My European 102hp has more torque than an American 145hp?

[MaxMidnight]

Unless you know what the fueling is doing you will be chasing your tail until (if you are lucky) you stumble across the problem.
By all means check the basics; air and fuel filter clean, carbs sychronised, all cylinders firing, air leaks, choke plungers, V Boost operation and the like...you have haven't you??

Once you have exhausted the basics then IMO the quickest way forward is to get a dyno base run. This will either highlight where you have a problem and corrective action taken or is fueling as Yameringha intended.

The alternative is to throw time and money at it.

As for weave and wobble have a read of this which may offer further insight.

 

[Screwloose]

As for weave and wobble have a read of this which may offer further insight.

Interesting write-up Prof.

 

[AP76ita]

Can I give a suggestion. Apologies if it has already been said before.

The American model would have the a/f screw plugged off (maybe) and if the trouble is at low rpm where the pilot screw adjustment is essential, and also being an old engine. Then drill out the a/f plugs, take out the screws and put new rubbers in, blast out with carb cleaner, and adjust the screws. Then balance the carbs. Its just what I would try.

For wobble, I would still consider shocky’s and forks as when I mentioned above, I should have included that when I went into a wobble it felt like a front end problem at the time with maybe a flat front tyre (and if have had one of them at speed like I have, then I do not need to elaborate further on the fight you have trying to hold on right down to stopping). Yes I held onto that one also , when your young your legs are worth less than the bike

Thanks I only can wait chance to put hands on this bike again, didn't decide to buy it yet and he lives in another town
But I'll watch this too if thing go on with the purchase

 

[AP76ita]

About the 'choke,' it's an enrichener. Yes, more fuel is introduced to the engine. A traditional choke is a simple plate blocking-off the air inlet to varying degrees, according to its position. The same amount of fuel is presented to the engine, but the amount of air is less, causing an enriched mixture to the engine. The VMax works by supplying more fuel, the CV carb slides still flow the same amount of air.

Recently one of the members discovered their enrichener plungers weren't synchronized. They weren't allowing the same amount of additional fuel to enter the fuel venturi pathway. A good cleaning of the brass plungers, lubrication, and carefully ensuring that the rods and lever system opening and closing the enrichener pistons was functioning properly was needed. See the pic:

View attachment 80333

If you own a VMax, either you pay-attention to the condition of the fuel delivery system, or you have problems. A clean gas tank, meaning no rust, and unobstructed pilot jets in the jet block will allow you to have a decently-performing bike which idles properly, doesn't have any low-speed issues, is easy to synchronize the carburetors, and which operates as it is supposed to behave.

Over time, certain gremlins arise. Intake leak(s) can come from a variety of places. The points of connection of the airbox to the carburetor bellmouths, the lower carburetor bodies' attachment to the VBoost manifold, and the VBoost manifold's O-rings to the cylinder heads are all places where air infiltration can cause you to pull-out your hair until you discover that/those leak(s).

Other likely places for leaks are deteriorated fuel lines. Say you bought a 1988 VMax, and you're having issues. Think about the age of the bike, and whatever service it has, or hasn't-had. The molded T-line to service the carburetor bank is original to the bike, most-likely. It's 33 years-old! As are the other rubber components, including the CV carburetor diaphragms. The gas tank is rusty. Fine particulate material from that rusty tank is plugging your pilot jets, and that's what when you have the bike idling, one or more of the pilot jets has become obstructed by sediment/rust particles. Sure, try the 'peashooter,' try the 'shotgun,' or go straight for the cure: pull the carburetors, split them into-two, and remove the float bowls, remove the jet blocks, and then remove the gas delivery jets, and clean the jets and their passages. You want to be able to see light at the end of the jets' tunnels! The carburetor bodies also need to be cleaned, for this purpose, an ultrasonic tank is what I consider to be the best way to do this.

View attachment 80334

While the carbs are apart, check for proper fuel level, you can use the carb body casting behind the float for a rough starting point, but a 'wet-check' will allow the best fuel delivery and best gas economy. If I open the carbs on a new to me bike, the float needles with their Viton-rubber tips are replaced, and the brass seat they go-to is cleaned.

