck everything if something is not right. The simple stuff is easily overlooked. And it’s in those details where the devil can be found.

 

[user 16790]

great job, mine are coming off soon as one cylinder is not firing at idle

 

[Fire-medic]

great job, mine are coming off soon as one cylinder is not firing at idle

A dime to a dollar, it's a plugged pilot jet!

Good on-ya, desert max, for persevering on the causes of your carburetor dilemma.

 

[Geoff Lewie]

The devil definitely in the Carbs on a VMax!!! I had recently pulled my 2005 Max out of a number of years of being garaged and not ridden. Just got released from a “witch” I was married to for about 6 years… I got the house and the mortgage but that is ok… The Max had the typical jellied gas disease from sitting up. This is my third Max and bought it used in 2008 and drove a long way to get it; a 2005 Anniversary model like my second. Someone hit me and ran on that one. Had an FJR after that for several years until someone took it and totaled it…

First 2 were bought new and modified them pretty well. This one somewhat but replaced the stock mufflers with Supertrapp Silencers part of a set of headers. Short on $ so these work well with the adjustable baffles and I like the black with the black wheels, Jetting, K&N, Nology Wires, etc. Not as much a punch as tuned header pipes, but still strong and not as loud as previous. Numerous other tweaks. Have not replaced the rear wheel with a 17” as before, but put a Shinko Tour master on the rear and yes no wobble up to 130mph!!! Have not pushed farther yet.

The point is after 2 carb rebuilds and installing rebuild kits, checking diaphragms, spacing needle, adjusting everything and using a high “E” guitar string to clean out fuel ports the cleaner could not, got everything right or so I thought. Have a set of carb gauges and tried to sync the carbs up. Old girl would not idle below 1800 rpm. Set the carb air mix at 2 ½ turns as in the past still would not idle below 1500 to 1800 rpm. Had to set the slow jet air mixture screws to “3” turns out. Of course these are sealed from the factory so it is trial and error. But most I have discussed with and read it is 1 ¾ to 2 ½ . Actually 3 ¼ did the trick. Now 1000 rpm smooth and lopey. The carbs have always been the devil with the Max if they get out sync. The setup is somewhat complex and most dearler’s do not have someone savvy enough get them right. Just variations of close…

But all hail to the legendary VMAX… Second to my FJR, the only bike I have ever had that got regular compliments and I have had a bunch. Gen 2 has my interest, but I am considering a Spider. Just addicted I guess.

 

[Fire-medic]

The devil definitely in the Carbs on a VMax!!! I had recently pulled my 2005 Max out of a number of years of being garaged and not ridden. Just got released from a “witch” I was married to for about 6 years… I got the house and the mortgage but that is ok… The Max had the typical jellied gas disease from sitting up. This is my third Max and bought it used in 2008 and drove a long way to get it; a 2005 Anniversary model like my second. Someone hit me and ran on that one. Had an FJR after that for several years until someone took it and totaled it…

First 2 were bought new and modified them pretty well. This one somewhat but replaced the stock mufflers with Supertrapp Silencers part of a set of headers. Short on $ so these work well with the adjustable baffles and I like the black with the black wheels, Jetting, K&N, Nology Wires, etc. Not as much a punch as tuned header pipes, but still strong and not as loud as previous. Numerous other tweaks. Have not replaced the rear wheel with a 17” as before, but put a Shinko Tour master on the rear and yes no wobble up to 130mph!!! Have not pushed farther yet.

The point is after 2 carb rebuilds and installing rebuild kits, checking diaphragms, spacing needle, adjusting everything and using a high “E” guitar string to clean out fuel ports the cleaner could not, got everything right or so I thought. Have a set of carb gauges and tried to sync the carbs up. Old girl would not idle below 1800 rpm. Set the carb air mix at 2 ½ turns as in the past still would not idle below 1500 to 1800 rpm. Had to set the slow jet air mixture screws to “3” turns out. Of course these are sealed from the factory so it is trial and error. But most I have discussed with and read it is 1 ¾ to 2 ½ . Actually 3 ¼ did the trick. Now 1000 rpm smooth and lopey. The carbs have always been the devil with the Max if they get out sync. The setup is somewhat complex and most dearler’s do not have someone savvy enough get them right. Just variations of close…

But all hail to the legendary VMAX… Second to my FJR, the only bike I have ever had that got regular compliments and I have had a bunch. Gen 2 has my interest, but I am considering a Spider. Just addicted I guess.

