Accelerator Pump Volume? Vacuum testing? Stumbling around..

[pinholenz]

Roro, thanks for the great links in the "New and updated XZ550 and XZ400 resources" post. Brilliant bookmark.

I was intrigued by the very technical review about improvements to the '83 Vision over the '82 model at this link:
Tour Testing: Yamaha XZ550RK Vision - Rider May 1983

In it, the reviewer writes, "The throttle valves, linked directly to the accelerator pumps, formerly opened at the time of initial pump actuation; in the new setup, throttle opening precedes pump action by 5 degrees. The pumps output has been halved from 0.45cc to 0.25cc, and a control valve in the pump prevents fuel from entering the throats when the engine isn't running....  The combined effect of these modifications (new 36mm venturis and change to the position of the pilot air passage) eliminates the off-idle stumble that plagued the '82 Visions."

So what do experienced Visionaries recommend as an accelerator pump setup for the '82.5 Vision? Delayed actuation? 0.25 or 0.45cc  pump volume? (Assuming that the carbs are squeeky clean!)

AND when spraying carb cleaner on to the various hoses and connections while the bike is running to test for vacuum leaks, is the tell-tale sign of a leak an increase of revs when carb cleaner gets sucked in?

Thanks

[The Prophet of Doom]

Happy to help :-)

If you look at the air box mod, you will see the advice to back off the accelerator pump by 5mm
Do you have the vacuum operated flapper, larger air jets etc

Carb balance and iridium plugs were my best weapons in eliminating stumble, that and sealing up the airbox (it's supposed to have a gasket, but long gone) and repairing the YICS.

[pinholenz]

I have got the vacuum operated flapper. Couldn't work out why it stuck open when I operated it by hand when the airbox was screwed down. I had put the air filter in backwards and it interfered with the actuator rod. (doh!!)

I'll play with the accelerator rod length. At present I have it set up to actuate the pump as soon as I open up the throttle, but I notice that the '83 mod has a 5 degree delay between the butterfly opening and the accelerator pump being active. Looks like I need to tweak it some.

I am not sure what jets I have at present. I'll let you know. Tested the YICS the other day, found a leak, so I have just rebuilt that and it seems sound.

Hows your new ceramic coated exhaust looking?

[The Prophet of Doom]

I haven't sent them off for coating yet.

I can't decide if I want them the original length, or an inch or two shorter

I also can't decide if I want:
black coated pipes, alloy mufflers (stock for the SpecII) OR
silver coated pipes, black coated mufflers - (my original plan) OR
black coated pipes, black coated mufflers OR
silver coated pipes, alloy mufflers OR
silver coated pipes, silver coated mufflers OR
some other colour scheme entirely

Trouble is once those alloy cans are coated, there is no cutting or going back to the original

I'l post pics once I decide and they are done - they told me about 10-14 days turnaround

[pinholenz]

I'm only a little bit jealous...

[fret not]

Roro, does the coating shop offer a goldish or cooked 'titanium' look?  Otherwise either silver or black would look good.  Something I learned many years ago is if you do a neat and tidy job of it the color will look good no matter what it is.

[The Prophet of Doom]

@ pinholenz - No need to be jealous I can sell you a nice pair of stock looking, but actually custom made stainless steel mufflers AND/OR a set of NOS Macs

@ fretnut - yes - they do have a gold, but I don't want the pipes to clash with the inverted forks when I get round to them.

[Rikugun]

AND when spraying carb cleaner on to the various hoses and connections while the bike is running to test for vacuum leaks, is the tell-tale sign of a leak an increase of revs when carb cleaner gets sucked in?

I don't know if anyone else has noticed this but depending on which chemical (or brand?) is used the RPMs will either drop OR rise. Either is indicating a vacuum leak and no change indicates all is well.  ;) Some things I've tried are carb/choke cleaner, disk brake cleaner, electrical contact cleaner and starting fluid.

[pinholenz]

Thanks Rikugun. As we say around here, "we will have to suck it and see!" -but any RPM change is a bad thing.

Roro that's wonderful thanks. Jealousy cured. Cheers