88 Royal Popping

[Kc9ojn]

So that this is not a long drawn out post I just got a 88 Royal that the guy said needed a new CDI. It came with a parts bike so I grabbed the one off the other bike and switched it out( just the box) not all the other stuff on the mounting plate. Same problem, it will not rev over 3 grand so it tops out at 55 ish and getting there is slow. It pops in the carbs and sometimes in the pipes. My gut tells me carbs but I wanted to throw this out there. I will be parting out my 84 I loved that bike but it has had better days. So right now I won 3 Royals , most bikes I have ever owned at one time LOL

[KenP]

I used to have an '84.....followed the "receipe" below and no more popping......

 

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Rough idle !

The Venture is temperamental about her plugs. At the onset of the plug starting to break down, while you can feel the engine stumbling, you can't always see a problem when you pull the plugs. The lumpy idle is a characteristic of the Jason mod. The Mod should help give you a little more power and throttle response and sometimes better mileage at the expense of a slightly lumpy idle. Sometimes a problem could be with the sparkplugs even though they look OK. Its happened to me a number of times. You might want to try switching to NGK DPR8EV-9 or NGK DPR8EX-9.

These are fine wire electrode either gold tip (first no. I mentioned) or platinum tip (second no.) Early in the life of the Venture, if a customer complained about rough running, Yamaha informed dealers to substitute these plugs for the stock DPR8EA-9. Here's a quote from 9-1984. "Some Ventures have developed a low speed misfire, usually in higher gears and when accelerating from low speed. There are several things that can cause this. Improper synchronization, improper air/fuel mixture, air leaks between intake manifold and head, dirty plugs, or plug wire leakage are some of the trouble spots." A later tip from 11-84, refers to the use of the fine wire tip sparkplugs. I've used the NGK DPR8EV-9 in my '83, and they completely eliminate any misfire, and they last twice as long as the standard plugs. Also, it's hard to tell when your spark plug wires are breaking down. It's a cheap fix that can make a big difference. And if your air cleaner is dirty it can screw up your air/fuel ratio.

 

Replace the plug caps with the NGK 5k ohm caps and new plug wires. NGK plug caps are (style no.)XD05F Stock No.8072. The plug caps have a prong inside like a sheet metal screw, they just screw into the end of the plug wire. Just unscrew the old caps and screw in the new ones.

Long lasting Spark Plugs! Denso X24EPR-U9 or (newer) IX24B NGK DPR8EA-9 (normal) NGK DPR8EIX-9 (Iridium) Same as Champion RA6HC

Disconnect the fuel tank line prior to the fuel pump, run the carbs dry, then fill the carbs with Seafoam, Berrymans or Yamaha carb cleaner (comes in pint cans) until it tries to start. Let it sit 30 mins to couple of hours. Replace the filter while you are down there (behind left passenger peg assy.). when you get everything hooked up give it a try. some recommend draining the bowls at this point, I just rehook and go with fresh gas.

The plugs often can cause rough running and when you pull them they look fine. You can't tell by looking at them, so first thing to do is replace the plugs. Cleaning the carb slides with a spray cleaner is a good idea, as John Legare said above. Do the easiest fix first. If this doesn't get all 4 slides moving about the same, you might have a vacuum leak in the carb slide diaphragm. After you remove the side panels, you'll see that each carb has a sort of round plate on it facing out, with 4 screws in each plate. Originally, one of these screws was a security screw that looked like an allen head screw with a dimple in the middle. Since yours is an '85, the security screws have probably been removed long ago, but just thought I'd mention it. under that round plate is the slide diaphragm, a rubber membrane that is attached to the slide in the middle. I've had the plastic collar that holds the diaphragm to the slide come off. You can put it back on and use some gas resistant silicone sealant to keep it in place. But what usually happens is the diaphragms develop pinholes in them from age. You can try sealing these pinholes with gas resistant silicone sealer (a thin coat, don't gob it on) but that is just a temporary fix. replacing the slide/diaphragm assembly can be expensive if you do all 4 like I finally did, but it makes a world of difference on how your Venture runs. They all need it eventually. I think if you look in the boneyard ads on this sight you can find some, or do a search for "carb slides", we've talked a lot about them in the past. $40 - $50 bucks a slide, much more through a Youmaha dealer, like over $100. By the way, there is a long coil spring under each round plate, so don't let the plate fly out after you remove the last screw. Hold the plate in place when you remove the last screw, the ease it off slowly.

With the air filter out, fire it up and "blip" the throttle a few times. Crack it and let off. Do this while using a bright flashlight to watch all 4 slides. If all 4 are NOT dancing around and don't respond fairly equally you need to pull off the carb covers and inspect the slide / diaphragm assembly. Hold each up to a bright light and look for tears, perforations and pin holes. Inspect the plastic slide for hairline cracks. If you find any... replace the slide / diaphragm assembly. Make sure the needle isn't scored and is clean. The vent hole in the cover needs to be open (shot of carb clean will work). Make sure you sync the carbs.