Since you're at 3-1/4 turns, you could probably go up one size on the pilot jets, and not have-to turn-out the air bleed jets so-far. But, hey, as-long as they don't fall-out, ride it!

I'm interested to hear what you did with the front tire, while riding a 17" wheel in the rear, and a radial tire. What was your riding experience like, compared to a stock bias-ply high-profile 15" rear wheel/tire?

 

[Geoff Lewie]

Since you're at 3-1/4 turns, you could probably go up one size on the pilot jets, and not have-to turn-out the air bleed jets so-far. But, hey, as-long as they don't fall-out, ride it!

I'm interested to hear what you did with the front tire, while riding a 17" wheel in the rear, and a radial tire. What was your riding experience like, compared to a stock bias-ply high-profile 15" rear wheel/tire?

I have thought about that. I have them plugged again once adjusted, but replacing I thought about. Just taking them off again does not thrill me much.

When I changed the rear to 17, I put z rated Michelin Pilot radials on both front and rear. I have stayed that type of radial on the front on this last one. Now I have a Brigstone Battlax which has been pretty good. I waited too long to get a new front and it started to bald in spots. So I went to the dealer as I was about to take a long ride out of town for a couple of days. Unfortuately that was all the dealer had in stock. But that low profile makes it steer quicker and tighter.

This last one was after my FJR so it really felt more natural. But with that you will need to get a Shinko Tourmaster to stabilize the rear. That tire was a surprize. I ran Metzler 888s on it before and though good tires, above 95 it would start to wobble unless I had 36 to 38 Lbs in the rear. The Shinko with 34 lbs is rock steady way over 125. I have not pushed over 130 since I got the Shinko yet.

 

[desert_max]

Hmm. I have also had really good service and performance with the Shinko Tourmaster. My “new” ‘86 has newish Dunlap Qualifiers on it. I’m getting a wobble near and over triple digits as well. I chalked it up to just being an unbraced Vmax. You have me wondering now if maybe it’s the danged tires...

 

[Geoff Lewie]

Hey man, no guess. I have had 3 VMaxs. My first was a 2004 black with the Silver strip down the middle of the Airbox cover/sudo tank cover. It was my favorite. Short of going into the motor I had it dialed up pretty good. I could peg the Speedometer somewhere above 160... And it was steady as a rock. I replaced the bushings in the headset and did the same as a stage 7 Dynajet kit, K&N, FZ1000 brakes and much more. But the most definite upgrade was the 17 inch rear wheel conversion done for me by Sandy Kosman. What a beautiful wheel with the z rated Metzler Z6. Man there was no wobble at any speed.

The 15 inch size for the longest time was not offered in a radial at all. They are all just rubber tires and around 90 mph the rubber starts to stretch and that is where the wobble come from. With a windshield it comes on at about 85 real fast. I learned that lesson preparing for a trip to the Black mountains and I ended up in the ditch. But no wreck, just it wobbled so bad it drove me off the road. I had a fellow VMax owner who we did the experiments together was following me. He thought I was a dead man and described it as something from a movie stunt. He was always trying to reach the 200HP club himself. We both got the Kosman wheels and put on radials front and back. Both righteous 160 plus with no wobble. He would run off and leave me so I do not know how fast his Max was but he had no wobble either.

Both my first 2-14 and first 2015 had the 17 inch Kosman rear wheel. There is no doubt to me that all the extra frame supports are for track racing, not necessary for street or dragging. I read about the Tour Masters last year and did not have the cash for a new wheel which is over a Grand with the tire and Sandy has retired. So I thought I would try them out. Oh what a happy that created! Now if you put 38 lbs in a Metzler 888 it will stabilize up over 100, but really that is a band-aid not an answer and it wears out the center fast.

Now just for a moment of bragging, the crème de la crème. I have always walked (wheelied) all my bikes. Including my 1971 Honda 750K which I still have. On a VMOA trip one year I walked my 2004 over a 1/8 of a mile in-front of about a dozen VMOA members up in the Ozarks where me net every summer. And I had to drop it as I was over redline and never tried to shift it above 3rd. I could never have done that on the 15 inch wheel. The 17 inch tire is a low profile tire and drops the rear of the bike down about "4 inches". You have to drop the forks about an 1.5 inches to compensate. Think about that. The standard tires have a 5 inch sidewall. That is a lot of rubber to stretch. The Shinko is only 3 inches and it is a radial design.

