Slow '96 VMax??

[iNDee]

So, I got my first vmax a few months ago. Had some issues and I've ironed them out quite a bit. BUT one glaring issue im having is it is SLOW. If im going down the interstate, going 70 mph, I have to be all the way in 5th gear and sitting around 5000 rpm.

Any ideas? Possibly a vacuum leak maybe?

 

[02GF74]

I'm confused.
What exactly do you mean by slow?
Rpm/gear ratio/final drive ratio and tyre size determine speed.

Those are more or less fixed.

Fast or slow can also be used to describe how quickly a given speed can be reached. That can vary by rpm nd which gears are used

 

[iNDee]

The acceleration is severely lacking. So is power. It struggles to hit 70 mph and stay there. I have to wind through all the gears to get up there, and if i really push it on a downhill slope, it can reach 100 mph but it isnt happy one bit. as far as i know, shes mostly stock

 

[02GF74]

Sounds like something is quite wrong. Even without Vboost, these IMO are fast bikes.
Have you done a CR test?
Do you know carbs are running correctly?
It possible although I doubt it, the brakes are binding as you would see the disc glowing.
Is the the fuel fitler clear and pump working - could be fuel starvation, most noticeable when loading the engine.
Fuel tank vent clear?

I's been like this since you bought it - what work did you carry out/parts replaced to get it running?

Havr you checked spark on all 4 plugs ? An easy test is to measure header temperature to see if all cylinders are firing, I'm pretty sure that have been been posts where a Vmax was running on two.

 

[Fire-medic]

You have a non-performing VMax there. You should be able to get close to 140 pretty easily. Top speed is ~149 mph for a stock bike.

I agree w/02GF74, I'd look at basics. Will it rev freely in neutral? Sounds like you have two cylinders not firing, did you know that the left front coil fires the right front cylinder & vice-versa? I'd check that you have all 4 cylinders' plugs firing. Remove one plug cap at a time & ground a spare plug to the engine to check the spark. Drain the float bowls 1 at a time & see what comes out.

When you get all four cylinders working and the first time you hit VBoost, you are going to be screaming for joy. Or in fear....

 

[iNDee]

Thanks for the replies guys!

i guess this weekend ill go ahead and pull the carbs off and fully clean them and check the bowls.
if the cylinders arent firing correctly, what could be causing that? im sure lots of things, but what would be a common cause i should say. valves maybe??

i do have to hit the kill switch on and off a couple times to get it to start... could very well just be fuel

 

[Fire-medic]

Basics first.

Drain the float bowls, one at a time. Do you have any sediment, debris, or a 'lens' of water floating on the bottom of your glass or whatever you're using?


The pilot jet often is the cause of low-speed issues, especially in bikes used infrequently, and which sit for weeks or months between rides.


Poke a wire through the gas tank pipe on-top which is the tank vent (0.8mm). If it was totally obstructed, the bike would eventually quit running as the tank developed a partial vacuum. If you get a 'whoosh' upon opening the gas cap, your vent is probably plugged. A partially-obstructed gas tank vent could restrict gas flow to the carbs, but not stop it. However, I don't believe that's his issue. I think he's running on only two cylinders.



Easy things to check:
gas filter
spark plugs
spark plug leads, both into the ignition coils towers, and into the spark plug cap. See green corrosion? Trim the wire back to shiny metal, check both ends!
float bowl contents once drained, one at a time
gas tank vent pipe
sidestand switch brass plunger lever-some CRC 5-56 or WD-40 and a few pushes should have its internal spring extending the shaft fully
handlebar control pods are clean and operating properly (removal required, can stay plugged-in)
https://www.vmaxforum.net/threads/how-to-recondition-the-clutch-side-switch-pod.20783/https://www.vmaxforum.net/threads/h...ts-of-the-throttle-side-switch-housing.17272/https://www.vmaxforum.net/threads/stuck-start-switch.29226/#post-314743
air filter is clean
high-tension ignition coil connectors for cylinders 1 and 3 (under the seat) are not mistakenly switched



I've had dirty air filters or gas filters stop sufficient air or gas to allow proper engine running on one vehicle or another, a motorcycle is no-different

carburetor float levels are correct



That should get you started.

http://vmoa.net/VMX12-Service-Manual01.pdf

 

[02GF74]

Thanks for the replies guys!

i guess this weekend ill go ahead and pull the carbs off and fully clean them and check the bowls.

I would suggest figure out the problem rather than remove and overhaul parts at random.

If say the problem is due to a faulty coil, then a carb overhaul ain't gonna fix it.

 

[Dansmaxresto]

Agree with 02GF74. Start it up and make sure all 4 cylinders are firing. A couple times I was running in three because the left rear cylinder fouled the plug.

 

[Dansmaxresto]

Ride it around for a couple miles then spritz or spit on each exhaust pipe right at cylinder and see if it boils off immediately.

 

[Gbianchi]

I was having similar issues, finally first start of the morning I bare handed grabbed each header pipe.....! Found left rear cold???? Pulled carbs (after checking for spark) and found my float needle stuck, on a positive note was getting good gas mileage, fixed the needle, and was back to the OMG that a properly running vmax is. Good luck on fixing it is worth it.

 

[Fire-medic]

I bare handed grabbed each header pipe

Even though it's a cold-start, I'd try the back of my hand to sense the radiated heat, instead of 'grabbing it!' Harbor Freight has a decent infra-red thermal sensing tool inexpensive in price. Be sure to read the directions, the cone it measures widens considerably with distance from the object being measured.

The K&L carburetor kit is a good value for carb rebuilds, and is much less expensive than the OEM parts purchased individually. I find it best to have the kits/parts on-hand before dismantling/disassembly.