View attachment 80336

Have new jet block gaskets on-hand for the tear-down, because they inevitably tear when you try to remove the jet blocks.

View attachment 80335

About splitting the carburetors into two banks: to do this, you need to work around the molded-rubber T-line, and don't be surprised if your 33 year-old rubbers fall-apart. Thank Yamaha for still allowing us access to as-many parts as they do for our bikes, because when they decide to stop supporting the replacement parts, the value of your bike is going to plummet. Some parts are now unavailable, but thankfully there is a cottage industry of what the UK members know as 'breakers:' people who part-out the bikes. They will be the resource of last-refuge when the lack of OEM, new parts happens.

Currently there are suppliers of the rubber donuts used for the carb joints and the CV slide diaphragms. Surface cracks on the rubber donuts which don't leak air will still provide proper air levels. use the old method of spraying something like starting ether, carb cleaner or another aromatic hydrocarbon on the boots or the cyl. head-VBoost joints, and listen for the increase in rpm's, a sign you have located a leak. Don't stop at that one leak, continue to search for more. In the case of an O-ring leaking at the VBoost to cyl head point, replace all four of the O-rings since it's apart. it is likely that disturbing the seal all four O-rings have will cause the others to leak, so replace them-all.

These tips are based on my work on these bikes for nearly 30 years, they represent issues I've dealt-with on multiple VMaxes. Remember that no-matter how-well that you clean all the parts in that set of carburetors, replacing anything which could be causing an air leak, or removing deposits which plugged-solid your pilot jets, if your gas tank isn't shiny-clean inside, you're just going to soon find your pilot jets are plugged again as an uneven idle, cold exhaust header(s) at idle, and poor throttle response off-idle happen again because of rust in the gas tank. Removal of the gas tank isn't difficult, follow Buster's how-to, and if you decide to use a kit to line the gas tank, follow the directions exactly or end-up with more problems than you began-with. Heed the input of the specialists on-here, who work on these for a living, people like Sean Morley, danymax for the carburetors, Captain Kyle and Damian, they are the subject matter experts whose experience and knowledge collectively have see anything you're experiencing with your ride. Here's an example of something I had happen, the bike ran, but was obviously not running properly, and fortunately, the position of the cam when it happened was not on the lobe, so there was no piston-to-valve interference, which would have been a much more-involved repair.

View attachment 80337
View attachment 80338

Once you've dealt with your issues, and solved them, put your experiences here so we all can see what worked for you. You will be helping the next fellow with a similar issue or issues.

Wow Fire-Medic that's an encyclopedia you reported me down there! Thanks a lot. I'll study it all and apply on my '91 european (which never had issues by the way unless the water temperature I'm still investigating)

 

[AP76ita]

Unless you know what the fueling is doing you will be chasing your tail until (if you are lucky) you stumble across the problem.
By all means check the basics; air and fuel filter clean, carbs sychronised, all cylinders firing, air leaks, choke plungers, V Boost operation and the like...you have haven't you??

Once you have exhausted the basics then IMO the quickest way forward is to get a dyno base run. This will either highlight where you have a problem and corrective action taken or is fueling as Yameringha intended.

The alternative is to throw time and money at it.

As for weave and wobble have a read of this which may offer further insight.

Same herr regarding wobble, big thanks from Italy, I'll study it all

 

[AP76ita]

I wish yo thank you all for so many advices and aids.
Please take a look at this picture
I removed side cover under carbs in my '91 european 102hp and found a pipe connecting the carbs
Is inside this pipe that the vboost throttle stays on American 145hp versions? So when it opens @5.750rpm the 2 carbs are connected?
Then how come it's present in mine? (No vboost and no throttle present in mine obviously, but just the connecting pipe)

Do you know if europeam restricted and non-vboost engines have this pipe?
If not then this could explain why mine pushes so strong. Have to say it always runs very rich and I never have to choke even in morning g cold starts

 

[MaxMidnight]

If memory serves well the restricted bikes had that link between the two inlet stubs but it was solid and not a tube. It is possible that a PO converted it to a tube but that would mean you couldn't balance the carbs using a manometer.

The pic below shows what the boost equipped bike looks like.



