Poor running at low revs

[Gaz 88]

Hi my 1988 vmax runs like a pig at low revs and back fires but if i put the choke up about a quarter it runs ok
Any moor than a quarter throttle and she runs great. Any idea's i think it may be the pilot jets ??
Thanks for reading

 

[Fire-medic]

Yes, possibly the pilot jets, 1 or more. Do you have access to an ultrasonic cleaner? The 'cheapest by price' is probably a Vevor.

Here's a decent sized & powered one, 15 liters. It pays for itself the first time you use it.

https://www.vevor.com/ultrasonic-cl...nic-cleaner-heater-w-timer-usa-p_010646323549




13" X 11" X 6" should allow you to split the carbs into 2 sets of two carbs, and to soak them at the same time. Be sure that you immediately purge all cleaning liquid (water) from the idle piston and the coasting valve. Failure to do that will result in seizing of the idle piston in its bore and crud in the coasting valve. Of course, if you completely break-down the carbs into 4 separate pieces, and then remove the idle piston and the coasting diaphragm, that will take care of having to purge them of the cleaning fluid (water w or w/o detergent) This one is $134 and there are larger ones.

Reading this entire thread may help you.

https://www.vmaxforum.net/threads/whats-going-on-here-k-n-pods.53979/#post-540719

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