So with all that talk, I recommend the Shinko Tour Master. IT is worth every penny and it isn't pricey. A Z6 is about the same price right at $100.00 give or take $5.00 and shipping. You can also put a radial on the front. Like I said before it takes a little getting used to but works great. Just a little more road vibration.

 

[Fire-medic]

Hmm. I have also had really good service and performance with the Shinko Tourmaster. My “new” ‘86 has newish Dunlap Qualifiers on it. I’m getting a wobble near and over triple digits as well. I chalked it up to just being an unbraced Vmax. You have me wondering now if maybe it’s the danged tires...

The 15" radial rear tire isn't a V rated tire (to 150 MPH), the one that I've seen. If you get a modded rear wheel (17", 18"), you can use a front radial too, but do not be tempted to go to a larger size than stock front radial tire. Radial tires have a much-wider width than a bias-ply tire. The front VMax rim is narrow, compared to what is optimal for an 18" radial tire, which usually takes a 3-1/2" wheel width.

Also, do not mix two brands of radial tires! The type of construction will make a big difference in handling, if you have a zero-angle rear tire, and an oblique-angle front tire, both being radials. The formulation of the rubber should be the same, and that can be different within the same tire manufacturer. A sport-tour on the rear, a sportbike on the front, your rear will break traction well-before the front.

I've found that a V-rated tire for the VMax is what you need if you're riding in the top 1/3 of the speedo at-all. Sure, you can run an H-rated tire (to 130 MPH) but don't you want something designed for what your bike is capable-of?

Brand-new radial and bias ply tires actually handle in a similar fashion for maybe the first 1000 miles, then the bias-ply tires start to deteriorate, while radial tires maintain their traction and consistency better, is what I've experienced. That's assuming they're the same tire manufacturer F&R, and in the same style. A longer-wearing tire sacrifices grip, a sticky pair sacrifices mileage. I usually get two rears to one front, for replacement.

 

[desert_max]

Heh, heh. Yeah, at the rate I'm going, this rear Dunlap won't last long. Did I mention it was nice to have a Vmax again?

Thanks for the chatter, gentlemen. As noted, I'll be looking for tires soon. Based on past experience and Geoff's confirmation, Shinko will likely get the nod. Not ready to go down the radial path yet.

 

[Geoff Lewie]

Desert Max, Good to have you back on a VMax. I felt the same way when I got my third after my FJR.

Fire-Medic, What "they" say is opinion. I have been riding since 1972. I have bought 12 bikes over the years. I have ridden well over 100,000 miles on a motocycle. As far as the radial on the front and a bias on the back, it would be dangerous for a novice. Usually they fall once and never get back on anyway.

But a seasoned rider who rides curves like the Tail of the Dragon at Deals Gap with 318 curves in 11 miles: America’s number one motorcycle and sports car road will do just fine. The Mix if one cannot get a rear radial is ok. Put an extra 4 lbs in the rear and it is will work. The traction and handling is great.

I did not make it up. I have ridden a VMax
that way for 9 years. I got the idea from a friend who owned a MotoGuzi dealership in Talahassee Fl. It takes adjustment, but it handles curves a lot better and steers quickly. But put 4 extra pounds in the rear tire to stiffen it up. Actually the tire will last longer if one puts 35 lbs in tires. Learned that too from multiple people.

Oh and I don't agree with mixing brands of radials. I have done that too and itis more a good verses loosey tire experience. As far a V or Z rated, they are close. The Michelin Pilot is Z rated and wears fast so it is not great for touring. I burned a set up riding from Sheveport, LA to Grand Juction, CO on a 2 week treck some years ago. But handling is great in heavy rain!!! Been there and done that. I like soft/sticky rubber. It will save you in a unexpected quick correction or pouring rain. I slid across a intersection once due to the tires were H rated loosing traction in the rain. Your life is worth the cost of the quick wear...

