Hello From Devon.

[BigNick]

I have a '91 Vmax 1200 Full power, it starts fine when cold, but when it gets hot it looses power ,goes sluggish, and stops, it will not start. Any help will be appreciated. The fan does work.

 

[Fire-medic]

Welcome, here are some pieces to help you work:

https://ia800204.us.archive.org/14/...ice-manual/yamahavmaxvmx12-service-manual.pdf

I suggest printing a copy of the manual and also saving it on your computer. Put the hard-copy into a 3-ring binder.

https://www.vmaxforum.net/threads/new-vmax-owner-faqs-new-members-please-read.21240/

You can use the 'search' function for posts/threads similar to your current issues. It's in the upper-right of the page.



Blow-up this and sleeve it in plastic to keep it from dirt, grease, or a spilled Guiness. The color rendition is much easier to follow than the b & w one in the service manual.

Maybe your ignition box is giving troubles? Swapping a known good one in is one way to see if that is the issue. The 1985-'89 boxes were the same. The bikes from 1990-on had a different one.

 

[Dkid]

Welcome to the Classroom. Enjoy the Max.

 

[MaxMidnight]

I have a '91 Vmax 1200 Full power, it starts fine when cold, but when it gets hot it looses power ,goes sluggish, and stops, it will not start. Any help will be appreciated. The fan does work.

Is this a sudden loss of power or does it just fade away?
Is the time before it 'performs' consistent or does it vary with (say) ambient temperature or type of riding. If time how long?
Does it need to be cold before it will start or can there still be some heat in the engine.
After it has died have you tried removing the fuel cap and is there any sound of air being sucked in or will it re-start?
After it has performed have you checked if there is fuel in the float chambers and/ or have a spark?

 

[BigNick]

Is this a sudden loss of power or does it just fade away?
Is the time before it 'performs' consistent or does it vary with (say) ambient temperature or type of riding. If time how long?
Does it need to be cold before it will start or can there still be some heat in the engine.
After it has died have you tried removing the fuel cap and is there any sound of air being sucked in or will it re-start?
After it has performed have you checked if there is fuel in the float chambers and/ or have a spark?

Hi,
We checked the petrol tank, filter and pump, all working. I do about 4 miles before I start to loose power and go sluggish before it cuts out.
It will start again once it's cooled down considerably.

 

[MaxMidnight]

Check the fuel tank breather is clear.

 

[CaptainKyle]

Welcome