 

Check / replace the plugs. Also check the plug wires... unscrew the ends from the wire and see if it's green and corroded. You can nip off a little to get to good wire. Same with the coil end of the plug wires.

I used a set of Autozone lifetime plug wires for a 1993 Suzuki Swift 4 cyl. Use the plug boot that comes with the new wires, and cut the other end off to the correct length. Reuse the coil caps and O-Ring. Use a dab of silicon O-ring lube. The coils have a knurled plastic cap with a hole in the center. The wire goes through the hole in the cap, through an O-ring and pushes into the coil "tower". When you snug down the cap, it compresses the O-ring and that holds / seals the wire in. No "metal thing"... just cut the wire off square and push it in. I think there's a pointed contact in the coil that shoves into the end of the wire. By the way.. the original wires are still available from the dealer if you wanted to go that route.

Actually the mixtures screws can affect not only idle, but low speed up to about 2000 rpm.

NOTE: A rich problem gets worse as the engine heats up. If the throttle is lightly "blipped" at idle, and the rpm drops below the set idle speed, then rises up to the set idle speed, the low speed mixture screws are probably set too rich: try 1/2 turn in, to lean the idle mixture.

NOTE: A lean problem gets better as the engine heats up. If the throttle is lightly "blipped" at idle, and the rpm "hangs up" before dropping to the set idle speed, and there are no intake leaks and the idle speed is set at less than 1000 rpm, the mixture screws are probably too lean: try 1/2 turn out, to richen mixture. Be sure there are no intake leaks and the idle speed is set at less than 1000 rpm!

 

Always Sync the carbs

Hook up the 4 tube vacuum gauge and adjust the left for balance (1-2) then over on the right, adjust the #3-#4 with the rear adjust screw and finally balance the left to right sides with the right side front adjust...

Most running is at less than 1/4 throttle.. where the idle jet screw owns the road. the book says to use a 2-gas analyzer in the exhaust...In the old school, before emission and gas analysers were invented, we used to hook a tach up and adjust the carb air screws to get the highest, steadiest reading we could achieve. Or the other way we would sometimes do it, and this should work on our motorcycles, is use the vacuum gauge or mercury tube, which is what I prefer, hooked up to each individual carb,one at a time, and adjust that one carb's air screw to the highest steadiest reading that can be achieved on the tubes scale. I haven't tried that just yet, but I will. I'll just bet cha that the motor will start, idle, and run so much nicer. Once you've done that, you can resync the carbs for the final touch. Dave Budrewicz E-mail Address: vze2hzk5@netscape.net

Pilot circuit (zero to 1/8 throttle)-

 

 

 

The mixture is lean if:

 

The bike surges while holding a steady throttle at about 4000 rpm in second gear.

there is excessive back-firing on closed-throttle overrun.

the throttle is lightly 'blipped' and the idle speed 'hangs up' before dropping to the set idle speed (set the idle to 1000 rpm to start).

 

 

Correction: turn the pilot screws OUT 1/2 turn or so. If the pilot screws end up turned out very much more than three and one half turns total (stock is about 2 1/2 turns), you should use larger pilot jets.

 

The mixture is rich if:

the plugs are excessively soot-ed up or fouled.

the throttle is lightly 'blipped' and the idle speed drops below the set idle speed before rising up to the set speed.

 

 

 

Correction: turn pilot screws IN 1/2 turn.

 

 

 

Running rough?... I think, first, check the air filter, be sure that it is clean.

Next, the carb mixtures. Common pre set is 2 1/2 turns out from gentle bottom (don't push too hard to find bottom, it is a needle valve and you DON'T want to damage the needle or the seat in the carb body). Should be between 1 1/2 turns and 3 1/2 turns on each carb. I tune my carbs with a digital tach, turn each idle mixture screw for peak rpm and then go back through again, then I turn each one OUT 1/16 turn to set it 'slightly rich'... the healthy side to be on.

 

It could be float level too high, but seems like it wouldn't be all the way around. It could be a too cool sparkplug (Yamaha recommends an "8" range plug, that is what I run). I'd say check the air cleaner and mixture, and see what happens. And a LOT of troubles have been found to be air leaks at the rubber connection of the lower carb manifold or age cracks on the sync blocking nipples below each carb. The

lower half of the lower rubber carb manifolds have a metal insert for mount integrity and a lot of our bikes develop cracks near the bottom on the outside... this is almost always cosmetic and NOT a leak source, if it's a bother, use some black RTV and smear it in the crack and wipe off excess.