Matt Tries – 1984 VF500F Overhaul

Carbs need setting up.

 

A positive step in the right direction!

 

They sure do. I'm sure the sync is all off, and I'm probably too lean on the A/F screws.

*Edit--lmao, just realized why it might be running lean... I never capped off the vacuum port on cylinder #1 that goes to the petcock. That would explain some erratic behavior. Will be getting out the 'ole sync gauges today.

 

Found some interesting behavior after playing with the bike for much of Sunday. The warm bike would idle all the way up to 3,700RPM with the idle set screw all the way backed off. So I pulled the air filter off to look through the throttle bodies to see that the throttle valves looked like they were seating with a flashlight. Then I decided to run it without the airbox. The bike sounded... really good. From cold to warm it ended up with a high idle of about 1,900 RPM.

I'm pretty confident I can remove the remainder of the high idle with A/F screw adjustment and, more importantly, synchronizing the very out-of-sync carburetors. It didn't sound that far off of being correct despite the poor synchronization. I have a bendy screwdriver coming on Friday because I couldn't reach the synch screws with any of the contraptions I was cobbling together.


What I'm not certain about is what to do about the air filter. Obviously that's going to change the mixture quite a bit, but I think I should be able to sync it at least closer without the airbox on. I am kicking myself for throwing away the old air filter. I hoard everything for too long, yet I threw that away. Ugh. The new air filter is an Emgo. I'm not certain if it's possible to install the air filter incorrectly, but if it is, I'm sure I did that.

 

You are synchronizing them to each other, regardless of what air filter (or no filter) you have.

 

Also, what size pilot jet are you running? You really should go up one size, it helps tremendously on the V4. I think it's 35 stock, go to 38 if you can't get the idle to drop. With the stock pilot, you'll need to be AT LEAST 2 turns out (prob close to 2.5) with that exhaust and aftermarket air filter.

One thing to be careful of, when you have the screws that far out, you don't have as much pressure from the spring holding them in place. They can potentially vibrate out. Some times I give the spring a little "stretch" to apply more pressure.

And, you are running even leaner without the air filter, exacerbating a potential lean high idle.

 

Alright, that's what I was thinking. My understanding per the manual is that you are not balancing them in pairs like an inline-4; but rather, carburetor 4 has no synchronization adjustability, and all three other carburetors are balanced to that vacuum reading to within 60 torr. Am I right in thinking all 3 are sync'd independently?

90% certain they're 38 pilots. I have them all written down in my notebook though, so I can verify. I took record after noticing all my mains were 104 instead front/rear pairs at 102 and 106 if I recall correctly. When I took apart the carburetor for the first time, the A/F were all backed out between 2.75-3 turns. So I know I've got to go richer. I tried turning them to 2.5 while it was running and it increased idle, so I just shut it off to think.

I'll keep an eye out on the A/F for backing out once it's up and running. Thanks for the tip. It's nice how easy the access is to the screws! One positive of this arrangement.

That's what I was thinking... but the bike idles at 3700rpm with air filter on (richer). 1900 with air filter off (leaner). I will go back through and set the screws to 2.75, synchronize the carburetors without the air filter on, and then verify I didn't do something stupid like put the air filter in upside down or with some protective film on it or who knows what.

 

The carbs are synched in a certain order. I can't tell you cyl numbers off the top of my head at work, but it's based on the linkage arrangement from the base carb.

You might have to go to a #40. The tipping point for me is when I have to approach 2.5 turns or more. Ideally, I like to be around 2.

Also, verify that your new Uni is oiled properly.

 

Will do. The order of sync is in the manual, so I'll just follow that exactly. Will grab some 40 pilots if it requires more than 2.75 turns out once I get the rest of the idle figured out.

The new air filter is an Emgo paper filter... should I be oiling that? I thought paper filters were left dry, but cotton required oil. That might explain some things. I can't find a definitive source on when you are and are not supposed to oil a filter.

Ahhhhhh god I'm an idiot for throwing that other filter away. That looks like a reusable/cleanable one too... It'd give me something to test against.

 

Sorry... my mind read Uni. Emgo makes good OEM replacements. No oil of course. Uni (foam) and K&N style (gauze) require oil.