You can see (under the red arrow) the casting has additional features to accommodate the butterfly shaft and linking bracket.

 

[AP76ita]

Then I have to loosen the screws in pic below and check if that part is solid or pass-through

 

[AP76ita]

If memory serves well the restricted bikes had that link between the two inlet stubs but it was solid and not a tube. It is possible that a PO converted it to a tube but that would mean you couldn't balance the carbs using a manometer.

The pic below shows what the boost equipped bike looks like.

View attachment 80424

You can see (under the red arrow) the casting has additional features to accommodate the butterfly shaft and linking bracket.

I'm not sure mechanics here do balance carbs, have to check this, in case it comes out my carbs are connected

 

[Fire-medic]

There are guys on here right-now dismantling bikes, I would buy a complete VBoost manifold, stepper motor and cable from them , and the wire harness with the electronics for the VBoost, if you want the system to work.

 

[AP76ita]

There are guys on here right-now dismantling bikes, I would buy a complete VBoost manifold, stepper motor and cable from them , and the wire harness with the electronics for the VBoost, if you want the system to work.

Cool but I'm not interested in improving performance of my bike which I'm greatly satisfied
Matter is since I put it back on road I experienced water temp running highest (where red zone begins) and my mechanic fears a head gasket failure so instead of sending money in a very old bike i was thinking about a newer one and found this amazing single-owner 145hp year 2000
But then after riding it I found much less lowend power than mine
And so I started bothering you all here!

 

[MaxMidnight]

Matter is since I put it back on road I experienced water temp running highest (where red zone begins) and my mechanic fears a head gasket failure...

I'd interested to know why he has come to that conclusion.

Has he ruled out any issues with the thermostat, performed a coolant pressure test, established if the radiator is partially blocked, established if it is loosing coolant or tried running it without the rad shield?
Have you also checked that there isn't an issue with the temperature indicator?

IMO if your man suggests replacing the head gasket (which one would he do first?) without checking any of the above then I would be inclined to look for another mechanic.
Better still, learn how to do the checks and jobs yourself and save a whole lot of dosh which you can 'invest' in 'safety related'* items.

* The term 'Safety related' refers to absolutely anything you desire for your bike, regardless of function.
As your nearest and dearest could not deny you anything related to your personal safety they would not query the purchase.

 

[AP76ita]

I'd interested to know why he has come to that conclusion.

Has he ruled out any issues with the thermostat, performed a coolant pressure test, established if the radiator is partially blocked, established if it is loosing coolant or tried running it without the rad shield?
Have you also checked that there isn't an issue with the temperature indicator?

IMO if your man suggests replacing the head gasket (which one would he do first?) without checking any of the above then I would be inclined to look for another mechanic.
Better still, learn how to do the checks and jobs yourself and save a whole lot of dosh which you can 'invest' in 'safety related'* items.

* The term 'Safety related' refers to absolutely anything you desire for your bike, regardless of function.
As your nearest and dearest could not deny you anything related to your personal safety they would not query the purchase.

Hi Max you're totally right, in fact he just fears about gasket failure because when temp goes high the small pipe between radiator cap and water recover tank, allows water to flow through and go in the tank. So he thought about pressure from combustion chamber passing throguh and creating pressure in water circulation.

Removed thermostat, same problem
Radiator checked under pressure and so water pump
What we miss is a check on instrument and to do so I bought an instrument with passing sensor
I'll install it and check aftual water temp
It really could be an instrument mistake, because engine starts cold just touching the start button and without choke
Pushes strong so we both have doubts regarding engine failures
I'll do this test AND I'll open then pipe between the carbs to see if my bike is in constant boost

 

[AP76ita]

https://www.amazon.it/gp/aw/d/B096XFCNLF?ref=ppx_pt2_mob_b_prod_image
This one

 

[AP76ita]

I'd interested to know why he has come to that conclusion.

Has he ruled out any issues with the thermostat, performed a coolant pressure test, established if the radiator is partially blocked, established if it is loosing coolant or tried running it without the rad shield?
Have you also checked that there isn't an issue with the temperature indicator?