 

[Fire-medic]

I doubt that a dealership would even mount a radial tire in-front if you have a bias-ply rear tire. I believe there was one model of H-D that came that way, so there is an exception. My point is that the same rubber F&R is going to give the typical rider a much-more consistent ride than mix & match. As I mentioned, having different handling characteristics in your F&R tires is not a good way to start-off on a motorcycle. If it works for you, great, but manufacturers warn-against it for good reason. The 'different handling characteristics' could be due to different rubber compounds or it could be due to different methods of construction; either can be dangerous. Chainsaws are great tools for a very-specific purpose, you can juggle them if you wish, I'm sure someone will 'hold your beer.'

In our litigious society, doing something which is not approved by a manufacturer should give one to pause, "why is the manufacturer saying, 'don't do this?'" It's probably because their engineers have determined the safest choice being the best choice, if someone wants to ignore that advice from the manufacturer, that is a choice bearing responsibility for ignoring the manufacturer's instructions for use of their product.

 

[Geoff Lewie]

I am not making a ground braking claim or statement of what anyone should do. What is your deal? I do not care what a dealer will or will not do. No dealer touches my bikes. I take the wheels in for rubber change which I normally order directly to me. This is an experience of results I have found by trying it. And the reason is the traction is much better. And yes the stiff nature of a radial can increase the wobble from a bias ply rubber tire on the rear on a VMax. But because the Gen 1 VMax came with a 15" wheel someone had to get a bias ply tire because until recently no one offed a radial except one that was close to $200.00 spcail order from the manufacurer for the tire and the new Michelin Commander II 170/80B15 Rear Tire. Though not a radial, it has that short sidewall so less rubber to stretch. You are stating this is NOT something to do by someone else's opinion not yours. "I tried it and it is a great improvement on a VMax which is a very different motorcycle. Up until the last few years it has been a legion. Quoted from Cycle magazine; "The VMAX is one of the most iconic motorcycle designs Yamaha has ever created and it's back in 2020 for more arm-stretching antics for those brave enough to ride it." The VMax is not a sport bike. It is one of the few "MUSCLE" bikes produced and has earned its legion status. I have smoked every Harley I have ever matched up with. But I admit I do not drag race or have mine competition modified.

Well the MotoGuzi dealer I mentioned sold me the tire. He had track raced for years and we discussed this in length. I was skeptical too, but after making the change it is an excellent choice and as I mentioned the first 2 VMaxes had the V rated on the first and z rated tires on the 2nd. Oh and a Harley is a completely different dynamic in a riding machine. I have worked on them for others, but otherwise have no interest. Worked my way 3/4 the way through my first degree working on Hondas, Yamahas and Kawasakis. Honda factory certified in 1978.

At the end of the day, it is all about enjoyment and utilitarian value. What works for me may not work for you...

 

[desert_max]

Devil indeed. I've put probably 900 miles on my "new" '86 since I rolled it off the operating table in March. Had been laid up for years prior. It has been running flawlessly - including a couple of 300+ mile days.

But...

A couple of weekends ago, on a 30 mile run up the freeway to a buddy's house, I smelled gas when I got off the freeway and find fuel puking out of the right rear carb. Sheesh. Stuck float? Couldn't free it up. We trailered the bike back to my house. Today, I finally got around to investigating and I see that fuel is welling up and pouring out of the Main Jet Air Bleed while it's running. That ain't right.

So, is this a symptom of a stuck float? Or something else? If it's a float, it sure is stuck. I guess I could have crap in the needle valve, but the filter is clean as a whistle. Anybody have any insight? (I poked around the archives here and didn't see a similar complaint, but I'm sure there are others...

 

[Fire-medic]

If the gas is pouring out of that jet in the airhorn, then, I believe the diagnosis is correct, a stuck float. A build-up of varnish, a piece of crud on the seat, a worn seat, a worn viton tip on the needle valve, a weak spring on the needle valve: whatever, the needle valve is stuck open. Find it, fix it.

 

[desert_max]

If the gas is pouring out of that jet in the airhorn, then, I believe the diagnosis is correct, a stuck float. A build-up of varnish, a piece of crud on the seat, a worn seat, a worn viton tip on the needle valve, a weak spring on the needle valve: whatever, the needle valve is stuck open. Find it, fix it.

Ugh. Thanks FM. I pretty much knew the deal, but was hoping an obscure Vmax quirk might be at play.