 

Are there any tricks or essential tools to accessing the synchronization screws buried on the underside of the carburetor?

I purchased this bendy 1/4" socket driver. I was able to get the socket over the hex head of the sync screws, but only with the aid of positioning it from the other side of the bike with a screwdriver and my arm wrapped around the underside of the bike. And this took many tries. If I use this method when the bike is running, it's going to end up with me burning my hands, shoulders, and likely face. That doesn't seem like the right way to go.

 

There are 90*, gear driven tools, not cheap, but they are effective. Motion Pro, Pit Posse, etc.

 

Cheaper than a skin graft?

~$70 for the Motion Pro... That seems like quite a bit for a tool that I've never had any use for prior. I'm gonna give my bendy socket a shot this weekend. If that doesn't work... I'll pick up the Motion Pro and try again the following weekend.

Thanks Norcal.

 

No worries.

 

Something like this might help and quite a bit cheaper:

https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.co.uk/ulk/itm/291171100527

(UK link but presume similar/cheap versions available in the US!)

 

it may be time to pull the carbs off and do a traditional, old-fashioned eyeball synch referencing throttle plates and the first progression hole.

 

Thanks for the suggestion Shields. I think that could potentially work, but something with a 1/4" socket receiver on the end would allow more range and they're pretty far deep in there. I have gotten to looking, and I think that this ABN Flex Shaft Carb Adjuster would work much better than the one I got. The shaft looks way more flexible. I'd just need a 7mm socket on the adapter. The one I purchased is super rigid--which is probably great for other applications, but I just need a little flex. Unfortunately, it's de-prioritized at Amazon until May 1st. And I don't think Harbor Freight offers anything similar.

• ABN Carb Adjuster Tool - https://www.amazon.com/ABN-Carburetor-Adjustment-Tool-Screwdriver/dp/B072K31TJJ
• ARES 51000 - Flexible Screwdriver (the one I bought) - https://www.amazon.com/gp/product/B082BJ47W9/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

Granted, I could just suck it up and get that fancy Motion Pro one. I'm probably overthinking this. I'm going to burn my cheek on the exhaust no matter what tool I'm holding.

If I don't have a solution in two weeks, I'll pop them back off and try 40 pilots instead of the 38s in there now. Hadn't heard about referencing the progression hole. I just used a piece of fishing line under to try to get them as close as possible--you can see, it wasn't a great effort.

 

Oh. And I've discovered just how hard it is to get brake fluid into a dry system with new stainless lines and rebuilt calipers. Yikes. Doesn't help that my Mighty Vac reservoir is sitting at a friends house 100 miles away.

I tried reverse filling with a syringe I bought for this purpose. I've gotten... some... brake fluid into both front calipers. I've verified that there is clear passage from the master cylinder to both of the calipers because each one I can hear whooshing noises when I pull on the brake and open the bleeders. There just must be a shit ton of air in there. I was pushing hard enough on the syringe I was afraid it was going to blow past the seal. I'll just keep moving it around and hopefully more and more air comes to the top. I don't need brakes for a while anyway.

 

Don't know if you have side access, but cheapie 1/4 drive ratchets and extend the handle... issue is perhaps not fine enough teeth to ratchet?
https://www.ebay.ca/itm/6-35mm-Driv...121275?hash=item341905f93b:g:4OMAAOSweRpd1JvY
https://www.ebay.ca/itm/1-4-Drive-6...139987?hash=item1ce6ac5d13:g:pgMAAOSwPPheeqis

 

That's where I started! And you're right--my issue was that it was not fine enough. I can get the extension onto the screws, but the clearance is such that I only can move the handle ~1" at the end of the handle (maybe less). Not enough to click. I tried jamming the gear with wire and taping it in, so then I had a rigid extension, and I was able to move the handle that inch. The problem then was, since it was a socket, I couldn't move it any further. So I could get about 1/8-1/5 of a turn adjustability in total.

Picture of the one I have. I also tried an extension on a u-joint spark plug puller to no avail.

But the right tool exists for this job, so I'll just try my cheap-o methods and if it doesn't work I'll pony up and buy the right one. Funny, it's gonna cost as much to synchronize the damn carburetors than it was to rebuild them.