IMO if your man suggests replacing the head gasket (which one would he do first?) without checking any of the above then I would be inclined to look for another mechanic.
Better still, learn how to do the checks and jobs yourself and save a whole lot of dosh which you can 'invest' in 'safety related'* items.

* The term 'Safety related' refers to absolutely anything you desire for your bike, regardless of function.
As your nearest and dearest could not deny you anything related to your personal safety they would not query the purchase.

Just to add you more details, it happened in hot summer mornings in slow traffic, temperature staying mid for 30 min than starts quickly raising until high limit of instrument, fan starts but temp won't lower so I just put engine off for 10-15 min and then back on the road

Some other times, in no sun afternoons, driving fast on highway 7-8krpm (so also a lot of wind in radiator) similarly temp started raising up to limit.
And this without thermostat

 

[MaxMidnight]

Hi Max you're totally right, in fact he just fears about gasket failure because when temp goes high the small pipe between radiator cap and water recover tank, allows water to flow through and go in the tank. So he thought about pressure from combustion chamber passing through and creating pressure in water circulation.

Removed thermostat, same problem
Radiator checked under pressure and so water pump
What we miss is a check on instrument and to do so I bought an instrument with passing sensor
I'll install it and check actual water temp
It really could be an instrument mistake, because engine starts cold just touching the start button and without choke
Pushes strong so we both have doubts regarding engine failures
I'll do this test AND I'll open then pipe between the carbs to see if my bike is in constant boost

The Max has a semi sealed cooling system. As the coolant heats up and expands it will be displaced into the header tank and the higher the temperature the more coolant is displaced. As the motor cools down and contracts it returns to the motor.
If I'm understanding you correctly then what you describe sounds normal.
If a head gasket had gone then I would expect the gas to displace more coolant into the header and eventually this would be ejected from the overflow.

One other thing to check is to feel for cold spots in the radiator core as the motor heats up which would indicate a partial blockage.

 

[AP76ita]

The Max has a semi sealed cooling system. As the coolant heats up and expands it will be displaced into the header tank and the higher the temperature the more coolant is displaced. As the motor cools down and contracts it returns to the motor.
If I'm understanding you correctly then what you describe sounds normal.
If a head gasket had gone then I would expect the gas to displace more coolant into the header and eventually this would be ejected from the overflow.

One other thing to check is to feel for cold spots in the radiator core as the motor heats up which would indicate a partial blockage.

Then unless coolant also being pushed out of recovery tank, if it just passes through and then comes back is normal behaviour? Not symptom of gasket failure?

 

[AP76ita]

Max here are temp checked with laser
Water instrument on red limit

Engine taken on heads in both exhaust and intake sides
Radiator took high and low in right side of bike (higher) center (lower temp) and left

These 3 temperatures in the 3 spots of radiator are normal or not?

 

[AP76ita]

Engine heads temperatures seem normal to me, and are the same I checked on the 145hp bike

So really could be my dash instrument goes wrong?

 

[MaxMidnight]

Then unless coolant also being pushed out of recovery tank, if it just passes through and then comes back is normal behavior? Not symptom of gasket failure?

Assuming that the fluid that goes into the expansion tank returns when the engine cools down then that is normal. Indicators of a blown head gasket would be coolant being forced out of the header tank over flow pipe and, with the pressure cap off, you may see bubbles in the header manifold. If you have access to a CO meter you may also get a reading with the probe held over the coolant (NOT in it!).

I've never checked rad temperature with an IR thermometer so can't say with any certainty if the data you have collected is normal or not. I assume that they were taken when the motor was at 'operating' temperature, the readings taken one immediately after the other and the fan not running?
Perhaps someone else who doesn't have any cooling issues could do a similar exercise and report back their finding?

Your pictures show the coolant entering the top of the rad at 66°C and exiting at 50°C. What I don't understand is how the temperature rises to 74°C at the bottom LH corner, is 38°C at the middle top and 51°C RH top.
Without the fan running I would have expected the temperatures across the top to be similar and show a reasonably consistent drop as you go down the rad. That is my theory which may be a load of 'olloks and I'm happy to be corrected.

My gut feel (dangerous, I know) is that the radiator is partially blocked and it is this which is causing the issue.

Have a look here to see how to check the coolant temperature indicator operation.