<sigh> Carbs off for the 3rd time in as many months...

 

[desert_max]

I am fairly secure in my masculinity and have been spinning wrenches on cars and motorcycles for over 40 years. All of that means nothing sometimes. I haven’t confirmed this yet, but I believe I am a fully mature dumb ass.

About this overflowing carburetor. Keep in mind my last Vmax was over five years ago and it had a stage seven intake set up. So, on a recent trip of 330 miles I noticed a PVCs split hose resulting in oil fog in the valley between the cylinders. Before the 2nd trip described above where I encountered this massive fuel leak, I cobbled together a PVC line with a few bits and pieces and plumbed to the airbox… Or so I thought.

Pulled the airbox yesterday in preparation of yanking the carburetors, and noticed that I did not plumb that PVC line into the air box at all. I plugged it into the bowl vent for that right rear carburetor! In my defense, it was dark and crowded up there and I didn’t pay enough attention to what I was plug in where. I thought I was hitting a port on the airbox. That’s the dumbass part.

The real question is, would that pressure coming from the crank case be enough to upset the delicate balance of the float in the chamber? If so, my problem is already solved and I chalk it up to a case of anal cranial inversion. I think I already know the answer, but as I said above, I’m not afraid to share my stupidity with others…

 

[Fire-medic]

I am fairly secure in my masculinity and have been spinning wrenches on cars and motorcycles for over 40 years. All of that means nothing sometimes. I haven’t confirmed this yet, but I believe I am a fully mature dumb ass.

About this overflowing carburetor. Keep in mind my last Vmax was over five years ago and it had a stage seven intake set up. So, on a recent trip of 330 miles I noticed a PVCs split hose resulting in oil fog in the valley between the cylinders. Before the 2nd trip described above where I encountered this massive fuel leak, I cobbled together a PVC line with a few bits and pieces and plumbed to the airbox… Or so I thought.

Pulled the airbox yesterday in preparation of yanking the carburetors, and noticed that I did not plumb that PVC line into the air box at all. I plugged it into the bowl vent for that right rear carburetor! In my defense, it was dark and crowded up there and I didn’t pay enough attention to what I was plug in where. I thought I was hitting a port on the airbox. That’s the dumbass part.

The real question is, would that pressure coming from the crank case be enough to upset the delicate balance of the float in the chamber? If so, my problem is already solved and I chalk it up to a case of anal cranial inversion. I think I already know the answer, but as I said above, I’m not afraid to share my stupidity with others…

Oh, yeah! Especially-at higher RPM's. Well, glad to find-out it was something we can learn-from. The Mechanic's College of Industrial Knowledge diploma, with School of Hard-Knocks leaf-clusters. I'm glad you reported back with it.

It's a good idea to keep a file with what you did on your ride/to your ride/for your ride. That can help you to recall the order of things and perhaps give you a clue as-to where you should continue to-look, if you have nagging issues.

Big V-twins have a need for controlling crankcase venting, H-D's can run very-poorly if you don't pay-attention to that, and it can interfere with oil delivery. That's the purpose of the Dynojet Stage 7 'drain-back-to the crankcase' oil breather tube in-place of the OEM closed oil cap, and the oil baffle ass'y, where oil vapor can condense and allow gravity to return the oil mist to the engine sump.

 

[desert_max]

Confirmed. Problem was self-induced. Sometimes I am my own worst enemy.

Note to self: when hooking up ventilation, vacuum and/or drain lines, make sure the ‘goesintas’ and the ‘goesouttas’ match up.

 

[Fire-medic]

Confirmed. Problem was self-induced. Sometimes I am my own worst enemy.

Note to self: when hooking up ventilation, vacuum and/or drain lines, make sure the ‘goesintas’ and the ‘goesouttas’ match up.

I usually use tan masking tape and a Sharpie fine-tip marker to label things. Make a 'flag' around hoses or wires, and each pair gets an 'A', or a 'B', 'C', etc. works well for me.

A piece of cardboard, & punching holes into it with an awl, after tracing the outline of the side case, is a good way to make sure that screws and washers go-back where they need to-be.

I also use one of those configurable double-sided parts storage cases, when I'm disassembling a bike, w/the tan masking tape and Sharpie labels inside each compartment.