A kidd in need of some wise motorman knowledge seriously hello god bless please help! Thanks

[Richard Callaway]

My grandma sue just passed in a car accident and left me 3000 to spend on a automobile and i fell in love with a 1992 vmax 1200 aka "grandma sue" and did not test ride as i should have it will start up great and accelerate decent but once it gets to 80 she bogs out horribly its a fight to get her to do 90 ive checked comppression and all cylinders are at 115 there is alot of rust on the spark pligs porcline so put new ones in and she hated em even though they were the same ngks so put the old back in has a new air filter and oil change please help my grandma sue needs you god bless

 

[MaxMidnight]

The compressions are below minimum (128psi) and should be around 142psi. Did you do the check with the engine at operating temperature and throttle open?
If yes then I would run a tin of engine cleaner (this sort of thing) through which should help.
You don't say if you have synchronised the carburettors or indeed done a full service (First rule of diagnosis - assume the PO did B. all to the bike)
I assume the bike has V Boost? Do you hear that cycle when the ignition is switched on?

Could you also elaborate on what the issue was with the new plugs?

If the HT leads and caps are the original I would change them.

 

[VMAXXIMUM]

Maybe grandma sue is letting you know how she feels about leaving you money for an automobile and instead you get a motor bike.

 

[Woody]

Drain the float bowls.add fresh fuel to the tank.
Put in new plugs.
And take it for a spin.

 

[Pighuntingpuppy]

Compression is kinda subjective. Elevation will skew numbers. Here is an altitude chart for your specific elevation....

Altitude Factor
1000' .9711
2000' .9428
3000' .9151
4000' .8881
5000' .8617
6000' .8359
7000' .8106
8000' .7860

I am between 5000-6000 feet and my lower compression numbers always lead those at sea level to think something is wrong with the compression when there isnt. Now since I do not know where you are located, IF for some reason you are at my elevation level, your 115 compression reading would be within specifications of the readings Midnight Max gave you of the average of 142psi. Correction factors of even the bare minimum 128psi would be for my particular elevation would be 106-110psi.

Now....for the sake of argument, saying you are not as high in elevation as me, yes your compression is too low. I would be taking running compressions next. See what those are like. The valve adjustment specs would be the first thing I would look at. Maybe you are too tight causing valves to hang open. Second, if you have access to a boroscope, I would take a look inside the cylinders to see what the walls look like. Is there rusting? Scoring? Can you see the cylinder wall cross hatch?

As for the rest of your comment.....you can pull to 80mph. Getting higher is struggling. Could be carb related. It sounds like the Vboost isnt opening or opening far enough to kick in. Do you know if this is a restricted model or full power bike?

 

[Fire-medic]

Open the airbox and remove the element, blow it out from the inside-out. Check the air passages to be sure no critters made a nest inside the box or the intake funnels to the carbs.

Look inside the gas tank and see if the bottom of the gas tank is shiny-clean as it should be. If you see rust, or something like dark sludge on the floor and sides, you need some work on things. Change the gas filter, ypou can buy a similar substitute at any big parts store, bring yours in (drain it first!) and match it up.

https://dn790009.ca.archive.org/0/i...ice-manual/yamahavmaxvmx12-service-manual.pdf
Print this out, put it into a looseleaf 3 ring binder and read it, front to back. The first ~64 pages are yearly updates. After that are chapters for each area of the bike. At the end, the Appendix has data on how to route the throttle cables, electrical harness, nut and bolt sizes, and torque values, and much more.

The more knowledge you get, the better-informed you will be for being able to troubleshoot your issues. For example, you want to find out about what type of brake fluid to use, and where to put it. How worn down can the brake pads go before being replaced? Look it up in the table of contents. Use the search function in the upper right hand of this screen and type in something you need to know, like brakes, battery, oil, coolant, etc.